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Sample records for mn fe ni

  1. Longitudinal and perpendicular exchange bias in FeMn/(FeNi/FeMn)n multilayers

    NASA Astrophysics Data System (ADS)

    Sun, L.; Zhou, S. M.; Searson, P. C.; Chien, C. L.

    2003-05-01

    Exchange bias in ferromagnetic (FM)/antiferromagnetic (AF) bilayers is usually investigated in the longitudinal configuration with the exchange coupling established in the film plane. In this work, we report on the perpendicular exchange bias in FeMn(8 nm)/[FeNi(2 nm)/FeMn(8 nm)]n multilayers induced by perpendicular field cooling. The thin FeNi layers give rise to large values of the exchange field and coercivity, and n=15 allows a sufficiently large magnetization for the measurements. Even though the soft FeNi layers have an intrinsic in-plane anisotropy, perpendicular exchange bias has been observed after cooling in a perpendicular external field. The exchange field in the perpendicular configuration is about 0.85 that of the longitudinal case. In both the longitudinal and perpendicular configurations, the exchange field decreases quasilinearly with temperature. The squareness of perpendicular hysteresis loops decreases with increasing temperature.

  2. Ni spin switching induced by magnetic frustration in FeMn/Ni/Cu(001)

    SciTech Connect

    Wu, J.; Choi, J.; Scholl, A.; Doran, A.; Arenholz, E.; Hwang, Chanyong; Qiu, Z. Q.

    2009-03-08

    Epitaxially grown FeMn/Ni/Cu(001) films are investigated by Photoemission Electron Microscopy and Magneto-Optic Kerr Effect. We find that as the FeMn overlayer changes from paramagnetic to antiferromagnetic state, it could switch the ferromagnetic Ni spin direction from out-of-plane to in-plane direction of the film. This phenomenon reveals a new mechanism of creating magnetic anisotropy and is attributed to the out-of-plane spin frustration at the FeMn-Ni interface.

  3. Ferromagnetic interactions and martensitic transformation in Fe doped Ni-Mn-In shape memory alloys

    SciTech Connect

    Lobo, D. N.; Priolkar, K. R.; Emura, S.; Nigam, A. K.

    2014-11-14

    The structure, magnetic, and martensitic properties of Fe doped Ni-Mn-In magnetic shape memory alloys have been studied by differential scanning calorimetry, magnetization, resistivity, X-ray diffraction (XRD), and EXAFS. While Ni{sub 2}MnIn{sub 1−x}Fe{sub x} (0 ≤ x ≤ 0.6) alloys are ferromagnetic and non martensitic, the martensitic transformation temperature in Ni{sub 2}Mn{sub 1.5}In{sub 1−y}Fe{sub y} and Ni{sub 2}Mn{sub 1.6}In{sub 1−y}Fe{sub y} increases for lower Fe concentrations (y ≤ 0.05) before decreasing sharply for higher Fe concentrations. XRD analysis reveals presence of cubic and tetragonal structural phases in Ni{sub 2}MnIn{sub 1−x}Fe{sub x} at room temperature with tetragonal phase content increasing with Fe doping. Even though the local structure around Mn and Ni in these Fe doped alloys is similar to martensitic Mn rich Ni-Mn-In alloys, presence of ferromagnetic interactions and structural disorder induced by Fe affect Mn-Ni-Mn antiferromagnetic interactions resulting in suppression of martensitic transformation in these Fe doped alloys.

  4. Influence of He-ion irradiation on thin NiMn/FeNi exchange bias films

    NASA Astrophysics Data System (ADS)

    Cantelli, V.; von Borany, J.; Grenzer, J.; Fassbender, J.; Kaltofen, R.; Schumann, J.

    2006-04-01

    Using synchrotron x-ray diffraction and reflectivity, we studied the transition from the paramagnetic NiMn phase to the chemically ordered, antiferromagnetic L10 phase of NiMn/Fe19Ni81 thin films deposited on a Si/SiO2 substrate as a function of the annealing temperature. The transformation to a dominating L10-ordered NiMn film takes place between 300 and 400 °C irrespective of the irradiation. This is also consistent with magnetization reversal measurements of the corresponding permalloy layers. The benefit of the ion irradiation is a reduction of the mosaicity for both the NiMn and the permalloy film, and a smoothening of internal interfaces.

  5. Influence of He-ion irradiation on thin NiMn/FeNi exchange bias films

    SciTech Connect

    Cantelli, V.; Borany, J. von; Grenzer, J.; Fassbender, J.; Kaltofen, R.; Schumann, J.

    2006-04-15

    Using synchrotron x-ray diffraction and reflectivity, we studied the transition from the paramagnetic NiMn phase to the chemically ordered, antiferromagnetic L1{sub 0} phase of NiMn/Fe{sub 19}Ni{sub 81} thin films deposited on a Si/SiO{sub 2} substrate as a function of the annealing temperature. The transformation to a dominating L1{sub 0}-ordered NiMn film takes place between 300 and 400 deg. C irrespective of the irradiation. This is also consistent with magnetization reversal measurements of the corresponding permalloy layers. The benefit of the ion irradiation is a reduction of the mosaicity for both the NiMn and the permalloy film, and a smoothening of internal interfaces.

  6. In-plane magnetic anisotropies in Ni/FeMn and Ni90Fe10/FeMn exchange biased bilayers

    NASA Astrophysics Data System (ADS)

    Pires, M. J. M.; de Oliveira, R. B.; Martins, M. D.; Ardisson, J. D.; Macedo, W. A. A.

    2007-12-01

    The in-plane magnetic anisotropy in Ni/FeMn and Ni90Fe10/FeMn exchange-biased bilayers prepared by co-evaporation under molecular beam epitaxy conditions is investigated employing longitudinal magneto-optical Kerr effect (MOKE) and ferromagnetic resonance (FMR). The exchange anisotropy was induced by a magnetic field cooling immediately after the deposition of the bilayers. Besides the induced term, the presence of an additional uniaxial anisotropy in the FM layers was detected both by MOKE and FMR, and the characteristic directions of these two anisotropy terms are not coincident. The interplay between the anisotropy contributions is discussed considering micromagnetic simulations and the in-plane resonance condition for different magnetic field orientation. X-ray diffraction, X-ray photoelectron spectroscopy, and Mössbauer spectroscopy were used to complement the characterization of the samples.

  7. 90° magnetic coupling in a NiFe/FeMn/biased NiFe multilayer spin valve component investigated by polarized neutron reflectometry

    SciTech Connect

    Callori, S. J. Bertinshaw, J.; Cortie, D. L.; Cai, J. W. Zhu, T.; Le Brun, A. P.; Klose, F.

    2014-07-21

    We have observed 90° magnetic coupling in a NiFe/FeMn/biased NiFe multilayer system using polarized neutron reflectometry. Magnetometry results show magnetic switching for both the biased and free NiFe layers, the latter of which reverses at low applied fields. As these measurements are only capable of providing information about the total magnetization within a sample, polarized neutron reflectometry was used to investigate the reversal behavior of the NiFe layers individually. Both the non-spin-flip and spin-flip neutron reflectometry signals were tracked around the free NiFe layer hysteresis loop and were used to detail the evolution of the magnetization during reversal. At low magnetic fields near the free NiFe coercive field, a large spin-flip signal was observed, indicating magnetization aligned perpendicular to both the applied field and pinned layer.

  8. NiFe/CoFe/Cu/CoFe/MnIr spin valves studied by ferromagnetic resonance

    NASA Astrophysics Data System (ADS)

    Timopheev, A. A.; Sobolev, N. A.; Pogorelov, Y. G.; Bunyaev, S. A.; Teixeira, J. M.; Cardoso, S.; Freitas, P. P.; Kakazei, G. N.

    2013-05-01

    Ion-beam deposited (Glass/Ta/NiFe/CoFe/Cu/CoFe/MnIr/Ta) spin valves (SVs) with a Cu-spacer thickness (tCu) varying from 14 to 28 Å have been studied by ferromagnetic resonance (FMR) and magnetoresistance (MR) measurements. With respect to the interlayer coupling strength between the free and fixed ferromagnetic layers, the samples have been divided in those with a weak coupling (for tCu > 16 Å) and a strong coupling regimes (for tCu ≤ 16 Å). The FMR behavior in these two regimes is quite different. For the weakly coupled series, there are two well-defined FMR peaks stemming from the free and fixed layers. Their in-plane angular dependences exhibit 180° and 360° symmetries, respectively. For the strongly coupled SVs, the resonance modes are hybridized and possess features of both layers simultaneously. The main coupling mechanism between the two layers, as concluded from the FMR and MR measurements, is the Néel "orange-peel" magnetostatic interaction, accompanied by a direct exchange due to pinholes in the Cu spacer for tCu < 17 Å.

  9. Investigation of nanostructures based on Ni80Fe20/(Ni80Fe20)20Mn80 bilayers with a unidirectional exchange anisotropy

    NASA Astrophysics Data System (ADS)

    Blinov, I. V.; Korolev, A. V.; Krinitsina, T. P.; Matveev, S. A.; Milyaev, M. A.; Popov, V. V.; Ustinov, V. V.

    2012-08-01

    The magnetic properties of nanostructures based on Ni80Fe20/(Ni80Fe20)20Mn80 bilayers have been investigated depending on the thickness of the antiferromagnetic layer and the material of the substrate. The possibility of using the antiferromagnetic alloy (Ni80Fe20)20Mn80 as the material for the pinning layer in spin valves has been considered.

  10. Magnetic properties and martensitic transformation in quaternary Heusler alloy of NiMnFeGa

    NASA Astrophysics Data System (ADS)

    Liu, Z. H.; Zhang, M.; Wang, W. Q.; Wang, W. H.; Chen, J. L.; Wu, G. H.; Meng, F. B.; Liu, H. Y.; Liu, B. D.; Qu, J. P.

    2002-11-01

    Quaternary Heusler alloy Ni2)(Mn,FeGa has been studied systematically for the structure, martensitic transformation, and magnetic properties in two systems of Ni50.5Mn25-xFexGa24.5 and Ni50.4Mn28-xFexGa21.6. Substituting Fe for Mn up to about 70%, the pure L21 phase and the thermoelastic martensitic transformation still can be observed in these quaternary systems. Iron doping dropped the martensitic transformation temperature from 220 to 140 K, increased the Curie temperature from 351 to 429 K, and broadened the thermal hysteresis from about 7 to 18 K. Magnetic analysis revealed that Fe atoms contribute to the net magnetization of the material with a moment lower than that of Mn. The temperature dependence of magnetic-field-induced strains has been improved by this doping method.

  11. Exchange bias in sputtered FeNi/FeMn systems: Effect of short low-temperature heat treatments

    NASA Astrophysics Data System (ADS)

    Savin, Peter; Guzmán, Jorge; Lepalovskij, Vladimir; Svalov, Andrey; Kurlyandskaya, Galina; Asenjo, Agustina; Vas'kovskiy, Vladimir; Vazquez, Manuel

    2016-03-01

    Short (5 min) post-deposition thermal treatments under magnetic field at low temperature (up to 200 °C) performed in exchange-coupled FeNi(40 nm)/FeMn(20 nm) bilayer thin films prepared by magnetron sputtering are shown to be effective to significantly modify their exchange field (from around 40 Oe down to 27 Oe) between FeNi and FeMn layers. A similar exchange field decrease was observed for the first deposited FeNi layer of the FeNi(40 nm)/FeMn(20 nm)/FeNi(40 nm) trilayer films after the same thermal treatments. The exchange field value for the second FeNi layer was not substantially changed. The X-ray diffraction patterns indicates that such a heat treatment has no effect on the grain size and crystalline texture of the films, while atomic force microscope studies reveal an increase of the surface roughness after the treatment which is more noticeable in the case of the trilayer film. Analysis of the experimental results leads us to conclude that the variations of the exchange field after heat treatment are likely caused by a modification of interfacial roughness and/or interfacial magnetic structure, but unlikely by the changes in the microstructure and/or changes of composition of the antiferromagnetic FeMn layer.

  12. Magnetostructural transition behavior in Fe-doped Heusler Mn-Ni-In ribbon materials

    NASA Astrophysics Data System (ADS)

    Li, Hongwei; Fang, Yue; Feng, Shutong; Zhai, Qijie; Luo, Zhiping; Zheng, Hongxing

    2016-11-01

    In the present work, we investigated magnetostructural transition behavior in Mn-rich Heusler Mn50-xFexNi41In9 (x=0, 1, 2, 3 at%) ribbon materials. Microstructural observations showed that substituting Mn with Fe in Mn50Ni41In9 led to striking grain refinement from ∼50 μm to 5-10 μm, and formation of a secondary phase when Fe content was increased up to 2 at%. Differential scanning calorimetric and thermomagnetic measurements indicated that a paramagnetic→ferromagnetic transition in austenite occurred first, followed with a weak-magnetic martensitic transition upon cooling for the Mn50-xFexNi41In9 (x=0, 1, 2). In case of Mn47Fe3Ni41In9, the martensitic transformation happened between paramagnetic austenite and weak-magnetic martensite, without the presence of the magnetic transition in austenite. The effective refrigeration capacity of Mn49Fe1Ni41In9 reached 137.1 J kg-1 under a magnetic field change of 30 kOe.

  13. Oxidation of CoCrFeMnNi High Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Holcomb, Gordon R.; Tylczak, Joseph; Carney, Casey

    2015-06-01

    Eight model high entropy alloys (HEAs) in the CoCrFeMnNi family (including one alloy each in the CoCrFeNi and CoFeMnNi subfamilies) were made, prepared, and exposed to laboratory air for 1100 h at 650°C and 750°C. Two commercial alloys, nickel-base superalloy 230 (N06230) and austenitic stainless steel 304H (S30409), were simultaneously exposed for comparison. Mass change oxidation kinetics were measured and cross-sections of exposed samples were observed. Seven of these HEAs contained much more Mn (12-24 wt.%) than is found in commercial heat-resistant stainless steels and superalloys. The oxidation resistance of CoCrFeNi was excellent and comparable to 304H at 650°C and only slightly worse at 750°C. The thin oxide scale on CoCrFeNi was primarily Cr oxide (presumably Cr2O3) with some Mn oxide at the outer part of the scale. The CoCrFeMnNi HEAs all experienced more rapid oxidation than CoCrFeNi and, especially at 750°C, experienced oxide scale spallation. The addition of Y in the alloy to lower S improved the oxidation resistance of these HEAs. Alloy CoFeMnNi, without Cr, experienced much higher oxidation rates and scale spallation than the Cr-containing alloys. A linear regression analysis of the log of the parabolic rate constant, log(kp), as functions of wt.% Cr and Mn found a good correlation for the compositional dependence of the oxidation rate constant, especially at 650°C. Mn was found to be more detrimental increasing log(k p) than Cr was helpful reducing log(k p). If CoCrFeMnNi HEAs are to be used in high temperature oxidizing environments, then examining lower levels of Mn, while maintaining Cr levels, should be pursued.

  14. Observation of Precipitation Evolution in Fe-Ni-Mn-Ti-Al Maraging Steel by Atom Probe Tomography

    NASA Astrophysics Data System (ADS)

    Pereloma, E. V.; Stohr, R. A.; Miller, M. K.; Ringer, S. P.

    2009-12-01

    We describe the full decomposition sequence in an Fe-Ni-Mn-Ti-Al maraging steel during isothermal annealing at 550 °C. Following significant pre-precipitation clustering reactions within the supersaturated martensitic solid solution, (Ni,Fe)3Ti and (Ni,Fe)3(Al,Mn) precipitates eventually form after isothermal aging for ~60 seconds. The morphology of the (Ni,Fe)3Ti particles changes gradually during aging from predominantly plate-like to rod-like, and, importantly, Mn and Al were observed to segregate to these precipitate/matrix interfaces. The (Ni,Fe)3(Al,Mn) precipitates occurred at two main locations: uniformly within the matrix and at the periphery of the (Ni,Fe)3Ti particles. We relate this latter mode of precipitation to the Mn-Al segregation.

  15. Observation of Precipitation Evolution in Fe-Ni-Mn-Ti-Al Maraging Steel using Atom Probe Tomography

    SciTech Connect

    Pereloma, E. V.; Stohr, R A; Miller, Michael K; Ringer, S. P.

    2009-01-01

    We describe the full decomposition sequence in an Fe-Ni-Mn-Ti-Al maraging steel during isothermal annealing at 550 C. Following significant pre-precipitation clustering reactions within the supersaturated martensitic solid solution, (Ni,Fe){sub 3}Ti and (Ni,Fe){sub 3}(Al,Mn) precipitates eventually form after isothermal aging for {approx}60 seconds. The morphology of the (Ni,Fe){sub 3}Ti particles changes gradually during aging from predominantly plate-like to rod-like, and, importantly, Mn and Al were observed to segregate to these precipitate/matrix interfaces. The (Ni,Fe){sub 3}(Al,Mn) precipitates occurred at two main locations: uniformly within the matrix and at the periphery of the (Ni,Fe){sub 3}Ti particles. We relate this latter mode of precipitation to the Mn-Al segregation.

  16. Simultaneous enhancement of magnetic and mechanical properties in Ni-Mn-Sn alloy by Fe doping

    PubMed Central

    Tan, Changlong; Tai, Zhipeng; Zhang, Kun; Tian, Xiaohua; Cai, Wei

    2017-01-01

    Both magnetic-field-induced reverse martensitic transformation (MFIRMT) and mechanical properties are crucial for application of Ni-Mn-Sn magnetic shape memory alloys. Here, we demonstrate that substitution of Fe for Ni can simultaneously enhance the MFIRMT and mechanical properties of Ni-Mn-Sn, which are advantageous for its applications. The austenite in Ni44Fe6Mn39Sn11 shows the typical ferromagnetic magnetization with the highest saturation magnetization of 69 emu/g at 223 K. The result shows that an appropriate amount of Fe substitution can really enhance the ferromagnetism of Ni50Mn39Sn11 alloy in austenite, which directly leads to the enhancement of MFIRMT. Meanwhile, the mechanical property significantly improves with Fe doping. When there is 4 at.% Fe added, the compressive and maximum strain reach the maximum value (approximately 725.4 MPa and 9.3%). Furthermore, using first-principles calculations, we clarify the origin of Fe doping on martensitic transformation and magnetic properties. PMID:28230152

  17. Electrochemical deposition and microstructural characterization of AlCrFeMnNi and AlCrCuFeMnNi high entropy alloy thin films

    NASA Astrophysics Data System (ADS)

    Soare, V.; Burada, M.; Constantin, I.; Mitrică, D.; Bădiliţă, V.; Caragea, A.; Târcolea, M.

    2015-12-01

    Al-Cr-Fe-Mn-Ni and Al-Cr-Cu-Fe-Mn-Ni high entropy alloy thin films were prepared by potentiostatic electrodeposition and the microstructure of the deposits was investigated. The thin films were co-deposited in an electrolyte based on a DMF (N,N-dimethylformamide)-CH3CN (acetonitrile) organic compound. The energy dispersive spectrometry investigation (EDS) indicated that all the five respectively six elements were successfully co-deposited. The scanning electron microscopy (SEM) analysis revealed that the film consists of compact and uniform particles with particle sizes of 500 nm to 4 μm. The X-ray diffractometry (XRD) patterns indicated that the as-deposited thin films were amorphous. Body-centered-cubic (BCC) structures were identified by XRD after the films were annealed at various temperatures under inert Ar atmosphere. The alloys adhesion on the substrate was determined by the scratch-testing method, with higher values obtained for the Al-Cr-Cu-Fe-Mn-Ni alloy.

  18. Dislocations in nanostructured two-phase Fe30Ni20Mn20Al30.

    PubMed

    Wu, X; Baker, I

    2013-03-01

    In a previous study, the dislocations in Fe(30)Ni(20)Mn(25)Al(25) (at. %), which consist of 50 nm wide alternating b.c.c. and B2 phases, were shown to have a/2<111> Burgers vectors after room temperature deformation. The dislocations were found to glide in pairs on both {110} and {112} slip planes and were relatively widely separated in the b.c.c. phase, where the dislocations were uncoupled, and closely spaced in the B2 phase, where the dislocations were connected by an anti-phase boundary. In this article, we analyze the dislocations in the two ~5 nm-wide B2 phases in a related two-phase alloy Fe(30)Ni(20)Mn(20)Al(30), with compositions Fe-23Ni-21Mn-24Al and Fe-39Ni-12Mn-34Al, compressed to ~3% strain at a strain rate 5 × 10(-4) s(-1) at 873 K (the lowest temperature at which substantial plastic flow was observed). It is shown that slip occursby the glide of a<100> dislocations. A review of the literature suggests that the differences in the observed slip vector between these B2 phases could be due to the differences in composition, differences in deformation temperature, or possibly both.

  19. Spin polarization of Ni2MnIn and Ni80Fe20 determined by point-contact Andreev spectroscopy

    NASA Astrophysics Data System (ADS)

    Bocklage, Lars; Scholtyssek, Jan M.; Merkt, Ulrich; Meier, Guido

    2007-05-01

    We present point-contact Andreev reflection (PCAR) spectroscopy on Permalloy (Ni80Fe20) and on the half-metallic Heusler alloy Ni2MnIn. The thin Permalloy films are deposited on Si, the Ni2MnIn films on Si as well as on in situ cleaved (110) surfaces of InAs. A highly conductive layer under the ferromagnetic film almost eliminates a series resistance and thus facilitates the determination of the spin polarization from the differential conductance curves. We obtain a spin polarization of Permalloy of 35%. The spin polarization of Ni2MnIn depends on the substrate, presumably due to the growth of different crystal structures. It is shown that the surface sensitive PCAR spectroscopy cannot determine the spin polarization of the bulk material of half-metals where the degree of spin polarization strongly depends on the crystal structure.

  20. Construction of the Magnetic Phase Diagram of FeMn/Ni/Cu(001) Using Photoemission Electron Microscopy

    SciTech Connect

    Wu, J.; Scholl, A.; Arenholz, E.; Hwang, C.; Qiu, Z. Q.

    2011-01-04

    Single crystalline FeMn/Ni bilayer was epitaxially grown on Cu(001) substrate and investigated by photoemission electron microscopy (PEEM). The FeMn and Ni films were grown into two cross wedges to facilitate an independent control of the FeMn (0-20 ML) and Ni (0-20 ML) film thicknesses. The Ni magnetic phases were determined by Ni domain images as a function of the Ni thickness (d{sub Ni}) and the FeMn thickness (d{sub FeMn}). The result shows that as the Ni thickness increases, the Ni film undergoes a paramagnetic-to-ferromagnetic state transition at a critical thickness of d{sub FM} and an in-plane to out-of-plane spin reorientation transition at a thicker thickness d{sub SRT}. The phase diagram shows that both d{sub FM} and d{sub SRT} increase as the FeMn film establishes its antiferromagnetic order.

  1. Connection between orbital moment enhancement and exchange bias in a [Ni80Fe20/Mn]3 multilayer

    NASA Astrophysics Data System (ADS)

    Su, H.-C.; Huang, M.-J.; Lin, H.-J.; Lee, C.-H.; Chen, C.-T.; Liu, C.-H.; Hsu, H.-F.; Lin, K.-W.; van Lierop, J.

    2013-01-01

    The overall and element specific magnetism in an exchange biased [Ni80Fe20/Mn]3 film system, with film layers 3.5 nm thick, has been studied to examine the magnetism between interfacial Mn, Ni, and Fe spins. Field-cooling the film results in large exchange bias loop shifts at temperatures from 2 to 30 K, and an enhanced coercivity remains until 75 K. The elemental magnetism ascertained from x-ray magnetic circular dichroism measurements shows that Mn appears to be a fully compensated antiferromagnet down to 20 K, and there is clear evidence of an enhanced orbital moment for both Fe and Ni from 20 to 300 K. This magnetism is likely due to overlapping d orbitals between Fe-Mn and Ni-Mn, with this coupling increasing the local anisotropy resulting in the enhanced coercivity and enabling exchange bias.

  2. Plasma-Sprayed High Entropy Alloys: Microstructure and Properties of AlCoCrFeNi and MnCoCrFeNi

    NASA Astrophysics Data System (ADS)

    Ang, Andrew Siao Ming; Berndt, Christopher C.; Sesso, Mitchell L.; Anupam, Ameey; S, Praveen; Kottada, Ravi Sankar; Murty, B. S.

    2015-02-01

    High entropy alloys (HEAs) represent a new class of materials that present novel phase structures and properties. Apart from bulk material consolidation methods such as casting and sintering, HEAs can also be deposited as a surface coating. In this work, thermal sprayed HEA coatings are investigated that may be used as an alternative bond coat material for a thermal barrier coating system. Nanostructured HEAs that were based on AlCoCrFeNi and MnCoCrFeNi were prepared by ball milling and then plasma sprayed. Splat studies were assessed to optimise the appropriate thermal spray parameters and spray deposits were prepared. After mechanical alloying, aluminum-based and manganese-based HEA powders revealed contrary prominences of BCC and FCC phases in their X-ray diffraction patterns. However, FCC phase was observed as the major phase present in both of the plasma-sprayed AlCoCrFeNi and MnCoCrFeNi coatings. There were also minor oxide peaks detected, which can be attributed to the high temperature processing. The measured porosity levels for AlCoCrFeNi and MnCoCrFeNi coatings were 9.5 ± 2.3 and 7.4 ± 1.3 pct, respectively. Three distinct phase contrasts, dark gray, light gray and white, were observed in the SEM images, with the white regions corresponding to retained multicomponent HEAs. The Vickers hardness (HV0.3kgf) was 4.13 ± 0.43 and 4.42 ± 0.60 GPa for AlCoCrFeNi and MnCoCrFeNi, respectively. Both type of HEAs coatings exhibited anisotropic mechanical behavior due to their lamellar, composite-type microstructure.

  3. Thermal stability of exchange-biased NiFe/FeMn multilayered thin films

    NASA Astrophysics Data System (ADS)

    Chen, H. Y.; Phuoc, Nguyen N.; Ong, C. K.

    2012-09-01

    A systematic study of the effect of ferromagnetic thickness on magnetic and microwave properties of exchange-biased NiFe/FeMn multilayered thin films was carried out with regards to thermal stability. The temperature-dependent microwave characteristics of the films were obtained from the near-field microwave microscopy technique and analysed based on Landau-Lifshitz-Gilbert equation. The complex microwave permeability spectra of the magnetic thin films up to 5 GHz in the temperature range from room temperature to 420 K were measured. It was found that thicker ferromagnetic layers helped to reduce the dependence of the magnetic properties on temperature, leading to better thermal stability. The saturation magnetization MS, dynamic magnetic anisotropy field HKdyn, and ferromagnetic resonance frequency fFMR were found to decrease with temperature, while the effective damping coefficient αeff was increased with temperature. We also investigate the rotational magnetic anisotropy field HKrot with temperature which gives a measure of the rotatable magnetization of the antiferromagnetic layers and its thermal stability.

  4. Magnetic characteristics of a high-layer-number NiFe/FeMn multilayer

    SciTech Connect

    Paterson, G. W. Gonçalves, F. J. T.; McFadzean, S.; Stamps, R. L.; O'Reilly, S.; Bowman, R.

    2015-11-28

    We report the static and dynamic magnetic characteristics of a high-layer-number NiFe/FeMn multilayer test structure with potential applications in broadband absorber and filter devices. To allow fine control over the absorption linewidths and to understand the mechanisms governing the resonances in a tailored structure similar to that expected to be used in real world applications, the multilayer was intentionally designed to have layer thickness and interface roughness variations. Magnetometry measurements show that the sample has complex hysteresis loops with features consistent with single ferromagnetic film reversals. Characterisation by transmission electron microscopy allows us to correlate the magnetic properties with structural features, including the film widths and interface roughnesses. Analysis of resonance frequencies from broadband ferromagnetic resonance measurements as a function of field magnitude and orientation provide values of the local exchange bias, rotatable anisotropy, and uniaxial anisotropy fields for specific layers in the stack and explain the observed mode softening. The linewidths of the multilayer are adjustable around the bias field, approaching twice that seen at larger fields, allowing control over the bandwidth of devices formed from the structure.

  5. Exchange anisotropy in polycrystalline FeNi /FeMn films with hysteresis loop asymmetry

    NASA Astrophysics Data System (ADS)

    Merenkov, D. N.; Bludov, A. N.; Gnatchenko, S. L.; Baran, M.; Szymczak, R.; Novosad, V. A.

    2007-11-01

    The process of magnetization reversal of a FeNi(50Å )/FeMn(50Å) polycrystalline film prepared in a magnetic field has been investigated at temperatures ranging from 25to300K. The external field was oriented in the film plane along the easy or difficult axis of the ferromagnetic layer. In the process of magnetization reversal of the film along the easy axis, strong asymmetry of the hysteresis loop is observed together with an exchange shift. As temperature decreases, the asymmetry becomes more pronounced and the shift increases. The field dependences of the magnetization of the film are symmetric and are not shifted when the external field is applied along the difficult axis. The magnetization reversal process is examined on the basis of a model that takes account of the appearance of high-order exchange anisotropy in polycrystalline films. It is shown that the observed strong asymmetry of the hysteresis loop is associated with the formation of a canted phase and the existence of a metastable state. As the film temperature decreases, the interval of fields where the canted phase can exist becomes wider as a result of an increase of the exchange anisotropy constants.

  6. Magnetic characteristics of a high-layer-number NiFe/FeMn multilayer

    NASA Astrophysics Data System (ADS)

    Paterson, G. W.; Gonçalves, F. J. T.; McFadzean, S.; O'Reilly, S.; Bowman, R.; Stamps, R. L.

    2015-11-01

    We report the static and dynamic magnetic characteristics of a high-layer-number NiFe/FeMn multilayer test structure with potential applications in broadband absorber and filter devices. To allow fine control over the absorption linewidths and to understand the mechanisms governing the resonances in a tailored structure similar to that expected to be used in real world applications, the multilayer was intentionally designed to have layer thickness and interface roughness variations. Magnetometry measurements show that the sample has complex hysteresis loops with features consistent with single ferromagnetic film reversals. Characterisation by transmission electron microscopy allows us to correlate the magnetic properties with structural features, including the film widths and interface roughnesses. Analysis of resonance frequencies from broadband ferromagnetic resonance measurements as a function of field magnitude and orientation provide values of the local exchange bias, rotatable anisotropy, and uniaxial anisotropy fields for specific layers in the stack and explain the observed mode softening. The linewidths of the multilayer are adjustable around the bias field, approaching twice that seen at larger fields, allowing control over the bandwidth of devices formed from the structure.

  7. Role of the antiferromagnetic pinning layer on spin wave properties in IrMn/NiFe based spin-valves

    NASA Astrophysics Data System (ADS)

    Gubbiotti, G.; Tacchi, S.; Del Bianco, L.; Bonfiglioli, E.; Giovannini, L.; Tamisari, M.; Spizzo, F.; Zivieri, R.

    2015-05-01

    Brillouin light scattering (BLS) was exploited to study the spin wave properties of spin-valve (SV) type samples basically consisting of two 5 nm-thick NiFe layers (separated by a Cu spacer of 5 nm), differently biased through the interface exchange coupling with an antiferromagnetic IrMn layer. Three samples were investigated: a reference SV sample, without IrMn (reference); one sample with an IrMn underlayer (10 nm thick) coupled to the bottom NiFe film; one sample with IrMn underlayer and overlayer of different thickness (10 nm and 6 nm), coupled to the bottom and top NiFe film, respectively. The exchange coupling with the IrMn, causing the insurgence of the exchange bias effect, allowed the relative orientation of the NiFe magnetization vectors to be controlled by an external magnetic field, as assessed through hysteresis loop measurements by magneto-optic magnetometry. Thus, BLS spectra were acquired by sweeping the magnetic field so as to encompass both the parallel and antiparallel alignment of the NiFe layers. The BLS results, well reproduced by the presented theoretical model, clearly revealed the combined effects on the spin dynamic properties of the dipolar interaction between the two NiFe films and of the interface IrMn/NiFe exchange coupling.

  8. Role of the antiferromagnetic pinning layer on spin wave properties in IrMn/NiFe based spin-valves

    SciTech Connect

    Gubbiotti, G. Tacchi, S.; Del Bianco, L.; Bonfiglioli, E.; Giovannini, L.; Spizzo, F.; Zivieri, R.; Tamisari, M.

    2015-05-07

    Brillouin light scattering (BLS) was exploited to study the spin wave properties of spin-valve (SV) type samples basically consisting of two 5 nm-thick NiFe layers (separated by a Cu spacer of 5 nm), differently biased through the interface exchange coupling with an antiferromagnetic IrMn layer. Three samples were investigated: a reference SV sample, without IrMn (reference); one sample with an IrMn underlayer (10 nm thick) coupled to the bottom NiFe film; one sample with IrMn underlayer and overlayer of different thickness (10 nm and 6 nm), coupled to the bottom and top NiFe film, respectively. The exchange coupling with the IrMn, causing the insurgence of the exchange bias effect, allowed the relative orientation of the NiFe magnetization vectors to be controlled by an external magnetic field, as assessed through hysteresis loop measurements by magneto-optic magnetometry. Thus, BLS spectra were acquired by sweeping the magnetic field so as to encompass both the parallel and antiparallel alignment of the NiFe layers. The BLS results, well reproduced by the presented theoretical model, clearly revealed the combined effects on the spin dynamic properties of the dipolar interaction between the two NiFe films and of the interface IrMn/NiFe exchange coupling.

  9. Microstructure and corrosion properties of CrMnFeCoNi high entropy alloy coating

    NASA Astrophysics Data System (ADS)

    Ye, Qingfeng; Feng, Kai; Li, Zhuguo; Lu, Fenggui; Li, Ruifeng; Huang, Jian; Wu, Yixiong

    2017-02-01

    Equimolar CrMnFeCoNi high entropy alloy (HEA) is one of the most notable single phase multi-component alloys up-to-date with promising mechanical properties at cryogenic temperatures. However, the study on the corrosion behavior of CrMnFeCoNi HEA coating has still been lacking. In this paper, HEA coating with a nominal composition of CrMnFeCoNi is fabricated by laser surface alloying and studied in detail. Microstructure and chemical composition are determined by X-ray diffraction (XRD), optical microscope (OM), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) are used to investigate the corrosion behavior. The coating forms a simple FCC phase with an identical dendritic structure composed of Fe/Co/Ni-rich dendrites and Mn/Ni-rich interdendrites. Both in 3.5 wt.% NaCl solution and 0.5 M sulfuric acid the coating exhibits nobler corrosion resistance than A36 steel substrate and even lower icorr than 304 stainless steel (304SS). EIS plots coupled with fitted parameters reveal that a spontaneous protective film is formed and developed during immersion in 0.5 M sulfuric acid. The fitted Rt value reaches its maximum at 24 h during a 48 h' immersion test, indicating the passive film starts to break down after that. EDS analysis conducted on a corroded surface immersed in 0.5 M H2SO4 reveals that corrosion starts from Cr-depleted interdendrites.

  10. Galvanomagnetic properties of Heusler alloy Co2 YAl ( Y = Ti, V, Cr, Mn, Fe, and Ni)

    NASA Astrophysics Data System (ADS)

    Kourov, N. I.; Marchenkov, V. V.; Perevozchikova, Yu. A.; Weber, H. W.

    2017-01-01

    The Hall effect and the magnetoresistance of ferromagnetic Heusler alloys Co2 YAl, where Y = Ti, V, Cr, Mn, Fe, and Ni have been studied at T = 4.2 K in magnetic fields H ≤ 100 kOe. Normal R 0 and anomalous R S Hall coefficients are shown to be maximal in magnitudes in the middle of the 3 d period of the periodic table of elements. Coefficient R 0 changes the negative sign to positive sign in going from weak ( Y = Ti, V) to strong ( Y = Cr, Mn, Fe, and Ni) ferromagnetic alloys. Constant R S is positive and proportional to ρ2.9 in all the alloys. The magnetoresistance of the alloys is not higher than several percent and its magnitude is changed fairly significantly in the dependence on the number of valence electrons z; the magnetoresistance signs vary arbitrarily.

  11. Magnetic and mechanical properties of Ni-Mn-Ga/Fe-Ga ferromagnetic shape memory composite

    NASA Astrophysics Data System (ADS)

    Tan, Chang-Long; Zhang, Kun; Tian, Xiao-Hua; Cai, Wei

    2015-05-01

    A ferromagnetic shape memory composite of Ni-Mn-Ga and Fe-Ga was fabricated by using spark plasma sintering method. The magnetic and mechanical properties of the composite were investigated. Compared to the Ni-Mn-Ga alloy, the threshold field for magnetic-field-induced strain in the composite is clearly reduced owing to the assistance of internal stress generated from Fe-Ga. Meanwhile, the ductility has been significantly improved in the composite. A fracture strain of 26% and a compressive strength of 1600 MPa were achieved. Projects supported by the National Natural Science Foundation of China (Grant Nos. 51271065 and 51301054), the Program for New Century Excellent Talents in Heilongjiang Provincial Education Department, China (Grant No. 1253-NCET-009), the Youth Academic Backbone in Heilongjiang Provincial Education Department, China (Grant No. 1251G022), the Projects of Heilongjiang, China, and China Postdoctoral Science Foundation.

  12. Enhancement of electrochemical performance by simultaneous substitution of Ni and Mn with Fe in Ni-Mn spinel cathodes for Li-ion batteries

    NASA Astrophysics Data System (ADS)

    Kiziltas-Yavuz, Nilüfer; Yavuz, Murat; Indris, Sylvio; Bramnik, Natalia N.; Knapp, Michael; Dolotko, Oleksandr; Das, Bijoy; Ehrenberg, Helmut; Bhaskar, Aiswarya

    2016-09-01

    LiNi0.5-xFe2xMn1.5-xO4 (x = 0, 0.1, 0.15, 0.2) spinel cathode materials are synthesized using citric acid-assisted sol-gel method with final calcination temperature of 1000 °C. The structure and morphology of the materials are characterized by using synchrotron and neutron powder diffraction as well as scanning electron microscopy. Different from the parent LiNi0.5Mn1.5O4 (LNMO) material, the Fe-doped spinels do not contain a rock-salt type impurity phase. However, they contain additional layered (C2/m) and spinel Fe3O4 (Fd 3 bar m) phases in small amounts. The substitution of Fe into the spinel structure has been confirmed by Mössbauer spectroscopy. The Fe-doped spinels exhibit improved cycling stability (with a C/2 charge-discharge rate) and rate capability compared to the parent LNMO at room temperature in a voltage range 3.5-5.0 V. Among all these samples, the composition LiNi0.4Fe0.2Mn1.4O4 shows the best room temperature cycling stability (capacity retention of 92% after 300 cycles) as well as the highest initial discharge capacity (134 mAh g-1). The delivered capacities at high C-rates (especially at 10C and 20C) with respect to the capacity delivered at C/2 are higher for all Fe-doped samples compared to the parent LNMO. Furthermore, Fe-doping improves the thermal stability of the Ni-Mn spinels in the delithiated state.

  13. Mechanical Properties and Microstructure of the CoCrFeMnNi High Entropy Alloy Under High Strain Rate Compression

    NASA Astrophysics Data System (ADS)

    Wang, Bingfeng; Fu, Ao; Huang, Xiaoxia; Liu, Bin; Liu, Yong; Li, Zezhou; Zan, Xiang

    2016-07-01

    The equiatomic CoCrFeMnNi high entropy alloy, which crystallizes in the face-centered cubic (FCC) crystal structure, was prepared by the spark plasma sintering technique. Dynamic compressive tests of the CoCrFeMnNi high entropy alloy were deformed at varying strain rates ranging from 1 × 103 to 3 × 103 s-1 using a split-Hopkinson pressure bar (SHPB) system. The dynamic yield strength of the CoCrFeMnNi high entropy alloy increases with increasing strain rate. The Zerilli-Armstrong (Z-A) plastic model was applied to model the dynamic flow behavior of the CoCrFeMnNi high entropy alloy, and the constitutive relationship was obtained. Serration behavior during plastic deformation was observed in the stress-strain curves. The mechanism for serration behavior of the alloy deformed at high strain rate is proposed.

  14. Compressive deformation behavior of CrMnFeCoNi high-entropy alloy

    NASA Astrophysics Data System (ADS)

    Jang, Min Ji; Joo, Soo-Hyun; Tsai, Che-Wei; Yeh, Jien-Wei; Kim, Hyoung Seop

    2016-11-01

    The compressive deformation behavior of a single phase CrMnFeCoNi high-entropy alloy (HEA) is investigated using experimental and theoretical approaches. The equiaxed microstructures are observed using optical microscope, electron backscattered diffraction, and synchrotron X-ray diffraction (XRD) techniques. Compressive results reveal that the CrMnFeCoNi HEA has a high strain-hardening exponent in spite of its large grain size due to increased dislocation density and severe lattice distortion. The compressive texture of the HEA resembles those of typical FCC metals. The phenomenological dislocation-based constitutive model well describes the compressive deformation behavior. The predicted dislocation density is in good quantitative agreement with the experimental value measured using whole-profile fitting of synchrotron XRD peaks. It can be confirmed from the experimental and theoretical findings that the deformation mechanism of the CrMnFeCoNi HEA is the conventional dislocation glide and mechanical twinning is negligible contrary to general belief.

  15. Analysis of the weak coupling of the IrMn/Co/Ru/NiFe structures by ferromagnetic resonance

    NASA Astrophysics Data System (ADS)

    Alayo, W.; Sousa, M. A.; Pelegrini, F.; Baggio-Saitovitch, E.

    2011-04-01

    The Ir20Mn80/Co/Ru/Ni81Fe19 spin valve structures have been produced by sputtering deposition and analyzed by ferromagnetic resonance. Two well resolved modes are identified in the FMR spectra as the resonance of the Co and NiFe layers. The in-plane angular dependence of the resonance peaks for the NiFe layer present a small asymmetry, which is attributed to the interlayer exchange interaction between ferromagnetic layers across the nonmagnetic spacer. The data were analyzed considering the exchange bias at the IrMn/Co interface and the indirect coupling between Co and NiFe. The in-plane angular dependence of the resonance fields of both Co and NiFe layers present an upward (downward) shift for antiferromagnetic (ferromagnetic) coupling with respect to a system with no interlayer coupling.

  16. Analysis of the weak coupling of the IrMn/Co/Ru/NiFe structures by ferromagnetic resonance

    SciTech Connect

    Alayo, W.; Baggio-Saitovitch, E.; Sousa, M. A.; Pelegrini, F.

    2011-04-15

    The Ir{sub 20}Mn{sub 80}/Co/Ru/Ni{sub 81}Fe{sub 19} spin valve structures have been produced by sputtering deposition and analyzed by ferromagnetic resonance. Two well resolved modes are identified in the FMR spectra as the resonance of the Co and NiFe layers. The in-plane angular dependence of the resonance peaks for the NiFe layer present a small asymmetry, which is attributed to the interlayer exchange interaction between ferromagnetic layers across the nonmagnetic spacer. The data were analyzed considering the exchange bias at the IrMn/Co interface and the indirect coupling between Co and NiFe. The in-plane angular dependence of the resonance fields of both Co and NiFe layers present an upward (downward) shift for antiferromagnetic (ferromagnetic) coupling with respect to a system with no interlayer coupling.

  17. Quaternary PtMnCuX/C (X = Fe, Co, Ni, and Sn) and PtMnMoX/C (X = Fe, Co, Ni, Cu and Sn) alloys catalysts: Synthesis, characterization and activity towards ethanol electrooxidation

    NASA Astrophysics Data System (ADS)

    Ammam, Malika; Easton, E. Bradley

    2012-10-01

    In this account, two series of quaternary PtMnCuX/C (X = Fe, Co, Ni, and Sn) and PtMnMoX/C (X = Fe, Co, Ni, Cu and Sn) alloys catalysts have been synthesized and characterized by ICP, XRD, XPS, TEM and cyclic voltammetry. XRD spectra of each series illustrated that PtMnCuX/C (X = Fe, Co and Ni) and PtMnMoX/C (X = Fe, Co, Ni and Cu) alloys have been formed without significant free Mn, Cu, Mo or X co-catalysts. For PtMnCuSn/C and PtMnMoSn/C, in addition to alloy formation, significant free Sn-oxides are present in each catalyst. Cyclic voltammetry and chronoamperometry revealed that all quaternary showed superior electrocatalytic activity towards ethanol oxidation compared to the ternary precursor. Also, shift of the onset potential of ethanol oxidation towards less positive values were also recorded with the quaternary alloys, demonstrating a facilitated oxidation with the quaternary alloys compared to ternary alloy precursor. The magnitude of the gain in potential depend on the alloy composition and PtMnMoSn/C was found to be the best of all synthetized quaternary alloys with an onset potential of ethanol oxidation of only 0.059 V vs. Ag/AgCl.

  18. Azimuthal angular dependent hysteresis loops of Fe50Mn50/Ni81Fe19 bilayers grown under a magnetic field

    NASA Astrophysics Data System (ADS)

    Choi, Hyeok-Cheol; You, Chun-Yeol; Kim, Ki-Yeon

    2016-11-01

    The azimuthal angular dependence of the vectorial hysteresis loops in the Fe50Mn50(AF)/Ni81Fe19(F) bilayer grown under a magnetic field was investigated using a combination of vectorial magneto-optic Kerr effect and model calculation. From a comparison of the experimental and calculation results, it is found that the AF easy axis is not parallel with but rotated by about 20° away from the applied magnetic field during the sample growth. Moreover, the transverse loop at the AF easy axis does not vanish but displays an open full circle (i.e., magnetization changes sign between decreasing and increasing field branches for the full hysteresis measurement). Our model calculation reveals that they are reminiscent of the non-collinear uniaxial and unidirectional anisotropies. Specifically, the angular dependence of the transverse hysteresis is well reproduced with our model calculation taking non-collinear magnetic anisotropies into account. Coercivity determined from the longitudinal loops, on the other hand, is found to be nonzero and comparatively large at all azimuthal angles. This is in stark contrast with previous results regarding FeMn/NiFe bilayers field-cooled after sample growth. Neither domain wall nor incoherent magnetic rotation in the F layer is likely to be responsible for this coercivity discrepancy between theory and experiments. Apart from the uniaxial F and unidirectional AF-F anisotropies, we suggest that the F rotatable anisotropy equivalent of 40% to 60% of the interfacial coupling energy should be taken into account to properly address the coercivity enhancement in the FeMn/NiFe bilayer grown under a magnetic field.

  19. The structural and magnetic properties of Mn{sub 2-x}Fe{sub x}NiGa Heusler alloys

    SciTech Connect

    Luo Hongzhi; Meng Fanbin; Feng Zhongqiu; Li Yangxian; Zhu Wei; Wu Guangheng; Zhu Xiaoxi; Jiang Chengbao; Xu Huibin

    2010-01-15

    The effect of Fe substitution on the phase transformation and magnetic properties of Mn{sub 2}NiGa has been studied. A single bcc phase was obtained in Mn{sub 2-x}Fe{sub x}NiGa (x=0-0.6). With the substitution of Fe for Mn, the lattice constant decreases gradually. The martensitic transformation can be observed when x=0-0.3. Both the martensitic transformation and austenitic transformation temperatures decrease monotonically with increasing Fe content, which is different from common electron concentration dependence in Ni-Mn-Ga system. The saturation magnetizations M{sub s} of Mn{sub 2-x}Fe{sub x}NiGa in both austenitic and martensitic phases increase obviously with the doping of Fe, while the variation of T{sub C} shows an opposite tendency. Theoretical calculations indicate that both austenitic and martensitic phases are ferrimagnets. The Fe moment varies from positive to negative after the tetragonal distortion, which leads to the decrease of the saturation magnetization.

  20. Synthesis of Waste Form in the Gd-Fe-Al-Ni-Mn-Cr-O System

    SciTech Connect

    Chae, S.C.; Jang, Y.N.; Bae, I.K.; Ryu, K.W.

    2006-07-01

    Poly-phase waste form which was the mixture of Gd{sub 3}Fe{sub 2}Al{sub 3}O{sub 12} and (Ni{sub x}Mn{sub 1-x})(Fe{sub y}Cr{sub 1-y}){sub 2}O{sub 4} was synthesized. Also, we are intended to examine phase relation and physicochemical properties of coexisted phases in the compositions and to confirm accommodation relation of elements and phases. Two types of phase series were observed: Garnet-perovskite-spinel and Garnet-spinel. The compositions of garnets and spinels were nonstoichiometric, and especially, this poly-phase ceramics may be in a good waste form. The excessive Gd in garnets indicated the immobilization of higher content of actinides. The nonstoichiometric compositions of garnet and spinel were attributed to the formation of perovskite in that perovskite contained Gd, Fe and Al from garnet and Cr from spinel. (authors)

  1. Magnetic Properties of Liquid Gd-TM (TM = Mn, Fe, Co, Ni) Alloys

    NASA Astrophysics Data System (ADS)

    Ohno, Satoru; Shimakura, Hironori; Tahara, Shuta; Okada, Tatsuya

    2016-12-01

    Liquid Gd-TM (TM = Mn, Fe, Ni) alloys on the TM-rich side have relatively small and negative temperature coefficients of the magnetic susceptibility χ, which become large and negative with increasing Gd content. The large and negative temperature coefficient of χ for liquid Co gradually weakens at up to 70 at. % Co with the addition of Gd. Liquid Gd and GdcCo1-c alloys with c ≥ 0.5 also have a relatively large and negative temperature coefficient of χ. Liquid Gd-TM alloys on the Gd-rich side obey the Curie law. The magnetic susceptibilities of liquid Gd-Fe and Gd-Co alloys exhibit Curie-Weiss behavior on the TM-rich side. The dependence of χ on the composition for liquid Gd-TM (TM = Mn, Fe, Ni) alloys gradually increases with the Gd content, and that for liquid Gd-Co alloys has a minimum at the composition of 20 at. % Gd. The dependences of χ3d and χ4f on the composition due to the 3d- and 4f-electrons were analyzed by subtracting the corresponding data for liquid La-TM alloys from χ for the liquid Gd-TM alloys.

  2. [Study on the chemical form and extraction rate of Cr, Cu, Fe, Mn, Ni and Zn in tea].

    PubMed

    Gao, G; Tao, R

    2000-07-01

    The content of Cr, Cu, Fe, Mn, Ni and Zn in the tea commonly available in China market were measured by inductivity coupled plasma-optical emission spectrometry (ICP-OES). The extraction rates of the six elements in tea leachate were measured. The solubilitied were 39.8% for Cr, 42.5% for Cu, 8.6% for Fe, 45.5% for Mn, 87.1% for Ni and 71.0% for Zn. The process of making tea leachate affects the elements extraction rates. The content of the microelements in tea leave extracts decreases gradually with the processing. About 80% of Cr, Cu, Mn, Ni and Zn and 60% of Fe were in the first infusion of tea. Moreover, the chemical forms of six elements were determined. The ratios of organic to inorganic forms were 0.33 for Cr, 0.022 for Cu, 0.18 for Fe, 0.002 for Mn, 0.01 for Ni and 0.18 for Zn. It is concluded that the six elements from the tea infusion extracted from 5 g tea are too little to meet the recommend dietary allowance (RDA). Therefore, tea is not a rich food source of Cr, Cu, Fe, Mn, Ni and Zn.

  3. Aspects of thermal martensite in a FeNiMnCo alloy.

    PubMed

    Güler, M; Güler, E; Kahveci, N

    2010-07-01

    Thermal martensite characteristics in Fe-29%Ni-2%Mn-2%Co alloy were investigated with scanning electron microscopy (SEM) and Mössbauer spectroscopy characterization techniques. SEM observations obviously revealed the lath martensite morphology in the prior austenite phase of examined alloy. As well, the martensitic transformation kinetics was found to be as athermal type. On the other hand, Mössbauer spectroscopy offered the paramagnetic austenite phase and ferromagnetic martensite phase with their volume fractions. Also, the internal magnetic field of the martensite was measured as 32.9T from the Mössbauer spectrometer.

  4. Multiscale twin hierarchy in NiMnGa shape memory alloys with Fe and Cu

    DOE PAGES

    Barabash, Rozaliya I.; Barabash, Oleg M.; Popov, Dmitry; ...

    2015-01-31

    X-ray microdiffraction and scanning electron microscopy studies reveal 10 M martensitic structure with a highly correlated multiscale twin hierarchy organization in NiMnGaFeCu shape memory alloys. In this paper, high compatibility is found at the twin interfaces resulting in a highly correlated twinned lattice orientation across several laminate levels. The lattice unit cell is described as monoclinic I-centered with a = 4.28 Å, b = 4.27 Å, c = 5.40 Å, γ = 78.5°. The modulation is found parallel to the b axis. Finally, thin tapered needle-like lamellae and branching are observed near the twin boundaries.

  5. Weldability of a high entropy CrMnFeCoNi alloy

    SciTech Connect

    Wu, Zhenggang; David, Stan A.; Feng, Zhili; Bei, Hongbin

    2016-07-19

    We present the high-entropy alloys are unique alloys in which five or more elements are all in high concentrations. In order to determine its potential as a structural alloy, a model face-centered-cubic CrMnFeCoNi alloy was selected to investigate its weldability. Welds produced by electron beam welding show no cracking. The grain structures within the fusion zone (FZ) are controlled by the solidification behavior of the weld pool. The weldment possesses mechanical properties comparable to those of the base metal (BM) at both room and cryogenic temperatures. Finally, compared with the BM, deformation twinning was more pronounced in the FZ of the tested alloy.

  6. Investigation of the mechanical properties of FeNiCrMnSi high entropy alloy wear resistant

    NASA Astrophysics Data System (ADS)

    Buluc, G.; Florea, I.; Chelariu, R.; Popescu, G.; Carcea, I.

    2016-06-01

    In this paper we investigated microstructure, hardness and wear resistance for FeNiCrMnAl, high entropy alloy. The FeNiCrMnSi, high entropy alloy was elaborated in a medium induction furnace, by choosing the silicon, as an alliance element within the equi- atomic high entropy alloy, we managed to obtain a dendritic structure, the formation of intermetallic compounds or separated silicon. The medium hardness value of the investigated alloy was 948.33 HV and the medium value of the friction coefficient was 0.6655 in the first 20 seconds and 0.5425 for 1667 seconds. The volume loss of the high entropy alloy FeNiCrMnSi was 0.0557 mm3.

  7. Calculations of structural, elastic, electronic, magnetic and phonon properties of FeNiMnAl by the first principles

    SciTech Connect

    Uğur, Şule; İyigör, Ahmet

    2014-10-06

    The electronic, elastic and dynamical properties of the quaternary alloy FeNiMnAl have been investigated using a pseudopotential plane wave method within the generalized gradient approximation (GGA). We determined the lattice parameters and the bulk modulus B. In addition, the elastic properties such as elastic constans (C{sub 11}, C{sub 12} and C{sub 44}), the shear modulus G, the young modulus E, the poisson's ratio σ and the B/G ratio are also given. The FeNiMnAl Heusler alloy exhibit a ferromagnetic half-metallic behavior with the total magnetic moment of 4.02 μ{sub B}. The phonon dispersion of FeNiMnAl has been performed using the density functional theory and the direct method with 2×2×2 supercell.

  8. Magnetoelasticity in ACr2O4 spinel oxides (A= Mn, Fe, Co, Ni, and Cu)

    NASA Astrophysics Data System (ADS)

    Kocsis, V.; Bordács, S.; Varjas, D.; Penc, K.; Abouelsayed, A.; Kuntscher, C. A.; Ohgushi, K.; Tokura, Y.; Kézsmárki, I.

    2013-02-01

    Dynamical properties of the lattice structure were studied by optical spectroscopy in ACr2O4 chromium spinel oxide magnetic semiconductors over a broad temperature region of T=10-335 K. The systematic change of the A-site ions (A= Mn, Fe, Co, Ni and Cu) showed that the occupancy of 3d orbitals on the A site has strong impact on the lattice dynamics. For compounds with orbital degeneracy (FeCr2O4, NiCr2O4, and CuCr2O4), clear splitting of infrared-active phonon modes and/or activation of silent vibrational modes have been observed upon the Jahn-Teller transition and at the onset of the subsequent long-range magnetic order. Although MnCr2O4 and CoCr2O4 show multiferroic and magnetoelectric character, no considerable magnetoelasticity was found in spinel compounds without orbital degeneracy as they closely preserve the high-temperature cubic spinel structure even in their magnetic ground state. Aside from lattice vibrations, intra-atomic 3d-3d transitions of the A2+ ions were also investigated to determine the crystal field and Racah parameters and the strength of the spin-orbit coupling.

  9. Galvanomagnetic properties of Fe{sub 2}YZ (Y = Ti, V, Cr, Mn, Fe, Ni; Z = Al, Si) heusler alloys

    SciTech Connect

    Kourov, N. I. Marchenkov, V. V.; Belozerova, K. A.; Weber, H. W.

    2015-11-15

    The Hall effect and the magnetoresistance of Fe{sub 2}YZ Heusler alloys, where Y = Ti, V, Cr, Mn, Fe, and Ni, are the 3d transition metals and Z = Al and Si are the s, p elements of the third period of the periodic table, are studied at T = 4.2 K in magnetic fields H ≤ 100 kOe. It is shown that, in the high-field limit (H > 10 kOe), the value and the sign of the normal (R{sub 0}) and anomalous (R{sub s}) Hall coefficients change anomalously during transition from paramagnetic (Y = Ti, V) to ferromagnetic (Y = Cr, Mn, Fe, Ni) alloys. These coefficients have different signs for all alloys. Constant R{sub s} in the ferromagnetic alloys is positive, proportional to the residual resistivity ratio (R{sub s} ∝ ρ{sub 0}{sup 3.1}), and inversely proportional to spontaneous magnetization. The magnetoresistance of the alloys is a few percent and has a negative sign. A positive addition to transverse magnetoresistance is only detected in high magnetic fields, H > 10 kOe.

  10. Galvanomagnetic properties of Fe2YZ (Y = Ti, V, Cr, Mn, Fe, Ni; Z = Al, Si) heusler alloys

    NASA Astrophysics Data System (ADS)

    Kourov, N. I.; Marchenkov, V. V.; Belozerova, K. A.; Weber, H. W.

    2015-11-01

    The Hall effect and the magnetoresistance of Fe2YZ Heusler alloys, where Y = Ti, V, Cr, Mn, Fe, and Ni, are the 3 d transition metals and Z = Al and Si are the s, p elements of the third period of the periodic table, are studied at T = 4.2 K in magnetic fields H ≤ 100 kOe. It is shown that, in the high-field limit ( H > 10 kOe), the value and the sign of the normal ( R 0) and anomalous ( R s ) Hall coefficients change anomalously during transition from paramagnetic (Y = Ti, V) to ferromagnetic (Y = Cr, Mn, Fe, Ni) alloys. These coefficients have different signs for all alloys. Constant R s in the ferromagnetic alloys is positive, proportional to the residual resistivity ratio ( R s ∝ ρ 0 3.1 ), and inversely proportional to spontaneous magnetization. The magnetoresistance of the alloys is a few percent and has a negative sign. A positive addition to transverse magnetoresistance is only detected in high magnetic fields, H > 10 kOe.

  11. Microstructural Evolution and Functional Properties of Fe-Mn-Al-Ni Shape Memory Alloy Processed by Selective Laser Melting

    NASA Astrophysics Data System (ADS)

    Niendorf, Thomas; Brenne, Florian; Krooß, Philipp; Vollmer, Malte; Günther, Johannes; Schwarze, Dieter; Biermann, Horst

    2016-06-01

    In the current study, a Fe-Mn-Al-Ni shape memory alloy is processed by additive manufacturing for the first time. Microstructural evolution upon processing is strongly affected by thermal gradients and solidification velocity and, thus, by processing parameters and the actual specimen geometry. By single-step solutionizing heat treatment pronounced grain growth is initiated leading to microstructures showing good reversibility. The compressive stress-strain response revealed maximum reversible pseudo-elastic strain of about 7.5 pct. Critical steps toward further optimization of additively manufactured Fe-Mn-Al-Ni shape memory alloys are discussed.

  12. Using granular C0-AI2O3 spacer for optimization of functional parameters of the FeMn/Fe20Ni80 magnetoresistive films

    NASA Astrophysics Data System (ADS)

    Gorkovenko, A. N.; Lepalovskij, V. N.; Adanakova, O. A.; Vas'kovskiy, V. O.

    2016-03-01

    In this paper we studied the possibility of tailoring the functional properties of the multilayer magnetoresistive medium with unidirectional anisotropy and the anisotropic magnetoresistance effect (AMR). Objects of the research were composite Co-Al2O3 films and Ta/Fe20Ni80/Fe50Mn50/Fe20Ni80/Co-Al2O3/Fe20Ni80/Ta multilayers structures obtained by magnetron sputtering and selectively subjected vacuum annealing. Structure, magnetic and magnetoresistive properties of the films in the temperature range 77÷440 K were investigated.

  13. Structural transitions, magnetic properties, and electronic structures of Co(Fe)-doped MnNiSi compounds

    SciTech Connect

    Li, Y.; Wei, Z. Y.; Liu, E. K. Wang, S. G.; Wang, W. H.; Wu, G. H.; Liu, G. D.

    2015-05-07

    The structural transitions, magnetic properties, and electronic structures of Co(Fe)-doped MnNiSi compounds are investigated by x-ray powder diffraction, differential scanning calorimetry (DSC), magnetic measurements, and first-principles calculations. Results indicate that all samples undergo a martensitic transition from the Ni{sub 2}In-type parent phase to TiNiSi-type orthorhombic phase at high temperatures. The substitution of Co(Fe) for Mn in Mn{sub 1−x}Co{sub x}NiSi (x = 0.2, 0.3, and 0.4) and Mn{sub 1−y}Fe{sub y}NiSi (y = 0.26, 0.30, 0.36, 0.46, and 0.55) samples decreases the structural transition temperature and Curie temperature of martensite. The martensite phases show a typical ferromagnetic behavior with saturation field being basically unchanged with increasing Co(Fe) content, while the saturation magnetization shows a decreasing tendency. The theoretically calculated moments are in good agreement with the experimentally measured results. The orbital hybridizations between different 3d elements are analyzed from the distribution of density of states.

  14. Rotatable anisotropy of Ni81Fe19/Ir20Mn80 films: A study using broadband ferromagnetic resonance

    NASA Astrophysics Data System (ADS)

    Dutra, R.; Gonzalez-Chavez, D. E.; Marcondes, T. L.; de Andrade, A. M. H.; Geshev, J.; Sommer, R. L.

    2013-11-01

    We investigate the broadband ferromagnetic resonance dispersion relation of NiFe/IrMn multilayers using the vector network analyzer ferromagnetic resonance (VNA-FMR) method. Multilayered films with structure [NiFe(20 nm)/IrMn (tIrMn)/Ta(3 nm)]×10 (with tIrMn=4 and 15 nm) were produced onto Si(100) substrates using magnetron sputtering. The dispersion relations of the samples were extracted from the resonance spectra in the range of 0.1-7 GHz under magnetic fields of up to±300 Oe. Static magnetization curves were also obtained in the same field range. The experimental data were compared with numerical calculations performed using the granular exchange-bias model which takes into account both, the unidirectional and rotatable anisotropy present in the samples. A good agreement between numerical and experimental results was achieved without the need of any frequency or field-dependent parameter.

  15. Ab initio prediction of the mechanical properties of alloys: The case of Ni/Mn-doped ferromagnetic Fe

    NASA Astrophysics Data System (ADS)

    Wang, Guisheng; Schönecker, Stephan; Hertzman, Staffan; Hu, Qing-Miao; Johansson, Börje; Kwon, Se Kyun; Vitos, Levente

    2015-06-01

    First-principles alloy theory, formulated within the exact muffin-tin orbital method in combination with the coherent-potential approximation, is used to study the mechanical properties of ferromagnetic body-centered cubic (bcc) Fe1 -xMx alloys (M = Mn or Ni, 0 ≤x ≤0.1 ). We consider several physical parameters accessible from ab initio calculations and their combinations in various phenomenological models to compare the effect of Mn and Ni on the properties of Fe. Alloying is found to slightly alter the lattice parameters and produce noticeable influence on elastic moduli. Both Mn and Ni decrease the surface energy and the unstable stacking fault energy associated with the {110 } surface facet and the {110 }<111 > slip system, respectively. Nickel is found to produce larger effect on the planar fault energies than Mn. The semiempirical ductility criteria by Rice and Pugh consistently predict that Ni enhances the ductility of Fe but give contradictory results in the case of Mn doping. The origin of the discrepancy between the two criteria is discussed and an alternative measure of the ductile-brittle behavior based on the theoretical cleavage strength and single-crystal shear modulus G {110 }<111 > is proposed.

  16. High-field magnetization of band ferromagnets Co2 YAl ( Y = Ti, V, Cr, Mn, Fe, Ni)

    NASA Astrophysics Data System (ADS)

    Kourov, N. I.; Marchenkov, V. V.; Perevozchikova, Yu. A.; Korolev, A. V.; Weber, H. W.

    2016-12-01

    The temperature dependences of the magnetization of ferromagnetic Heusler alloys Co2 YAl, where Y = Ti, V, Cr, Mn, Fe, and Ni have been studied at H = 50 kOe in the range 2 K < T < 1100 K. It is shown that the high-field ( H ≥ 20 kOe) magnetization is described within the Stoner model.

  17. Nanomechanical Behavior of CoCrFeMnNi High-Entropy Alloy

    NASA Astrophysics Data System (ADS)

    Mridha, Sanghita; Das, Santanu; Aouadi, Samir; Mukherjee, Sundeep; Mishra, Rajiv S.

    2015-08-01

    The nanomechanical behavior of the Co20Cr20Fe20Mn20Ni20 high-entropy alloy was investigated in as-cast, rolled, annealed, and thin-film forms. Dislocation nucleation was studied by repeated indents at a low load for each of the different processing conditions. Distinct displacement bursts (pop in) were observed in the loading curve marked by incipient plasticity for all the samples. The as-cast and annealed samples showed pop ins for 100% of the indents, whereas the rolled and thin-film samples showed a much lower fraction of displacement bursts. This was explained by the high density of dislocations for the cold-worked and thin-film conditions. The strong depth dependence of hardness was explained by geometrically necessary dislocations. The nanomechanical behavior and twinned microstructure indicate low stacking-fault energy for this high-entropy alloy.

  18. Antiparallel interface coupling evidenced by negative rotatable anisotropy in IrMn/NiFe bilayers

    SciTech Connect

    Schafer, D.; Grande, P. L.; Pereira, L. G.; Azevedo, G. M.; Harres, A.; Geshev, J.; Sousa, M. A. de; Pelegrini, F.

    2015-06-07

    Negative rotatable anisotropy is estimated via ferromagnetic resonance measurements in as-made, annealed, and ion-irradiated IrMn{sub 3}/Ni{sub 81}Fe{sub 19} bilayers. Opposite to previous observations, inverse correlation between rotatable anisotropy and coercivity is observed. The exchange-bias field, determined from hysteresis loop measurements, is higher than that obtained from ferromagnetic resonance for all samples. The results are discussed in terms of majority antiparallel coupling and magnetic-field-induced transitions from antiparallel to parallel states of uncompensated spins at ferromagnet/antiferromagnet interface. We affirm that an observation of negative rotatable anisotropy evidences antiparallel coupling even in systems presenting conventional exchange bias.

  19. Weldability of a high entropy CrMnFeCoNi alloy

    DOE PAGES

    Wu, Zhenggang; David, Stan A.; Feng, Zhili; ...

    2016-07-19

    We present the high-entropy alloys are unique alloys in which five or more elements are all in high concentrations. In order to determine its potential as a structural alloy, a model face-centered-cubic CrMnFeCoNi alloy was selected to investigate its weldability. Welds produced by electron beam welding show no cracking. The grain structures within the fusion zone (FZ) are controlled by the solidification behavior of the weld pool. The weldment possesses mechanical properties comparable to those of the base metal (BM) at both room and cryogenic temperatures. Finally, compared with the BM, deformation twinning was more pronounced in the FZ ofmore » the tested alloy.« less

  20. Microstructures and mechanical properties of compositionally complex Co-free FeNiMnCr18 FCC solid solution alloy

    DOE PAGES

    Wu, Z.; Bei, H.

    2015-07-01

    Recently, a structurally-simple but compositionally-complex FeNiCoMnCr high entropy alloy was found to have excellent mechanical properties (e.g., high strength and ductility). To understand the potential of using high entropy alloys as structural materials for advanced nuclear reactor and power plants, it is necessary to have a thorough understanding of their structural stability and mechanical properties degradation under neutron irradiation. Furthermore, this requires us to develop a similar model alloy without Co because material with Co will make post-neutron-irradiation testing difficult due to the production of the 60Co radioisotope. In order to achieve this goal, a FCC-structured single-phase alloy with amore » composition of FeNiMnCr18 was successfully developed. This near-equiatomic FeNiMnCr18 alloy has good malleability and its microstructure can be controlled by thermomechanical processing. By rolling and annealing, the as-cast elongated-grained-microstructure is replaced by homogeneous equiaxed grains. The mechanical properties (e.g., strength and ductility) of the FeNiMnCr18 alloy are comparable to those of the equiatomic FeNiCoMnCr high entropy alloy. Both strength and ductility increase with decreasing deformation temperature, with the largest difference occurring between 293 and 77 K. Extensive twin-bands which are bundles of numerous individual twins are observed when it is tensile-fractured at 77 K. No twin bands are detected by EBSD for materials deformed at 293 K and higher. Ultimately the unusual temperature-dependencies of UTS and uniform elongation could be caused by the development of the dense twin substructure, twin-dislocation interactions and the interactions between primary and secondary twinning systems which result in a microstructure refinement and hence cause enhanced strain hardening and postponed necking.« less

  1. Structure, magnetic properties and magnetocaloric effects of Fe50Mn15- x Co x Ni35 alloys

    NASA Astrophysics Data System (ADS)

    Zhong, XiChun; Tian, HuaCun; Tang, PengFei; Liu, ZhongWu; Zheng, ZhiGang; Zeng, DeChang

    2014-03-01

    Fe50Mn15- x Co x Ni35 ( x=0, 1, 3, 5, 7) alloys were prepared by arc melting under purified argon atmosphere. The ingots were homogenized at 930°C for 90 h followed by water quenching. The crystal structure, magnetic properties and magnetocaloric effects of the alloys were studied by X-ray diffraction (XRD) and MPMS-7-type SQUID. The results show that all samples still maintained a single γ-(Fe, Ni)-type phase structure. With the increase of the content of Co, the Curie temperatures of these alloys increased and exhibited a second-order magnetic transition from ferromagnetic (FM) to paramagnetic (PM) state near Curie temperature. The maximum magnetic entropy change and the relative cooling power of Fe50Mn10Co5Ni35 alloy was 2.55 J/kg·K and 181 J/kg, respectively, for an external field change of 5 T. Compared with rare earth metal Gd, Fe50Mn15- x Co x Ni35 series of alloys have obvious advantage in resource price; their Curie temperatures can be tuned to near room temperature, maintain a relatively large magnetic entropy change at the same time and they are a type of potential magnetic refrigeration materials near room temperature.

  2. Atomic displacement in the CrMnFeCoNi high-entropy alloy - A scaling factor to predict solid solution strengthening

    NASA Astrophysics Data System (ADS)

    Okamoto, Norihiko L.; Yuge, Koretaka; Tanaka, Katsushi; Inui, Haruyuki; George, Easo P.

    2016-12-01

    Although metals strengthened by alloying have been used for millennia, models to quantify solid solution strengthening (SSS) were first proposed scarcely seventy years ago. Early models could predict the strengths of only simple alloys such as dilute binaries and not those of compositionally complex alloys because of the difficulty of calculating dislocation-solute interaction energies. Recently, models and theories of SSS have been proposed to tackle complex high-entropy alloys (HEAs). Here we show that the strength at 0 K of a prototypical HEA, CrMnFeCoNi, can be scaled and predicted using the root-mean-square atomic displacement, which can be deduced from X-ray diffraction and first-principles calculations as the isotropic atomic displacement parameter, that is, the average displacements of the constituent atoms from regular lattice positions. We show that our approach can be applied successfully to rationalize SSS in FeCoNi, MnFeCoNi, MnCoNi, MnFeNi, CrCoNi, CrFeCoNi, and CrMnCoNi, which are all medium-entropy subsets of the CrMnFeCoNi HEA.

  3. The effects of annealing on the microstructure and mechanical properties of Fe28Ni18Mn33Al21

    DOE PAGES

    Meng, Fanling; Qiu, Jingwen; Baker, Ian; ...

    2015-08-20

    In this paper, As-cast Fe28Ni18Mn33Al21, which consists of aligned, 50 nm, (Ni, Al)-rich B2, and (Fe, Mn)-rich f.c.c. phases, was annealed at a variety of temperatures up to 1423 K and the microstructure and mechanical properties were examined. It was shown that the as-cast microstructure arises from a eutectoid transformation at ~1300 K. Annealing at temperatures ≤1073 K produces β-Mn-structured precipitates and hardness values up to 816 HV, while annealing at temperatures >1073 K leads to dramatic coarsening of the two-phase B2/f.c.c. microstructure (up to 5.5 µm after 50 h at 1273 K), but does not lead to β-Mn precipitation.more » Interestingly, annealing at temperatures >1073 K delays the onset of β-Mn precipitation during subsequent anneals at lower temperatures. Coarsening the B2/f.c.c. lamellar structure by annealing at higher temperatures softens it and leads to increases in ductility from fracture before yield to ~8 % elongation. Finally, the presence of β-Mn precipitates makes the very fine, brittle B2/f.c.c. microstructures even more brittle, but significant ductility (8.4 % elongation) is possible even with β-Mn precipitates present if the B2/f.c.c. matrix is coarse and, hence, more ductile.« less

  4. First principles investigation of domain walls and exchange stiffness in ferromagnetic Fe and antiferromagnetic NiMn

    NASA Astrophysics Data System (ADS)

    Nakamura, Kohji; Ito, Tomonori; Freeman, A. J.; Zhong, Lieping; Fernandez-de-Castro, Juan

    2003-05-01

    We investigate the domain walls in ferromagnetic Fe and antiferromagnetic NiMn with the first principles full-potential linearized augmented plane-wave method including intra-atomic noncollinear magnetism. In both cases, the self-consistent results demonstrate that the magnetization changes continuously from one orientation to another as seen in a Bloch wall. The formation energy of the domain wall (ΔEDW) significantly decreases when the wall thickness increases, which leads to an exchange stiffness of 1.13×10-11 J/m for Fe and 1.43×10-11 J/m for NiMn. The predictions agree with those determined separately for Fe from a phenomenological calculation.

  5. The effect of substitution of Mn by Fe and Cr on the martensitic transition in the Ni50Mn34In16 alloy.

    PubMed

    Sharma, V K; Chattopadhyay, M K; Nath, S K; Sokhey, K J S; Kumar, R; Tiwari, P; Roy, S B

    2010-12-08

    The potential shape memory alloy Ni(50)Mn(34)In(16) is studied with partial substitution of Mn with Fe and Cr to investigate the effect of such substitution on the martensitic transition in the Ni-Mn-In alloy system. The results of ac susceptibility, magnetization and electrical resistivity measurements show that while the substitution with Cr increases the martensitic transition temperature, the substitution with Fe decreases it. Possible reasons for this shift in martensitic transition are discussed. Evidence of kinetic arrest of the austenite to martensite phase transition in the Fe substituted alloys is also presented. Unlike the kinetic arrest of the austenite to martensite phase transition in the parent Ni(50)Mn(34)In(16) alloy which takes place in the presence of high external magnetic field, the kinetic arrest of the austenite to martensite phase transition in the Fe doped alloy occurs even in zero magnetic field. The Cr substituted alloys, on the other hand, show no signature of kinetic arrest of this phase transition.

  6. Non-collinear magnetism and exchange bias at the FM NiFe/AFM NiMn interface: local spin density FLAPW study

    NASA Astrophysics Data System (ADS)

    Nakamura, K.; Freeman, A. J.; Wang, D.-S.; Zhong, L.; Fernandez-de-Castro, J.

    2001-03-01

    Magnetism at interfaces, such as the exchange bias between ferromagnetic (FM) and antiferromagnetic (AFM) materials, has attracted great attention because of technological applications. In order to investigate magnetic structures at the FM/AFM interface, we have implemented the FLAPW (E. Wimmer, H. Krakauer, M. Weinert and A.J. Freeman, PRB 24, 864(1981)) methodologies including non-collinear magnetism, in which the magnetic moment direction as well as the magnitude can vary continuously all over space. We first demonstrate this approach to determine the structure of a magnetic structure at an interface between FM NiFe and AFM NiMn. Although both bulk systems each show collinear FM and AFM structures, we found that a perpendicular magnetic orientation at their interface is energetically favorable, where the magnetic moments of the FM NiFe tend to lie perpendicular to those of AFM NiMn.

  7. Crystallographic, magnetic, and electronic structures of ferromagnetic shape memory alloys Ni2XGa (X=Mn,Fe,Co) from first-principles calculations

    NASA Astrophysics Data System (ADS)

    Bai, J.; Raulot, J. M.; Zhang, Y. D.; Esling, C.; Zhao, X.; Zuo, L.

    2011-01-01

    The crystallographic, magnetic and electronic structures of the ferromagnetic shape memory alloys Ni2XGa (X=Mn, Fe, and Co), are systematically investigated by means of the first-principles calculations within the framework of density functional theory using the VIENNA AB INITIO SOFTWARE PACKAGE. The lattice parameters of both austenitic and martensitic phases in Ni2MnGa have been calculated. The formation energies of the cubic phase of Ni2XGa are estimated, and show a destabilization tendency if Mn atom is substituted by Fe or Co. From Ni2MnGa to Ni2CoGa, the down spin total density of states (DOS) at Fermi level is gradually increasing, whereas that of the up spin part remains almost unchanged. This is the main origin of the difference of the magnetic moment in these alloys. The partial DOS is dominated by the Ni and Mn 3d states in the bonding region below EF. There are two bond types existing in Ni2XGa: one is between neighboring Ni atoms in Ni2MnGa; the other is between Ni and X atoms in Ni2FeGa and Ni2CoGa alloys.

  8. NaxMV(PO4)3 (M = Mn, Fe, Ni) Structure and Properties for Sodium Extraction.

    PubMed

    Zhou, Weidong; Xue, Leigang; Lü, Xujie; Gao, Hongcai; Li, Yutao; Xin, Sen; Fu, Gengtao; Cui, Zhiming; Zhu, Ye; Goodenough, John B

    2016-12-14

    NASICON (Na(+) super ionic conductor) structures of NaxMV(PO4)3 (M = Mn, Fe, Ni) were prepared, characterized by aberration-corrected STEM and synchrotron radiation, and demonstrated to be durable cathode materials for rechargeable sodium-ion batteries. In Na4MnV(PO4)3, two redox couples of Mn(3+)/Mn(2+) and V(4+)/V(3+) are accessed with two voltage plateaus located at 3.6 and 3.3 V and a capacity of 101 mAh g(-1) at 1 C. Furthermore, the Na4MnV(PO4)3 cathode delivers a high initial efficiency of 97%, long durability over 1000 cycles, and good rate performance to 10 C. The robust framework structure and stable electrochemical performance makes it a reliable cathode materials for sodium-ion batteries.

  9. Detection of the dynamic magnetic behavior of the antiferromagnet in exchange-coupled NiFe/IrMn bilayers.

    PubMed

    Spizzo, F; Tamisari, M; Bonfiglioli, E; Del Bianco, L

    2013-09-25

    The magnetothermal behavior of antiferromagnetic IrMn layers of different thickness (3, 6, 10 nm) has been studied by exploiting the exchange coupling with a ferromagnetic 5 nm-thick NiFe layer. A procedure has been devised for the measurement of the magnetization of the NiFe/IrMn bilayers as a function of temperature and time at different values of an external magnetic field, Hinv, antiparallel to the unidirectional exchange anisotropy. This analysis allows one to probe the effective distribution of anisotropy energy barriers of the antiferromagnetic phase, as sensed by the ferromagnetic layer. Two magnetic regimes have been distinguished. At temperature T < 100 K, the interfacial IrMn spins are frozen in a glassy state and are collectively involved in the exchange coupling with the NiFe spins. At T ∼ 100 K the collective state breaks up; thus, above this temperature, only the interfacial IrMn spins which are tightly polarized by the IrMn nanograins, forming the bulk of the layer, are effectively involved in the exchange coupling mechanism. Due to that, for T > 100 K the exchange coupling is ruled by the anisotropy energy barriers of the bulk IrMn nanograins, namely by the layer thickness. The thermal evolution of the exchange field and of the coercivity in the three samples is coherently explained in the framework of this description of the dynamic magnetic behavior of the IrMn phase.

  10. Fluctuations of chemical composition of austenite and their consequence on shape memory effect in Fe-Mn-(Si, Cr, Ni, C, N) alloys

    SciTech Connect

    Bliznuk, V.V.; Gavriljuk, V.G. . E-mail: gavr@imp.kiev.ua; Kopitsa, G.P.; Grigoriev, S.V.; Runov, V.V.

    2004-09-20

    Polycrystalline samples of shape memory iron-based alloys containing 17, and 30 mass% Mn and alloyed with Si, Cr, Ni, C, N were studied by means of small angle scattering of polarized neutrons (SAPNS). A direct correlation between chemical homogeneity of the Fe-Mn, Fe-Mn-Si, Fe-Mn-Si-Cr, Fe-Mn-Si-Cr-Ni solid solutions and the values of reversible strain caused by the {gamma} {yields} {epsilon} {yields} {gamma} martensitic transformation was found. The addition of silicon to the Fe-Mn alloys significantly improves chemical homogeneity of the fcc solid solution on the scale of larger than several nm, which correlates with the essential increase of reversible strain. A similar to silicon but weaker effect was observed in the case of nitrogen addition to the Fe-Mn-Si-Cr, Fe-Mn-Si-Cr-Ni alloys. Based on the obtained experimental data and in consistency with the previously expressed idea by Sade et al., the positive effect of silicon and nitrogen on chemical homogeneity and SME in Fe-Mn alloys is attributed to the short-range atomic ordering induced by these elements.

  11. The effects of Ni, Mo, Ti and Si on the mechanical properties of Cr free Mn steel (Fe-25Mn-5Al-2C)

    NASA Technical Reports Server (NTRS)

    Schuon, S. R.

    1982-01-01

    The FeMnAlC alloys may hold potential as Cr-free replacements for high strategic material iron base superalloys, but little is known about their intermediate temperature (650 C to 870 C) mechanical properties. The effects of alloying elements on the mechanical properties of model FeMnAlC alloys were studied. Results showed that modified FeMnAlC alloys had promising short term, intermediate temperature properties but had relatively poor stress rupture lives at 172 MPa and 788 C. Room temperature and 788 C tensile strength of FeMnAlC alloys were better than common cast stainless steels. Changes in room temperature tensile and 788 C tensile strength and ductility, and 788 C stress rupture life were correlated with changes in Ni, Mo, Ti, and Si levels due to alloying effects on interstitial carbon levels and carbide morphology. Fe-25Mn-5Al-2C had a very poor stress rupture life at 172 MPa and 788 C. Addition of carbide-forming elements improved the stress rupture life.

  12. Magnetic ordering in the rutile molecular magnets MII[N(CN)2]2 (M=Ni, Co, Fe, Mn, Ni0.5Co0.5, and Ni0.5Fe0.5)

    NASA Astrophysics Data System (ADS)

    Lappas, Alexandros; Wills, Andrew S.; Green, Mark A.; Prassides, Kosmas; Kurmoo, Mohamedally

    2003-04-01

    Rietveld refinement of powder neutron diffraction data, combined with group theory considerations, is used to determine the magnetic structures of the binary metal dicyanamide, MII[N(CN)2]2 where M=Ni, Co, Fe, Mn, Ni0.5Co0.5, and Ni0.5Fe0.5. Compounds with M=Mn or Fe show a canted antiferromagnetic arrangement of spin oriented in the ab crystallographic plane, with antiparallel components of the two sublattices along the a axis and parallel along the b axis. Symmetry considerations forbid an additional moment, whether compensated or not, to be present along the c axis. The compounds with fewer unpaired electrons (Co and Ni) are ferromagnets, with all moments oriented along the c axis. The mixed composition of Ni0.5Co0.5 displays the same collinear ferromagnetic structure as its parent compounds. However, the composition with M=Ni0.5Fe0.5, whose parent compounds show different magnetic behavior, does not exhibit long-range magnetic ordering down to 1.7 K. Magnetostriction was observed for the ferromagnets for which we investigated the variable temperature powder neutron diffraction. The cobalt-rich compounds show more pronounced effects, consistent with their increasing magnetocrystalline anisotropy.

  13. Low-temperature heat capacity upon the transition from paramagnetic to ferromagnetic Heusler alloys Fe2 MeAl ( Me = Ti, V, Cr, Mn, Fe, Co, Ni)

    NASA Astrophysics Data System (ADS)

    Kourov, N. I.; Marchenkov, V. V.; Korolev, A. V.; Lukoyanov, A. V.

    2016-07-01

    The heat capacity of band magnets Fe2 MeAl ( Me = Ti, V, Cr, Mn, Fe, Co, Ni) ordered in crystal structure L21 has been measured in the range 2 K ≤ T ≤ 50 K. The dependences of the Debye temperature ΘD, the Sommerfeld coefficient γ, and the temperature-independent contribution to heat capacity C 0 on the number of valence electrons z in the alloys have been determined.

  14. High-field magnetization of heusler alloys Fe2 XY ( X = Ti, V, Cr, Mn, Fe, Co, Ni; Y = Al, Si)

    NASA Astrophysics Data System (ADS)

    Kourov, N. I.; Marchenkov, V. V.; Korolev, A. V.; Belozerova, K. A.; Weber, H. W.

    2015-10-01

    The magnetization curves of ferromagnetic Heusler alloys Fe2 XY (where X = Ti, V, Cr, Mn, Fe, Co, Ni are transition 3 d elements and Y = Al, Si are the s and p elements of the third period of the Periodic Table) have been measured at T = 4.2 K in the field range H ≤ 70 kOe. It has been shown that the high-field ( H ≥ 20 kOe) magnetization is described within the Stoner model.

  15. Exchange bias in (FeNi/IrMn)n multilayer films evaluated by static and dynamic techniques

    NASA Astrophysics Data System (ADS)

    Khanal, Shankar; Diaconu, Andrei; Vargas, Jose M.; Lenormand, Denny R.; Garcia, Carlos; Ross, C. A.; Spinu, Leonard

    2014-06-01

    Exchange bias properties of [FeNi/IrMn]n multilayer films with variable thickness of the ferromagnetic layers and different repetitions n were determined by using static and dynamic measurement techniques. The static magnetic properties were revealed through magnetometry measurements at room temperature following major hysteresis loops and first-order reversal curves protocols. Room temperature x-band ferromagnetic resonance (FMR) and vector network analyser (VNA)-FMR experiments were used to determine dynamically the exchange anisotropy in the FeNi/IrMn multilayers. From the static measurements the exchange anisotropy was determined while dynamic measurements allowed the determination of additional parameters including anisotropy field, saturation magnetization and rotatable anisotropy. The differences between the values of the exchange biased obtained from each technique are discussed.

  16. Effects of interfacial roughness on the planar Hall effect in NiFe/Cu/IrMn multilayers

    NASA Astrophysics Data System (ADS)

    Li, Xu-Jing; Feng, Chun; Chen, Xi; Liu, Yang; Liu, Yi-Wei; Li, Ming-Hua; Yu, Guang-Hua

    2015-02-01

    This paper reports that the planar Hall effect in NiFe/Cu/IrMn multilayers was strongly influenced by the Cu spacer thickness ( t Cu), which was due to the variation of interfacial roughness. With t Cu increasing, a peculiar change of planar Hall voltage was observed. The reason for the voltage behaviors was that the interfacial roughness influenced the spin-asymmetry of spin-polarized electrons in ferromagnetic metals. The diffuse scattering to the electrons turned to specular scattering when the interface became flat, leading to the variation of resistivity change (Δ ρ). As the increase in t Cu, the extremum field was reduced because of the weaken exchange coupling between NiFe and IrMn layers.

  17. Alternating magnetic anisotropy of Li2(Li1–xTx)N (T = Mn, Fe, Co, and Ni)

    DOE PAGES

    Jesche, A.; Ke, L.; Jacobs, J. L.; ...

    2015-05-11

    Substantial amounts of the transition metals Mn, Fe, Co, and Ni can be substituted for Li in single crystalline Li2(Li1–xTx)N. Isothermal and temperature-dependent magnetization measurements reveal local magnetic moments with magnitudes significantly exceeding the spin-only value. The additional contributions stem from unquenched orbital moments that lead to rare-earth-like behavior of the magnetic properties. Accordingly, extremely large magnetic anisotropies have been found. Most notably, the magnetic anisotropy alternates as easy plane→easy axis→easy plane→easy axis when progressing from T = MnFe → Co → Ni. This behavior can be understood based on a perturbation approach in an analytical, single-ion model.more » As a result, the calculated magnetic anisotropies show surprisingly good agreement with the experiment and capture the basic features observed for the different transition metals.« less

  18. Mixing antiferromagnets to tune NiFe-[IrMn/FeMn] interfacial spin-glasses, grains thermal stability, and related exchange bias properties

    SciTech Connect

    Akmaldinov, K.; Ducruet, C.; Portemont, C.; Joumard, I.; Prejbeanu, I. L.; Dieny, B.; Baltz, V.

    2014-05-07

    Spintronics devices and in particular thermally assisted magnetic random access memories require a wide range of ferromagnetic/antiferromagnetic (F/AF) exchange bias (EB) properties and subsequently of AF materials to fulfil diverse functionality requirements for the reference and storage. For the reference layer, large EB energies and high blocking temperature (T{sub B}) are required. In contrast, for the storage layer, mostly moderate T{sub B} are needed. One of the present issues is to find a storage layer with properties intermediate between those of IrMn and FeMn and in particular: (i) with a T{sub B} larger than FeMn for better stability at rest-T but lower than IrMn to reduce power consumption at write-T and (ii) with improved magnetic interfacial quality, i.e., with reduced interfacial glassy character for lower properties dispersions. To address this issue, the EB properties of F/AF based stacks were studied for various mixed [IrMn/FeMn] AFs. In addition to EB loop shifts, the F/AF magnetic interfacial qualities and the AF grains thermal stability are probed via measurements of the low- and high-temperature contributions to the T{sub B} distributions, respectively. A tuning of the above three parameters is observed when evolving from IrMn to FeMn via [IrMn/FeMn] repetitions.

  19. In-Situ Fracture Observation and Fracture Toughness Analysis of Ni-Mn-Ga-Fe Ferromagnetic Shape Memory Alloys

    NASA Astrophysics Data System (ADS)

    Euh, Kwangjun; Lee, Jung-Moo; Nam, Duk-Hyun; Lee, Sunghak

    2011-12-01

    The fracture property improvement of Ni-Mn-Ga-Fe ferromagnetic shape memory alloys containing ductile γ particles was explained by direct observation of microfracture processes using an in-situ loading stage installed inside a scanning electron microscope (SEM) chamber. The Ni-Mn-Ga-Fe alloys contained a considerable amount of γ particles in β grains after the homogenization treatment at 1073 K to 1373 K (800 °C to 1100 °C). With increasing homogenization temperature, γ particles were coarsened and distributed homogeneously along β grain boundaries as well as inside β grains. According to the in-situ microfracture observation, γ particles effectively acted as blocking sites of crack propagation and provided the stable crack growth, which could be confirmed by the R-curve analysis. The increase in fracture resistance with increasing crack length improved overall fracture properties of the Ni-Mn-Ga-Fe alloys. This improvement could be explained by mechanisms of blocking of crack propagation and crack blunting and bridging.

  20. Effect of one-step recrystallization on the grain boundary evolution of CoCrFeMnNi high entropy alloy and its subsystems.

    PubMed

    Chen, Bo-Ru; Yeh, An-Chou; Yeh, Jien-Wei

    2016-02-29

    In this study, the grain boundary evolution of equiatomic CoCrFeMnNi, CoCrFeNi, and FeCoNi alloys after one-step recrystallization were investigated. The special boundary fraction and twin density of these alloys were evaluated by electron backscatter diffraction analysis. Among the three alloys tested, FeCoNi exhibited the highest special boundary fraction and twin density after one-step recrystallization. The special boundary increment after one-step recrystallization was mainly affected by grain boundary velocity, while twin density was mainly affected by average grain boundary energy and twin boundary energy.

  1. Effect of one-step recrystallization on the grain boundary evolution of CoCrFeMnNi high entropy alloy and its subsystems

    NASA Astrophysics Data System (ADS)

    Chen, Bo-Ru; Yeh, An-Chou; Yeh, Jien-Wei

    2016-02-01

    In this study, the grain boundary evolution of equiatomic CoCrFeMnNi, CoCrFeNi, and FeCoNi alloys after one-step recrystallization were investigated. The special boundary fraction and twin density of these alloys were evaluated by electron backscatter diffraction analysis. Among the three alloys tested, FeCoNi exhibited the highest special boundary fraction and twin density after one-step recrystallization. The special boundary increment after one-step recrystallization was mainly affected by grain boundary velocity, while twin density was mainly affected by average grain boundary energy and twin boundary energy.

  2. Effects of cold rolling on the microstructure and mechanical properties of Fe-Ni-Mn-Mo-Ti-Cr maraging steels

    NASA Astrophysics Data System (ADS)

    Mahmudi, Abbas; Nedjad, Syamak Hossein; Behnam, Mir Masud Jabbari

    2011-10-01

    Effects of cold rolling on the microstructure and mechanical properties of Fe-Ni-Mn-Mo-Ti-Cr maraging steels were studied. To investigate the microstructure and mechanical properties, optical microscopy, scanning electron microscopy, X-ray diffraction, tensile test, and hardness test were used. The results show that the solution-annealing treatment in the cold-rolled steel redounds to the formation of submicrocrystalline Fe2(Mo, Ti) Laves phase particles, which are stable at high temperatures. These secondary Laves phase particles prevent from recrystallization at high temperatures and correspond to semi-brittle fracture in the subsequent aging treatment.

  3. Magnetic structures at the ferromagnetic NiFe and antiferromagnetic NiMn interface in exchange-biased films: Role of noncollinear magnetism and roughness

    NASA Astrophysics Data System (ADS)

    Nakamura, Kohji; Freeman, A. J.; Wang, Ding-Sheng; Zhong, Lieping; Fernandez-de-Castro, Juan

    2002-01-01

    The magnetic structures at the compensated ferromagnetic/antiferromagnetic (FM/AFM) interface of exchange bias FM NiFe/AFM NiMn films were determined with first-principles full-potential linearized augmented plane-wave calculations including noncollinear magnetism. The results predict that the magnetic moments of the FM NiFe layer lie perpendicular to those of the AFM NiMn layer. The intra-atomic noncollinear magnetism that arises near the interface is found to play an important role in stabilizing the perpendicular coupling that leads to a large biquadratic exchange energy (BEE). The BEE is large enough to require formation of a magnetic domain wall (with an estimated thickness ~370 Å) in the AFM NiMn layers, which may account for the observed large coercivity and exchange bias. We also discuss magnetic structures at a rough FM/AFM interface-as simulated in model calculations with the inclusion of line step defects-which may contribute to a unidirectional magnetic anisotropy.

  4. Electrical conduction mechanism of LaNi{sub x}Me{sub 1−x}O{sub 3−δ} (Me = Fe, Mn)

    SciTech Connect

    Niwa, Eiki; Maeda, Hiroki; Uematsu, Chie; Hashimoto, Takuya

    2015-10-15

    Graphical abstract: Compositional dependence of (a) electrical conductivity and (b) E{sub a} for hopping conduction of LaNi{sub x}Me{sub 1−x}O{sub 3} (Me = Fe, Mn). - Highlights: • Electrical conduction mechanism of LaNi{sub x}Me{sub 1−x}O{sub 3} (Me = Fe, Mn) was investigated. • Hopping conduction model could be applied for conductivity of both specimens. • The difference of E{sub a} due to that of energy level of Fe and Mn was observed. • Hole concentration estimated by iodimetry increases with increasing Ni content. - Abstract: Electrical conduction mechanism of LaNi{sub x}Fe{sub 1−x}O{sub 3−δ} and LaNi{sub x}Mn{sub 1−x}O{sub 3+δ} expected as Sr-free new cathode material for solid oxide fuel cells was analyzed. Electrical conduction behaviors of both specimens could be well fitted by small polaron hopping conduction model. The electrical conductivity of LaNi{sub x}Fe{sub 1−x}O{sub 3−δ} increased with increasing Ni content, showing agreement with decrease of activation energy for hopping conduction. The decrease of electrical conductivity and increase of activation energy of LaNi{sub x}Mn{sub 1−x}O{sub 3+δ} were observed with increasing Ni content for 0.0 ≤ x ≤ 0.4. Further Ni substitution increased electrical conductivity and decreased activation energy for 0.4 ≤ x ≤ 0.6. It was revealed using iodometry that the difference of hole carrier density between LaNi{sub x}Fe{sub 1−x}O{sub 3−δ} and LaNi{sub x}Mn{sub 1−x}O{sub 3+δ} was small. It was suspected that the origin of the difference of electrical conduction behavior of LaNi{sub x}Fe{sub 1−x}O{sub 3−δ} and LaNi{sub x}Mn{sub 1-x}O{sub 3+δ} was difference of energy level of e{sub g} band composed of Fe 3d or Mn 3d orbitals and their overlapping quantity with O 2p and Ni 3d band.

  5. Critical dependence of magnetostructural coupling and magnetocaloric effect on particle size in Mn-Fe-Ni-Ge compounds.

    PubMed

    Wu, Rongrong; Shen, Feiran; Hu, Fengxia; Wang, Jing; Bao, Lifu; Zhang, Lei; Liu, Yao; Zhao, Yingying; Liang, Feixiang; Zuo, Wenliang; Sun, Jirong; Shen, Baogen

    2016-02-17

    Magnetostructural coupling, which is the coincidence of crystallographic and magnetic transition, has obtained intense attention for its abundant magnetoresponse effects and promising technological applications, such as solid-state refrigeration, magnetic actuators and sensors. The hexagonal Ni2In-type compounds have attracted much attraction due to the strong magnetostructural coupling and the resulted giant negative thermal expansion and magnetocaloric effect. However, the as-prepared samples are quite brittle and naturally collapse into powders. Here, we report the effect of particle size on the magnetostructural coupling and magnetocaloric effect in the Ni2In-type Mn-Fe-Ni-Ge compound, which undergoes a large lattice change across the transformation from paramagnetic austenite to ferromagnetic martensite. The disappearance of martensitic transformation in a large amount of austenitic phase with reducing particle size, to our best knowledge, has not been reported up to now. The ratio can be as high as 40.6% when the MnNi0.8Fe0.2Ge bulk was broken into particles in the size range of 5~15 μm. Meanwhile, the remained magnetostructural transition gets wider and the magnetic hysteresis becomes smaller. As a result, the entropy change drops, but the effective cooling power RCeffe increases and attains to the maximum at particles in the range of 20~40 μm. These observations provide constructive information and highly benefit practical applications for this class of novel magnetoresponse materials.

  6. Critical dependence of magnetostructural coupling and magnetocaloric effect on particle size in Mn-Fe-Ni-Ge compounds

    NASA Astrophysics Data System (ADS)

    Wu, Rongrong; Shen, Feiran; Hu, Fengxia; Wang, Jing; Bao, Lifu; Zhang, Lei; Liu, Yao; Zhao, Yingying; Liang, Feixiang; Zuo, Wenliang; Sun, Jirong; Shen, Baogen

    2016-02-01

    Magnetostructural coupling, which is the coincidence of crystallographic and magnetic transition, has obtained intense attention for its abundant magnetoresponse effects and promising technological applications, such as solid-state refrigeration, magnetic actuators and sensors. The hexagonal Ni2In-type compounds have attracted much attraction due to the strong magnetostructural coupling and the resulted giant negative thermal expansion and magnetocaloric effect. However, the as-prepared samples are quite brittle and naturally collapse into powders. Here, we report the effect of particle size on the magnetostructural coupling and magnetocaloric effect in the Ni2In-type Mn-Fe-Ni-Ge compound, which undergoes a large lattice change across the transformation from paramagnetic austenite to ferromagnetic martensite. The disappearance of martensitic transformation in a large amount of austenitic phase with reducing particle size, to our best knowledge, has not been reported up to now. The ratio can be as high as 40.6% when the MnNi0.8Fe0.2Ge bulk was broken into particles in the size range of 5~15 μm. Meanwhile, the remained magnetostructural transition gets wider and the magnetic hysteresis becomes smaller. As a result, the entropy change drops, but the effective cooling power RCeffe increases and attains to the maximum at particles in the range of 20~40 μm. These observations provide constructive information and highly benefit practical applications for this class of novel magnetoresponse materials.

  7. Critical dependence of magnetostructural coupling and magnetocaloric effect on particle size in Mn-Fe-Ni-Ge compounds

    PubMed Central

    Wu, Rongrong; Shen, Feiran; Hu, Fengxia; Wang, Jing; Bao, Lifu; Zhang, Lei; Liu, Yao; Zhao, Yingying; Liang, Feixiang; Zuo, Wenliang; Sun, Jirong; Shen, Baogen

    2016-01-01

    Magnetostructural coupling, which is the coincidence of crystallographic and magnetic transition, has obtained intense attention for its abundant magnetoresponse effects and promising technological applications, such as solid-state refrigeration, magnetic actuators and sensors. The hexagonal Ni2In-type compounds have attracted much attraction due to the strong magnetostructural coupling and the resulted giant negative thermal expansion and magnetocaloric effect. However, the as-prepared samples are quite brittle and naturally collapse into powders. Here, we report the effect of particle size on the magnetostructural coupling and magnetocaloric effect in the Ni2In-type Mn-Fe-Ni-Ge compound, which undergoes a large lattice change across the transformation from paramagnetic austenite to ferromagnetic martensite. The disappearance of martensitic transformation in a large amount of austenitic phase with reducing particle size, to our best knowledge, has not been reported up to now. The ratio can be as high as 40.6% when the MnNi0.8Fe0.2Ge bulk was broken into particles in the size range of 5~15 μm. Meanwhile, the remained magnetostructural transition gets wider and the magnetic hysteresis becomes smaller. As a result, the entropy change drops, but the effective cooling power RCeffe increases and attains to the maximum at particles in the range of 20~40 μm. These observations provide constructive information and highly benefit practical applications for this class of novel magnetoresponse materials. PMID:26883719

  8. Defect formation energy and magnetic structure of shape memory alloys Ni-X-Ga (X=Mn, Fe, Co) by first principle calculation

    NASA Astrophysics Data System (ADS)

    Bai, J.; Raulot, J. M.; Zhang, Y. D.; Esling, C.; Zhao, X.; Zuo, L.

    2010-09-01

    The crystallographic and magnetic structures of the Ni2XGa (X=Mn, Fe, Co), are systematically investigated by means of the first-principles calculations within the framework of density functional theory using the VIENNA AB INITIO SOFTWARE PACKAGE. The formation energies of several kinds of defects (atomic exchange, antisite, vacancy) are estimated. The Ga atoms stabilize the cubic structure, and the effect of X atoms on the structural stability is opposite. For most cases of the site occupation, the excess atoms of the rich component directly occupy the site(s) of the deficient one(s), except for Ga-rich Ni-deficient type. The magnitude of the variation in Ni moments is much larger than that of Mn in defective Ni2XGa. The value of Ni magnetic moment sensitively depends on the distance between Ni and X. Excess Mn could be ferromagnetic or antiferromagnetic, depending on the distance between the neighboring Mn atoms.

  9. Nanostructure evolution under irradiation of Fe(C)MnNi model alloys for reactor pressure vessel steels

    NASA Astrophysics Data System (ADS)

    Chiapetto, M.; Becquart, C. S.; Domain, C.; Malerba, L.

    2015-06-01

    Radiation-induced embrittlement of bainitic steels is one of the most important lifetime limiting factors of existing nuclear light water reactor pressure vessels. The primary mechanism of embrittlement is the obstruction of dislocation motion produced by nanometric defect structures that develop in the bulk of the material due to irradiation. The development of models that describe, based on physical mechanisms, the nanostructural changes in these types of materials due to neutron irradiation are expected to help to better understand which features are mainly responsible for embrittlement. The chemical elements that are thought to influence most the response under irradiation of low-Cu RPV steels, especially at high fluence, are Ni and Mn, hence there is an interest in modelling the nanostructure evolution in irradiated FeMnNi alloys. As a first step in this direction, we developed sets of parameters for object kinetic Monte Carlo (OKMC) simulations that allow this to be done, under simplifying assumptions, using a "grey alloy" approach that extends the already existing OKMC model for neutron irradiated Fe-C binary alloys [1]. Our model proved to be able to describe the trend in the buildup of irradiation defect populations at the operational temperature of LWR (∼300 °C), in terms of both density and size distribution of the defect cluster populations, in FeMnNi model alloys as compared to Fe-C. In particular, the reduction of the mobility of point-defect clusters as a consequence of the presence of solutes proves to be key to explain the experimentally observed disappearance of detectable point-defect clusters with increasing solute content.

  10. Sediment fractionation of Cu, Ni, Zn, Cr, Mn, and Fe in one experimental and three natural marshes

    SciTech Connect

    Lindau, C.W.; Hossner, L.R.

    1982-07-01

    Dredged sediments from the Gulf Intracoastal Waterway near Galveston, Tex., were used as a substrate material in the construction of an experimental intertidal salt marsh. Selected substrate properties were compared with those of established marshes. Clay mineralogical properties of the experimental marsh were compared with those of three nearby natural marshes. A sequential chemical extraction procedure was used to obtain data on the partitioning of micronutrients and heavy metals among selected marsh substrate fractions. Clay minerals found in the sediments of the experimental marsh were equivalent to those identified in the natural marshes. Total elemental substrate concentrations of Cu, Ni, Cr, Zn, Mn, and Fe averaged 7.9, 8.6, 25.5, 25.2, 123, and 12,200 ..mu..g/g, respectively, over the four marsh sites. Copper, nickel, zinc, and chromium displayed only minor variations in substrate partitioning between the experimental and natural marsh samples. Micronutrients and heavy metal concentrations in the exchangeable and water-soluble fraction were low compared with other fractions. Approximately 30% of the total substrate Cu, Ni, and Zn was associated with the organic matter fraction. Metals fixed within the lattice structures of clay and silicate minerals ranged from 20% Mn for experimental marsh samples to 90% Cr for one of the natural marshes. Major differences in Mn and Fe substrate partitioning were observed when the experimental marsh samples were compared with those of the natural marshes.

  11. Defect Structures for Fe3+, Mn2+, and Ni3+ Impurities in Wuritzite GaN Crystals

    NASA Astrophysics Data System (ADS)

    Zheng, Wen-Chen; Wu, Shao-Yi; Zi, Jian

    2001-07-01

    Electron paramagnetic resonance (EPR) zero-field splittings D for Mn2+ and Fe3+ in wurtzite GaN crystals are studied from high-order perturbation formulas based on the spin-orbit mechanism in both weak- and strong-field schemes. From these studies it can be seen that the Mn2+ or Fe3+ impurity does not occupy the exact Ga3+ position, but is displaced by ΔR on the C3 axis. The displacements are confirmed from a study of the superposition model, based on which a normal value of b̅2 (Ro) ( ≈ -0 .34 (15) cm-1 ) for the Fe3+-N3- combination is suggested. The EPR parameters D, g|| and g ⟂ for Ni3+ in GaN crystals are also studied. It is found that Ni3+ is almost not displaced. The impurity displacements in GaN are discussed by considering the valences and radii of these impurity ions and the replaced Ga3+ ion. - Pacs: 61.16Hn; 76.30Fc; 71.70Ch

  12. The use of diffusion multiples to explore the Co-Cr-Fe-Mn-Ni high entropy system

    NASA Astrophysics Data System (ADS)

    Wilson, Paul Nathaniel

    High entropy alloys (HEAs) or Multi-principal element alloys (MEAs) are a relatively new class of alloys. These alloys are defined as having at least five major alloying elements in atomic percent from 5% to 35%. There are hundreds of thousands of equiatomic compositions possible and only a fraction have been explored. This project examines diffusion multiples as a method to accelerate alloy development in these systems. The system chosen for this experiment is the Co-Cr-Fe-Mn-Ni system. The methodology developed for creating these diffusion multiples involved a two-step process. In the first step two binary alloys (50at-% Fe-Mn and 50 at%- Ni-Co ) were diffusion bonded together. In the second step, under uniaxial compression, was used to bond Cr to diffusion couple prepared in Step I. Successful diffusion multiples were created by this method. An auxiliary method named differential melting liquid impingement (DMLI) was developed that created diffusion multiples using liquid processing methods that will be described. After creation of these multiples, the ternary and quinary interface regions were examined using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), and nanoindentation. The Cr/NiCo region experienced interdiffusion but no intermediate phase formation retaining the FCC / BCC interface at the hot-pressing temperature (1200 °C). However, upon cooling from 1200 °C, the BCC region adjacent to the interface decomposed into BCC + sigma. In contrast, the Cr/FeMn interface region developed a layered structure of FCC/sigma/BCC suggesting that sigma is stable at 1200 °C in contradiction to the published 1200 °C ternary phase diagram. Upon cooling, the sigma present at 1200 °C decomposed into FCC + sigma, except in samples that were contaminated with C; in those cases, FCC + M23C6 was observed as the decomposition product. The quinary regions were evaluated using the various HEA parameters, namely

  13. Specific features of the electrical resistivity of half-metallic ferromagnets Fe2MeAl (Me = Ti, V, Cr, Mn, Fe, Ni)

    NASA Astrophysics Data System (ADS)

    Kourov, N. I.; Marchenkov, V. V.; Belozerova, K. A.; Weber, H. W.

    2014-03-01

    The transport properties of half-metallic ferromagnetic Heusler alloys Fe2MeAl (where Me = Ti, V, Cr, Mn, Fe, and Ni are 3 d transition elements) have been measured in the temperature range of 4-900 K. The specific features in the behavior of the electrical resistivity have been considered in terms of the two-current conduction model, which takes into account the presence of an energy gap in the electron spectrum of the alloys near the Fermi level.

  14. Magnetism and superconductivity in MxFe1+yTe1-zSez (M = Cr, Mn, Co, Ni, Cu, and Zn) single crystals

    NASA Astrophysics Data System (ADS)

    Zhang, Z. T.; Yang, Z. R.; Li, L.; Zhang, C. J.; Pi, L.; Tan, S.; Zhang, Y. H.

    2011-04-01

    High-quality single crystals with nominal composition M0.05Fe0.95Te0.8Se0.2 (M = Cr, Mn, Co, Ni, Cu, and Zn) have been grown, through which the doping effect on magnetism and superconductivity is studied. Elementary analysis reveals that Cu, Co, and Ni, with smaller ionic radii for valence state 2+, can substitute effectively for Fe with doping levels near 5%. In contrast, the solid solution of Cr, Mn, and Zn in the host system is low. Magnetic and electronic investigations show that the substitution of Co, Ni, or Cu for Fe leads to the formation of spin-glass state and suppression of superconductivity. The superconductivity is partly suppressed by Co doping, while completely destroyed by Ni and Cu doping. Compared with Cu- and Ni-doped samples, the Co-doped sample has the smallest lattice constant, indicating that the superconductivity might be also modulated by the changes of microstructure.

  15. Quantification of site disorder and its role on spin polarization in the nearly half-metallic Heusler alloy NiFeMnSn

    NASA Astrophysics Data System (ADS)

    Mukadam, M. D.; Roy, Syamashree; Meena, S. S.; Bhatt, Pramod; Yusuf, S. M.

    2016-12-01

    The electronic structure and magnetism of the quaternary Heusler alloy NiFeMnSn are studied using the full-potential linearized augmented plane-wave (FPLAPW) method. The calculation for the perfectly LiMgPdSn-type ordered crystal structure (type I) of NiFeMnSn shows a high spin polarization (˜76 %) with a ferromagnetic ground state. The total spin magnetic moment is in good agreement with the Slater-Pauling rule. The structural investigations using neutron diffraction at 500 K, and Mössbauer spectroscopy at 300 K on the NiFeMnSn alloy, prepared using an arc melting, show the presence of atomic site disorder. The electronic structure calculation for the disordered structure shows that the site disorder destroys the nearly half-metallic nature of this alloy. The magnetization measurements indicate that the Curie temperature is well above room temperature (˜405 K) as desired for the spintronics application.

  16. Nano-twin Mediated Plasticity in Carbon-containing FeNiCoCrMn High Entropy Alloys

    SciTech Connect

    Wu, Zhenggang; Bei, Hongbin; Parish, Chad M

    2015-06-14

    Equiatomic FeNiCoCrMn alloy has been reported to exhibit promising strength and ductility at cryogenic temperature and deformation mediated by nano-twining appeared to be one of the main reasons. We use the FeNiCoCrMn alloy as a base alloy to seek further improvement of its mechanical properties by alloying additional elements, i.e., interstitial carbon. Moreover, the effects of carbon on microstructures, mechanical properties and twinning activities were investigated in two different temperatures (77 and 293 K). With addition of 0.5 at% C, the high entropy alloy still remains entirely single phase face-centered cubic (FCC) crystal structure. We found that these materials can be cold rolled and recrystallized to produce a microstructure with equiaxed grains. Both strain hardening rate and strength are enhanced while high uniform elongations to fracture (~70% at 77 K and ~40% at 293 K) are still maintained. The increased strain hardening and strength could be caused by the promptness of deformation twinning in C-containing high entropy alloys.

  17. Nano-twin Mediated Plasticity in Carbon-containing FeNiCoCrMn High Entropy Alloys

    DOE PAGES

    Wu, Zhenggang; Bei, Hongbin; Parish, Chad M

    2015-06-14

    Equiatomic FeNiCoCrMn alloy has been reported to exhibit promising strength and ductility at cryogenic temperature and deformation mediated by nano-twining appeared to be one of the main reasons. We use the FeNiCoCrMn alloy as a base alloy to seek further improvement of its mechanical properties by alloying additional elements, i.e., interstitial carbon. Moreover, the effects of carbon on microstructures, mechanical properties and twinning activities were investigated in two different temperatures (77 and 293 K). With addition of 0.5 at% C, the high entropy alloy still remains entirely single phase face-centered cubic (FCC) crystal structure. We found that these materials canmore » be cold rolled and recrystallized to produce a microstructure with equiaxed grains. Both strain hardening rate and strength are enhanced while high uniform elongations to fracture (~70% at 77 K and ~40% at 293 K) are still maintained. The increased strain hardening and strength could be caused by the promptness of deformation twinning in C-containing high entropy alloys.« less

  18. Effect of Pre-straining on the Shape Recovery of Fe-Mn-Si-Cr-Ni Shape Memory Alloys

    NASA Astrophysics Data System (ADS)

    Maji, Bikas C.; Krishnan, Madangopal; Verma, Amit; Basu, R.; Samajdar, I.; Ray, Ranjit K.

    2015-02-01

    The effect of pre-straining on the shape recovery behavior of Fe-14Mn-6Si-9Cr-5Ni (wt pct) shape memory alloy (SMA) has been studied. The shape recovery associated with the reverse ɛ martensitic transformation, i.e., ɛ → γ, was characterized by dilatometry using specimens which were pre-strained to different extent (0 to 14 pct). Dilatometric studies revealed that in Fe-Mn-Si-Cr-Ni SMA, the shape recovery takes place in two stages: (i) in the first stage, the unpinned fraction of stress-induced ɛ martensite reverts back to parent phase γ in the temperature regime of 353 K to 653 K (80 °C to 380 °C) and (ii) in the second stage the remaining "pinned" ɛ martensite is unpinned by the decomposition of deformation-induced α' martensite in the temperature range of 743 K to 893 K (470 °C to 620 °C). The amount of recovery in the first stage decreases with pre-strain, whereas it increases in the second stage. The ɛ → γ transformation finish temperature, A f, increases with increase in pre-strain amount, though the reverse transformation start temperature, A S, remains unaffected. Microstructural characterization revealed that the amount of deformation-induced α' martensite depends on the mode of straining and the crystallographic texture of the starting material. The reversion of α' martensite is seen to occur by the precipitation of Fe5Ni3Si2-type intermetallic π-phase within these plates.

  19. Large enhancement of Blocking temperature by control of interfacial structures in Pt/NiFe/IrMn/MgO/Pt multilayers

    SciTech Connect

    Chen, Xi; Wang, Shouguo Han, Gang; Jiang, Shaolong; Yang, Kang; Liu, Qianqian; Yu, Guanghua; Liu, Jialong; Wang, Rongming

    2015-09-15

    The Blocking temperature (T{sub B}) of Pt/NiFe/IrMn/MgO/Pt multilayers was greatly enhanced from far below room temperature (RT) to above RT by inserting 1 nm thick Mg layer at IrMn/MgO interface. Furthermore, the exchange bias field (H{sub eb}) was increased as well by the control of interfacial structures. The evidence for a significant fraction of Mn-O bonding at IrMn/MgO interface without Mg insertion layer was provided by X-ray photoelectron spectroscopy. The bonding between Mn and O can decrease the antiferromagnetism of IrMn film, leading to lower value of T{sub B} in Pt/NiFe/IrMn/MgO/Pt multilayers. Ultrathin Mg film inserted at IrMn/MgO interface acting as an oxygen sinking layer can suppress the oxidation reactions between Mn and O and reduce the formation of Mn-O bonding greatly. The oxidation suppression results in the recovery of the antiferromagnetism of IrMn film, which can enhance T{sub B} and H{sub eb}. Furthermore, the high resolution transmission electron microscopy demonstrates that the Mg insertion layer can efficiently promote a high-quality MgO (200) texture. This study will enhance the understanding of physics in antiferromagnet-based spintronic devices.

  20. Determination of ratios of Auger electrons emission probabilities and K-L shell vacancy transfer probability of Cr, Mn, Fe, Co, Ni, Cu and Zn compounds

    NASA Astrophysics Data System (ADS)

    Küçükönder, Adnan; Kavşut, Onur

    2017-02-01

    Ratios of emission probabilities of Auger electrons [u = p(KLX)/p(KLL), ν = p(KXY)/p(KLL)] and the vacancy transfer probabilities from K to L shell, ηKL for Cr, Mn, Fe, Co,Ni, Cu and Zn compounds were obtained using the experimental Kx-ray emission ratios and K-shell fluorescence yields. We were used the experimental Kβ/Kα intensity ratios and K shell fluorescence yields WK. Ratios of emission probabilities of Auger electrons and the vacancy transfer probabilities are changed by chemical effect for different for Cr, Mn, Fe, Co,Ni, Cu and Zn compounds.

  1. Magnetic properties of Mg12O12 nanocage doped with transition metal atoms (Mn, Fe, Co and Ni): DFT study

    NASA Astrophysics Data System (ADS)

    Javan, Masoud Bezi

    2015-07-01

    Binding energy of the Mg12O12 nanocage doped with transition metals (TM=Mn, Fe, Co and Ni) in endohedrally, exohedrally and substitutionally forms were studied using density functional theory with the generalized gradient approximation exchange-correlation functional along 6 different paths inside and outside of the Mg12O12 nanocage. The most stable structures were determined with full geometry optimization near the minimum of the binding energy curves of all the examined paths inside and outside of the Mg12O12 nanocage. The results reveal that for all stable structures, the Ni atom has a larger binding energy than the other TM atoms. It is also found that for all complexes additional peaks contributed by TM-3d, 4s and 4p states appear in the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) gap of the host MgO cluster. The mid-gap states are mainly due to the hybridization between TM-3d, 4s and 4p orbitals and the cage π orbitals. The magnetic moment of the endohedrally doped TM atoms in the Mg12O12 are preserved to some extent due to the interaction between the TM and Mg12O12 nanocage, in contrast to the completely quenched magnetic moment of the Fe and Ni atoms in the Mg11(TM)O12 complexes. Furthermore, charge population analysis shows that charge transfer occurs from TM atom to the cage for endohedrally and substitutionally doping.

  2. Structural and magnetic transition in stainless steel Fe-21Cr-6Ni-9Mn up to 250 GPa

    NASA Astrophysics Data System (ADS)

    Liu, Lei; Hou, Qi-Yue; Zhang, Yi; Jing, Qiu-Min; Wang, Zhi-Gang; Bi, Yan; Xu, Ji-An; Li, Xiao-Dong; Li, Yan-Chun; Liu, Jing

    2015-06-01

    Stainless steel Fe-21Cr-6Ni-9Mn (SS 21-6-9), with ˜21% Cr, ˜6% Ni, and ˜9% Mn in weight percentage, has wide applications in extensive fields. In the present study, SS 21-6-9 is compressed up to 250 GPa, and its crystal structures and compressive behaviors are investigated simultaneously using the synchrotron angle-dispersive x-ray diffraction technique. The SS 21-6-9 undergoes a structural phase transition from fcc to hcp structure at ˜12.8 GPa with neglectable volume collapse within the determination error under the quasi-hydrostatic environment. The hcp structure remains stable up to the highest pressure of 250 GPa in the present experiments. The antiferromagnetic-to-nonmagnetic state transition of hcp SS 21-6-9 with the changes of inconspicuous density and structure, is discovered at ˜50 GPa, and revealed by the significant change in c/a ratio. The hcp SS-21-6-9 is compressive anisotropic: it is more compressive in the c-axis direction than in the a-axis direction. Both the equations of states (EOSs) of fcc and hcp SS 21-6-9, which are in accordance with those of fcc and hcp pure irons respectively, are also presented. Furthermore, the c/a ratio of hcp SS 21-6-9 at infinite compression, R∞, is consistent with the values of pure iron and Fe-10Ni alloy. Project supported by the National Natural Science Foundation of China (Grant Nos. U1230201, 11274281, and 11304294), the Industrial Technology Development Program, China (Grant No. 9045140509), and the Funds from the Chinese Academy of Sciences (Grant Nos. KJCX2-SW-N03 and KJCX2-SW-N20).

  3. Transport of trace metals (Mn, Fe, Ni, Zn and Cd) in the western Arctic Ocean (Chukchi Sea and Canada Basin) in late summer 2012

    NASA Astrophysics Data System (ADS)

    Kondo, Yoshiko; Obata, Hajime.; Hioki, Nanako; Ooki, Atsushi; Nishino, Shigeto; Kikuchi, Takashi; Kuma, Kenshi

    2016-10-01

    Distributions of trace metals (Mn, Fe, Ni, Zn and Cd) in the western Arctic Ocean (Chukchi Sea and Canada Basin) in September 2012 were investigated to elucidate the mechanisms behind the transport of these metals from the Chukchi Shelf to the Canada Basin. Filtered (<0.22 μm) and unfiltered seawater samples were analyzed to determine dissolved (D) and total dissolvable (TD) trace metal concentrations, respectively. We identified maxima in vertical profiles for the concentrations of D-Fe and TD-Fe, as well as for the other four analyzed trace metals, which occurred in the halocline and/or near-bottom waters. Concentration profiles of all trace metals except for Cd also tended to show peaks near the surface, which suggest that the inflow of low-salinity Pacific-origin water from the Bering Strait, as well as local fresh water inputs such as river water and melting sea-ice, influenced trace metal concentrations. The distribution patterns and concentration ranges were generally similar between the D and TD fractions for Ni, Zn and Cd, which indicate that Ni, Zn and Cd were present mainly in their dissolved forms, whereas the concentrations of TD-Fe and TD-Mn were generally higher than those of D-Fe and D-Mn, respectively. These results are consistent with the results of previous studies of this region. For both Fe and Mn, labile particulate (LP) concentrations (the difference between the TD and D fractions, which is acid-leachable fraction in the particles during storage at pH 1.5-1.6) were highest in the near-bottom waters of the Chukchi Shelf region. The relationships between the distance from the shelf break and the concentrations of trace metals revealed that Fe and Mn concentrations in halocline waters tended to decrease logarithmically with distance, whereas changes in the concentrations of Ni, Zn, Cd and phosphate with distance were small. These results suggest that the distributions of Fe and Mn were controlled mainly by input from shelf sediment and removal

  4. PdM nanoparticles (M = Ni, Co, Fe, Mn) with high activity and stability in formic acid oxidation synthesized by sonochemical reactions

    NASA Astrophysics Data System (ADS)

    Matin, Md. Abdul; Jang, Ji-Hoon; Kwon, Young-Uk

    2014-09-01

    Bimetallic alloy PdnM (n = 1 for M = Mn, Fe, and Co; n = 1, 2, and 3 for M = Ni) nanoparticles (NPs) are synthesized on carbon supports by sonochemical reactions of Pd(acac)2 (acac = acetylacetonate) with M(acac)2 (M = Ni, Co, Mn) or Fe(acac)3 in ethylene glycol. The NPs are characterized by powder X-ray diffractometry, transmission electron microscopy (TEM), and inductively coupled plasma-atomic emission spectroscopy to determine their crystal structures, particle sizes, morphology, and elemental compositions. Alloy formation of the NPs is proven by energy dispersive X-ray spectroscopy line profiles using scanning TEM. The electronic structures and the surface compositions of NPs are analyzed using X-ray photoelectron spectroscopy, and Fourier-transform infrared spectroscopy, respectively. PdnM NPs are applied as electrocatalysts for formic acid oxidation. The incorporation of M in Pd reduces the poisoning by surface hydroxyl groups. Activities based on the current densities are in the order of PdNi > PdFe > PdCo > PdMn. Within the PdnNi series, the activity is in the order of PdNi > Pd2Ni > Pd3Ni. The PdnM NP electrocatalysts show higher activity by a factor of 2-3.5 and improved durability than similarly prepared Pd NP electrocatalyst.

  5. Role of Si in Improving the Shape Recovery of FeMnSiCrNi Shape Memory Alloys

    NASA Astrophysics Data System (ADS)

    Maji, Bikas C.; Krishnan, Madangopal; Gouthama; Ray, R. K.

    2011-08-01

    The effect of Si addition on the microstructure and shape recovery of FeMnSiCrNi shape memory alloys has been studied. The microstructural observations revealed that in these alloys the microstructure remains single-phase austenite ( γ) up to 6 pct Si and, beyond that, becomes two-phase γ + δ ferrite. The Fe5Ni3Si2 type intermetallic phase starts appearing in the microstructure after 7 pct Si and makes these alloys brittle. Silicon addition does not affect the transformation temperature and mechanical properties of the γ phase until 6 pct, though the amount of shape recovery is observed to increase monotonically. Alloys having more than 6 pct Si show poor recovery due to the formation of δ-ferrite. The shape memory effect (SME) in these alloys is essentially due to the γ to stress-induced ɛ martensite transformation, and the extent of recovery is proportional to the amount of stress-induced ɛ martensite. Alloys containing less than 4 pct and more than 6 pct Si exhibit poor recovery due to the formation of stress-induced α' martensite through γ- ɛ- α' transformation and the large volume fraction of δ-ferrite, respectively. Silicon addition decreases the stacking fault energy (SFE) and the shear modulus of these alloys and results in easy nucleation of stress-induced ɛ martensite; consequently, the amount of shape recovery is enhanced. The amount of athermal ɛ martensite formed during cooling is also observed to decrease with the increase in Si.

  6. Study of certain features of the electronic structure of the ternary alloys Ni2(Mn, Fe) and Ni3(Mn, Co)

    NASA Technical Reports Server (NTRS)

    Zhukova, V. M.; Fadin, V. P.

    1981-01-01

    The changes in electronic structure related to transport processes occurring during the alloying of he alloy Ni3Mn with iron and cobalt, and the ordering of the ternary alloys thus formed are presented. The Hall effect, the absolute thermal emf, the internal saturation induction, the Nernst-Ettingshausen constant, and the electrical resistivity were measured. Results show a decrease in the contribution of hole sections of the Fermi surface to the transport process occurs together with a considerable increase in the contribution of electron sections. In this case, the mobility of 3 dimensional holes decreases and the mobility of 4s electrons increases considerably.

  7. Optical properties of layered III-VI semiconductor γ-InSe:M (M=Mn, Fe, Co, Ni)

    NASA Astrophysics Data System (ADS)

    Milutinović, Aleksandra; Lazarević, Zorica Ž.; Jakovljević, Milka; Hadzić, Branka; Petrović, Milica; Gilić, Martina; Dobrowolski, Witold Daniel; Romčević, Nebojša Ž.

    2016-02-01

    Indium selenide belongs to layered III-VI semiconductors with highly anisotropic optical and electronic properties. Energy gap of 1.32 eV makes this material very attractive for solar energy conversion. We investigated the influence of 1% 3-d transition metals M=Mn, Fe, Co, Ni, used as dopants, on energy levels of InSe:M in the range 1.4-6.5 eV and especially in the range of energy gap <1.4 eV by means of ellipsometric measurements. It was concluded that at ambient temperature foregoing dopants, all divalent, with 4s2 valent electrons, in the similar way influenced on blue-shift of energy levels in valent zone, but did not influence on the fundamental energy gap. Photoluminescence measurements confirmed blue-shift of the valent zone energy levels and an existence of deep impurity levels.

  8. Robust paramagnetism in Bi2- xMxRu2O7 (M=Mn,Fe,Co,Ni,Cu) pyrochlore

    NASA Astrophysics Data System (ADS)

    Haas, M. K.; Cava, R. J.; Avdeev, M.; Jorgensen, J. D.

    2002-09-01

    We report magnetic susceptibility, resistivity, and Seebeck coefficients for Bi2-xMxRu2O7 pyrochlore. The solid solution exists up to x=0.5 for M=Cu,Ni,Co and up to x=0.1 for M=Fe,Mn. The doped materials do not exhibit ferromagnetism or any localized ruthenium moment behavior. Instead we find the Ru-O and Bi-O sublattices to be essentially independent, with any magnetism resulting from the unpaired first-row transition metal dopant spins. Cobalt substitution for bismuth results in localized Co2+ and low-temperature spin-glass transitions in several cases. Nickel moments on the pyrochlore lattice display properties intermediate to localized and itinerant. Finally, copper doping results in an enhancement of the Pauli metallic density of states.

  9. Strain-induced martensite to austenite reverse transformation in an ultrafine-grained Fe-Ni-Mn martensitic steel

    NASA Astrophysics Data System (ADS)

    Ghasemi-Nanesa, H.; Nili-Ahmadabadi, M.; Koohdar, H. R.; Habibi-Parsa, M.; Nedjad, S. Hossein; Alidokht, S. A.; Langdon, Terence G.

    2014-05-01

    Research was conducted to evaluate the effect of heavy cold rolling on microstructural evolution in an Fe-10Ni-7Mn (wt.%) martensitic steel. The chemical driving force for the strain-induced martensite to austenite reverse transformation was calculated using thermodynamic principles and a model was developed for estimating the effect of applied stress on the driving force of the martensite to austenite reverse transformation through heavy cold rolling. These calculations show that, in order to make a reverse transformation feasible, the applied stress on the material should supply the total driving force, both chemical and non-chemical, for the transformation. It is demonstrated that after 60% cold rolling the required driving force for the reverse transformation may be provided. Experimental results, including cold rolling and transmission electron microscopy images, are utilized to verify the thermodynamic calculations.

  10. Microstructures and mechanical properties of compositionally complex Co-free FeNiMnCr18 FCC solid solution alloy

    SciTech Connect

    Wu, Z.; Bei, H.

    2015-07-01

    Recently, a structurally-simple but compositionally-complex FeNiCoMnCr high entropy alloy was found to have excellent mechanical properties (e.g., high strength and ductility). To understand the potential of using high entropy alloys as structural materials for advanced nuclear reactor and power plants, it is necessary to have a thorough understanding of their structural stability and mechanical properties degradation under neutron irradiation. Furthermore, this requires us to develop a similar model alloy without Co because material with Co will make post-neutron-irradiation testing difficult due to the production of the 60Co radioisotope. In order to achieve this goal, a FCC-structured single-phase alloy with a composition of FeNiMnCr18 was successfully developed. This near-equiatomic FeNiMnCr18 alloy has good malleability and its microstructure can be controlled by thermomechanical processing. By rolling and annealing, the as-cast elongated-grained-microstructure is replaced by homogeneous equiaxed grains. The mechanical properties (e.g., strength and ductility) of the FeNiMnCr18 alloy are comparable to those of the equiatomic FeNiCoMnCr high entropy alloy. Both strength and ductility increase with decreasing deformation temperature, with the largest difference occurring between 293 and 77 K. Extensive twin-bands which are bundles of numerous individual twins are observed when it is tensile-fractured at 77 K. No twin bands are detected by EBSD for materials deformed at 293 K and higher. Ultimately the unusual temperature-dependencies of UTS and uniform elongation could be caused by the development of the dense twin substructure, twin-dislocation interactions and the interactions between primary and secondary twinning systems which result in a microstructure refinement and hence cause enhanced strain hardening and postponed necking.

  11. Martensitic transition, magnetic, magnetocaloric and exchange bias properties of Fe-substituted Mn-Ni-Sn Heusler alloys

    NASA Astrophysics Data System (ADS)

    Sharma, Jyoti; Suresh, K. G.

    2016-12-01

    In this report, effect of Fe substitution on martensitic transition, magnetic, magnetocaloric and exchange bias (EB) properties of Mn50Ni40-xFexSn10 (x=0, 0.5, 1, 1.5, 2 and 3) Heusler alloys series has been investigated systematically. Fe substitution has been found to affect the ferromagnetic/antiferromagnetic interactions significantly in both the martensite and austenite phases. Martensitic transition temperature decreases with increasing Fe content, which is attributed to the decrease in number of average valence electrons per atom (e/a ratio) of these alloys. Large magnetic entropy change (ΔSM) and refrigerant capacity (RC) have been observed in these alloys, as a maximum ΔSM of 12.6 J/kg. K is observed for composition x=0.5. Present alloys have also been found to show large exchange bias properties, as maximum exchange bias fields (HEB) of 890 Oe and 810 Oe are observed for x=0 and 0.5, respectively at 5 K. Composition and temperature dependencies of EB are associated with the change in exchange anisotropy at interfaces of competing magnetic phases. Study of minor loop and training effect also corroborates with the presence of EB in these alloys.

  12. Microstructural stability and mechanical behavior of FeNiMnCr high entropy alloy under ion irradiation

    SciTech Connect

    Leonard, Keith J.; Bei, Hongbin; Zinkle, Steven J.; Kiran Kumar, N. A. P.; Li, C.

    2016-05-13

    In recent years, high entropy alloys (HEAs) have attracted significant attention due to their excellent mechanical properties and good corrosion resistance, making them potential candidates for high temperature fission and fusion structural applications. However there is very little known about their radiation resistance, particularly at elevated temperatures relevant for energy applications. In the present study, a single phase (face centered cubic) concentrated solid solution alloy of composition 27%Fe-28%Ni-27%Mn-18%Cr was irradiated with 3 or 5.8 MeV Ni ions at temperatures ranging from room temperature to 700 °C and midrange doses from 0.03 to 10 displacements per atom (dpa). Transmission electron microscopy (TEM), scanning transmission electron microscopy with energy dispersive x-ray spectrometry (STEM/EDS) and X-ray diffraction (XRD) were used to characterize the radiation defects and microstructural changes. Irradiation at higher temperatures showed evidence of relatively sluggish solute diffusion with limited solute depletion or enrichment at grain boundaries. The main microstructural feature at all temperatures was high-density small dislocation loops. Voids were not observed at any irradiation condition. Nano-indentation tests on specimens irradiated at room temperature showed a rapid increase in hardness ~35% and ~80% higher than the unirradiated value at 0.03 and 0.3 dpa midrange doses, respectively. The irradiation-induced hardening was less pronounced for 500 °C irradiations (<20% increase after 3 dpa). Overall, the examined HEA material exhibits superior radiation resistance compared to conventional single phase Fe-Cr-Ni austenitic alloys such as stainless steels. Furthermore, the present study provides insight on the fundamental irradiation behavior of a single phase HEA material over a broad range of irradiation temperatures.

  13. Microstructural stability and mechanical behavior of FeNiMnCr high entropy alloy under ion irradiation

    DOE PAGES

    Leonard, Keith J.; Bei, Hongbin; Zinkle, Steven J.; ...

    2016-05-13

    In recent years, high entropy alloys (HEAs) have attracted significant attention due to their excellent mechanical properties and good corrosion resistance, making them potential candidates for high temperature fission and fusion structural applications. However there is very little known about their radiation resistance, particularly at elevated temperatures relevant for energy applications. In the present study, a single phase (face centered cubic) concentrated solid solution alloy of composition 27%Fe-28%Ni-27%Mn-18%Cr was irradiated with 3 or 5.8 MeV Ni ions at temperatures ranging from room temperature to 700 °C and midrange doses from 0.03 to 10 displacements per atom (dpa). Transmission electron microscopymore » (TEM), scanning transmission electron microscopy with energy dispersive x-ray spectrometry (STEM/EDS) and X-ray diffraction (XRD) were used to characterize the radiation defects and microstructural changes. Irradiation at higher temperatures showed evidence of relatively sluggish solute diffusion with limited solute depletion or enrichment at grain boundaries. The main microstructural feature at all temperatures was high-density small dislocation loops. Voids were not observed at any irradiation condition. Nano-indentation tests on specimens irradiated at room temperature showed a rapid increase in hardness ~35% and ~80% higher than the unirradiated value at 0.03 and 0.3 dpa midrange doses, respectively. The irradiation-induced hardening was less pronounced for 500 °C irradiations (<20% increase after 3 dpa). Overall, the examined HEA material exhibits superior radiation resistance compared to conventional single phase Fe-Cr-Ni austenitic alloys such as stainless steels. Furthermore, the present study provides insight on the fundamental irradiation behavior of a single phase HEA material over a broad range of irradiation temperatures.« less

  14. Elastic properties of fcc Fe-Mn-X (X = Cr, Co, Ni, Cu) alloys studied by the combinatorial thin film approach and ab initio calculations.

    PubMed

    Reeh, S; Kasprzak, M; Klusmann, C D; Stalf, F; Music, D; Ekholm, M; Abrikosov, I A; Schneider, J M

    2013-06-19

    The elastic properties of fcc Fe-Mn-X (X = Cr, Co, Ni, Cu) alloys with additions of up to 8 at.% X were studied by combinatorial thin film growth and characterization and by ab initio calculations using the disordered local moments (DLM) approach. The lattice parameter and Young's modulus values change only marginally with X. The calculations and experiments are in good agreement. We demonstrate that the elastic properties of transition metal alloyed Fe-Mn can be predicted by the DLM model.

  15. Experimental investigation of off-stoichiometry and 3d transition metal (Mn, Ni, Cu)-substitution in single-crystalline FePt thin films

    NASA Astrophysics Data System (ADS)

    Ono, Takuya; Nakata, Hitoshi; Moriya, Tomohiro; Kikuchi, Nobuaki; Okamoto, Satoshi; Kitakami, Osamu; Shimatsu, Takehito

    2016-05-01

    In L10 (fct)-FePt thin films, both tuning Fe and Pt concentrations and substitution with third-metal were studied for magnetic characteristic optimization. We investigated single-crystalline FePt-X (X = Mn, Ni, Cu) thin films grown epitaxially on MgO(001) substrates at a substrate temperature of 350 °C by changing Fe, Pt, and X contents, and explored the effects of off-stoichiometry and 3d-metal-substitution. The magnetic moment per atom (m) of FePt-X films as a function of the effective number of valence electrons (neff) in 3d metal sites follows the Slater-Pauling-type trend, by which m decreases by the neff deviation from neff = 8, independently of the X metal and the Pt concentration. The magnetic anisotropy (Ku) exhibits neff dependence similar to m. This trend was almost independent of the Pt concentration after compensation using the theoretical prediction on the relation between Ku and Fe/Pt concentrations. Such a trend has been proved for stoichiometric FePt-X films, but it was clarified as robust against off-stoichiometry. The compensated Ku ( Ku comp ) of FePt-Mn and FePt-Cu followed a similar trend to that predicted by the rigid-band model, although the Ku comp of the FePt-Mn thin films dropped more rapidly than the rigid band calculation. However, it followed the recent first-principles calculation.

  16. Dye-Sensitized Cu2 XSnS4 (X=Zn, Ni, Fe, Co, and Mn) Nanofibers for Efficient Photocatalytic Hydrogen Evolution.

    PubMed

    Gonce, Mehmet Kerem; Aslan, Emre; Ozel, Faruk; Hatay Patir, Imren

    2016-03-21

    The photocatalytic hydrogen evolution activities of low-cost and noble-metal-free Cu2 XSnS4 (X=Zn, Ni, Fe, Co, and Mn) nanofiber catalysts have been investigated using triethanolamine as an electron donor and eosin Y as a photosensitizer under visible-light irradiation. The rates of hydrogen evolution by Cu2 XSnS4 (X=Zn, Ni, Fe, Co, and Mn) nanofibers have been compared with each other and with that of the noble metal Pt. The hydrogen evolution rates for the nanofibers change in the order Cu2 NiSnS4 >Cu2 FeSnS4 >Cu2 CoSnS4 >Cu2 ZnSnS4 >Cu2 MnSnS4 (2028, 1870, 1926, 1420, and 389 μmol g(-1) h(-1) , respectively). The differences between the hydrogen evolution rates of the nanofibers could be attributed to their energy levels. Moreover, Cu2 NiSnS4, Cu2 FeSnS4 , and Cu2 CoSnS4 nanofibers show higher and more stable photocatalytic hydrogen production rates than that of the noble metal Pt under long-term irradiation with visible light.

  17. Exact ab initio transport coefficients in bcc Fe-X (X=Cr, Cu, Mn, Ni, P, Si) dilute alloys

    NASA Astrophysics Data System (ADS)

    Messina, Luca; Nastar, Maylise; Garnier, Thomas; Domain, Christophe; Olsson, Pär

    2014-09-01

    Defect-driven diffusion of impurities is the major phenomenon leading to formation of embrittling nanoscopic precipitates in irradiated reactor pressure vessel (RPV) steels. Diffusion depends strongly on the kinetic correlations that may lead to flux coupling between solute atoms and point defects. In this work, flux coupling phenomena such as solute drag by vacancies and radiation-induced segregation at defect sinks are systematically investigated for six bcc iron-based dilute binary alloys, containing Cr, Cu, Mn, Ni, P, and Si impurities, respectively. First, solute-vacancy interactions and migration energies are obtained by means of ab initio calculations; subsequently, self-consistent mean field theory is employed in order to determine the exact Onsager matrix of the alloys. This innovative multiscale approach provides a more complete treatment of the solute-defect interaction than previous multifrequency models. Solute drag is found to be a widespread phenomenon that occurs systematically in ferritic alloys and is enhanced at low temperatures (as for instance RPV operational temperature), as long as an attractive solute-vacancy interaction is present, and that the kinetic modeling of bcc alloys requires the extension of the interaction shell to the second-nearest neighbors. Drag occurs in all alloys except Fe(Cr); the transition from dragging to nondragging regime takes place for the other alloys around (Cu, Mn, Ni) or above (P, Si) the Curie temperature. As far as only the vacancy-mediated solute migration is concerned, Cr depletion at sinks is foreseen by the model, as opposed to the other impurities which are expected to enrich up to no less than 1000 K. The results of this study confirm the current interpretation of the hardening processes in ferritic-martensitic steels under irradiation.

  18. Electron microscopy investigation and electrochemical performance of carbon-coated LiFe0.7Mn0.2Ni0.1PO4 for lithium ion battery

    NASA Astrophysics Data System (ADS)

    Rohman, Fadli; Suwandi, Endang; Majid, Nurhalis; Subhan, Achmad

    2016-02-01

    The carbon-coated LiFe0.7Mn0.2Ni0.1PO4 was synthesized using solid state reaction method and sintering process. The carbon was coated on the surface of the LiFe0.7Mn0.2Ni0.1PO4 particle using citric acid as the carbon source. the crystal phase and diffraction peak of the particle was shown from X-Ray Diffraction characterization. The particle morphology and size distribution of this material was investigated using Scanning Electron Microscopy (SEM). The thickness of the carbon coating and the crystal lattice spacing was investigated using Transmission Electron Microscopy (TEM). The particle size, carbon coating thickness, and crystal lattice spacing were found to be 10 - 50 µm, 4 nm, and Å, respectively. The effect of the carbon layer on the surface of the LiFe0.7Mn0.2Ni0.1PO4 particle as a cathode material in lithium-ion battery exhibited in the electrochemical performance test as shown in cyclic voltammetry and charge-discharge measurement test. According to the cyclic voltammetry test, it was shown that the redox peaks of the carbon-coated LiFe0.7Mn0.2Ni0.1PO4 from Fe2+ to Fe3+ were at 3.579 V and 2.96 V, but there was lower peak at 3.52 V. This phenomenon indicated the presence of doped Mn and Ni. The specific capacity of carbon coated LiFe0.7Mn0.2Ni0.1PO4 was 49 mAh/g, which was higher than uncoated LiFe0.7Mn0.2Ni0.1PO4, 30 mAh/g. On the other hand, after 40 cycles the specific capacity of carbon-coated LiFe0.7Mn0.2Ni0.1PO4 was decreasing to 10%, while the specific capacity of uncoated LiFe0.7Mn0.2Ni0.1PO4 remained almost similar before and after 40 cycles. In term of columbic efficiency, carbon-coated LiFe0.7Mn0.2Ni0.1PO4 was more stable, better than uncoated LiFe0.7Mn0.2Ni0.1PO4. Moreover, all samples were in close proximity to 100% efficiency. The C-rates test result showed that the discharge C-rates ability of the carbon coated LiFe0.7Mn0.2Ni0.1PO4 had been better than uncoated LiFe0.7Mn0.2Ni0.1PO4. At 1.5 C rate, the capacity loss of carbon-coated LiFe0

  19. Magneto-optical Kerr effect in ZnTMO2 (TM=Cr, Mn, Fe, Co and Ni)

    NASA Astrophysics Data System (ADS)

    Merikhi, R.; Bennecer, B.; Hamidani, A.

    2017-02-01

    First principles generalized gradient full potential density-functional calculations were performed to predict the optical and magneto-optical (MO) properties of the chalcopyrite compounds ZnTMO2, TM=Cr, Mn, Fe, Co and Ni. Detailed investigation of the electronic band structure and density of states is reported. The optical properties in the 0-8 eV energy range are analyzed in terms of band structure transitions. As for the magneto-optical properties, our results show that the studied compounds have peaks in the Kerr rotation ranging from infrared to ultraviolet radiation, with ZnFeO2 having the highest Kerr rotation angle of 10 ° and - 8.46 ° at 0.35 eV and 4.59 eV, respectively. The peaks in the Kerr spectra were assigned to the optical and magneto-optic contributions. Our calculated function of merit for these compounds indicates that these compounds might be useful for technological application in high density storage.

  20. Enhancement of exchange bias and training effect in ion-beam sputtered Fe{sub 46}Mn{sub 54}/Ni{sub 81}Fe{sub 19} bilayers

    SciTech Connect

    Fulara, Himanshu; Chaudhary, Sujeet Kashyap, Subhash C.; Granville, Simon

    2014-01-28

    We present a remarkable enhancement by 300% of the exchange-bias field at room temperature, without affecting the coercivity value, via optimum magnetic annealing (250 °C/3 kOe) in ion-beam sputtered FeMn(30 nm)/NiFe(10 nm) bilayers. This specific behavior has been attributed to a higher degree of γ-FeMn(111) orientation that offers more interfacial FeMn moments to get pinned with the moments of the adjacent NiFe layer. Unlike the absence of training effect at room temperature, a pronounced training effect and an accompanying magnetization reversal asymmetry are evidenced upon field cooling below 50 K due to the presence of biaxial exchange induced anisotropy across the interdiffused FeMn/NiFe interface. The present findings not only have technological significance but also are of relevance to the understanding of interfacial spin disorder and frustration in these exchange-biased systems.

  1. Alternating magnetic anisotropy of Li2(Li1–xTx)N (T = Mn, Fe, Co, and Ni)

    SciTech Connect

    Jesche, A.; Ke, L.; Jacobs, J. L.; Harmon, B.; Houk, R. S.; Canfield, P. C.

    2015-05-11

    Substantial amounts of the transition metals Mn, Fe, Co, and Ni can be substituted for Li in single crystalline Li2(Li1–xTx)N. Isothermal and temperature-dependent magnetization measurements reveal local magnetic moments with magnitudes significantly exceeding the spin-only value. The additional contributions stem from unquenched orbital moments that lead to rare-earth-like behavior of the magnetic properties. Accordingly, extremely large magnetic anisotropies have been found. Most notably, the magnetic anisotropy alternates as easy plane→easy axis→easy plane→easy axis when progressing from T = MnFe → Co → Ni. This behavior can be understood based on a perturbation approach in an analytical, single-ion model. As a result, the calculated magnetic anisotropies show surprisingly good agreement with the experiment and capture the basic features observed for the different transition metals.

  2. Structure and magnetic properties of the double-perovskites Ba2(B,Re)2O6 (B = Fe, Mn, Co and Ni)

    NASA Astrophysics Data System (ADS)

    Rammeh, N.; Ehrenberg, H.; Fuess, H.; Cheikkh-Rouhou, A.

    2006-09-01

    Structural and magnetic properties of Ba2(B,Re)2O6 (B = Fe, Mn, Co and Ni) double-perovskite oxides have been investigated. Rietveld analysis shows that all our synthesized samples are single phase and crystallize at room temperature in the cubic double-perovskite structure with Fm3m space group. Magnetization measurements versus temperature and versus magnetic applied field up to 5 T show that Ba2(Fe,Re)2O6, Ba2(Mn,Re)2O6 and Ba2(Ni,Re)2O6 are ferromagnetic at low temperature with TC = 318 K, 113 K and 32 K respectively while Ba2(Co,Re)2O6 is antiferromagnetic below TN = 25 K.

  3. Preparation, crystal structure and magnetic behavior of new double perovskites Sr{sub 2} B'UO{sub 6} with B'=Mn, Fe, Ni, Zn

    SciTech Connect

    Pinacca, R.M.; Viola, M.C.; Pedregosa, J.C.; Martinez-Lope, M.J.; Carbonio, R.E.; Alonso, J.A.

    2007-05-15

    Sr{sub 2} B'UO{sub 6} double perovskites with B'=Mn, Fe, Ni, Zn have been prepared in polycrystalline form by solid-state reaction, in air or reducing conditions. These new materials have been studied by X-ray diffraction (XRD), magnetic susceptibility and magnetization measurements. The room-temperature crystal structure is monoclinic (space group P2{sub 1}/n), and contains alternating B'O{sub 6} and UO{sub 6} octahedra sharing corners, tilted along the three pseudocubic axes according to the Glazer notation a {sup -} a {sup -} b {sup +}. The magnetic measurements show a spontaneous magnetic ordering below T {sub N}=21 K for B'=Mn, Ni, and T {sub C}=150 K for B'=Fe. From a Curie-Weiss fit, the effective paramagnetic moment for B'=Mn (5.74 {mu}{sub B}/f.u.) and B'=Ni(3.51 {mu}{sub B}/f.u.) are significantly different from the corresponding spin-only moments for the divalent cations, suggesting the possibility of a partial charge disproportionation B'{sup 2+}+U {sup 6+}{r_reversible}B'{sup 3+}+U {sup 5+}, also accounting for plausible ferrimagnetic interactions between B' and U sublattices. The strong curvature of the reciprocal susceptibility for B'=Fe precludes a Curie-Weiss fit but also suggests the presence of ferrimagnetic interactions in this compound. This charge disproportionation effect is also supported by the observed B'-O distances, which are closer to the expected values for high-spin, trivalent Mn, Fe and Ni cations. - Graphical abstract: The title double perovskites are monoclinic, space group P2{sub 1}/n, and the magnetic properties suggest the possibility of a partial charge disproportionation B'{sup 2+}+U {sup 6+}{r_reversible}B'{sup 3+}+U {sup 5+}, accounting for plausible ferrimagnetic interactions between B' and U sublattices.

  4. Temperature dependencies of the elastic moduli and thermal expansion coefficient of an equiatomic, single-phase CoCrFeMnNi high-entropy alloy

    DOE PAGES

    Laplanche, G.; Gadaud, P.; Horst, O.; ...

    2014-11-15

    The equiatomic CoCrFeMnNi alloy is now regarded as a model face-centered cubic single-phase high-entropy alloy. Consequently, determination of its intrinsic properties such as the temperature dependencies of elastic moduli and thermal expansion coefficient are important to improve understanding of this new class of material. Lastly, these temperature dependencies were measured over a large temperature range (200–1270 K) in this study.

  5. Reverse Shape Memory Effect Related to α → γ Transformation in a Fe-Mn-Al-Ni Shape Memory Alloy

    NASA Astrophysics Data System (ADS)

    Peng, Huabei; Huang, Pan; Zhou, Tiannan; Wang, Shanling; Wen, Yuhua

    2017-02-01

    In this study, we investigated the shape memory behavior and phase transformations of solution-treated Fe43.61Mn34.74Al13.38Ni8.27 alloy between room temperature and 1173 K (900 °C). This alloy exhibits the reverse shape memory effect resulting from the phase transformation of α (bcc) → γ (fcc) between 673 K and 1073 K (400 °C and 800 °C) in addition to the shape memory effect resulting from the martensitic reverse transformation of γ' (fcc) → α (bcc) below 673 K (400 °C). There is a high density of hairpin-shaped dislocations in the α phase undergoing the martensitic reverse transformation of γ' → α. The lath γ phase, which preferentially nucleates and grows in the reversed α phase, has the same crystal orientation with the reverse-transformed γ' martensite. However, the vermiculate γ phase, which is precipitated in the α phase between lath γ phase, has different crystal orientations. The lath γ phase is beneficial to attaining better reverse shape memory effect than the vermiculate γ phase.

  6. Nanoscale origins of the damage tolerance of the high-entropy alloy CrMnFeCoNi

    PubMed Central

    Zhang, ZiJiao; Mao, M. M.; Wang, Jiangwei; Gludovatz, Bernd; Zhang, Ze; Mao, Scott X.; George, Easo P.; Yu, Qian; Ritchie, Robert O.

    2015-01-01

    Damage tolerance can be an elusive characteristic of structural materials requiring both high strength and ductility, properties that are often mutually exclusive. High-entropy alloys are of interest in this regard. Specifically, the single-phase CrMnFeCoNi alloy displays tensile strength levels of ∼1 GPa, excellent ductility (∼60–70%) and exceptional fracture toughness (KJIc>200 MPa√m). Here through the use of in situ straining in an aberration-corrected transmission electron microscope, we report on the salient atomistic to micro-scale mechanisms underlying the origin of these properties. We identify a synergy of multiple deformation mechanisms, rarely achieved in metallic alloys, which generates high strength, work hardening and ductility, including the easy motion of Shockley partials, their interactions to form stacking-fault parallelepipeds, and arrest at planar slip bands of undissociated dislocations. We further show that crack propagation is impeded by twinned, nanoscale bridges that form between the near-tip crack faces and delay fracture by shielding the crack tip. PMID:26647978

  7. Effect of precipitated austenite on the fracture of a ferritic cryogenic steel. [Fe-8Ni-2Mn-0. 1Ti

    SciTech Connect

    Frear, D.R.

    1984-05-01

    The effect of precipitated austenite on the fracture of an Fe-8Ni-2Mn-0.1Ti steel was investigated. To understand the effect an attempt was made to correlate the microstructure, mechanical properties, and the fracture surface appearance of specimens heat treated to contain austenite or be austenite-free. The fracture surfaces were quantitatively studied using a 3D imaging technique in the SEM. It was found that the presence of austenite had a beneficial influence on mechanical properties by lowering the DBTT. Part of this decrease was found to be due to the austenite gettering deleterious elements off the grain boundaries. Specimens that contained precipitated austenite were also found to have a smaller median facet size, when fractured in a brittle transgranular mode, than specimens with no austenite. The decrease in DBTT and change in fracture surface appearance is related to the austenite transforming to martensite of a different variant than the matrix which effectively grain refines the steel and raises the cleavage stress.

  8. Nanoscale origins of the damage tolerance of the high-entropy alloy CrMnFeCoNi.

    PubMed

    Zhang, ZiJiao; Mao, M M; Wang, Jiangwei; Gludovatz, Bernd; Zhang, Ze; Mao, Scott X; George, Easo P; Yu, Qian; Ritchie, Robert O

    2015-12-09

    Damage tolerance can be an elusive characteristic of structural materials requiring both high strength and ductility, properties that are often mutually exclusive. High-entropy alloys are of interest in this regard. Specifically, the single-phase CrMnFeCoNi alloy displays tensile strength levels of ∼ 1 GPa, excellent ductility (∼ 60-70%) and exceptional fracture toughness (KJIc>200 MPa√m). Here through the use of in situ straining in an aberration-corrected transmission electron microscope, we report on the salient atomistic to micro-scale mechanisms underlying the origin of these properties. We identify a synergy of multiple deformation mechanisms, rarely achieved in metallic alloys, which generates high strength, work hardening and ductility, including the easy motion of Shockley partials, their interactions to form stacking-fault parallelepipeds, and arrest at planar slip bands of undissociated dislocations. We further show that crack propagation is impeded by twinned, nanoscale bridges that form between the near-tip crack faces and delay fracture by shielding the crack tip.

  9. In Situ Observation of Austenite Growth During Continuous Heating in Very-Low-Carbon Fe-Mn and Ni Alloys

    NASA Astrophysics Data System (ADS)

    Enomoto, M.; Wan, X. L.

    2017-02-01

    The growth of austenite during continuous heating was observed in situ under a confocal scanning laser microscope in Fe-Mn and Ni alloys containing less than 0.01 mass pct C. The advancements of the α/γ boundary were measured in the temperature range of ca. 40 K, which encompassed the Ae3 line of the alloys. Below Ae3, the growth rates were of the same order of magnitude as those predicted from the carbon diffusion-controlled negligible partition local equilibrium in the (α + γ) two-phase region, whereas those observed near and above the Ae3 were ca. two orders of magnitude greater. The α/γ boundary mobilities evaluated therefrom were somewhat smaller than those obtained previously in massive ferrite transformation during continuous cooling in the same alloys, albeit the experimental scatter was large and fell near the mobilities proposed in the literature. The α/γ boundary migrated probably with a carbon diffusion spike ahead of the boundary and the solute drag of the carbon or alloy element is unlikely to be operative during the growth of austenite.

  10. Determination of Co, Cu, Fe, Mn, Ni and V in diesel and biodiesel samples by ETV-ICP-MST.

    PubMed

    Chaves, Eduardo S; Lepri, Fábio G; Silva, Jessee S A; de Quadros, Daiane P C; Saint'Pierre, Tatiana D; Curtius, Adilson J

    2008-10-01

    This work presents the determination of Co, Cu, Fe, Mn, Ni and V in diesel and biodiesel samples by ETV-ICP MS using emulsion sample preparation. The emulsion composition was: 1.0 g of the diesel or biodiesel sample, 2.0 mL of a 5% m/v Triton X-100 solution, 0.5 mL of HNO3 and deionized water to a 10 mL final volume. The optimized parameters were mass of carrier/modifier (1.0 microg Pd), RF power (1100 W), carrier gas flow rate (0.95 L min(-1)) and inner ETV gas flow rate (0.15 L min(-1)). The determinations were performed against aqueous solutions using 10 microg L(-1) Rh as internal standard. The accuracy of the method was verified through the analysis of the NIST 1634c reference residual fuel oil, recovery tests and comparison of the results with those obtained by GF AAS. The results were in agreement according to the t-test at a 95% confidence level. The RSD values were lower than 20%, the recoveries were between 80 and 120% and the LOD values were in the order of ng g(-1), showing the good accuracy and sensitivity of the method.

  11. Nano- and microvoid formation in ultrafine-grained martensitic Fe-Ni-Mn steel after severe cold rolling

    NASA Astrophysics Data System (ADS)

    Ghasemi-Nanesa, Hadi; Nili-Ahmadabadi, Mahmoud; Mirsepasi, Arya; Zamani, Cyrus

    2014-03-01

    Severe cold-rolling was applied on solution annealed Fe-Ni-Mn steel with fully lath martensite structure to obtain ultrafine-grained structure. Field emission scanning electron microscopy and high resolution transmission electron microscopy (HRTEM) were employed to investigate the microstructural evolution after severe cold-rolling. HRTEM images showed the typical deformed structure consisting of lamellar dislocation cell blocks. HRTEM study also revealed strain-induced reverse martensitic transformation (activated during grain refinement). It was assumed that severe plastic deformation route and related deformation mode were responsible for microstructural evolutions. X-ray diffraction (XRD) diagram revealed 7% (volume fraction) reverted austenite after final deformation pass. Moreover, HRTEM images revealed nano-void nucleation at the interface of severely deformed martensite and reverted austenite presumably due to high strain energy of misfit and molar volume difference between the austenite and the martensite. It seems that the coalescence of nano-voids could lead to the formation of microvoids in the microstructure.

  12. In Situ Observation of Austenite Growth During Continuous Heating in Very-Low-Carbon Fe-Mn and Ni Alloys

    NASA Astrophysics Data System (ADS)

    Enomoto, M.; Wan, X. L.

    2017-04-01

    The growth of austenite during continuous heating was observed in situ under a confocal scanning laser microscope in Fe-Mn and Ni alloys containing less than 0.01 mass pct C. The advancements of the α/ γ boundary were measured in the temperature range of ca. 40 K, which encompassed the Ae3 line of the alloys. Below Ae3, the growth rates were of the same order of magnitude as those predicted from the carbon diffusion-controlled negligible partition local equilibrium in the ( α + γ) two-phase region, whereas those observed near and above the Ae3 were ca. two orders of magnitude greater. The α/ γ boundary mobilities evaluated therefrom were somewhat smaller than those obtained previously in massive ferrite transformation during continuous cooling in the same alloys, albeit the experimental scatter was large and fell near the mobilities proposed in the literature. The α/ γ boundary migrated probably with a carbon diffusion spike ahead of the boundary and the solute drag of the carbon or alloy element is unlikely to be operative during the growth of austenite.

  13. Nanoscale origins of the damage tolerance of the high-entropy alloy CrMnFeCoNi

    DOE PAGES

    Zhang, ZiJiao; Mao, M. M.; Wang, Jiangwei; ...

    2015-12-09

    Damage tolerance can be an elusive characteristic of structural materials requiring both high strength and ductility, properties that are often mutually exclusive. High-entropy alloys are of interest in this regard. Specifically, the single-phase CrMnFeCoNi alloy displays tensile strength levels of ~1 GPa, excellent ductility (~60–70%) and exceptional fracture toughness (KJIc>200M Pa√m). Here through the use of in situ straining in an aberration-corrected transmission electron microscope, we report on the salient atomistic to micro-scale mechanisms underlying the origin of these properties. We identify a synergy of multiple deformation mechanisms, rarely achieved in metallic alloys, which generates high strength, work hardening andmore » ductility, including the easy motion of Shockley partials, their interactions to form stacking-fault parallelepipeds, and arrest at planar slip bands of undissociated dislocations. In conclusion, we further show that crack propagation is impeded by twinned, nanoscale bridges that form between the near-tip crack faces and delay fracture by shielding the crack tip.« less

  14. Nanoscale origins of the damage tolerance of the high-entropy alloy CrMnFeCoNi

    SciTech Connect

    Zhang, ZiJiao; Mao, M. M.; Wang, Jiangwei; Gludovatz, Bernd; Zhang, Ze; Mao, Scott X.; George, Easo P.; Yu, Qian; Ritchie, Robert O.

    2015-12-09

    Damage tolerance can be an elusive characteristic of structural materials requiring both high strength and ductility, properties that are often mutually exclusive. High-entropy alloys are of interest in this regard. Specifically, the single-phase CrMnFeCoNi alloy displays tensile strength levels of ~1 GPa, excellent ductility (~60–70%) and exceptional fracture toughness (KJIc>200M Pa√m). Here through the use of in situ straining in an aberration-corrected transmission electron microscope, we report on the salient atomistic to micro-scale mechanisms underlying the origin of these properties. We identify a synergy of multiple deformation mechanisms, rarely achieved in metallic alloys, which generates high strength, work hardening and ductility, including the easy motion of Shockley partials, their interactions to form stacking-fault parallelepipeds, and arrest at planar slip bands of undissociated dislocations. In conclusion, we further show that crack propagation is impeded by twinned, nanoscale bridges that form between the near-tip crack faces and delay fracture by shielding the crack tip.

  15. Unravelling the Role of Electrochemically Active FePO4 Coating by Atomic Layer Deposition for Increased High-Voltage Stability of LiNi0.5Mn1.5O4 Cathode Material.

    PubMed

    Xiao, Biwei; Liu, Jian; Sun, Qian; Wang, Biqiong; Banis, Mohammad Norouzi; Zhao, Dong; Wang, Zhiqiang; Li, Ruying; Cui, Xiaoyu; Sham, Tsun-Kong; Sun, Xueliang

    2015-05-01

    Ultrathin amorphous FePO4 coating derived by atomic layer deposition (ALD) is used to coat the 5 V LiNi0.5Mn1.5O4 cathode material powders, which dramatically increases the capacity retention of LiNi0.5Mn1.5O4. It is believed that the amorphous FePO4 layer could act as a lithium-ions reservoir and electrochemically active buffer layer during the charge/discharge cycling, helping achieve high capacities in LiNi0.5Mn1.5O4, especially at high current densities.

  16. Electronic structure and magnetic properties in T2AlB2 (T =Fe, Mn, Cr, Co, and Ni) and their alloys

    NASA Astrophysics Data System (ADS)

    Ke, Liqin; Harmon, Bruce N.; Kramer, Matthew J.

    2017-03-01

    The electronic structure and intrinsic magnetic properties of Fe2AlB2 -related compounds and their alloys have been investigated using density functional theory. For Fe2AlB2 , the crystallographic a axis is the easiest axis, which agrees with experiments. The magnetic ground state of Mn2AlB2 is found to be ferromagnetic in the basal a b plane, but antiferromagnetic along the c axis. All 3 d dopings considered decrease the magnetization and Curie temperature in Fe2AlB2 . Electron doping with Co or Ni has a stronger effect on the decreasing of Curie temperature in Fe2AlB2 than hole doping with Mn or Cr. However, a larger amount of Mn doping on Fe2AlB2 promotes the ferromagnetic to antiferromagnetic transition. A very anisotropic magnetoelastic effect is found in Fe2AlB2 : the magnetization has a much stronger dependence on the lattice parameter c than on a or b , which is explained by electronic-structure features near the Fermi level. Dopings of other elements on B and Al sites are also discussed.

  17. Electronic structure and magnetic properties in T2AlB2 (T = Fe, Mn, Cr, Co, and Ni) and their alloys

    DOE PAGES

    Ke, Liqin; Harmon, Bruce N.; Kramer, Matthew J.

    2017-03-20

    In this study, the electronic structure and intrinsic magnetic properties of Fe2AlB2-related compounds and their alloys have been investigated using density functional theory. For Fe2AlB2, the crystallographic a axis is the easiest axis, which agrees with experiments. The magnetic ground state of Mn2AlB2 is found to be ferromagnetic in the basal ab plane, but antiferromagnetic along the c axis. All 3d dopings considered decrease the magnetization and Curie temperature in Fe2AlB2. Electron doping with Co or Ni has a stronger effect on the decreasing of Curie temperature in Fe2AlB2 than hole doping with Mn or Cr. However, a larger amountmore » of Mn doping on Fe2AlB2 promotes the ferromagnetic to antiferromagnetic transition. A very anisotropic magnetoelastic effect is found in Fe2AlB2: the magnetization has a much stronger dependence on the lattice parameter c than on a or b, which is explained by electronic-structure features near the Fermi level. Dopings of other elements on B and Al sites are also discussed.« less

  18. Air breathing cathodes for microbial fuel cell using Mn-, Fe-, Co- and Ni-containing platinum group metal-free catalysts

    DOE PAGES

    Kodali, Mounika; Santoro, Carlo; Serov, Alexey; ...

    2017-02-07

    Here we discuss the oxygen reduction reaction (ORR) is one of the major factors that is limiting the overall performance output of microbial fuel cells (MFC). In this study, Platinum Group Metal-free (PGM-free) ORR catalysts based on Fe, Co, Ni, Mn and the same precursor (Aminoantipyrine, AAPyr) were synthesized using identical sacrificial support method (SSM). The catalysts were investigated for their electrochemical performance, and then integrated into an air-breathing cathode to be tested in “clean” environment and in a working microbial fuel cell (MFC). Their performances were also compared to activated carbon (AC) based cathode under similar conditions. Results showedmore » that the addition of Mn, Fe, Co and Ni to AAPyr increased the performances compared to AC. Fe-AAPyr showed the highest open circuit potential (OCP) that was 0.307 ± 0.001 V (vs. Ag/AgCl) and the highest electrocatalytic activity at pH 7.5. On the contrary, AC had an OCP of 0.203 ± 0.002 V (vs. Ag/AgCl) and had the lowest electrochemical activity. In MFC, Fe-AAPyr also had the highest output of 251 ± 2.3 μWcm–2, followed by Co-AAPyr with 196 ± 1.5 μWcm–2, Ni-AAPyr with 171 ± 3.6 μWcm–2, Mn-AAPyr with 160 ± 2.8 μWcm–2 and AC 129 ± 4.2 μWcm–2. The best performing catalyst (Fe-AAPyr) was then tested in MFC with increasing solution conductivity from 12.4 mScm–1 to 63.1 mScm–1. A maximum power density of 482 ± 5 μWcm–2 was obtained with increasing solution conductivity, which is one of the highest values reported in the field.« less

  19. Novel active heterogeneous Fenton system based on Fe3-xMxO4 (Fe, Co, Mn, Ni): the role of M2+ species on the reactivity towards H2O2 reactions.

    PubMed

    Costa, Regina C C; Lelis, M F F; Oliveira, L C A; Fabris, J D; Ardisson, J D; Rios, R R V A; Silva, C N; Lago, R M

    2006-02-28

    In this work, the effect of incorporation of M2+ species, i.e. Co2+, Mn2+ and Ni2+, into the magnetite structure to increase the reactivity towards H2O2 reactions was investigated. The following magnetites Fe3-xMnxO4, Fe3-xCoxO4 and Fe3-xNixO4 and the iron oxides Fe3O4, gamma-Fe2O3 and alpha-Fe2O3 were prepared and characterized by Mössbauer spectroscopy, XRD, BET surface area, magnetization and chemical analyses. The obtained results showed that the M2+ species at the octahedral site in the magnetite strongly affects the reactivity towards H2O2, i.e. (i) the peroxide decomposition to O2 and (ii) the oxidation of organic molecules, such as the dye methylene blue and chlorobenzene in aqueous medium. Experiments with maghemite, gamma-Fe2O3 and hematite, alpha-Fe2O3, showed very low activities compared to Fe3O4, suggesting that the presence of Fe2+ in the oxide plays an important role for the activation of H2O2. The presence of Co or Mn in the magnetite structure produced a remarkable increase in the reactivity, whereas Ni inhibited the H2O2 reactions. The obtained results suggest a surface initiated reaction involving Msurf2+ (Fe, Co or Mn), producing HO radicals, which can lead to two competitive reactions, i.e. the decomposition of H2O2 or the oxidation of organics present in the aqueous medium. The unique effect of Co and Mn is discussed in terms of the thermodynamically favorable Cosurf3+ and Mnsurf3+ reduction by Femagnetite2+ regenerating the active species M2+.

  20. Study of angular dependence of exchange bias and misalignment in uniaxial and unidirectional anisotropy in NiFe(111)/FeMn(111)/CoFeB(amorphous) stack

    NASA Astrophysics Data System (ADS)

    Singh, Braj Bhusan; Chaudhary, Sujeet

    2015-07-01

    We report the investigation of the in-plane azimuthal angular dependence of the magnetization reversal in the ion beam sputtered exchanged biased NiFe(111)/FeMn(111)/CoFeB(amorphous) stack. Compared to the as-deposited case, the magnetic annealing resulted in 3 fold enhancement in exchange bias but decrease in coercivity. The observed cosine dependence of exchange biased CoFeB layer on the in-plane azimuthal angle of applied field is corroborated with Meiklejohn and Bean model. The training effect associated with the exchange bias showed unconventional increase in coercivity after first cycle of hysteresis loop, while the exchange bias decreases sharply, and for subsequent cycles the exchange bias follows the empirical relation based on the energy dissipation in the AF layer. The ferromagnetic resonance (FMR) measurements also exhibited the in-plane azimuthal angle dependence of the magnetic resonance field indicating that the uniaxial and unidirectional anisotropies are not collinear, although they lie in the same plane. However, no misalignment between the unidirectional anisotropy and the exchange bias direction is observed. The misalignment angle between the uniaxial and unidirectional anisotropy, as measured by FMR, is found to be 10° and 14° for CoFeB and NiFe, respectively. This misalignment is attributed to the interface roughness as revealed by x-ray reflectance measurements.

  1. AlM2B2 (M  =  Cr, Mn, Fe, Co, Ni): a group of nanolaminated materials

    NASA Astrophysics Data System (ADS)

    Kádas, K.; Iuşan, D.; Hellsvik, J.; Cedervall, J.; Berastegui, P.; Sahlberg, M.; Jansson, U.; Eriksson, O.

    2017-04-01

    Combining theory with experiments, we study the phase stability, elastic properties, electronic structure and hardness of layered ternary borides AlCr2B2, AlMn2B2, AlFe2B2, AlCo2B2, and AlNi2B2. We find that the first three borides of this series are stable phases, while AlCo2B2 and AlNi2B2 are metastable. We show that the elasticity increases in the boride series, and predict that AlCr2B2, AlMn2B2, and AlFe2B2 are more brittle, while AlCo2B2 and AlNi2B2 are more ductile. We propose that the elasticity of AlFe2B2 can be improved by alloying it with cobalt or nickel, or a combination of them. We present evidence that these ternary borides represent nanolaminated systems. Based on SEM measurements, we demonstrate that they exhibit the delamination phenomena, which leads to a reduced hardness compared to transition metal mono- and diborides. We discuss the background of delamination by analyzing chemical bonding and theoretical work of separation in these borides.

  2. Electronic structures and magnetic properties of the transition-metal atoms (Mn, Fe, Co and Ni) doped WS2: A first-principles study

    NASA Astrophysics Data System (ADS)

    Xie, Ling-Yun; Zhang, Jian-Min

    2016-10-01

    The spin-polarized first-principles calculations are performed to study the electronic structures and magnetic properties of a single or double identical transition metal (TM) atoms X (X = Mn, Fe, Co and Ni) doped monolayer WS2 systems. Although the pristine monolayer WS2 system is a nonmagnetic semiconductor with a direct band gap of 1.820 eV, a single Mn, Fe, Co or Ni doped WS2 systems exhibit the magnetic half-metallic (HM) characters with the total magnetic moments Mtot of 1, 2, 3 and 4 μB and the smaller spin-down gaps Eg of 1.262, 1.154, 1.407 and 1.073 eV, respectively. For double identical TM atoms doped monolayer WS2 systems, except for the cases of two Ni atoms doped at the first (0,1), second (0,2) and third (0,3) nearest-neighbor cation configuration which are antiferromagnetic (AFM), ferromagnetic (FM) and FM metals, respectively, the other cases are all HM ferromagnets, and the total magnetic moment Mtot increases not only for double identical TM dopants Mn, Fe, Co and Ni (except for (0,1) AFM case) successively at the same nearest-neighbor cation configuration but also for each of the double identical TM dopants at the first (0,1), second (0,2) and third (0,3) nearest-neighbor cation configurations successively. These results provide a theoretical guide to choose new two-dimensional HM ferromagnetic materials in spintronic applications.

  3. Magnetic properties of NixFe100-x layers in exchange-coupled FeMn/NixFe100-x film structures

    NASA Astrophysics Data System (ADS)

    Adanakova, Olga; Lepalovskij, Vladimir; Svalov, Andrey; Larrañaga, Aitor; Trubin, Anton; Vas'kovskiy, Vladimir

    2016-09-01

    Thin Fe20Ni80/FeMn/NixFe100-x multilayers were prepared using magnetron sputtering. The influence of composition on crystalline structure, exchange bias, magnetic hysteresis, and spontaneous magnetization of FeNi ferromagnetic layers coupled with the antiferromagnetic FeMn layer was investigated.

  4. High-voltage cathode materials for lithium-ion batteries: freeze-dried LiMn0.8Fe0.1M0.1PO4/C (M = Fe, Co, Ni, Cu) nanocomposites.

    PubMed

    Iturrondobeitia, Amaia; Goñi, Aintzane; Gil de Muro, Izaskun; Lezama, Luis; Kim, Chunjoong; Doeff, Marca; Cabana, Jordi; Rojo, Teófilo

    2015-03-16

    Four LiMn0.8Fe0.1M0.1PO4/C (M = Fe, Co, Ni, Cu) cathode materials have been synthesized via a freeze-drying method. The samples have been characterized by powder X-ray diffraction, transmission electron microscopy, magnetic susceptibility, and electrochemical measurements. The composition and effective insertion of the transition-metal substituents in LiMnPO4 have been corroborated by elemental analysis, the evolution of the crystallographic parameters, and the magnetic properties. The morphological characterization of the composites has demonstrated that the phosphate nanoparticles are enclosed in a matrix of amorphous carbon. Among them, LiMn0.8Fe0.1Ni0.1PO4/C is the most promising cathode material, providing a good electrochemical performance in all aspects: high voltage and specific capacity values, excellent cyclability, and good rate capability. This result has been attributed to several factors, such as the suitable morphology of the sample, the good connection afforded by the in situ generated carbon, and the amelioration of the structural stress provided by the presence of Ni(2+) and Fe(2+) in the olivine structure.

  5. Electrochemical studies of DNA interaction and antimicrobial activities of MnII, FeIII, CoII and NiII Schiff base tetraazamacrocyclic complexes

    NASA Astrophysics Data System (ADS)

    Kumar, Anuj; Vashistha, Vinod Kumar; Tevatia, Prashant; Singh, Randhir

    2017-04-01

    Tetraazamacrocyclic complexes of MnII, FeIII, CoII and NiII have been synthesized by template method. These tetraazamacrocycles have been analyzed with various techniques like molar conductance, IR, UV-vis, mass spectral and cyclic voltammetric studies. On the basis of all these studies, octahedral geometry has been assigned to these tetraazamacrocyclic complexes. The DNA binding properties of these macrocyclic complexes have been investigated by electronic absorption spectra, fluorescence spectra, cyclic voltammetric and differential pulse voltammetric studies. The cyclic voltammetric data showed that ipc and ipa were effectively decreased in the presence of calf thymus DNA, which is a strong evidence for the interaction of these macrocyclic complexes with the calf thymus DNA (ct-DNA). The heterogeneous electron transfer rate constant found in the order: KCoII > KNiII > KMnII which indicates that CoII macrocyclic complex has formed a strong intercalated intermediate. The Stern-Volmer quenching constant (KSV) and voltammetric binding constant were found in the order KSV(CoII) > KSV(NiII) > KSV(MnII) and K+(CoII) > K+(NiII) > K+(MnII) which shows that CoII macrocyclic complex exhibits the high interaction affinity towards ct-DNA by the intercalation binding. Biological studies of the macrocyclic complexes compared with the standard drug like Gentamycin, have shown antibacterial activities against E. coli, P. aeruginosa, B. cereus, S. aureus and antifungal activity against C. albicans.

  6. Microstructures and Mechanical Performance of Plasma-Nitrided Al0.3CrFe1.5MnNi0.5 High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Tang, Wei-Yeh; Chuang, Ming-Hao; Lin, Su-Jien; Yeh, Jien-Wei

    2012-07-01

    This study investigates the effect of plasma nitriding at 798 K (525 °C) on microstructures and the mechanical performance of Al0.3CrFe1.5MnNi0.5 high-entropy alloys (HEAs) obtained using different cast and wrought processing. All the alloys can be well nitride, with a thickness of around 80 μm, and attain a peak hardness level around Hv 1300 near the surface. The main nitride phases are CrN, AlN, and (Mn, Fe)4N. Those of the substrates are bcc, fcc, Al-, and Ni-rich B2 precipitates, and ρ phase. Their relative amounts depend on the prior processing and also change under the heat treatment during nitriding. The formation of ρ phase during nitriding could in-situ harden the substrate to attain the suitable level required for wear applications. This gives the advantage in simplifying the processing for making a wear-resistance component or a mold since austenitizing, quench hardening, and tempering required for steels such as SACM and SKD steels are no longer required and final finishing can be accomplished before nitriding. Nitrided Al0.3CrFe1.5MnNi0.5 samples have much better wear resistance than un-nitrided ones by 49 to 80 times and also exhibit superior adhesive wear resistance to conventional nitrided alloys: nitriding steel SACM-645 (AISI 7140), 316 stainless steel, and hot-mold steel SKD-61 (AISI H13) by 22 to 55 times depending on prior processing. The superiority is due to the fact that the present nitrided alloys possess a much thicker highly hardened layer than the conventional alloys.

  7. Synthesis and characterization of (smif)2M(n) (n = 0, M = V, Cr, Mn, Fe, Co, Ni, Ru; n = +1, M = Cr, Mn, Co, Rh, Ir; smif =1,3-di-(2-pyridyl)-2-azaallyl).

    PubMed

    Frazier, Brenda A; Bartholomew, Erika R; Wolczanski, Peter T; DeBeer, Serena; Santiago-Berrios, Mitk'El; Abruña, Hector D; Lobkovsky, Emil B; Bart, Suzanne C; Mossin, Susanne; Meyer, Karsten; Cundari, Thomas R

    2011-12-19

    A series of Werner complexes featuring the tridentate ligand smif, that is, 1,3-di-(2-pyridyl)-2-azaallyl, have been prepared. Syntheses of (smif)(2)M (1-M; M = Cr, Fe) were accomplished via treatment of M(NSiMe(3))(2)(THF)(n) (M = Cr, n = 2; Fe, n = 1) with 2 equiv of (smif)H (1,3-di-(2-pyridyl)-2-azapropene); ortho-methylated ((o)Mesmif)(2)Fe (2-Fe) and ((o)Me(2)smif)(2)Fe (3-Fe) were similarly prepared. Metatheses of MX(2) variants with 2 equiv of Li(smif) or Na(smif) generated 1-M (M = Cr, Mn, Fe, Co, Ni, Zn, Ru). Metathesis of VCl(3)(THF)(3) with 2 Li(smif) with a reducing equiv of Na/Hg present afforded 1-V, while 2 Na(smif) and IrCl(3)(THF)(3) in the presence of NaBPh(4) gave [(smif)(2)Ir]BPh(4) (1(+)-Ir). Electrochemical experiments led to the oxidation of 1-M (M = Cr, Mn, Co) by AgOTf to produce [(smif)(2)M]OTf (1(+)-M), and treatment of Rh(2)(O(2)CCF(3))(4) with 4 equiv Na(smif) and 2 AgOTf gave 1(+)-Rh. Characterizations by NMR, EPR, and UV-vis spectroscopies, SQUID magnetometry, X-ray crystallography, and DFT calculations are presented. Intraligand (IL) transitions derived from promotion of electrons from the unique CNC(nb) (nonbonding) orbitals of the smif backbone to ligand π*-type orbitals are intense (ε ≈ 10,000-60,000 M(-1)cm(-1)), dominate the UV-visible spectra, and give crystals a metallic-looking appearance. High energy K-edge spectroscopy was used to show that the smif in 1-Cr is redox noninnocent, and its electron configuration is best described as (smif(-))(smif(2-))Cr(III); an unusual S = 1 EPR spectrum (X-band) was obtained for 1-Cr.

  8. First-order magnetic and magnetostructural transitions in the magnetocaloric compound MnNi0.73Fe0.27Ge

    NASA Astrophysics Data System (ADS)

    Sun, Aili; Liu, Jinghua; Jiang, Chengbao; Liu, Enke; Wu, Guangheng

    2015-10-01

    Magnetic and magnetostructural transitions of MnNi0.73Fe0.27Ge have been studied by calorimetry and by magnetic measurements. The first-order MST from paramagnetic to ferromagnetic martensite shows a giant magnetic entropy change of -27 J/kg K for a magnetic-field change of 50 kOe around 233 K. A weak first-order magnetic transition is observed in the martensite phase over a large low-temperature range, with clear thermal hysteresis and increased saturation field. The origin is discussed on the basis of the competitiom between ferromagnetic and antiferromagnetic coupling with magneto-elastic coupling.

  9. Microstructure and room-temperature mechanical properties of Fe{sub 30}Ni{sub 20}Mn{sub 35}Al{sub 15}

    SciTech Connect

    Liao Yifeng; Baker, Ian

    2008-11-15

    A novel alloy with nominal composition Fe{sub 30}Ni{sub 20}Mn{sub 35}Al{sub 15} was prepared by arc melting. Secondary electron microscopy and transmission electron microscopy examinations showed that it had a eutectoid structure, consisting of alternating FCC and B2 lamellae, whose widths were {approx} 500 nm and {approx} 200 nm, respectively. The room-temperature yield strength and Vickers hardness of the as-cast alloy were 740 {+-} 30 MPa and HV310 {+-} 15, respectively, and the alloy exhibited {approx} 8% elongation under tension.

  10. A Novel Training-Free Processed Fe-Mn-Si-Cr-Ni Shape Memory Alloy Undergoing δ → γ Phase Transformation

    NASA Astrophysics Data System (ADS)

    Peng, Huabei; Wang, Gaixia; Du, Yangyang; Wang, Shanling; Chen, Jie; Wen, Yuhua

    2016-07-01

    We not only suppress the formation of twin boundaries but also introduce a high density of stacking faults by taking advantage of δ → γ phase transformation in a processed Fe-19.38Mn-5.29Si-8.98Cr-4.83Ni shape memory alloy. As a result, its shape memory effect is remarkably improved after heating at 1533 K (1260 °C) (single-phase region of δ ferrite) and air cooling due to δ → γ phase transformation.

  11. Assessment of heavy metal (Cu, Ni, Fe, Co, Mn, Cr, Zn) pollution in effluent dominated rivulet water and their effect on glycogen metabolism and histology of Mastacembelus armatus.

    PubMed

    Javed, Mehjbeen; Usmani, Nazura

    2013-01-01

    The present study was conducted to examine the contamination of rivulet situated at Kasimpur, Aligarh (27.218° N; 79.378° E). It receives the wastewater of Harduaganj Thermal Power Plant (HTPS) containing fly ash and heavy metals. Among the heavy metals estimated in the rivulet water, Fe (8.71 mgL(-1)) was present in the highest concentration followed by Cu (0.86 mgL(-1)), Zn (0.30 mgL(-1)) Mn (0.21 mgL(-1)), Ni (0.12 mgL(-1)), Co (0.11 mgL(-1)) and Cr (0.10 mgL(-1)). The values for the heavy metals such as Fe, Ni and Mn were beyond the limits set by UNEPGEMS. Bioaccumulation of these heavy metals was detected in tissues such as gills, liver, kidney, muscle and integument of the fish Mastacembelus armatus. Accumulation of Fe (213.29 - 2601.49 mgkg(-1).dw) was highest in all the organs. Liver was the most influenced organ and integument had the least metal load. The accumulation of Fe, Zn, Cu and Mn, observed in the tissues were above the values recommended by FAO/WHO. Biochemical estimation related to blood glucose, liver and muscle glycogen conducted showed significant (p < 0.01) elevation in blood glucose content over control (17.73%), whereas liver glycogen dropped significantly (p < 0.01) over control (-89.83%), and similarly muscle glycogen also decreased significantly (p < 0.05) over control (-71.95%), suggesting enhanced glycolytic capacity to fuel hepatic metabolism. Histopathological alterations were also observed in selected organs (gills, liver and kidney) of Mastacembelus armatus.

  12. Low hysteresis FeMn-based top spin valve.

    PubMed

    Ustinov, V V; Krinitsina, T P; Milyaev, M A; Naumova, L I; Proglyado, V V

    2012-09-01

    FeMn-based top spin valves Ta/[FeNi/CoFe]/Cu/CoFe/FeMn/Ta with different Cu and FeMn layers thicknesses were prepared by DC magnetron sputtering at room temperature. It was shown that low field hysteresis due to free layer magnetization reversal can be reduced down to (0.1 divided by 0.2) Oe keeping the GMR ratio higher 8% by using both layers thicknesses optimization and non-collinear geometry of magnetoresistance measurements. Dependence of low field hysteresis and GMR ratio on the angle between applied magnetic field and pinning direction are presented.

  13. High power factor in thiospinels Cu2 T r Ti3S8 ( T r = Mn, Fe, Co, Ni) arising from TiS6 octahedron network

    NASA Astrophysics Data System (ADS)

    Hashikuni, Katsuaki; Suekuni, Koichiro; Usui, Hidetomo; Ohta, Michihiro; Kuroki, Kazuhiko; Takabatake, Toshiro

    2016-10-01

    Thermoelectric properties and electronic structures of n-type thiospinels Cu2T r Ti3S8 composed of CuS4 tetrahedron and (Tr/Ti)S6 octahedron network have been studied for T r = Mn, Fe, Co, and Ni. The samples with T r = Mn, Co, and Ni exhibit metallic behaviors in the electrical resistivity (ρ) and rather large and negative thermopower (S), leading to a high power factor (S2/ρ) of 0.4-0.6 mW/K2 m at 650 K. In addition to the superior electrical properties, relatively low thermal conductivity of ˜2 W/Km gives rise to a dimensionless figure of merit ZT reaching 0.16-0.18 at 650 K. The analysis of the temperature dependent magnetic susceptibility indicates that the Mn, Fe, and Ni ions are in high-spin divalent states while the Co2+ ion is in a low-spin nonmagnetic state. This electronic state for the Co2+ in Cu2CoTi3S8 is consistent with our first-principles electronic structure calculation indicating that the Fermi level lies in the conduction bands composed mainly of Ti-3d, Co-3d, and S-3p orbitals. The Ti-3d and S-3p orbitals forming the octahedron network likely results in high power factors irrespective of Tr elements. The addition of Co-3d orbitals makes a peak with steep slope in the density of states near the Fermi level, leading to the further enhanced power factor.

  14. Ternary titanium transition metal bismuthides Ti{sub 4}TBi{sub 2} with T = Cr, Mn, Fe, Co, and Ni

    SciTech Connect

    Richter, C.G.; Jeitschko, W.; Kuennen, B.; Gerdes, M.H.

    1997-11-01

    The title compounds were prepared by reaction of the elemental components and with the exception of the isotypic chromium compound their tetragonal V{sub 4}SiSb{sub 2}-type crystal structures (I4/mcm, Z = 4) were determined and refined from single-crystal X-ray data. Ti{sub 4}CrBi{sub 2}: a = 1051.6(l), c = 506.7(1) pm; Ti{sub 4}Mn Bi{sub 2}: a = 1049.1 (1), c = 497.8 (1) pm, R = 0.031 for 176 structure factors; Ti{sub 4}FeBi{sub 2}: a = 1048.6(1), c = 493.3(1) pm, R = 0.013 (274 F values); Ti{sub 4}CoBi{sub 2}: a = 1050.6(2), c = 488.2(1) pm, R = 0.038 (472 F values); Ti{sub 4}NiBi{sub 2}: a = 1055.4(1), c = 481.4(1) pm, R = 0.020(373 F values), and 14 variable parameters each. The compounds are isotypic with V{sub 4}SiSb{sub 2}, a structure which is isopointal with U{sub 6}Mn and closely related to the structures of W{sub 5}Si{sub 3} and TlTe. All atoms have high coordination numbers. Unusual features of the structure are channels formed solely by the bismuth atoms and linear chains of the heavier transition metal ions with bond distances varying between 253.3 (Cr-Cr) and 240.7 pm (Ni-Ni). The electrical conductivities of Ti{sub 4}TBi{sub 2} (T= Fe,Co, Ni)--determined with a four-probe technique for sintered polycrystalline samples between 4 K and room temperature--indicate metallic behavior. The magnetic susceptibilities of the five compounds were determined with a SQUID magnetometer. Ti{sub 4}CrBi{sub 2}, T{sub i}4FeBi{sub 2}, and Ti{sub 4}NiBi{sub 2} are Pauli paramagnetic. The magnetic susceptibilities of Ti{sub 4}MnBi{sub 2} and Ti{sub 4}CoBi{sub 2} are strongly temperature dependent. The evaluation of these data according to a modified Curie-Weiss law suggests that both compounds contain one unpaired electron per formula unit. A brief discussion of chemical bonding in these compounds leads to the conclusion that considerable Ti-Ti bonding must be present in these bismuthides, in spite of the fact that the shortest Ti-Ti bonds are as long as 299 pm.

  15. Neutrino energy spectrum and electron capture of Nuclides 56Fe, 56Co, 56Ni, 56Mn, 56Cr and 56V in stellar interiors

    NASA Astrophysics Data System (ADS)

    Liu, Jing-Jing

    2014-08-01

    Based on the shell-model Monte Carlo method and random phase approximation theory, the neutrino energy spectrum (NES) and the electron capture (EC) of 56Fe 56Co 56Ni, 56Mn, 56Cr and 56V are investigated in presupernova surroundings. The results show that the EC rates are affected greatly at different densities and temperatures. The rates increase greatly and even exceed six orders of magnitude at lower temperature. On the other hand, the NES is very sensitive to stellar temperature and electron energy. The higher the temperature and the lower the electron energy, the larger the influence on NES is. For example, the maxima of NES in the ground state are 9.02, 160, 80, 24.01, 0.44, 1.42 me c2 for 56Fe, 56Co, 56Ni, 56Mn, 56Cr and 56V respectively at ρ7 = 10.7, Ye = 0.45 and T9 = 15. Furthermore, the influence on NES due to EC for different nuclei has some otherness because of different Q0-values. For example, the spectrum of 56Co shows a double bump structure.

  16. Concentrations of Mn, Fe, Cu, Zn, Cr, Cd, Pb, Ni in selected Nigerian tubers, legumes and cereals and estimates of the adult daily intakes.

    PubMed

    Akinyele, I O; Shokunbi, O S

    2015-04-15

    This study was designed to determine the levels of microminerals (manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), chromium (Cr)) and heavy metals (cadmium (Cd), lead (Pb) and nickel (Ni)) in some tubers, legumes and cereals obtained from the markets in Abeokuta city, South-West Nigeria. The food samples were digested by dry ashing procedure and their minerals were determined by atomic absorption spectrophotometer. The results show mean values of 1.67-32.00, 7.25-61.58, 1.59-10.56, 6.65-46.99, 0.02-0.58, <0.01-0.09, <0.08, and 0.06-0.14 mg/kg for Mn, Fe, Cu, Zn, Cr, Cd, Pb and Ni respectively. The levels of these metals in all the samples analysed were within the ranges reported for similar tubers, legumes and cereals from various parts of the world. The daily intakes of the metals through tubers, legumes and cereals were found to be lower than the provisional tolerable daily intakes proposed by Joint FAO/WHO Expert Committee on Food Additives.

  17. Effect of Ti content on the microstructure and mechanical behavior of (Fe36Ni18Mn33Al13)100–xTix high entropy alloys

    DOE PAGES

    Wang, Zhangwei; Wu, Margaret; Cai, Zhonghou; ...

    2016-06-13

    The microstructure and mechanical properties studies of a series of two-phase f.c.c./B2 (ordered b.c.c.) lamellar-structured, high entropy alloys (HEA) Fe36Ni18Mn33Al13Tix with x up to 6 at. % Ti have been investigated. X-ray microanalysis in a TEM showed that the Ti resided mostly in the B2 phase. The lamellar spacing decreased significantly with increasing Ti content from 1.56 μm for the undoped alloy to 155 nm with an addition of 4 at. % Ti, leading to a sharp increase in room-temperature yield strength,σy, from 270 MPa to 953 MPa, but with a concomitant decrease in ductility from 22% elongation to 2.3%.more » Annealing at 1173 K for 20 h greatly increased the lamellar spacing of Fe36Ni18Mn33Al13Ti4 to 577 nm, producing a corresponding decrease in σy to 511 MPa. The yield strengths of all the doped alloys decreased significantly when tensile tested at 973 K with a concomitant increase in ductility due to softening of the B2 phase. The fracture mode changed from cleavage at room temperature to a ductile dimple-type rupture at 973 K. Lastly, the results are discussed in terms of the Hall-Petch-type relationship.« less

  18. Field dependence of the dynamic properties of colloidal suspensions of Mn 0.66Zn 0.34Fe 2O 4 and Ni 0.5Zn 0.5Fe 2O 4 particles

    NASA Astrophysics Data System (ADS)

    Fannin, P. C.; Charles, S. W.; Dormann, J. L.

    1999-07-01

    Results of the magnetic field dependence of the complex susceptibility, of colloidal suspensions of Mn 0.66Zn 0.34Fe 2O 4 and Ni 0.5Zn 0.5Fe 2O 4 particles in a polarising magnetic field, H, covering the range 0-116 kA m -1 are presented. Ferromagnetic resonance is observed for both samples and from plots of the dependence of the resonant frequency fres on polarising field, average values of anisotropy field, H¯A, and anisotropy constant, K¯, are determined. In the case of the Ni 0.5Zn 0.5Fe 20 4 sample the variation in the ferromagnetic linewidth as a function of increasing polarising field shows a steady monotonic increase in contrast to that of the manganese zinc ferrite sample. This effect is attributed to the influence of the polarising field on the local canted structure.

  19. Experimental study of the microscopic mechanisms of magnetization reversal in FeNi/FeMn exchange-biased ferromagnet/antiferromagnet polycrystalline bilayers using the magneto-optical indicator film technique

    NASA Astrophysics Data System (ADS)

    Gornakov, V. S.; Kabanov, Yu. P.; Tikhomirov, O. A.; Nikitenko, V. I.; Urazhdin, S. V.; Yang, F. Y.; Chien, C. L.; Shapiro, A. J.; Shull, R. D.

    2006-05-01

    Remagnetization of the FeNi/FeMn bilayer was investigated using the magneto-optical indicator film imaging technique. We show the formation and breakdown of the homogeneous exchange spring into exchange springs of opposite chiralities during reversal in a rotating magnetic field. In reversal with a linear field, contrary to theoretical predictions, the winding of the exchange spring occurs without net magnetization rotation. It initiates by the formation of local spin spirals with opposite chirality and terminates with the formation of a single chiral state through the propagation of a specific kind of boundary separating regions with this single chirality from those with the mixed chiral state.

  20. Ageing behaviour of an Fe-20Ni-1.8Mn-1.6Ti-0.59Al (wt%) maraging alloy: clustering, precipitation and hardening

    SciTech Connect

    Pereloma, E.V. . E-mail: elena.pereloma@spme.monash.edu.au; Shekhter, A.; Miller, M.K.; Ringer, S.P.

    2004-11-08

    Changes in the solute distribution as well as the evolution of precipitation, microstructure and mechanical properties have been studied in an experimental maraging Fe-20Ni-1.8Mn-1.5Ti-0.59Al (wt%) alloy during ageing at 550 deg C. An initial hardening reaction within 5 s is reported, which is remarkable in terms of extent and rapidity. This strengthening was caused by the formation of complex multi-component atomic co-clusters containing primarily Ni-Ti-Al as well as some Mn. This cluster strengthened condition produced the optimum toughness observed throughout the ageing sequence. After 60 s ageing, the appearance of discrete precipitation of needle-shaped {eta}-Ni{sub 3}Ti particles was associated with a second rise in hardness towards an eventual peak at 600 s. This precipitation hardening was accompanied by an increase in tensile strength and a decrease in ductility. A reverse transformation of martensite to austenite occurs progressively during ageing and this contributes to the initial and secondary softening.

  1. Ab initio study of MF2 (M=Mn, Fe, Co, Ni) rutile-type compounds using the periodic unrestricted Hartree-Fock approach

    NASA Astrophysics Data System (ADS)

    de P. R. Moreira, Ibério; Dovesi, Roberto; Roetti, Carla; Saunders, Victor R.; Orlando, Roberto

    2000-09-01

    The ab initio periodic unrestricted Hartree-Fock method has been applied in the investigation of the ground-state structural, electronic, and magnetic properties of the rutile-type compounds MF2 (M=Mn, Fe, Co, and Ni). All electron Gaussian basis sets have been used. The systems turn out to be large band-gap antiferromagnetic insulators; the optimized geometrical parameters are in good agreement with experiment. The calculated most stable electronic state shows an antiferromagnetic order in agreement with that resulting from neutron scattering experiments. The magnetic coupling constants between nearest-neighbor magnetic ions along the [001], [111], and [100] (or [010]) directions have been calculated using several supercells. The resulting ab initio magnetic coupling constants are reasonably satisfactory when compared with available experimental data. The importance of the Jahn-Teller effect in FeF2 and CoF2 is also discussed.

  2. Mechanism of Fluorescence Enhancement of Biosynthesized XFe2O4-BiFeO3 (X = Cr, Mn, Co, or Ni) Membranes

    NASA Astrophysics Data System (ADS)

    Bian, Liang; Li, Hai-long; Dong, Hai-liang; Dong, Fa-qin; Song, Mian-xin; Wang, Li-sheng; Hou, Wen-ping; Gao, Lei; Zhang, Xiao-yan; Zhou, Tian-liang; Sun, Guang-ai; Li, Xin-xi; Xie, Lei

    2016-12-01

    Ferrites-bismuth ferrite is an intriguing option for medical diagnostic imaging device due to its magnetoelectric and enhanced near-infrared fluorescent properties. However, the embedded XFO nanoparticles are randomly located on the BFO membranes, making implementation in devices difficult. To overcome this, we present a facile bio-approach to produce XFe2O4-BiFeO3 (XFO-BFO) (X = Cr, Mn, Co, or Ni) membranes using Shewanella oneidensis MR-1. The perovskite BFO enhances the fluorescence intensity (at 660 and 832 nm) and surface potential difference (-469 385 meV and -80 525 meV) of the embedded spinel XFO. This mechanism is attributed to the interfacial coupling of the X-Fe (e- or h+) and O-O (h+) interfaces. Such a system could open up new ideas in the design of environmentally friendly fluorescent membranes.

  3. Spectra-structure correlation based study of complex molecules of 1-isonicotinoyl-3-thiosemicarbazide with Ni2+, Mn2+ and Fe3+ using Raman, UV-visible and DFT techniques

    NASA Astrophysics Data System (ADS)

    Gautam, Priyanka; Prakash, Om; Dani, R. K.; Bharty, M. K.; Singh, N. K.; Singh, Ranjan K.

    2017-01-01

    In present work, we have analysed the structural property of newly synthesized ligand and its coordination complex molecules with Ni2+, Mn2+ and Fe3+. The spectroscopic techniques UV-visible, IR, Raman and DFT methods are used. The newly synthesized ligand 1-isonicotinoyl-3-thiosemicarbazide (Hintsc) has supramolecular architecture stabilized through various intermolecular interactions viz. Nsbnd H⋯O, Csbnd H⋯O, Csbnd H⋯N, Nsbnd H⋯S and Csbnd H⋯S type hydrogen bonds as observed in the single crystal of the ligand. The single crystals of the complexes could not be obtained with high degree of homogeneity from the solutions therefore plausible geometry of the complexes have been proposed on the basis of Raman spectroscopy, UV-visible and DFT methods and coordination properties of Ni2+, Mn2+ and Fe3+ with ligand (Hintsc). The ligand Hintsc contains the thiosemicarbazide (TSC) moiety through which Ni2+, Mn2+ and Fe3+ metals are coordinated. Raman spectroscopy is used to investigate the binding of Ni2+, Mn2+ and Fe3+ with ligand (Hintsc). In Raman spectra, the disappearance of Nsbnd H bending/ Nsbnd H stretching and lower wavenumber region Raman spectra clearly confirms that Ni2+ and Mn2+ metals are coordinated through sbnd N3 and sbnd O sites of thiosemicarbazide (TSC) and consequently formed the chelate ring {C6sbnd N2sbnd N3sbnd Msbnd O}, where Mdbnd Ni2+ and Mn2+. In Fe complex, Fe3+ is coordinated through sbnd N2 and sbnd S sites of TSC and formed the chelate ring {C7sbnd N3sbnd N2sbnd Fesbnd S}. The structural and molecular property of 1-isonicotinoyl-3-thiosemicarbazide (Hintsc) and its complexes with transition metals Ni2+, Mn2+, Fe3+ have also been studied by DFT technique. By means of UV-visible, Raman spectroscopy and DFT technique, it is found that Ni2+, Mn2+ and Fe3+ exhibit the octahedral coordination property with 1-isonicotinoyl-3-thiosemicarbazide (Hintsc).

  4. Structural, EPR and optical properties of Zn0.75TM0.25O (TM = Mn, Fe, Co, Ni) aerogel nanoparticles

    NASA Astrophysics Data System (ADS)

    Sayari, Amor; El Mir, Lassaad; Jürgen von Bardeleben, Hans

    2014-07-01

    ZnO nanopowders with different 3d transition metal (TM) doping (TM = Mn, Fe, Co, Ni) were synthesized by a new protocol based on slow hydrolyse of zinc acetate dissolved in methanol and supercritical drying in ethyl alcohol. The prepared Zn1-xTMxO (x = 0.25) nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), optical absorption and electron paramagnetic resonance spectroscopy (EPR). The results demonstrated that the TM dopant significantly affects the structural and magnetic properties of the samples. From the XRD spectra, the lattice parameters, average crystallite size and microstrain values were obtained. All ZnTMO nanoparticles show an expansion of the lattice parameters compared those of the bulk samples. Unit cell volume was minimized with Fe doping and increased as the atomic number of the dopant moved away from Fe. The XRD pattern indicates the formation of hexagonal wurtzite phase of ZnO for all the TM dopants. Electron microscopy characterization showed that the size of the Zn1-xTMxO particles is about 25 nm did not change significantly for the different dopants. Optical absorption measurements show that band gap energies of the TM-doped ZnO nanoparticles are around 3.2 eV. The Urbach energy of the ZnTMO nanopowders varies with the TM dopant. From magnetic measurements we observed the presence of room temperature ferromagnetic order in our TM-doped ZnO samples. EPR spectra confirm that TM ions were mainly incorporated as TM2+, occupying the Zn2+ sites in the wurtzite structure of ZnO. Room temperature ferromagnetic order was observed only in Ni- and Co-doped ZnO samples, whereas Mn- and Fe-doped powders showed only antiferromagnetic and paramagnetic interactions, respectively. The correlation between the structural and magnetic properties as a function of the TM dopant is discussed.

  5. Effect of H2O on metal-silicate partitioning of Ni, Co, V, Cr, Mn and Fe: Implications for the oxidation state of the Earth and Mars

    NASA Astrophysics Data System (ADS)

    Clesi, V.; Bouhifd, M. A.; Bolfan-Casanova, N.; Manthilake, G.; Fabbrizio, A.; Andrault, D.

    2016-11-01

    This study investigates the metal-silicate partitioning of Ni, Co, V, Cr, Mn and Fe during core mantle differentiation of terrestrial planets under hydrous conditions. For this, we equilibrated a molten hydrous CI chondrite model composition with various Fe-rich alloys in the system Fe-C-Ni-Co-Si-S in a multi-anvil over a range of P, T, fO2 and water content (5-20 GPa, 2073-2500 K, from 1 to 5 log units below the iron-wüstite (IW) buffer and for XH2O varying from 500 ppm to 1.5 wt%). By comparing the present experiments with the available data sets on dry systems, we observes that the effect of water on the partition coefficients of moderately siderophile elements is only moderate. For example, for iron we observed a decrease in the partition coefficient of Fe (Dmet/silFe) from 9.5 to 4.3, with increasing water content of the silicate melt, from 0 to 1.44 wt%, respectively. The evolution of metal-silicate partition coefficients of Ni, Co, V, Cr, Mn and Fe are modelled based on sets of empirical parameters. These empirical models are then used to refine the process of core segregation during accretion of Mars and the Earth. It appears that the likely presence of 3.5 wt% water on Mars during the core-mantle segregation could account for ∼74% of the FeO content of the Martian mantle. In contrast, water does not play such an important role for the Earth; only 4-6% of the FeO content of its mantle could be due to the water-induced Fe-oxidation, for a likely initial water concentration of 1.8 wt%. Thus, in order to reproduce the present-day FeO content of 8 wt% in the mantle, the Earth could initially have been accreted from a large fraction (between 85% and 90%) of reducing bodies (similar to EH chondrites), with 10-15% of the Earth's mass likely made of more oxidized components that introduced the major part of water and FeO to the Earth. This high proportion of enstatite chondrites in the original constitution of the Earth is consistent with the 17O,48Ca,50Ti,62Ni

  6. Rapid Microwave-Assisted Solvothermal Synthesis of Non-Olivine Cmcm Polymorphs of LiMPO4 (M = Mn, Fe, Co, and Ni) at Low Temperature and Pressure.

    PubMed

    Assat, Gaurav; Manthiram, Arumugam

    2015-10-19

    Lithium transition-metal phosphates, LiMPO4 (M = Mn, Fe, Co, and Ni), have attracted significant research interest over the past two decades as an important class of lithium ion battery cathode materials. However, almost all of the investigations thus far have focused on the olivine polymorph that exists in the orthorhombic Pnma space group. In this study, a distinct orthorhombic but non-olivine polymorph of LiMPO4, described by a Cmcm space group symmetry, has been synthesized with M = Mn, Fe, Co, and Ni. Of these, LiMnPO4 in the Cmcm space group is reported for the first time. A rapid microwave-assisted solvothermal (MW-ST) heating process with tetraethylene glycol (TEG) as the solvent and transition-metal oxalates as precursors facilitates the synthesis of these materials. The peak reaction temperatures and pressures were below 300 °C and 30 bar, respectively, which are several orders of magnitude lower than those of the previously reported high-pressure (gigapascals) method. X-ray diffraction (XRD) confirms the crystal structure with the Cmcm space group, and scanning electron micrographs indicate a submicrometer thin platelet-like morphology. The synthesis process conditions have been optimized to obtain impurity-free samples with the correct stoichiometry, as characterized by XRD and inductively coupled plasma-optical emission spectroscopy (ICP-OES). Upon heat treatment to higher temperatures, an irreversible transformation of the metastable Cmcm polymorphs into olivine is observed by XRD and Fourier transform infrared spectroscopy. Although the electrochemical activity of these polymorphs as lithium ion cathodes turns out to be poor, the facile synthesis under mild conditions has permitted easy access to these materials in a nanomorphology, some of which were not even possible before.

  7. A comparative study on electrochemical cycling stability of lithium rich layered cathode materials Li1.2Ni0.13M0.13Mn0.54O2 where M = Fe or Co

    NASA Astrophysics Data System (ADS)

    Laisa, C. P.; Nanda Kumar, A. K.; Selva Chandrasekaran, S.; Murugan, P.; Lakshminarasimhan, N.; Govindaraj, R.; Ramesha, K.

    2016-08-01

    In this work we compare electrochemical cycling stability of Fe containing Li rich phase Li1.2Ni0.13Fe0.13Mn0.54O2 (Fe-Li rich) with the well-known Co containing Li rich composition Li1.2Ni0.13Co0.13Mn0.54O2 (Co-Li rich). During the first charge, the activation plateau corresponding to removal of Li2O from the structure is smaller (removal of 0.6 Li) in the case of Fe-Li rich compared to Co-Li rich composition (0.8 Li removal). Consequently, the Fe compound shows better capacity retention; for example, after 100 cycles Fe-Li rich compound exhibits 20% capacity degradation where as it is about 40% in the case of Co-Li rich phase. The electrochemical and microscopy studies support the fact that compared to Co-Li rich compound, the Fe-Li rich composition display smaller voltage decay and reduced spinel conversion. XPS studies on charged/discharged Fe-Li rich samples show participation of Fe+3/Fe+4 redox during electrochemical cycling which is further supported by our first principles calculations. Also the temperature dependent magnetic studies on charge-discharged samples of Fe-Li rich compound point out that magnetic behavior is sensitive to cation oxidation states and Ni/Li disorder.

  8. Electronic, magnetic and spectroscopic properties of doped Mn(1-x) A x WO4 (A  =  Co, Cu, Ni and Fe) multiferroic: an experimental and DFT study

    NASA Astrophysics Data System (ADS)

    Mal, Priyanath; Bera, G.; Rambabu, P.; Turpu, G. R.; Chakraborty, Brahmananda; Ramaniah, Lavanya M.; Singh, R. P.; Sen, Pintu; Das, Pradip

    2017-02-01

    The influence of dopants (Co, Cu, Fe and Ni) on the optical, electronic and magnetic properties of multiferroic MnWO4 was studied using Raman spectroscopy, ultraviolet-visible spectroscopy (UV-Vis), magnetization measurements and density functional theory (DFT) calculations. The evolution of Raman spectra with different elemental substitutions at the Mn site was also studied, where the peak width increased with doping of higher mass elements (Co, Cu, Fe and Ni). UV-Vis diffuse reflectance spectroscopy on polycrystalline Mn(1-x) A x WO4 (A  =  Co, Cu, Fe and Ni) (0  ⩽  x   ⩽  0. was performed. The evaluated electronic band gap decreasing with successive Co, Cu and Fe doping reflected the lower ionic radius of the substituted element, and for Ni-doped MnWO4 the band gap increased slightly compared to the parent MnWO4. Bader charge transfer and a partial density of states (PDOS) analysis from DFT simulations predict the appearance of impurity states in the band gap region (of pure MnWO4) from the d orbital of the dopant (Co, Cu and Fe) hybridized with the p orbital of the bonded O atoms due to charge transfer from O to the dopant, and reduced the band gap of Co, Cu and Fe-doped MnWO4. On the other hand, for Ni-doped MnWO4 strong W-O hybridization occurring due to large charge transfer from oxygen to tungsten leads to an increase in the band gap. The band gap, computed using the GGA  +  U method, is close to the experimental value. The signature of the d-d transition observed in the UV spectra is explained in terms of the crystal field stabilization energy caused by the octahedral distortion present in the lattice. Three different antiferromagnetic phases (AF1, AF2 and AF3) are identified in MnWO4 and also for the Co (18.75%)-doped sample. For Cu-doped samples, suppression of the AF1 phase and stabilization of the AF2 phase is observed up to 2 K. Successive doping of Cu leads to the diminution of magnetic frustration. A new

  9. Electronic, magnetic and spectroscopic properties of doped Mn(1-x) A x WO4 (A  =  Co, Cu, Ni and Fe) multiferroic: an experimental and DFT study.

    PubMed

    Mal, Priyanath; Bera, G; Rambabu, P; Turpu, G R; Chakraborty, Brahmananda; Ramaniah, Lavanya M; Singh, R P; Sen, Pintu; Das, Pradip

    2017-02-22

    The influence of dopants (Co, Cu, Fe and Ni) on the optical, electronic and magnetic properties of multiferroic MnWO4 was studied using Raman spectroscopy, ultraviolet-visible spectroscopy (UV-Vis), magnetization measurements and density functional theory (DFT) calculations. The evolution of Raman spectra with different elemental substitutions at the Mn site was also studied, where the peak width increased with doping of higher mass elements (Co, Cu, Fe and Ni). UV-Vis diffuse reflectance spectroscopy on polycrystalline Mn(1-x) A x WO4 (A  =  Co, Cu, Fe and Ni) (0  ⩽  [Formula: see text]  ⩽  0. was performed. The evaluated electronic band gap decreasing with successive Co, Cu and Fe doping reflected the lower ionic radius of the substituted element, and for Ni-doped MnWO4 the band gap increased slightly compared to the parent MnWO4. Bader charge transfer and a partial density of states (PDOS) analysis from DFT simulations predict the appearance of impurity states in the band gap region (of pure MnWO4) from the d orbital of the dopant (Co, Cu and Fe) hybridized with the p orbital of the bonded O atoms due to charge transfer from O to the dopant, and reduced the band gap of Co, Cu and Fe-doped MnWO4. On the other hand, for Ni-doped MnWO4 strong W-O hybridization occurring due to large charge transfer from oxygen to tungsten leads to an increase in the band gap. The band gap, computed using the GGA  +  U method, is close to the experimental value. The signature of the d-d transition observed in the UV spectra is explained in terms of the crystal field stabilization energy caused by the octahedral distortion present in the lattice. Three different antiferromagnetic phases (AF1, AF2 and AF3) are identified in MnWO4 and also for the Co (18.75%)-doped sample. For Cu-doped samples, suppression of the AF1 phase and stabilization of the AF2 phase is observed up to 2 K. Successive doping of Cu leads to the diminution of magnetic

  10. Influence of Na+, K+, Mn2+, Fe2+ and Zn2+ ions on the electrodeposition of Ni-Co alloys: Implications for the recycling of Ni-MH batteries

    NASA Astrophysics Data System (ADS)

    Blanco, S.; Orta-Rodriguez, R.; Delvasto, P.

    2017-01-01

    A hydrometallurgical recycling procedure for the recovery of a mixed rare earths sulfate and an electrodeposited Ni-Co alloy has been described. The latter step was found to be complex, due to the presence of several ions in the battery electrode materials. Electrochemical evaluation of the influence of the ions on the Ni-Co alloy deposition was carried out by cyclic voltammetry test. It was found that ions such as K+, Fe2+ and Mn2+ improved the current efficiency for the Ni-Co deposition process on a copper surface. On the other hand, Na+ and Zn2+ ions exhibited a deleterious behaviour, minimizing the values of the reduction current. The results were used to suggest the inclusion of additional steps in the process flow diagram of the recycling operation, in order to eliminate deleterious ions from the electroplating solution.

  11. Molten Pool Behavior and Mechanical Properties of Pulsed Current Double-Sided Synchronization GTA Welded Fe-18Cr-17Mn-Ni-N

    NASA Astrophysics Data System (ADS)

    Qiang, Wei; Wang, Kehong; Feng, Yuehai; Chen, Jiahe

    2016-12-01

    Double-sided synchronization vertical gas tungsten arc welding (DSSVW) procedure was used to weld high-nitrogen low-nickel stainless steel Fe-18Cr-17Mn-Ni-N without groove and filler wire. First, the molten pool behaviors and appearances of pulsed current DSSVW (PC-DSSVW) and constant current DSSVW (CC-DSSVW) were comparatively analyzed. The periodic variation occurs in the width of both the anode region of the arc and the molten pool tail during PC-DSSVW, while the contact angle first increases and then decreases, and both the width of the anode region and the length of arc plume increase progressively in CC-DSSVW. It is found that the weld appearance of PC-DSSVW is superior to that of CC-DSSVW. Second, the forces of the DSSVW molten pool were analyzed. The result indicates that the molten pool of the DSSVW procedure is in a state of unstable equilibrium, and it will easily lose balance after being disturbed, resulting in the asymmetrical weld or hump bead. Third, the PC-DSSVW experiments at various welding speeds were conducted to study the influence of welding speed on the weld profile, microstructure, tensile strength and impact toughness. Furthermore, the solidification mode of Fe-18Cr-17Mn-Ni-N was predicted to help determine the microstructure of the welded joint. Results indicate that the weld width, weld reinforcement and melting area all increase with decreasing welding speed, and Fe-18Cr-17Mn-Ni-N solidifies as A mode. The microstructure of the base metal (BM) and heat-affected zone (HAZ) is equiaxed austenite and that of the fusion zone (FZ) is austenite dendrite with some chromium carbides dispersed in the grain boundary; with decreasing welding speed, grains become coarse. The maximum tensile strength (UTS) and elongation of PC-DSSVW joint are 860 MPa and 8.1%, and the elongation decreases dramatically with decreasing welding speed. The impact toughness decreases substantially compared to the BM, achieving 48.2% of the BM.

  12. Molten Pool Behavior and Mechanical Properties of Pulsed Current Double-Sided Synchronization GTA Welded Fe-18Cr-17Mn-Ni-N

    NASA Astrophysics Data System (ADS)

    Qiang, Wei; Wang, Kehong; Feng, Yuehai; Chen, Jiahe

    2017-02-01

    Double-sided synchronization vertical gas tungsten arc welding (DSSVW) procedure was used to weld high-nitrogen low-nickel stainless steel Fe-18Cr-17Mn-Ni-N without groove and filler wire. First, the molten pool behaviors and appearances of pulsed current DSSVW (PC-DSSVW) and constant current DSSVW (CC-DSSVW) were comparatively analyzed. The periodic variation occurs in the width of both the anode region of the arc and the molten pool tail during PC-DSSVW, while the contact angle first increases and then decreases, and both the width of the anode region and the length of arc plume increase progressively in CC-DSSVW. It is found that the weld appearance of PC-DSSVW is superior to that of CC-DSSVW. Second, the forces of the DSSVW molten pool were analyzed. The result indicates that the molten pool of the DSSVW procedure is in a state of unstable equilibrium, and it will easily lose balance after being disturbed, resulting in the asymmetrical weld or hump bead. Third, the PC-DSSVW experiments at various welding speeds were conducted to study the influence of welding speed on the weld profile, microstructure, tensile strength and impact toughness. Furthermore, the solidification mode of Fe-18Cr-17Mn-Ni-N was predicted to help determine the microstructure of the welded joint. Results indicate that the weld width, weld reinforcement and melting area all increase with decreasing welding speed, and Fe-18Cr-17Mn-Ni-N solidifies as A mode. The microstructure of the base metal (BM) and heat-affected zone (HAZ) is equiaxed austenite and that of the fusion zone (FZ) is austenite dendrite with some chromium carbides dispersed in the grain boundary; with decreasing welding speed, grains become coarse. The maximum tensile strength (UTS) and elongation of PC-DSSVW joint are 860 MPa and 8.1%, and the elongation decreases dramatically with decreasing welding speed. The impact toughness decreases substantially compared to the BM, achieving 48.2% of the BM.

  13. Designed synthesis of MOx (M = Zn, Fe, Sn, Ni, Mn, Co, Ce, Mg, Ag), Pt, and Au nanoparticles supported on hierarchical CuO hollow structures.

    PubMed

    Zhang, Zailei; Jung, Ji Chul; Yan, Ning

    2016-12-01

    Despite intensive research into support substrates for the dispersal of nanoparticles and their applications, there has been a lack of general methods to produce metal oxide hollow substrates supporting a wide range of metal and metal oxides. Herein, a synthetic protocol for the preparation of CuO hollow structure-supported MOx (M = Zn, Fe, Ni, Sn, Mn, Co, Ce, Mg, and Ag) and noble metals (Pt and Au) with the desired properties and shell structure, such as CuO/Fe2O3, CuO/ZnO, CuO/SnO2, CuO/MgO, CuO/NiO, CuO/Mn2O3, CuO/CoO, CuO/CeO2, CuO/Ag2O, CuO/Pt, CuO/Au hollow cubes, CuO/ZnO double-shell hollow cubes, CuO/SnO2 double-shell hollow octahedra, CuO/SnO2/Fe2O3 and CuO/Mn2O3/NiO double-shell hollow cubes, was developed based on controlled calcination and etching. These hybrid hollow structures were employed not only as support substrates but also as active constituents for catalytic reactions. As an example, we demonstrated that CuO/ZnO hollow cubes are remarkably efficient in converting solid chitin biomass to liquid chemicals in methanol. In addition, CuO/ZnO double-shell hollow cubes were highly effective in the oxidation of benzyl alcohol in the presence of H2O2, whereas CuO/Pt and CuO/Au hollow cubes promoted the oxidation of benzyl alcohol in pure O2. The strategy developed in this work extends the controllable fabrication of high-quality CuO hollow structure-supported nanoparticles using various compositions and shell structures, paving the way to the exploration and systematic comparison of these materials in a wider range of applications.

  14. Structural and electronic properties of half-Heusler alloys PtXBi (with X=Mn, Fe, Co and Ni) calculated from first principles

    NASA Astrophysics Data System (ADS)

    Huang, Wenchao; Wang, Xiaofang; Chen, Xiaoshuang; Lu, Wei; Damewood, L.; Fong, C. Y.

    2015-03-01

    First principles calculations with spin polarization based on density functional theory have been performed on half-Heusler alloys PtXBi, with X=Mn, Fe, Co and Ni, in three different atomic configurations (i.e. α, β, and γ phases). For each configuration, their optimized lattice constants are determined. Electronic and magnetic properties are also investigated. The differences reflect the atomic arrangements of the three phases and varied transition metal elements X. Meanwhile, the possibility of having the integer magnetic moment for each phase is explored. PtMnBi in α phase show half-metallic (HM) properties when its lattice constant is reduced from -3.0% to -11.2% with magnetic moment consistent with the values given by the modified Slater-Pauling rule. Additionally, we examined the effects of the spin-orbit (S-O) interaction on half-metal PtMnBi by comparing the relative shifts of the valence bands and the indirect semiconducting gap with respect to the spin polarized results.

  15. Composition Dependence of Phase Stability, Deformation Mechanisms, and Mechanical Properties of the CoCrFeMnNi High-Entropy Alloy System

    NASA Astrophysics Data System (ADS)

    Tasan, C. C.; Deng, Y.; Pradeep, K. G.; Yao, M. J.; Springer, H.; Raabe, D.

    2014-10-01

    The proposal of configurational entropy maximization to produce massive solid-solution (SS)-strengthened, single-phase high-entropy alloy (HEA) systems has gained much scientific interest. Although most of this interest focuses on the basic role of configurational entropy in SS formability, setting future research directions also requires the overall property benefits of massive SS strengthening to be carefully investigated. To this end, taking the most promising CoCrFeMnNi HEA system as the starting point, we investigate SS formability, deformation mechanisms, and the achievable mechanical property ranges of different compositions and microstructural states. A comparative assessment of the results with respect to room temperature behavior of binary Fe-Mn alloys reveals only limited benefits of massive SS formation. Nevertheless, the results also clarify that the compositional requirements in this alloy system to stabilize the face-centered cubic (fcc) SS are sufficiently relaxed to allow considering nonequiatomic compositions and exploring improved strength-ductility combinations at reduced alloying costs.

  16. Mechanisms of plastic deformation in [1 ¯ 11 ]-oriented single crystals of FeNiMnCrCo high entropy alloy

    NASA Astrophysics Data System (ADS)

    Kireeva, Irina; Chumlyakov, Yurii; Pobedennaya, Zinaida; Kuksgauzen, Dmitrii; Karaman, Ibrahim; Sehitoglu, Huseyin

    2016-11-01

    Single crystals of fcc Fe20Ni20Mn20Cr20Co20 (atom percent) high entropy alloy oriented along the [1 ¯11 ] direction are used to study flow curves and deformation mechanisms—slip, twinning under tensile deformation at early stages of plastic flow, ɛ = 2.5-5.0%, at the test temperature of 77 and 296 K. It is shown that twinning in [1 ¯11 ] -oriented single crystals is observed from the beginning of plastic flow when ɛ = 2.5-5.0% from 77 to 296 K. Plastic flow in [1 ¯11 ]-oriented single crystals under tension is developed with the high strain hardening coefficients 1800 and 2000 MPa, respectively, at 296 and 77 K. It is also characterized by a good plasticity of 58 and 60% and by a high level of stresses before fracture, 980 and 1580 MPa, respectively, at 296 and 77 K.

  17. Monte Carlo and Ab-initio calculation of TM (Ti, V, Cr, Mn, Fe, Co, Ni) doped MgH2 hydride: GGA and SIC approximation

    NASA Astrophysics Data System (ADS)

    Salmani, E.; Laghrissi, A.; Laamouri, R.; Benchafia, E.; Ez-Zahraouy, H.; Benyoussef, A.

    2017-02-01

    MgH2: TM (TM: V, Cr, Mn, Fe, Co, Ni) based dilute magnetic semiconductors (DMS) are investigated using first principle calculations. Our results show that the ferromagnetic state is stable when TM introduces magnetic moments as well as intrinsic carriers in TM: Co, V, Cr, Ti; Mg0.95TM0.05H2. Some of the DMS Ferro magnets under study exhibit a half-metallic behavior, which make them suitable for spintronic applications. The double exchange is shown to be the underlying mechanism responsible for the magnetism of such materials. The exchange interactions obtained from first principle calculations and used in a classical Ising model by a Monte Carlo approach resulted in ferromagnetic states with Curie temperatures within the ambient conditions.

  18. Evolution of microstructure and crystallographic texture in severely cold rolled high entropy equiatomic CoCrFeMnNi alloy during annealing

    NASA Astrophysics Data System (ADS)

    Sathiaraj, G. D.; Lee, C.; Tsai, C. W.; Yeh, J. W.; Bhattacharjee, P. P.

    2015-04-01

    An equiatomic FCC CoCrFeMnNi high entropy alloy (HEA) was heavily cold rolled up to 90% reduction in thickness followed by isochronal annealing for 1 hour at temperatures ranging between 700°C to 1100°C. A strong brass texture was observed in the cold-rolled condition indicating the low stacking fault energy of the material. A fine stable microstructure was observed during annealing at low temperatures. The recrystallization texture was characterized by the presence of deformation texture components, in particular, the α-fiber (ND//<110>), S ({123} <634>) and the typical brass recrystallization texture component ({236} <385>). Annealing twins were shown to have important effect on the formation of annealing texture.

  19. Magnetocaloric effect and negative thermal expansion in hexagonal Fe doped MnNiGe compounds with a magnetoelastic AFM-FM-like transition

    NASA Astrophysics Data System (ADS)

    Xu, Kun; Li, Zhe; Liu, Enke; Zhou, Haichun; Zhang, Yuanlei; Jing, Chao

    2017-01-01

    We report a detailed study of two successive first-order transitions, including a martensitic transition (MT) and an antiferromagnetic (AFM)-ferromagnetic (FM)-like transition, in Mn1-xFexNiGe (x = 0, 0.06, 0.11) alloys by X-ray diffraction, differential scanning calorimetry, magnetization and linear thermal expansion measurements. Such an AFM-FM-like transition occurring in the martensitic state has seldom been observed in the M(T) curves. The results of Arrott plot and linear relationship of the critical temperature with M2 provide explicit evidence of its first-order magnetoelastic nature. On the other hand, their performances as magnetocaloric and negative thermal expansion materials were characterized. The isothermal entropy change for a field change of 30 kOe reaches an impressive value of ‑25.8 J/kg K at 203 K for x = 0.11 compared to the other two samples. It demonstrates that the magneto-responsive ability has been significantly promoted since an appropriate amount of Fe doping can break the local Ni-6Mn AFM configuration. Moreover, the Fe-doped samples reveal both the giant negative thermal expansion and near-zero thermal expansion for different temperature ranges. For instance, the average thermal expansion coefficient ā of x = 0.06 reaches ‑60.7 × 10‑6/K over T = 231–338 K and 0.6 × 10‑6/K over T = 175–231 K during cooling.

  20. Magnetocaloric effect and negative thermal expansion in hexagonal Fe doped MnNiGe compounds with a magnetoelastic AFM-FM-like transition.

    PubMed

    Xu, Kun; Li, Zhe; Liu, Enke; Zhou, Haichun; Zhang, Yuanlei; Jing, Chao

    2017-01-30

    We report a detailed study of two successive first-order transitions, including a martensitic transition (MT) and an antiferromagnetic (AFM)-ferromagnetic (FM)-like transition, in Mn1-xFexNiGe (x = 0, 0.06, 0.11) alloys by X-ray diffraction, differential scanning calorimetry, magnetization and linear thermal expansion measurements. Such an AFM-FM-like transition occurring in the martensitic state has seldom been observed in the M(T) curves. The results of Arrott plot and linear relationship of the critical temperature with M(2) provide explicit evidence of its first-order magnetoelastic nature. On the other hand, their performances as magnetocaloric and negative thermal expansion materials were characterized. The isothermal entropy change for a field change of 30 kOe reaches an impressive value of -25.8 J/kg K at 203 K for x = 0.11 compared to the other two samples. It demonstrates that the magneto-responsive ability has been significantly promoted since an appropriate amount of Fe doping can break the local Ni-6Mn AFM configuration. Moreover, the Fe-doped samples reveal both the giant negative thermal expansion and near-zero thermal expansion for different temperature ranges. For instance, the average thermal expansion coefficient ā of x = 0.06 reaches -60.7 × 10(-6)/K over T = 231-338 K and 0.6 × 10(-6)/K over T = 175-231 K during cooling.

  1. Magnetocaloric effect and negative thermal expansion in hexagonal Fe doped MnNiGe compounds with a magnetoelastic AFM-FM-like transition

    PubMed Central

    Xu, Kun; Li, Zhe; Liu, Enke; Zhou, Haichun; Zhang, Yuanlei; Jing, Chao

    2017-01-01

    We report a detailed study of two successive first-order transitions, including a martensitic transition (MT) and an antiferromagnetic (AFM)-ferromagnetic (FM)-like transition, in Mn1-xFexNiGe (x = 0, 0.06, 0.11) alloys by X-ray diffraction, differential scanning calorimetry, magnetization and linear thermal expansion measurements. Such an AFM-FM-like transition occurring in the martensitic state has seldom been observed in the M(T) curves. The results of Arrott plot and linear relationship of the critical temperature with M2 provide explicit evidence of its first-order magnetoelastic nature. On the other hand, their performances as magnetocaloric and negative thermal expansion materials were characterized. The isothermal entropy change for a field change of 30 kOe reaches an impressive value of −25.8 J/kg K at 203 K for x = 0.11 compared to the other two samples. It demonstrates that the magneto-responsive ability has been significantly promoted since an appropriate amount of Fe doping can break the local Ni-6Mn AFM configuration. Moreover, the Fe-doped samples reveal both the giant negative thermal expansion and near-zero thermal expansion for different temperature ranges. For instance, the average thermal expansion coefficient ā of x = 0.06 reaches −60.7 × 10−6/K over T = 231–338 K and 0.6 × 10−6/K over T = 175–231 K during cooling. PMID:28134355

  2. Solid-state reactions during mechanical alloying of ternary Fe-Al-X (X=Ni, Mn, Cu, Ti, Cr, B, Si) systems: A review

    NASA Astrophysics Data System (ADS)

    Hadef, Fatma

    2016-12-01

    The last decade has witnessed an intensive research in the field of nanocrystalline materials due to their enhanced properties. A lot of processing techniques were developed in order to synthesis these novel materials, among them mechanical alloying or high-energy ball milling. In fact, mechanical alloying is one of the most common operations in the processing of solids. It can be used to quickly and easily synthesize a variety of technologically useful materials which are very difficult to manufacture by other techniques. One advantage of MA over many other techniques is that is a solid state technique and consequently problems associated with melting and solidification are bypassed. Special attention is being paid to the synthesis of alloys through reactions mainly occurring in solid state in many metallic ternary Fe-Al-X systems, in order to improve mainly Fe-Al structural and mechanical properties. The results show that nanocrystallization is the common result occurring in all systems during MA process. The aim of this work is to illustrate the uniqueness of MA process to induce phase transformation in metallic Fe-Al-X (X=Ni, Mn, Cu, Ti, Cr, B, Si) systems.

  3. Defect chemistry of La{sub 2}Ni{sub 1{minus}x}M{sub x}O{sub 4} (M = Mn, Fe, Co, Cu): Relevance to catalytic behavior

    SciTech Connect

    Read, M.S.D.; Islam, M.S.; King, F.; Hancock, F.E.

    1999-03-04

    Atomistic computer simulation techniques are used to investigate the defect properties of the La{sub 2}Ni{sub 1{minus}x}M{sub x}O{sub 4} (M = Mn, Fe, Co, Cu) layered perovskite which are related to the mode of operation of the catalyst. The theoretical techniques are based upon efficient energy minimization procedures and Mott-Littleton methodology for accurate defect modeling. Effective ionic pairwise interatomic potentials correctly reproduce the tetragonal crystal structure. The formation energy of intrinsic atomic defects of the Schottky and Frenkel type are not particularly favorable. The oxidation of La{sub 2}NiO{sub 4+{delta}} was found to be an exothermic process with charge compensation occurring via hole formation preferentially on the Ni site. The highest solubility, for a range of dopants, is calculated for Sr and Ca, in accord with observation. Hole formation was most favorable for Mn > Fe > Co > Ni(undoped) > Cu, demonstrating that Mn and Fe enhance Ni(III) hole formation, which is believed to be an important factor in the observed catalytic activity.

  4. The effects of annealing on the microstructure and mechanical properties of Fe28Ni18Mn33Al21

    SciTech Connect

    Meng, Fanling; Qiu, Jingwen; Baker, Ian; Bei, Hongbin

    2015-08-20

    In this paper, As-cast Fe28Ni18Mn33Al21, which consists of aligned, 50 nm, (Ni, Al)-rich B2, and (Fe, Mn)-rich f.c.c. phases, was annealed at a variety of temperatures up to 1423 K and the microstructure and mechanical properties were examined. It was shown that the as-cast microstructure arises from a eutectoid transformation at ~1300 K. Annealing at temperatures ≤1073 K produces β-Mn-structured precipitates and hardness values up to 816 HV, while annealing at temperatures >1073 K leads to dramatic coarsening of the two-phase B2/f.c.c. microstructure (up to 5.5 µm after 50 h at 1273 K), but does not lead to β-Mn precipitation. Interestingly, annealing at temperatures >1073 K delays the onset of β-Mn precipitation during subsequent anneals at lower temperatures. Coarsening the B2/f.c.c. lamellar structure by annealing at higher temperatures softens it and leads to increases in ductility from fracture before yield to ~8 % elongation. Finally, the presence of β-Mn precipitates makes the very fine, brittle B2/f.c.c. microstructures even more brittle, but significant ductility (8.4 % elongation) is possible even with β-Mn precipitates present if the B2/f.c.c. matrix is coarse and, hence, more ductile.

  5. Effects of hydrogen annealing and codoping (Mn, Fe, Ni, Ga, Y) of nanocrystalline Cu-doped ZnO dilute magnetic semiconductor

    NASA Astrophysics Data System (ADS)

    Bououdina, Mohamed; Aziz Dakhel, Aqeel

    2015-01-01

    Zinc oxide (ZnO) codoped with Cu and M ions (M = Mn, Fe, Ni, Ga, Y) powders were synthesised by simultaneous thermal co-decomposition of a mixture of zinc and metal complexes. The synthesised chemical formula for the prepared solid solution is Zn0.97Cu0.01M0.02O. X-ray diffraction (XRD) analysis confirms the formation of single nanocrystalline structure of the as-prepared powders, thus, both Cu and M ions were incorporated into ZnO lattice forming solid solutions. Magnetic measurements reveal that all the as-synthesised doped ZnO powders gained partial (RT-FM) properties but with different strength and BH-behaviour depends on the nature of the doping (M). Furthermore, H2 post-treatment was subsequently carried out and it was found that the observed RT-FM is enhanced. Very interestingly, in case of Ni dopant, the whole powder becomes completely ferromagnetic with coercivity (Hc), remanence (Mr) and saturation magnetisation (Ms) of 133.6 Oe, 1.086 memu/g and 4.959 memu/g, respectively. The value of Ms was increased by ~ 95% in comparison with as-prepared.

  6. Atomic Linkage Flexibility Tuned Isotropic Negative, Zero, and Positive Thermal Expansion in MZrF6 (M = Ca, Mn, Fe, Co, Ni, and Zn).

    PubMed

    Hu, Lei; Chen, Jun; Xu, Jiale; Wang, Na; Han, Fei; Ren, Yang; Pan, Zhao; Rong, Yangchun; Huang, Rongjin; Deng, Jinxia; Li, Laifeng; Xing, Xianran

    2016-11-09

    The controllable isotropic thermal expansion with a broad coefficient of thermal expansion (CTE) window is intriguing but remains challenge. Herein we report a cubic MZrF6 series (M = Ca, Mn, Fe, Co, Ni and Zn), which exhibit controllable thermal expansion over a wide temperature range and with a broader CTE window (-6.69 to +18.23 × 10(-6)/K). In particular, an isotropic zero thermal expansion (ZTE) is achieved in ZnZrF6, which is one of the rarely documented high-temperature isotropic ZTE compounds. By utilizing temperature-dependent high-energy synchrotron X-ray total scattering diffraction, it is found that the flexibility of metal···F atomic linkages in MZrF6 plays a critical role in distinct thermal expansions. The flexible metal···F atomic linkages induce negative thermal expansion (NTE) for CaZrF6, whereas the stiff ones bring positive thermal expansion (PTE) for NiZrF6. Thermal expansion could be transformed from striking negative, to zero, and finally to considerable positive though tuning the flexibility of metal···F atomic linkages by substitution with a series of cations on M sites of MZrF6. The present study not only extends the scope of NTE families and rare high-temperature isotropic ZTE compounds but also proposes a new method to design systematically controllable isotropic thermal expansion frameworks from the perspective of atomic linkage flexibility.

  7. Stability and mobility of small vacancy-solute complexes in Fe-MnNi and dilute Fe-X alloys: A kinetic Monte Carlo study

    NASA Astrophysics Data System (ADS)

    Messina, Luca; Malerba, Lorenzo; Olsson, Pär

    2015-06-01

    Manganese and nickel solute atoms in irradiated ferritic steels play a major role in the nanostructural evolution of reactor pressure vessels (RPV), as they are responsible for the formation of embrittling nanofeatures even in the absence of copper. The stability and mobility of small vacancy-solute clusters is here studied with an atomistic kinetic Monte Carlo approach based on ab initio calculations, in order to investigate the influence of Mn and Ni on the early life of small radiation-induced vacancy clusters, and to provide the necessary parameters for advanced object kinetic Monte Carlo simulations of the RPV long-term nanostructural evolution. Migration barriers are obtained by direct ab initio calculations or through a binding energy model based on ab initio data. Our results show a clear immobilizing and stabilizing effect on vacancy clusters as the solute content is increased, whereas the only evident difference between the two solute species is a somewhat longer elongation of the cluster mean free path in the presence of a few Mn atoms.

  8. Simultaneous release of sulfide with Fe, Mn, Ni and Zn in marine harbour sediment measured using a combined metal/sulfide DGT probe.

    PubMed

    Naylor, C; Davison, W; Motelica-Heino, M; Van Den Berg, G A; Van Der Heijdt, L M

    2004-07-26

    The technique of DGT (Diffusive Gradients in Thin Films) was further developed to allow simultaneous measurement of sulfide and trace metals at the same location in sediment. The new combined DGT probe consisted of a layer of gel impregnated with AgI, overlain by (1) a layer of gel containing Chelex, (2) a layer of gel and (3) a filter membrane. Diffusion of sulfide was controlled by layers (1) to (3), while diffusion of metals was controlled by layers (2) and (3). The Chelex gel trapped metals that were measured after elution with acid. The AgI gel trapped sulfide through the formation of Ag2S. This was then measured densitometrically as the colour changed from pale yellow to grey. Experiments demonstrated that concentrations of metal or sulfide measured by the combined device were no different to the concentrations measured by more conventional devices. The presence of Chelex in the gel did not impede the diffusion of sulfide. Deployment of a combined probe in marine sediment revealed simultaneous remobilisation of metals and sulfide at the same location. Solubility calculations indicated that some precipitation of amorphous FeS was probably occurring at the maxima in sulfide concentrations. There was general undersaturation with respect to NiS, but ZnS was supersaturated at all locations. There appeared to be localised active zones of organic matter decomposition, where reduction of manganese oxides, iron oxides and sulfate occurred simultaneously. Mass balance calculations indicated that Ni could not be supplied by release from decomposing organic matter. Manganese oxides were the most likely source, but supply from reductive dissolution of iron oxides could not be entirely discounted. Supply from either Fe or Mn oxides could account for the Zn maxima. Application of the newly developed combined probe provides new information that helps understanding of the complex nature of trace metal and sulfur chemistry in sediments.

  9. Metal-organic niccolite: synthesis, structures, phase transition, and magnetic properties of [CH3NH2(CH2)2NH2CH3][M2(HCOO)6] (M=divalent Mn, Fe, Co, Ni, Cu and Zn).

    PubMed

    Li, Meng-Yuan; Kurmoo, Mohamedally; Wang, Zhe-Ming; Gao, Song

    2011-11-04

    We report the synthesis, crystal structures, thermal and magnetic characterizations of a family of metal-organic frameworks adopting the niccolite (NiAs) structure, [dmenH(2)(2+)][M(2)(HCOO)(6)(2-)] (dmen=N,N'-dimethylethylenediamine; M=divalent Mn, 1Mn; Fe, 2Fe; Co, 3Co; Ni, 4Ni; Cu, 5Cu; and Zn, 6Zn). The compounds could be synthesized by either a diffusion method or directly mixing reactants in methanol or methanol-water mixed solvents. The five members, 1Mn, 2Fe, 3Co, 4Ni, and 6Zn are isostructural and crystallize in the trigonal space group P31c, while 5Cu crystallizes in C2/c. In the structures, the octahedrally coordinated metal ions are connected by anti-anti formate bridges, thus forming the anionic NiAs-type frameworks of [M(2)(HCOO)(6)(2-)], with dmenH(2)(2+) located in the cavities of the frameworks. Owing to the Jahn-Teller effect of the Cu(2+) ion, the 3D framework of 5Cu consists of zigzag Cu-formate chains with Cu-OCHO-Cu connections through short basal Cu-O bonds, further linked by the long axial Cu-O bonds. 6Zn exhibits a phase transition probably as a result of the order-disorder transition of the dmenH(2)(2+) cation around 300 K, confirmed by differential scanning calorimetry and single crystal X-ray diffraction patterns under different temperatures. Magnetic investigation reveals that the four magnetic members, 1Mn, 2Fe, 3Co, and 4Ni, display spin-canted antiferromagnetism, with a Néel temperature of 8.6 K, 19.8 K, 16.4 K, and 33.7 K, respectively. The Mn, Fe, and Ni members show spin-flop transitions below 50 kOe. 2Fe possesses a large hysteresis loop with a large coercive field of 10.8 kOe. The Cu member, 5Cu, shows overall antiferromagnetism (both inter- and intra-chains) with low-dimensional characteristics.

  10. Chemical bonding in the ternary transition metal bismuthides Ti{sub 4}TBi{sub 2} with T=Cr, Mn, Fe, Co, and Ni

    SciTech Connect

    Rytz, R.; Hoffman, R.

    1999-04-05

    The electronic structure and chemical bonding in the ternary transition metal bismuthides Ti{sub 4}TBi{sub 2} (T = Cr, Mn, Fe, Co, and Ni) is investigated by approximate MO calculations of the extended Hueckel tight-binding type. These intermetallic compounds crystallize in a layer structure, repeating sequence T-Ti/Bi-T-Ti/Bi, stacking along c; the late transition metals form linear chains with short T-T bonds. Other important structural elements are face-sharing chains of Ti{sub 4}Bi{sub 2} octahedra and Bi channels. The decrease of the T-T bond lengths from Cr to Ni is more pronounced than expected from the decrease of the metallic radii alone. The analysis of the electronic structure indicates that this behavior arises from the titanium-titanium and titanium-bismuth interlayer interactions. Diminution of the titanium-titanium interlayer distances as one goes from Ti{sub 4}CrBi{sub 2} to Ti{sub 4}NiBi{sub 2} is due to Ti(d)-Ti(d) bonding, which increases with increasing electron filling of the titanium d levels. The titanium-bismuth interactions remain strong along this series, as can also be seen by the constant intralayer/titanium-bismuth distances. A distinguishing feature of the title compounds is the channels formed by bismuth atoms. These channels are filled by Bi-centered, essentially unhybridized 6p orbitals forming a 2D net stacking along c and interacting with each other, stronger in the c direction than perpendicular to it. The possibility of intercalating electrophilic species into these electron-filled voids is also investigated.

  11. Structural, Electronic and Magnetic Properties of Ti1+xFeSb and TiFe0.75M0.25Sb (M = Ni, Mn) Heusler Alloys

    NASA Astrophysics Data System (ADS)

    Al Azar, Said; Mousa, Ahmad

    Density functional theory calculations based on full potential linearized augmented plane-wave (FPLAPW) plus local orbital method in the framework of GGA-PBE, as embodied in the WIEN2k code, is used to investigate the structural, electronic and magnetic properties of intermetallic Ti1+xFeS Heusler compounds, where (x = i/4, i =-3,-2,-1,0,1,2,3,4) and the TiFe0.75M0.25Sb (M = Ni, Mn) quaternary semi-Heusler compounds. Moreover, the modified Becke-Johnson exchange potential, as a semi-local method, was employed to predict the band-gap more precisely. We examined the site preference of the parent compound TiFeSb and varying the electron concentration by doping or removing a Ti atom. It is found that they play a crucial role in physical properties of these material systems. The lattice parameters and spin magnetic moment calculated were consistent with the previous experimental and theoretical data available. Moreover, alloys with x<0 are found to exhibit a ferrimagnetic phase, and the alloy with x =0.25 exhibit a non-magnetic properties, whereas the rest have shown ferromagnetic phase. The band-structure analysis of Ti1.75FeSb, Ti2FeSb and TiFe0.75Ni0.25Sb alloys suggested that they could be a ferromagnetic half-metallic members with band-gaps 0.67, 0.41 and 0.54 eV, respectively.

  12. Organic-Acid-Assisted Fabrication of Low-Cost Li-Rich Cathode Material (Li[Li1/6Fe1/6Ni1/6Mn1/2]O-2) for Lithium-Ion Battery

    SciTech Connect

    Zhao, Taolin; Chen, Shi; Li, Li; Zhang, Xiaoxiao; Wu, Huiming; Wu, Tianpin; Sun, Cheng-Jun; Chen, Renjie; Wu, Feng; Lu, Jun; Amine, Khalil

    2014-12-24

    A novel Li-rich cathode Li[Li1/6Fe1/6Ni1/6Mn1/2]O-2 (0.4Li(2)MnO(3-)0.6LiFe(1/3)Ni(1/3)Mn(1/3)O(2)) was synthesized by a solgel method, which uses citric acid (SC), tartaric acid (ST), or adipic acid (SA) as a chelating agent. The structural, morphological, and electrochemical properties of the prepared samples were characterized by various methods. X-ray diffraction showed that single-phase materials are formed mainly with typical alpha-NaFeO2 layered structure (R3 m), and the SC sample has the lowest Li/Ni cation disorder. The morphological study indicated homogeneous primary particles in good distribution size (100 nm) with small aggregates. The Fe, Ni, and Mn valences were determined by X-ray absorption near-edge structure analysis. In coin cell tests, the initial reversible discharge capacity of an SA electrode was 289.7 mAh g(-1) at the 0.1C rate in the 1.54.8 V voltage range, while an SC electrode showed a better cycling stability with relatively high capacity retention. At the 2C rate, the SC electrode can deliver a discharge capacity of 150 mAh g(-1) after 50 cycles. Differential capacity vs voltage curves were employed to further investigate the electrochemical reactions and the structural change process during cycling. This low-cost, Fe-based compound prepared by the solgel method has the potential to be used as the high capacity cathode material for Liion batteries.

  13. Organic-acid-assisted fabrication of low-cost Li-rich cathode material (Li[Li1/6Fe1/6Ni1/6Mn1/2]O2) for lithium-ion battery.

    PubMed

    Zhao, Taolin; Chen, Shi; Li, Li; Zhang, Xiaoxiao; Wu, Huiming; Wu, Tianpin; Sun, Cheng-Jun; Chen, Renjie; Wu, Feng; Lu, Jun; Amine, Khalil

    2014-12-24

    A novel Li-rich cathode Li[Li1/6Fe1/6Ni1/6Mn1/2]O2 (0.4Li2MnO3-0.6LiFe1/3Ni1/3Mn1/3O2) was synthesized by a sol-gel method, which uses citric acid (SC), tartaric acid (ST), or adipic acid (SA) as a chelating agent. The structural, morphological, and electrochemical properties of the prepared samples were characterized by various methods. X-ray diffraction showed that single-phase materials are formed mainly with typical α-NaFeO2 layered structure (R3̅m), and the SC sample has the lowest Li/Ni cation disorder. The morphological study indicated homogeneous primary particles in good distribution size (100 nm) with small aggregates. The Fe, Ni, and Mn valences were determined by X-ray absorption near-edge structure analysis. In coin cell tests, the initial reversible discharge capacity of an SA electrode was 289.7 mAh g(-1) at the 0.1C rate in the 1.5-4.8 V voltage range, while an SC electrode showed a better cycling stability with relatively high capacity retention. At the 2C rate, the SC electrode can deliver a discharge capacity of 150 mAh g(-1) after 50 cycles. Differential capacity vs voltage curves were employed to further investigate the electrochemical reactions and the structural change process during cycling. This low-cost, Fe-based compound prepared by the sol-gel method has the potential to be used as the high capacity cathode material for Li-ion batteries.

  14. Substitution of Ni for Fe in superconducting Fe>0.98mn>Te>0.5mn>Se>0.5mn> depresses the normal-state conductivity but not the magnetic spectral weight

    SciTech Connect

    Wang, Jinghui; Zhong, Ruidan; Li, Shichao; Gan, Yuan; Xu, Zhijun; Zhang, Cheng; Ozaki, T.; Matsuda, M.; Zhao, Yang; Li, Qiang; Xu, Guangyong; Gu, Genda; Tranquada, J. M.; Birgeneau, R. J.; Wen, Jinsheng

    2015-01-05

    We have performed systematic resistivity and inelastic neutron scattering measurements on Fe₀.₉₈₋zNizTe₀.₅Se₀.₅ samples to study the impact of Ni substitution on the transport properties and the low-energy (≤ 12 meV) magnetic excitations. It is found that, with increasing Ni doping, both the conductivity and superconductivity are gradually suppressed; in contrast, the low-energy magnetic spectral weight changes little. Comparing with the impact of Co and Cu substitution, we find that the effects on conductivity and superconductivity for the same degree of substitution grow systematically as the atomic number of the substituent deviates from that of Fe. The impact of the substituents as scattering centers appears to be greater than any contribution to carrier concentration. The fact that low-energy magnetic spectral weight is not reduced by increased electron scattering indicates that the existence of antiferromagnetic correlations does not depend on electronic states close to the Fermi energy.

  15. Imaging the surface morphology, chemistry and conductivity of LiNi 1/3 Fe 1/3 Mn 4/3 O 4 crystalline facets using scanning transmission X-ray microscopy

    DOE PAGES

    Zhou, Jigang; Wang, Jian; Cutler, Jeffrey; ...

    2016-07-26

    We have employed scanning transmission X-ray microscopy (STXM) using the X-ray fluorescence mode in order to elucidate the chemical structures at Ni, Fe, Mn and O sites from the (111) and (100) facets of micron-sized LiNi1/3Fe1/3Mn4/3O4 energy material particles. Furthermore, STXM imaging using electron yield mode has mapped out the surface conductivity of the crystalline particles. Our study presents a novel approach that visualizes local element segregation, chemistry and conductivity variation among different crystal facets, which will assist further tailoring of the morphology and surface structure of this high voltage spinel lithium ion battery cathode material.

  16. Bimetallic cyanide-bridged complexes based on the photochromic nitroprusside anion and paramagnetic metal complexes. Syntheses, structures, and physical characterization of the coordination compounds [Ni(en)2]4[Fe(CN)5NO]2[Fe(CN)6]x5H2O, [Ni(en)2][Fe(CN)5NO]x3H2O, [Mn(3-MeOsalen)(H2O)]2[Fe(CN)5NO], and [Mn(5-Brsalen)]2[Fe(CN)5NO].

    PubMed

    Clemente-León, M; Coronado, E; Galán-Mascarós, J R; Gómez-García, C J; Woike, T; Clemente-Juan, J M

    2001-01-01

    The synthesis, crystal structure, and physical characterization of the coordination compounds [Ni(en)2]4[Fe(CN)5NO]2[Fe(CN)6]x5H2O (1), [Ni(en)2][Fe(CN)5NO]x3H2O (2), [Mn(3-MeOsalen)(H2O)]2[Fe(CN)5NO] (3), and [Mn(5-Brsalen)]2[Fe(CN)5NO] (4) are presented. 1 crystallizes in the monoclinic space group P2(1)/n (a = 7.407(4) A, b = 28.963(6) A, c = 14.744(5) A, alpha = 90 degrees, beta = 103.26(4) degrees, gamma = 90 degrees, Z = 2). Its structure consists of branched linear chains formed by cis-[Ni(en)2]2+ cations and ferrocyanide and nitroprusside anions. The presence of two kinds of iron(II) sites has been demonstrated by Mössbauer spectroscopy. 2 crystallizes in the monoclinic space group P2(1)/c (a = 11.076(3) A, b = 10.983(2) A, c = 17.018(5) A, alpha = 90 degrees, beta = 107.25(2) degrees, gamma = 90 degrees, Z = 4). Its structure consists of zigzag chains formed by an alternated array of cis-[Ni(en)2]2+ cations and nitroprusside anions. 3 crystallizes in the triclinic space group P1 (a = 8.896(5) A, b = 10.430(5) A, c = 12.699(5) A, alpha = 71.110(5) degrees, beta = 79.990(5) degrees, gamma = 89.470(5) degrees, Z = 1). Its structure comprises neutral trinuclear bimetallic complexes in which a central [Fe(CN)5NO]2- anion is linked to two [Mn(3-MeOsalen)]+ cations. 4 crystallizes in the tetragonal space group P4/ncc (a = 13.630(5) A, c = 21.420(8) A, Z = 4). Its structure shows an extended 2D neutral network formed by cyclic octameric [-Mn-NC-Fe-CN-]4 units. The magnetic properties of these compounds indicate the presence of quasi-isolated paramagnetic Ni2+ and Mn3+. Irradiated samples of the four compounds have been studied by differential scanning calorimetry to detect the existence of the long-lived metastable states of nitroprusside.

  17. Substitution effect on magnetic and electrical properties of half-Heusler alloy Ni{sub 1−x}Co{sub x}Mn{sub 1−y}Fe{sub y}Sb

    SciTech Connect

    Kushwaha, Varun Sharma, Himanshu Dixit, Dinesh Tomy, C. V.; Tulapurkar, Ashwin

    2014-04-24

    We have studied the effects of Co and Fe doping on the magnetic and electrical properties of half-Heusler compound NiMnSb. The alloys were prepared by arc-melting method in the presence of Argon gas. The powder X-ray diffraction of the each alloy was performed in air at room temperature. The magnetic and electrical properties were performed in the temperature range 2–400 K and in magnetic field up to 1 T.

  18. The role of magnetic excitations in magnetoresistance and Hall effect of slightly TM-substituted BaFe2As2 compounds (TM = Mn, Cu, Ni)

    NASA Astrophysics Data System (ADS)

    Peña, J. P.; Piva, M. M.; Jesus, C. B. R.; Lesseux, G. G.; Garitezi, T. M.; Tobia, D.; Rosa, P. F. S.; Grant, T.; Fisk, Z.; Adriano, C.; Urbano, R. R.; Pagliuso, P. G.; Pureur, P.

    2016-12-01

    We report on electrical resistivity, magnetoresistance (MR) and Hall effect measurements in four non-superconducting BaFe2-xTMxAs2 (TM = Mn, Cu and Ni) single crystals with small values of the chemical substitution x. The spin density wave (SDW) ordering that occurs in these systems at temperatures T ∼ (120-140) K, in close vicinity to a tetragonal/orthorhombic transition, produces significant modifications in their magneto-transport properties. While in the magnetically ordered phase the MR is positive and its magnitude increases with decreasing temperatures, in the paramagnetic regime the MR becomes vanishingly small. Above the spin density wave transition temperature (TSDW) the Hall coefficient RH is negative, small and weakly temperature dependent, but a remarkable change of slope occurs in the RH versus T curves at T =TSDW . The Hall coefficient amplitude, while remaining negative, increases steadily and significantly as the temperature is decreased below TSDW and down to T = 20 K. The qualitative behavior of both MR and Hall coefficient is weakly dependent on the chemical substitution in the studied limit. The experiments provide strong evidence that scattering of charge carriers by magnetic excitations has to be taken into account to explain the behavior of the resistivity, magnetoresistance and Hall effect in the ordered phase of the studied compounds. Effects of multiple band conduction also must be considered for a complete interpretation of the results.

  19. Size effect, critical resolved shear stress, stacking fault energy, and solid solution strengthening in the CrMnFeCoNi high-entropy alloy.

    PubMed

    Okamoto, Norihiko L; Fujimoto, Shu; Kambara, Yuki; Kawamura, Marino; Chen, Zhenghao M T; Matsunoshita, Hirotaka; Tanaka, Katsushi; Inui, Haruyuki; George, Easo P

    2016-10-24

    High-entropy alloys (HEAs) comprise a novel class of scientifically and technologically interesting materials. Among these, equatomic CrMnFeCoNi with the face-centered cubic (FCC) structure is noteworthy because its ductility and strength increase with decreasing temperature while maintaining outstanding fracture toughness at cryogenic temperatures. Here we report for the first time by single-crystal micropillar compression that its bulk room temperature critical resolved shear stress (CRSS) is ~33-43 MPa, ~10 times higher than that of pure nickel. CRSS depends on pillar size with an inverse power-law scaling exponent of -0.63 independent of orientation. Planar ½ < 110 > {111} dislocations dissociate into Shockley partials whose separations range from ~3.5-4.5 nm near the screw orientation to ~5-8 nm near the edge, yielding a stacking fault energy of 30 ± 5 mJ/m(2). Dislocations are smoothly curved without any preferred line orientation indicating no significant anisotropy in mobilities of edge and screw segments. The shear-modulus-normalized CRSS of the HEA is not exceptionally high compared to those of certain concentrated binary FCC solid solutions. Its rough magnitude calculated using the Fleischer/Labusch models corresponds to that of a hypothetical binary with the elastic constants of our HEA, solute concentrations of 20-50 at.%, and atomic size misfit of ~4%.

  20. Following electron impact excitation of single (Sc, Ti, V, Cr, Mn, Fe, Co, Ni) atom L subshells ionization cross section calculations by using Lotz's equation

    NASA Astrophysics Data System (ADS)

    Aydinol, Mahmut

    2017-02-01

    L shell and Li subshells ionization cross sections[σL and σLi i = 1, 2, 3 following electron impact on (Sc, Ti, V, Cr, Mn, Fe, Co, Ni) atoms calculated. By using Lotz' equation for non-relativistic cases in Matlab σL and σLi cross section values obtained for ten electron impact(Eo) values in the range of ELi

  1. Brillouin Light Scattering study of the rotatable magnetic anisotropy in exchange biased bilayers of Ni81 Fe19 Ir20 Mn80

    NASA Astrophysics Data System (ADS)

    Rodríguez, Roberto; Oliveira, Alexandre; Estrada, Francisco; Santos, Obed; Azevedo, Antonio; Rezende, Sergio

    It is known that when a ferromagnet (FM) is in atomic contact with an antiferromagnet (AF) the exchange coupling between the FM and AF spins at the interface induces a unidirectional anisotropy in the ferromagnetic film. This effect is known as exchange bias (EB). Despite the large amount of research on this topic there are still several aspects of the EB mechanism that are not well understood. One of this aspects is the origin of the rotatable anisotropy in polycrystalline AFs. By means of Brillouin Light Scattering (BLS) measurements, we investigated the dependence of the rotatable anisotropy field HRA and exchange field HE with the magnitude of the external magnetic field (Ho) in FM/AM bilayers of Ni81Fe19(10nm)/Ir20Mn80(tAF) . We developed an algorithm to numerically fit the in-plane angular dependence of the magnon frequency, at a fixed value of Ho measured by BLS. From the fit parameters we were able to investigate HRA and HE dependency on Ho. The results reveal that HRA value depends on Ho, so we argue that AF grain distribution at the interface is partially modified by the applied field strength. Contrary to this, the relation between HE and Ho is not straightforward, remaining constant at high values of Ho.

  2. In quest of cathode materials for Ca ion batteries: the CaMO3 perovskites (M = Mo, Cr, Mn, Fe, Co, and Ni).

    PubMed

    Arroyo-de Dompablo, M E; Krich, C; Nava-Avendaño, J; Palacín, M R; Bardé, F

    2016-07-20

    Basic electrochemical characteristics of CaMO3 perovskites (M = Mo, Cr, Mn, Fe, Co, and Ni) as cathode materials for Ca ion batteries are investigated using first principles calculations at the Density Functional Theory level (DFT). Calculations have been performed within the Generalized Gradient Approximation (GGA) and GGA+U methodologies, and considering cubic and orthorhombic perovskite structures for CaxMO3 (x = 0, 0.25, 0.5, 0.75 and 1). The analysis of the calculated voltage-composition profile and volume variations identifies CaMoO3 as the most promising perovskite compound. It combines good electronic conductivity, moderate crystal structure modifications, and activity in the 2-3 V region with several intermediate CaxMoO3 phases. However, we found too large barriers for Ca diffusion (around 2 eV) which are inherent to the perovskite structure. The CaMoO3 perovskite was synthesized, characterized and electrochemically tested, and results confirmed the predicted trends.

  3. Large single crystal diamond grown in FeNiMnCo-S-C system under high pressure and high temperature conditions

    NASA Astrophysics Data System (ADS)

    Zhang, He; Li, Shangsheng; Su, Taichao; Hu, Meihua; Li, Guanghui; Ma, Hongan; Jia, Xiaopeng

    2016-11-01

    Large diamonds have successfully been synthesized from FeNiMnCo-S-C system at temperatures of 1255-1393 °C and pressures of 5.3-5.5 GPa. Because of the presence of sulfur additive, the morphology and color of the large diamond crystals change obviously. The content and shape of inclusions change with increasing sulfur additive. It is found that the pressure and temperature conditions required for the synthesis decrease to some extent with the increase of S additive, which results in left down of the V-shape region. The Raman spectra show that the introduction of additive sulfur reduces the quality of the large diamond crystals. The x-ray photoelectron spectroscopy (XPS) spectra show the presence of S in the diamonds. Furthermore, the electrical properties of the large diamond crystals are tested by a four-point probe and the Hall effect method. When sulfur in the cell of diamond is up to 4.0 wt.%, the resistance of the diamond is 9.628×105 Ω·cm. It is shown that the large single crystal samples are n type semiconductors. This work is helpful for the further research and application of sulfur-doped semiconductor large diamond. Project supported by the National Natural Science Foundation of China (Grant No. 51172089), the Education Department of Henan Province, China (Grant No. 12A430010), and the Fundamental Research Funds for the Universities of Henan Province, China (Grant No. NSFRF140110).

  4. Size effect, critical resolved shear stress, stacking fault energy, and solid solution strengthening in the CrMnFeCoNi high-entropy alloy

    PubMed Central

    Okamoto, Norihiko L.; Fujimoto, Shu; Kambara, Yuki; Kawamura, Marino; Chen, Zhenghao M. T.; Matsunoshita, Hirotaka; Tanaka, Katsushi; Inui, Haruyuki; George, Easo P.

    2016-01-01

    High-entropy alloys (HEAs) comprise a novel class of scientifically and technologically interesting materials. Among these, equatomic CrMnFeCoNi with the face-centered cubic (FCC) structure is noteworthy because its ductility and strength increase with decreasing temperature while maintaining outstanding fracture toughness at cryogenic temperatures. Here we report for the first time by single-crystal micropillar compression that its bulk room temperature critical resolved shear stress (CRSS) is ~33–43 MPa, ~10 times higher than that of pure nickel. CRSS depends on pillar size with an inverse power-law scaling exponent of –0.63 independent of orientation. Planar ½ < 110 > {111} dislocations dissociate into Shockley partials whose separations range from ~3.5–4.5 nm near the screw orientation to ~5–8 nm near the edge, yielding a stacking fault energy of 30 ± 5 mJ/m2. Dislocations are smoothly curved without any preferred line orientation indicating no significant anisotropy in mobilities of edge and screw segments. The shear-modulus-normalized CRSS of the HEA is not exceptionally high compared to those of certain concentrated binary FCC solid solutions. Its rough magnitude calculated using the Fleischer/Labusch models corresponds to that of a hypothetical binary with the elastic constants of our HEA, solute concentrations of 20–50 at.%, and atomic size misfit of ~4%. PMID:27775026

  5. First principles study of structural, electronic, magnetic and elastic properties of Mg0.75TM0.25S (TM=Mn, Fe, Co, Ni)

    NASA Astrophysics Data System (ADS)

    Gous, M. H.; Meddour, A.; Bourouis, Ch.

    2017-01-01

    The objective of this work is to predict the structural, electronic, magnetic and elastic properties of Mg1-xTMxS (TM=Mn, Fe, Co and Ni) compound in the zinc blende Ferromagnetic phase using first principal approach. The structural and elastic properties are performed using the generalized gradient approximation proposed by Wu and Cohen(WC-GGA). However, the electronic and magnetic properties have been performed using modified Becke-Johnson potential combined with the LDA correlation (mBJLDA). The results show that all compounds Mg1-xMnxS, Mg1-xFexS and Mg1-xNixS exhibit a half-metallic ferromagnetic character with 100% spin-polarization at the Fermi level, except Mg1-xCoxS is a metal. For each compounds study here, the total magnetic momentum is an integer equal to magnetic moments of TM atom in their free space charge value. Due to the p-d hybridization, there is a small local magnetic moment on the Mg and S sites; whereas, the local magnetic moments of TM atom reduce from their free space charge value. In addition, we investigate the mechanical behavior of MgS and Mg1-xTMxS; all compounds studied here are mechanically stable and exhibit a strong anisotropic behavior.

  6. Size effect, critical resolved shear stress, stacking fault energy, and solid solution strengthening in the CrMnFeCoNi high-entropy alloy

    NASA Astrophysics Data System (ADS)

    Okamoto, Norihiko L.; Fujimoto, Shu; Kambara, Yuki; Kawamura, Marino; Chen, Zhenghao M. T.; Matsunoshita, Hirotaka; Tanaka, Katsushi; Inui, Haruyuki; George, Easo P.

    2016-10-01

    High-entropy alloys (HEAs) comprise a novel class of scientifically and technologically interesting materials. Among these, equatomic CrMnFeCoNi with the face-centered cubic (FCC) structure is noteworthy because its ductility and strength increase with decreasing temperature while maintaining outstanding fracture toughness at cryogenic temperatures. Here we report for the first time by single-crystal micropillar compression that its bulk room temperature critical resolved shear stress (CRSS) is ~33–43 MPa, ~10 times higher than that of pure nickel. CRSS depends on pillar size with an inverse power-law scaling exponent of –0.63 independent of orientation. Planar ½ < 110 > {111} dislocations dissociate into Shockley partials whose separations range from ~3.5–4.5 nm near the screw orientation to ~5–8 nm near the edge, yielding a stacking fault energy of 30 ± 5 mJ/m2. Dislocations are smoothly curved without any preferred line orientation indicating no significant anisotropy in mobilities of edge and screw segments. The shear-modulus-normalized CRSS of the HEA is not exceptionally high compared to those of certain concentrated binary FCC solid solutions. Its rough magnitude calculated using the Fleischer/Labusch models corresponds to that of a hypothetical binary with the elastic constants of our HEA, solute concentrations of 20–50 at.%, and atomic size misfit of ~4%.

  7. Fieldlike spin-orbit torque in ultrathin polycrystalline FeMn films

    NASA Astrophysics Data System (ADS)

    Yang, Yumeng; Xu, Yanjun; Zhang, Xiaoshan; Wang, Ying; Zhang, Shufeng; Li, Run-Wei; Mirshekarloo, Meysam Sharifzadeh; Yao, Kui; Wu, Yihong

    2016-03-01

    Fieldlike spin-orbit torque in FeMn/Pt bilayers with ultrathin polycrystalline FeMn has been characterized through planar Hall effect measurements. A large effective field of 2.05 ×10-5 to 2.44 ×10-5Oe (A-1cm2) is obtained for FeMn in the thickness range of 2-5 nm. The experimental observations can be reasonably accounted for by using a macrospin model under the assumption that the FeMn layer is composed of two spin sublattices with unequal magnetizations. The large effective field corroborates the spin Hall origin of the effective field, considering the much smaller uncompensated net moments in FeMn as compared to NiFe. The effective absorption of spin current by FeMn is further confirmed by the fact that spin current generated by Pt in NiFe/FeMn/Pt trilayers can only travel through the FeMn layer with a thickness of 1-4 nm. By quantifying the fieldlike effective field induced in NiFe, a spin diffusion length of 2 nm is estimated in FeMn, consistent with values reported in the literature by ferromagnetic resonance and spin-pumping experiments.

  8. Transport Properties of the Layered Transition Metal Oxypnictide Sr2ScMPO3 with MP layers (M =Mn, Ni and Co0.5Fe0.5)

    NASA Astrophysics Data System (ADS)

    Okada, S.; Kamihara, Y.; Ohkubo, N.; Ban, S.; Matoba, M.

    2014-12-01

    Polycrystalline samples of novel oxypnictides, Sr2ScMPO3, with MP layer (M = Mn, Ni and Co0.5Fe0.5) were synthesized, and their resistivities and Seebeck coefficients were measured. Sr2ScMPO3 crystallizes in a stacked, layered structure comprised of a ThCr2Si2- type MP layer alternating with a K2NiF4-type Sr2ScO3 layer. Sr2ScMnPO3 is an insulator at room temperature. The resistivities (ρ) of Sr2ScNiPO3 and Sr2ScCo0.5Fe0.5PO3 decrease with decreasing temperature like a metal. The Seebeck coefficients (S) of these materials are negative at room temperature. For Sr2ScNiPO3, S initially decreases slightly with decreasing temperature, and increases with decreasing temperature below 50 K. However, for Sr2ScCo0.5Fe0.5PO3, S increases with decreasing temperature, and attains to a positive value below 270 K.

  9. Magnetooptic coupling coefficients for one- and two-magnon Raman scattering in rutile-structure antiferromagnets FeF2, MnF2, CoF2, and NiF2

    NASA Astrophysics Data System (ADS)

    Lockwood, D. J.; Cottam, M. G.

    2012-07-01

    Inelastic light scattering intensities in response to magnetic excitations are governed by magnetooptic coupling coefficients, which have been previously evaluated, for instance, for the ferrimagnetic Y3Fe5O12 (YIG) and the metamagnetic FeCl2 and FeBr2. However, by far the most detailed studies to date were performed on the classic rutile-structure antiferromagnets, and here we summarize the results obtained from the many experimental and theoretical investigations of these compounds for both one-magnon and two-magnon excitations. A comparison of the magnitudes of the various coupling coefficients for MnF2, FeF2, CoF2, and NiF2 reveals a surprising similarity in many coefficients. In one-magnon Raman scattering the in-phase linear magnetooptic coefficient dominates, and the main differences between MnF2, FeF2, and NiF2 lie in the relative significance of the in-phase quadratic magnetooptic coefficient. Thus, the quadratic coefficients now appear to be of particular importance in determining the strength of one-magnon scattering in a variety of magnetic insulators. In two-magnon Raman scattering one magnetooptic coefficient is dominant for all of these antiferromagnets. However, the other six coefficients are in general remarkably similar in magnitude and not negligible in most cases, indicating some similarity in the way light interacts with the pairs of magnons of opposite and equal wave vectors in rutile structure antiferromagnets.

  10. Corrosion study of single crystal Ni-Mn-Ga alloy and Tb0.27Dy0.73Fe1.95 alloy for the design of new medical microdevices.

    PubMed

    Pouponneau, Pierre; Savadogo, Oumarou; Napporn, Teko; Yahia, L'Hocine; Martel, Sylvain

    2011-02-01

    Once placed in a magnetic field, smart magnetic materials (SMM) change their shape, which could be use for the development of smaller minimally invasive surgery devices activated by magnetic field. However, the potential degradation and release of cytotoxic ions by SMM corrosion has to be determined. This paper evaluates the corrosion resistance of two SMM: a single crystal Ni-Mn-Ga alloy and Tb(0.27)Dy(0.73)Fe(1.95) alloy. Ni-Mn-Ga alloy displayed a corrosion potential (E (corr)) of -0.58 V/SCE and a corrosion current density (i (corr)) of 0.43 μA/cm(2). During the corrosion assay, Ni-Mn-Ga sample surface was partially protected; local pits were formed on 20% of the surface and nickel ions were mainly found in the electrolyte. Tb(0.27)Dy(0.73)Fe(1.95) alloy exhibited poor corrosion properties such as E (corr) of -0.87 V/SCE and i (corr) of 5.90 μA/cm(2). During the corrosion test, this alloy was continuously degraded, its surface was impaired by pits and cracks extensively and a high amount of iron ions was measured in the electrolyte. These alloys exhibited low corrosion parameters and a selective degradation in the electrolyte. They could only be used for medical applications if they are coated with high strain biocompatible materials or embedded in composites to prevent direct contact with physiological fluids.

  11. Electronic structure and magnetic properties of LiMn{sub 1.5}M{sub 0.5}O{sub 4} (M=Al, Mg, Ni, Fe) and LiMn{sub 2}O{sub 4}/TiO{sub 2} nanocrystalline electrode materials

    SciTech Connect

    Talik, E.; Lipińska, L.; Zajdel, P.; Załóg, A.; Michalska, M.; Guzik, A.

    2013-10-15

    The process of sol–gel synthesis was applied to obtain LiMn{sub 1.5}M{sub 0.5}O{sub 4} (M=Al, Mg, Ni, Fe) and LiMn{sub 2}O{sub 4}/TiO{sub 2} nanopowders. The samples were characterized by following methods: X-ray diffraction (XRD), scanning electron microscopy (SEM/EDX), X-ray photoelectron spectroscopy (XPS) and SQUID magnetometry. XPS was used to examine the chemical composition and oxidation state of manganese, in particular the Mn{sup 3+}/Mn{sup 4+} ratio from the deconvolution of the complex Mn3p lines. The size of the grains and crystallites were independently obtained from SEM images and XRD patterns, respectively. In all the cases a critical interplay of electronic (Mn{sup 3+}/Mn{sup 4+} ratio), structural (unit cell volume) and magnetic properties was observed depending on the synthesis process. - Graphical abstract: SEM image of Li{sub 0.79}Ni{sub 0.41}Mn{sub 1.35}O{sub 4.45} sample. Display Omitted - Highlights: • LiMn{sub 1.5}M{sub 0.5}O{sub 4} (M=Al, Mg, Ni, Fe) and LiMn{sub 2}O{sub 4}/TiO{sub 2} obtained by sol–gel method. • XRD method was used to determine the crystal structure. • SEM/EDX imaging have been done. • XPS electronic structure was examined and discussed. • Experimental effective magnetic moment and the calculated one were compared.

  12. Magnetism and magnetic anisotropy of antiferromagnetic NiMn

    NASA Astrophysics Data System (ADS)

    Freeman, A. J.; Nakamura, K.; Kim, M.; Zhong, L.; Fernandez-de-Castro, J.

    2000-03-01

    Despite the importance of magnetic anisotropy in industrial applications, the magnetic anisotropy of AFM as well as FM/AFM interfaces is not well understood. We have performed first-principles FLAPW calculations(Wimmer, Krakauer, Weinert and Freeman, PRB 24, 864(1981)) in order to understand the magnetism and magnetic anisotropy of AFM NiMn with L10 structure. The bulk system shows AFM ordering of the Mn spins while the Ni atom has almost no magnetic moment, as expected from experiment. The Mn moment at the surface is enhanced compared to the bulk case. The magneto-crystalline anisotropy (MCA) energy was calculated by the state tracking and torque approaches(D.-S. Wang, R. Wu and A. J. Freeman, PRL 70, 869(1993))^,(X. Wang, R. Wu, D.-S. Wang and A. J. Freeman, PRB 54, 61(1996)) and found to be sensitive to the environment. The case of bulk clearly exhibits in-plane MCA - in agreement with experiment. In the surface case, if Mn is at the surface the MCA exhibits qualitatively the same behavior as bulk, while for Ni at the surface there is a larger MCA energy. Work in progress on exchange bias materials includes the AFM/FM interface, NiMn/NiFe.

  13. Magnetic anisotropy of Fe{sub 1−y}X{sub y}Pt-L1{sub 0} [X = Cr, Mn, Co, Ni, Cu] bulk alloys

    SciTech Connect

    Cuadrado, R.; Chantrell, R. W.; Klemmer, Timothy J.

    2014-10-13

    We demonstrate by means of fully relativistic first principles calculations that, by substitution of Fe by Cr, Mn, Co, Ni, or Cu in FePt-L1{sub 0} bulk alloys, with fixed Pt content, it is possible to tune the magnetocrystalline anisotropy energy by adjusting the content of the non-magnetic species in the material. The changes in the geometry due to the inclusion of each element induces different values of the tetragonality and hence changes in the magnetic anisotropy and in the net magnetic moment. The site resolved magnetic moments of Fe increase with the X content while those of Pt and X are simultaneously reduced. The calculations are in good quantitative agreement with experimental data and demonstrate that models with fixed band structure but varying numbers of electrons per unit cell are insufficient to describe the experimental data for doped FePt-L1{sub 0} alloys.

  14. The influences of temperature and microstructure on the tensile properties of a CoCrFeMnNi high-entropy alloy

    SciTech Connect

    Otto, Frederik; Dlouhy, A.; Somsen, Ch.; Bei, Hongbin; Eggeler, G.; George, Easo P

    2013-01-01

    An equiatomic CoCrFeMnNi high-entropy alloy, which crystallizes in the face-centered cubic (FCC) crystal structure, was produced by arc melting and drop casting. The drop-cast ingots were homogenized, cold rolled, and recrystallized to obtain single-phase microstructures with three different grain sizes in the range 4~160 m. Quasi-static tensile tests were then performed at temperatures between 77 and 1073 K. Yield strength, ultimate tensile strength and ductility all increased with decreasing temperature. During the initial stages of plasticity (up to ~2% strain), deformation occurs by planar dislocation glide on the normal FCC slip system {111} 110 at all temperatures and grain sizes investigated. Undissociated 1/2 110 dislocations were observed, as were numerous stacking faults, which imply the dissociation of several of these dislocations into 1/6 112 Shockley partials. At later stages ( 20% strain), nanoscale deformation twins were observed after interrupted tests at 77 K, but not in specimens tested at room temperature where plasticity occurred exclusively by dislocations which organized into cells. Deformation twinning, by continually decreasing the mean free path of dislocations during tensile testing, produces a high degree of work hardening and a significant increase in the ultimate tensile strength. This increased work hardening prevents the early onset of necking instability and is a reason for the enhanced ductility observed at 77 K. A second way in which twinning can contribute to ductility is by providing an additional deformation mode to accommodate plasticity. However, it cannot explain the increase in yield strength with decreasing temperature in our high-entropy alloy since twinning was not observed in the early stages of plastic deformation. Since strong temperature dependencies of yield strength are also seen in binary FCC solid solution alloys, it may be an inherent solute effect, which needs further study.

  15. Planar Hall effect bridge sensors with NiFe/Cu/IrMn stack optimized for self-field magnetic bead detection

    NASA Astrophysics Data System (ADS)

    Henriksen, Anders Dahl; Rizzi, Giovanni; Hansen, Mikkel Fougt

    2016-03-01

    The stack composition in trilayer Planar Hall effect bridge sensors is investigated experimentally to identify the optimal stack for magnetic bead detection using the sensor self-field. The sensors were fabricated using exchange-biased stacks Ni80Fe20(tFM)/Cu(tCu)/Mn80Ir20(10 nm) with tFM = 10, 20, and 30 nm, and 0 ≤ tCu ≤ 0.6 nm. The sensors were characterized by magnetic hysteresis measurements, by measurements of the sensor response vs. applied field, and by measurements of the sensor response to a suspension of magnetic beads magnetized by the sensor self-field due to the sensor bias current. The exchange bias field was found to decay exponentially with tCu and inversely with tFM. The reduced exchange field for larger values of tFM and tCu resulted in higher sensitivities to both magnetic fields and magnetic beads. We argue that the maximum magnetic bead signal is limited by Joule heating of the sensors and, thus, that the magnetic stacks should be compared at constant power consumption. For a fixed sensor geometry, the figure of merit for this comparison is the magnetic field sensitivity normalized by the sensor bias voltage. In this regard, we found that sensors with tFM = 20 nm or 30 nm outperformed those with tFM = 10 nm by a factor of approximately two, because the latter have a reduced AMR ratio. Further, the optimum layer thicknesses, tCu ≈ 0.6 nm and tFM = 20-30 nm, gave a 90% higher signal compared to the corresponding sensors with tCu = 0 nm.

  16. First-principles study on stability and magnetism of NdFe11M and NdFe11M N for M = Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn

    NASA Astrophysics Data System (ADS)

    Harashima, Yosuke; Terakura, Kiyoyuki; Kino, Hiori; Ishibashi, Shoji; Miyake, Takashi

    2016-11-01

    Recently synthesized NdFe12N has excellent magnetic properties, while it is thermodynamically unstable. Using the first-principles method, we study the effect of substitutional 3d transition metal elements to the mother compound NdFe12. We find that Co has a positive effect on the stability of the ThMn12 structure. In contrast to Ti substitution, Co substitution does not reduce the magnetization significantly. The crystal field parameter A20 is nearly unchanged by Co substitution, and nitrogenation to NdFe11Co greatly enhances A20 . This suggests that Co is a good candidate as a substitutional element for NdFe12N.

  17. oxide and FeNi alloy: product dependence on the reduction ability

    NASA Astrophysics Data System (ADS)

    Cao, Jungang; Qin, Yuyang; Li, Minglun; Zhao, Shuyuan; Li, Jianjun

    2014-12-01

    Based on the sol-gel combustion method, stoichiometric Fe3+, Mn2+, Ni2+ ions and citric acid were chosen as the initial reactants for the preparation of magnetic particles. Due to the different reduction ability of metal ions, completely different magnetic products (MnFe2O4 oxide and FeNi alloy) were obtained by heating the flakes at 600 °C under nitrogen atmosphere. MnFe2O4 particles exhibit superparamagnetic behavior at room temperature, and martensitic phase transformation is observed magnetically at 125 K for FeNi alloy particles.

  18. Periodic trends within a series of five-coordinate thiolate-ligated [MII(SMe2N4(tren))]+ (M = Mn, Fe, Co, Ni, Cu, Zn) complexes, including a rare example of a stable CuII-thiolate.

    PubMed

    Brines, Lisa M; Shearer, Jason; Fender, Jessica K; Schweitzer, Dirk; Shoner, Steven C; Barnhart, David; Kaminsky, Werner; Lovell, Scott; Kovacs, Julie A

    2007-10-29

    A series of five-coordinate thiolate-ligated complexes [M(II)(tren)N4S(Me2)]+ (M = Mn, Fe, Co, Ni, Cu, Zn; tren = tris(2-aminoethyl)amine) are reported, and their structural, electronic, and magnetic properties are compared. Isolation of dimeric [Ni(II)(SN4(tren)-RS(dang))]2 ("dang"= dangling, uncoordinated thiolate supported by H bonds), using the less bulky [(tren)N4S](1-) ligand, pointed to the need for gem-dimethyls adjacent to the sulfur to sterically prevent dimerization. All of the gem-dimethyl derivatized complexes are monomeric and, with the exception of [Ni(II)(S(Me2)N4(tren)]+, are isostructural and adopt a tetragonally distorted trigonal bipyramidal geometry favored by ligand constraints. The nickel complex uniquely adopts an approximately ideal square pyramidal geometry and resembles the active site of Ni-superoxide dismutase (Ni-SOD). Even in coordinating solvents such as MeCN, only five-coordinate structures are observed. The MII-S thiolate bonds systematically decrease in length across the series (Mn-S > Fe-S > Co-S > Ni-S approximately Cu-S < Zn-S) with exceptions occurring upon the occupation of sigma* orbitals. The copper complex, [Cu(II)(S(Me2)N4(tren)]+, represents a rare example of a stable CuII-thiolate, and models the perturbed "green" copper site of nitrite reductase. In contrast to the intensely colored, low-spin Fe(III)-thiolates, the M(II)-thiolates described herein are colorless to moderately colored and high-spin (in cases where more than one spin-state is possible), reflecting the poorer energy match between the metal d- and sulfur orbitals upon reduction of the metal ion. As the d-orbitals drop in energy proceeding across the across the series M(2+) (M= Mn, Fe, Co, Ni, Cu), the sulfur-to-metal charge-transfer transition moves into the visible region, and the redox potentials cathodically shift. The reduced M(+1) oxidation state is only accessible with copper, and the more oxidized M(+4) oxidation state is only accessible for

  19. Bis(azulene) "submarine" metal dimer sandwich compounds (C10H8)2M2(M = Ti, V, Cr, Mn, Fe, Co, Ni): Parallel and opposed orientations.

    PubMed

    Wang, Hongyan; Wang, Hui; King, R Bruce; Schaefer, Henry F

    2016-01-15

    The opposed and parallel structures for the binuclear bis(azulene) "submarine" sandwiches (C10H8)2M2 (M = Ti, V, Cr, Mn, Fe, Co, Ni) have been optimized using density functional theory. The lowest energy (C10H8)2 M2 structures of the early transition metals Ti, V, Cr, and Mn have the azulene units functioning as bis(pentahapto) ligands to each metal atom similar to the azulene ligand in the long-known molybdenum carbonyl complex (η(5),η(5)-C10H8 )Mo2 (CO)6 . The metal-metal bonds in these early transition metal structures have distances and Wiberg bond indices consistent with the formal bond orders required to give each metal atom an 18-electron configuration for the singlet structures and a 17-electron configuration for the triplet structures. For the later transition metals Fe, Co, and Ni, the lowest energy (C10H8)2 M2 structures contain pentahapto-trihapto azulene ligands with an uncomplexed C=C double bond, similar to that in the long-known iron carbonyl complex (η(5),η(3)-C10H8)Fe2 (CO)5 . The parallel (η(5),η(3)-C10H8 )2M2 (M = Fe, Co, Ni) structures contain metallocene subunits with their metal atoms at long nonbonding distances of 3.5-3.9 Å from the other metal atom, which is located between the azulene C7 rings. Higher energy opposed (C10H8)2 Fe2 structures contain an unprecedented distorted η(6) ,η(4) -azulene ligand using six carbon atoms for bonding to one iron atom as a hexahapto fulvene ligand and the remaining four carbon atoms for bonding to the other iron atom as a tetrahapto diene ligand.

  20. Influence of transition metal doping (X  =  Mn, Fe, Co, Ni) on the structure and bandgap of ferroelectric Bi3.15Nd0.85Ti2X1O12

    NASA Astrophysics Data System (ADS)

    Chen, Xiaoqin; Huang, Feng; Lu, Zhangwu; Xue, Yun; Min, Jingjing; Li, Jihui; Xiao, Jun; Yang, Fujun; Zeng, Xiangbin

    2017-03-01

    Although the internal field can effectively maintain the separation between photo-excited charge carriers, the wide bandgap restrains ferroelectric materials from visible light absorption. This study examined the effects of transition metal (TM) Mn, Fe, Co or Ni doping on the structure and bandgap of Bi3.15Nd0.85Ti3O12 (BNdT) prepared by the molten salt synthesis method. No other non-bismuth layered structure phases were introduced. Mn, Co or Ni doping does not change the three-layered perovskite structure of BNdT while Fe doping increases the layer number from three to four. The doping of TM ions decreases the bandgap obviously. Among them, Mn-doped BNdT shows the largest bandgap reduction by ~1.6 eV. The narrowed bandgap was discussed to be attributed to the electronegativity of TM ions and the lattice distortion induced by doping together. The present work provides an available way to control the bandgap of complex oxide materials and provides a new tool for manipulating oxide optoelectronics.

  1. Structure and magnetism of antiferromagnetic FeMN thin films

    NASA Astrophysics Data System (ADS)

    Maat, Stefan

    2000-09-01

    The magnetic and electronic structure of bulk fcc Fe 50Mn50 was studied by first principles calculations using the layer-version of the Korringa- Kohn-Rostocker method with the local spin density approximation and the coherent potential approximation to treat chemical disorder. The self-consistent calculations suggest a non-collinear spin-structure for Fe50Mn50 as the magnetic ground state, which can be understood from the electronic structure. Possible spin-structures identified are the 3Q structure with spins pointing along the body diagonals and the 2Q structure with spins pointing along the face diagonals. The collinear 1Q structure with spins pointing along the cube edges was found to be energetically unstable. Epitaxial FeMn/Cu multilayers were grown epitaxially by sputtering onto a thick buffer layer of twinned Cu(111) on H-terminated Si(110). The growth was characterized in situ by Auger electron spectroscopy and electron diffraction techniques and ex situ by X-ray diffraction. Neutron diffraction experiments were performed on these multilayers to investigate the spin structure of thin Fe50Mn50 films. The measurements confirmed that Fe50Mn50 has either a 3Q structure or equally populated domains of 2Q or 1Q structures. Hysteresis loops of polycrystalline and epitaxial exchange-biased Ni 80Fe20/Fe50Mn50 films were measured as a function of Fe50Mn50 layer thickness with the longitudinal Kerr effect. The variation of the loop-shift and the coercivity were observed over a full 360° in plane rotation and Fourier analyzed. Coercivities and loop shifts show a strong dependence on the antiferromagnetic layer thickness. Examination of the angular dependent results within different models of exchange bias verified that the Fourier coefficients obey necessary conditions to achieve energetic stability together with spontaneous magnetization.

  2. Varied roles of Pb in transition-metal PbMO3 perovskites (M = Ti, V, Cr, Mn, Fe, Ni, Ru).

    PubMed

    Goodenough, John B; Zhou, Jianshi

    2015-06-01

    Different structural chemistries resulting from the Pb(2+) lone-pair electrons in the PbMO3 perovskites are reviewed. The Pb(2+) lone-pair electrons enhance the ferroelectric transition temperature in PbTiO3, stabilize vanadyl formation in PbVO3, and induce a disproportionation reaction of Cr(IV) in PbCrO3. A Pb(2+) + Ni(IV) = Pb(4+) + Ni(II) reaction in PbNiO3 stabilizes the LiNbO3 structure at ambient pressure, but an A-site Pb(4+) in an orthorhombic perovskite PbNiO3 is stabilized at modest pressures at room temperature. In PbMnO3, a ferroelectric displacement due to the lone pair electron effect is minimized by the spin-spin exchange interaction and the strong octahedral site preference of the Mn(IV/III) cation. PbRuO3 is converted under pressure from the defective pyrochlore to the orthorhombic (Pbnm) perovskite structure where Pb-Ru interactions via a common O -2p orbital stabilize at low temperature a metallic Imma phase at ambient pressure. Above Pc [Formula: see text] a covalent Pb-Ru bond is formed by Pb(2+) + Ru(IV) = Pb(4+) + Ru(II) electron sharing.

  3. Unusual features of magnetism in transition-metal-doped phthalocyanines C32H16N8 TM (TM = Mn, Fe, Co, Ni, Cu)

    NASA Astrophysics Data System (ADS)

    Wang, Zhengjun; Seehra, Mohindar S.

    Transition-metal-doped phthalocyanines (TMPc), semiconductors with potential optoelectronic applications, are planar molecules with the TM atom at the center bound to four N atoms and forming a linear chain along the monoclinic b-axis. Because of this symmetry, the ground states of TMPc often violate the Hunds' rules; e.g. the S = 3/2 state for d5 Mn(II) in β-MnPc, S = 1/2 state for the d7 Co(II) in β-CoPc, and S =0 for Ni(II) in NiPc. The magnetic properties of TMPc are also affected by the stack angle δ between the orientation of the molecular plane and the b-axis, δ being 65°(45°) for α (β) phase. For β-CoPc, our M vs. T data fits well with the Bonner-Fisher model for S = 1/2 AFM Heisenberg linear chain yielding the Co2+-Co2+ exchange constant J/kB = - 1.5 K. For β-MnPc , a long-presumed ferromagnet with TC ~ 9 K, our magnetic studies show it to be an Ising chain magnet with Arrhenius magnetic relaxation governed by J/kB = 2.6 K and the zero-field splitting D/kB = 8.3 K. In β-MnPc, the absence of λ-type peak in specific heat and no peaks in ac susceptibilities near the quoted TC ~ 9 K confirms the absence of long range order (LRO). Instead we argue that LRO is absent in β-MnPc as D >J makes the spins in a chain parallel but canted with respect to spins in neighboring chains.

  4. Crystal chemistry of M[PO{sub 2}(OH){sub 2}]{sub 2}.2H{sub 2}O compounds (M=Mg, Mn, Fe, Co, Ni, Zn, Cd): Structural investigation of the Ni, Zn and Cd salts

    SciTech Connect

    Koleva, Violeta Effenberger, Herta

    2007-03-15

    The compounds M[PO{sub 2}(OH){sub 2}]{sub 2}.2H{sub 2}O (M=Mg, Mn, Fe, Co, Ni, Zn, Cd) were prepared from super-saturated aqueous solutions at room temperature. Single-crystal X-ray structure investigations of members with M=Ni, Zn, Cd were performed at 295 and 120 K. The space-group symmetry is P2{sub 1}/n, Z=2. The unit-cell parameters are at 295/120 K for M=Ni: a=7.240(2)/7.202(2), b=9.794(2)/9.799(2), c=5.313(1)/5.285(1) A, {beta}=94.81(1)/94.38(1){sup o}, V=375.4/371.9 A{sup 3}; M=Zn: a=7.263(2)/7.221(2), b=9.893(2)/9.899(3), c=5.328(1)/5.296(2) A, {beta}=94.79(1)/94.31(2){sup o}, V=381.5/377.5 A{sup 3}; M=Cd: a=7.356(2)/7.319(2), b=10.416(2)/10.423(3), c=5.407(1)/5.371(2) A, {beta}=93.85(1)/93.30(2){sup o}, V=413.4/409.1 A{sup 3}. Layers of corner-shared MO{sub 6} octahedra and phosphate tetrahedra are linked by three of the four crystallographically different hydrogen bonds. The fourth hydrogen bond (located within the layer) is worth mentioning because of the short O{sub h}...O bond distance of 2.57-2.61 A at room temperature (2.56-2.57 A at 120 K); only for M=Mg it is increased to 2.65 A. Any marked temperature-dependent variation of the unit-cell dimension is observed only vertical to the layers. The analysis of the infrared (IR) spectroscopy data evidences that the internal PO{sub 4} vibrations are insensitive to the size and the electronic configuration of the M {sup 2+} ions. The slight strengthening of the intra-molecular P-O bonds in the Mg salt is caused by the more ionic character of the Mg-O bonds. All IR spectra exhibit the characteristic 'ABC trio' for acidic salts: 2900-3180 cm{sup -1} (A band), 2000-2450 cm{sup -1} (B band) and 1550-1750 cm{sup -1} (C band). Both the frequency and the intensity of the A band provide an evidence that the PO{sub 2}(OH){sub 2} groups in M[PO{sub 2}(OH){sub 2}]{sub 2}.2H{sub 2}O compounds form weaker hydrogen bonds as compared with other acidic salts with comparable O...O bond distances of about 2.60 A. The

  5. In situ DRIFTs investigation of the reaction mechanism over MnOx-MOy/Ce0.75Zr0.25O2 (M = Fe, Co, Ni, Cu) for the selective catalytic reduction of NOx with NH3

    NASA Astrophysics Data System (ADS)

    Hu, Hang; Zha, Kaiwen; Li, Hongrui; Shi, Liyi; Zhang, Dengsong

    2016-11-01

    A series of MnOx-MOy/Ce0.75Zr0.25O2 (M = Fe, Co, Ni, Cu) catalysts were synthesized by an impregnation method and used for selective catalytic reduction (SCR) of NOx with NH3. The catalytic performances of various MnOx-MOy/Ce0.75Zr0.25O2 catalysts were studied. It was found that MnOx-FeOy/Ce0.75Zr0.25O2 catalyst showed excellent low-temperature activity and a broad temperature window. The catalysts were characterized by N2 adsorption/desorption, X-ray diffraction, X-ray photoelectron spectroscopy and in situ diffuse reflectance infrared transform spectroscopy (DRIFTS). Characterization of the catalyst confirmed the addition of iron oxide can enhance the NO oxidation ability of the catalyst which results in the outstanding low-temperature SCR activity. Meanwhile, iron oxides were well dispersed on catalyst surface which could avoid the agglomeration of active species, contributing to the strong interaction between active species and the support. More importantly, in situ DRIFTS results confirmed that bidentate nitrates are general active species on these catalysts, whereas the reactivity of gaseous NO2 and bridged nitrates got improved because of the addition of Fe.

  6. Molecule-based magnets formed by bimetallic three-dimensional oxalate networks and chiral tris(bipyridyl) complex cations. The series [ZII(bpy)3][ClO4][MIICrIII(ox)3] (ZII = Ru, Fe, Co, and Ni; MII = Mn, Fe, Co, Ni, Cu, and Zn; ox = oxalate dianion).

    PubMed

    Coronado, E; Galán-Mascarós, J R; Gómez-García, C J; Martínez-Agudo, J M

    2001-01-01

    The synthesis, structure, and physical properties of the series of molecular magnets formulated as [ZII(bpy)3][ClO4][MIICrIII(ox)3] (ZII = Ru, Fe, Co, and Ni; MII = Mn, Fe, Co, Ni, Cu, and Zn; ox = oxalate dianion) are presented. All the compounds are isostructural to the [Ru(bpy)3][ClO4][MnCr(ox)3] member whose structure (cubic space group P4(1)32 with a = 15.506(2) A, Z = 4) consists of a three-dimensional bimetallic network formed by alternating MII and CrIII ions connected by oxalate anions. The identical chirality (lambda in the solved crystal) of all the metallic centers determines the 3D chiral structure adopted by these compounds. The anionic 3D sublattice leaves some holes where the chiral [Z(bpy)3]2+ and ClO4- counterions are located. These compounds behave as soft ferromagnets with ordering temperatures up to 6.6 K and coercive fields up to 8 mT.

  7. Dual support ensuring high-energy supercapacitors via high-performance NiCo2S4@Fe2O3 anode and working potential enlarged MnO2 cathode

    NASA Astrophysics Data System (ADS)

    Jia, Ruyue; Zhu, Feng; Sun, Shuo; Zhai, Teng; Xia, Hui

    2017-02-01

    Development of high-energy and high-power asymmetric supercapacitors (ASCs) is still a great challenge due to the low specific capacitance of anode materials (carbon materials of about 100-200 F g-1) and limited voltage window (<2 V) in aqueous electrolytes. Herein, we demonstrate the rational design of the hybrid NiCo2S4@Fe2O3 nanoneedle array anode with large specific capacitance (342 F g-1 at 5 mV s-1) and MnO2 nanosheet array cathode working in wide potential window (0-1.3 V vs. SCE) for high-energy and high-power ASCs. The unique core-shell hierarchical nanoarchitecture of the hybrid NiCo2S4@Fe2O3 nanoneedle arrays not only provides large surface area for charge storage but also facilitates fast charge transport in the electrode. Moreover, the extended potential window of the MnO2 cathode can effectively increase the device voltage of the as-assembled ASC up to 2.3 V, resulting in significantly increased energy density. The obtained ASC device can deliver a high volumetric energy density of 2.29 mWh cm-3 at 196 mW cm-3 and retain 1.08 mWh cm-3 at 2063 mW cm-3, providing new opportunity for developing high-performance ASCs.

  8. Steam reforming of ethanol at moderate temperature: Multifactorial design analysis of Ni/La 2O 3-Al 2O 3, and Fe- and Mn-promoted Co/ZnO catalysts

    NASA Astrophysics Data System (ADS)

    Torres, José Antonio; Llorca, Jordi; Casanovas, Albert; Domínguez, Montserrat; Salvadó, Joan; Montané, Daniel

    Novel Co (10%) catalysts supported on ZnO and promoted with Fe and Mn (1%) were synthesized and characterized by high-resolution transmission electron microscopy (HRTEM), electron energy-loss spectroscopy (EELS), X-ray diffraction (XRD) and X-ray photoelectron spectra (XPS). Their catalytic activity for steam reforming of ethanol was compared with that of Ni catalysts supported on La 2O 3-Al 2O 3. Experiments at 400 and 500 °C, steam to carbon ratios of 2 and 4, and a wide interval of contact time were analyzed following a multifactorial experimental design. At 500 °C and a steam to carbon molar ratio of 4, complete conversion of ethanol was achieved above a contact time of 200 g min mol -1 for all catalysts. The ratio of selectivity between hydrogen and methane was around 23 mol H2/mol CH4 in the Co catalysts, while it approached the thermodynamic equilibrium (5.7 mol H2/mol CH4) in the Ni catalysts. The Co catalysts do not promote methane-forming reactions like ethanol cracking and acetaldehyde decarbonilation, nor do they facilitate the reverse methane steam reforming reaction. The catalytic behavior of cobalt is enhanced by promotion with iron or manganese through the formation of bimetallic particles, which facilitates cobalt reducibility. This suggests that Co-Mn/ZnO and Co-Fe/ZnO catalysts have a good potential for their use for ethanol reforming at moderate temperature.

  9. Quaternary M{sub 0.25}Cu{sub 0.25}Mg{sub 0.5}Fe{sub 2}O{sub 4} (M = Ni, Zn, Co, Mn) ferrite oxides: Synthesis, characterization and magnetic properties

    SciTech Connect

    Ciocarlan, Radu George; Pui, Aurel; Gherca, Daniel; Virlan, Constantin; Dobromir, Marius; Nica, Valentin; Craus, Mihail Liviu; Gostin, Irina Neta; Caltun, Ovidiu; Hempelman, Rolf; Cool, Pegie

    2016-09-15

    Highlights: • Superparamagnetic quaternary nanoferrite (M{sub 0.25}Cu{sub 0.25}Mg{sub 0.5}Fe{sub 2}O{sub 4,} where M = Mn, Zn, Co, Ni) were obtained. • C, O, H and metals were observed by XPS analysis. • Phases purity were confirmed by XRD diffraction and crystallite size (3–10 nm) were determind. - Abstract: We report the synthesis of M{sub 0.25}Cu{sub 0.25}Mg{sub 0.5}Fe{sub 2}O{sub 4} (where M = Mn, Zn, Co, Ni) nanoparticles using the coprecipitation method in the presence of carboxymethyl cellulose (CMC) as the in-situ surfactant. The crystalline structure and surface morphology were examined by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM) and it was established that the average diameter of the magnetic nanoparticles (MNPs) is in the range of 3–10 nm. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) show that the MNPs are activated by the hydrophilic groups of the surfactant, which coat them and enhance their stability. The vibrating sample magnetometry measurements show the superparamagnetic behavior of the nanoparticles. Due to their small crystallite size, which implies large surface area, and their functionalization with organic groups, the obtained nanoparticles could have medical and catalytic applications.

  10. Long-range antiferromagnetic order in malonate-based compounds Na2M(H2C3O4)2·2H2O (M = Mn, Fe, Co, Ni).

    PubMed

    Rousse, G; Radtke, G; Klein, Y; Ahouari, H

    2016-02-14

    The recently discovered metal-malonate compounds of formulae Na2M(H2C3O4)2·2H2O with M = Mn, Fe, Co, Ni are investigated for their magnetic properties. While the Cu-based material is a weak ferromagnet, all other members present antiferromagnetic interactions. Neutron powder diffraction experiments reveal the establishment of a long range magnetic order at low temperature in the Pbca Shubnikov magnetic group. The magnetic structures are characterized by antiferromagnetic layers perpendicular to [001]. These layers are stacked antiparallel (M = Fe) or parallel (M = Mn, Ni) in the (a, c) plane. Magnetic moments are collinear to b for the former and to c for the latter. The M = Co malonate exhibits a non-collinear magnetic structure intermediate between the two latter, with components along b and c. Density functional theory calculations indicate that the dominant magnetic interaction, J1, occurs along a malonate group via a carboxylate and links two transition metals within the same layer, while other interactions (inter- or intra-layer) are much weaker, so that these compounds present the dominant characteristics of 2D-antiferromagnets.

  11. Electric field control of Martensitic Phase Transitions in Thin Films of Ni-Mn-In

    NASA Astrophysics Data System (ADS)

    Al-Aqtash, Nabil; Sokolov, Andrei; Sabirianov, Renat

    2015-03-01

    We propose the electric field control of martensite transformation of Ni-Mn-In thin films deposited on ferroelectric (FE) substrate. DFT- based calculations indicate that the off-stochiometric Ni2Mn1.5In0.5 alloy shows that the ferromagnetic (FM) cubic phase undergoes transformation to tetragonal ferromagnetic (FiM) martensite phase at low temperature. The presence of FE substrate changes the relative stability of FM austenite and FiM martensite phases. (SrZrO3/PbZrO3) superlattices were considered as FE substrates with polarization perpendicular to the interface. The relative stability of two phases of the thin films can be tuned by polarization reversal in FE due to the change in sign of induced charges at the interface. The energetically favorable structures of the FE/Ni2Mn1.5In0.5 systems depend on interface structure between FE and Ni2Mn1.5In0.5 layers, e.g Ni-(Pb-O) interface. The energy difference (per NiMnIn f.u) between FM austenite and FiM martensite states of the film on FE substrate is ΔE = 0.22 eV with polarization away from interface, upon polarization reversal ΔE = 0.75 eV, compared to (ΔE = 0.24 eV) in the bulk. Additionally Pb atoms in PbO3 planes shifted in opposite direction with respect to oxygen planes and alter the chemical bonding of Pb with Ni atoms of the thin films. These changes possibly cause the shift of the martensite transition temperature. These results clearly indicate the possibility of control of martensitic transition in Ni-Mn-In thin films by FE substrate.

  12. Electronic structure of Mn and Fe oxides

    NASA Astrophysics Data System (ADS)

    Harrison, Walter

    2008-03-01

    We present a clear, simple tight-binding representation of the electronic structure and cohesive energy (energy of atomization) of MnO, Mn2O3, and MnO2, in which the formal charge states Mn^2+, Mn^3+, and Mn^4+, respectively, occur. It is based upon localized cluster orbitals for each Mn and its six oxygen neighbors. This approach is fundamentally different from local-density theory (or LDA+U), and perhaps diametrically opposite to Dynamical Mean Field Theory. Electronic states were calculated self-consistently using existing parameters [1], but it is found that the charge density is quite insensitive to charge state, so that the starting parameters are adequate. The cohesive energy per Mn is dominated by the transfer of two s electrons to oxygen p states, the same for all three compounds. The differing transfer of majority d electrons to oxygen p states, and the coupling between them, accounts for the observed variation in cohesion in the series. The same description applies to the perovskites, such as LaxSr1-xMnO3, and can be used for FeO, Fe2O3 (and FeO2), Because the formulation is local, it is equally applicable to impurities, defects and surfaces. [1] Walter A. Harrison, Elementary Electronic Structure, World Scientific (Singapore, 1999), revised edition (2004).

  13. Room temperature multiferroic properties of (Bi{sub 0.95}La{sub 0.05})(Fe{sub 0.97}Mn{sub 0.03})O{sub 3}/NiFe{sub 2}O{sub 4} double layered thin film

    SciTech Connect

    Raghavan, C.M.; Kim, H.J.; Kim, J.W.; Kim, S.S.

    2013-11-15

    Graphical abstract: - Highlights: • Chemical solution deposition of (Bi{sub 0.95}La{sub 0.05})(Fe{sub 0.97}Mn{sub 0.03})O{sub 3}–NiFe{sub 2}O{sub 4} double layered thin film. • Studies on structural, electrical and multiferroic properties. • NiFe{sub 2}O{sub 4} acts as both resistive buffer layer and magnetic source. - Abstract: (Bi{sub 0.95}La{sub 0.05})(Fe{sub 0.97}Mn{sub 0.03})O{sub 3}/NiFe{sub 2}O{sub 4} double layered thin film was prepared on a Pt(111)/Ti/SiO{sub 2}/Si(100) substrate by a chemical solution deposition method. X-ray diffraction and Raman scattering spectroscopy studies confirmed the formation of the distorted rhombohedral perovskite and the inverse spinel cubic structures for the (Bi{sub 0.95}La{sub 0.05})(Fe{sub 0.97}Mn{sub 0.03})O{sub 3}/NiFe{sub 2}O{sub 4} double layered thin film. The (Bi{sub 0.95}La{sub 0.05})(Fe{sub 0.97}Mn{sub 0.03})O{sub 3}/NiFe{sub 2}O{sub 4} double layered thin film exhibited well saturated ferromagnetic (2 M{sub r} of 18.1 emu/cm{sup 3} and 2H{sub c} of 0.32 kOe at 20 kOe) and ferroelectric (2P{sub r} of 60 μC/cm{sup 2} and 2E{sub c} of 813 kV/cm at 866 kV/cm) hysteresis loops with low order of leakage current density (4.5 × 10{sup −6} A/cm{sup 2} at an applied electric field of 100 kV/cm), which suggest the ferroelectric and ferromagnetic multi-layers applications in real devices.

  14. Effect of temperature on magnetization reversal characteristics of ferromagnetic 3 d metal layers within exchange-coupled FeMn-based structures

    NASA Astrophysics Data System (ADS)

    Vas'kovskiy, V. O.; Adanakova, O. A.; Gorkovenko, A. N.; Lepalovskij, V. N.; Svalov, A. V.; Stepanova, E. A.

    2015-12-01

    Multilayer films Fe20Ni80/FeMn/FM (with FM = Ni, Fe11Ni89, Fe20Ni80, Co30Ni70, Fe, Co) have been prepared and their structure has been estimated. Their hysteretic properties and interlayer coupling parameters have been studied in a temperature range of 5-350 K. Regularities of the magnetization reversal of ferromagnetic layers under magnetic exchange-bias conditions have been interpreted.

  15. Bioaccumulation of Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb and Zn in trophosome and vestimentum of the tube worm Riftia pachyptila from Guaymas basin, Gulf of California

    NASA Astrophysics Data System (ADS)

    Ruelas-Inzunza, J.; Páez-Osuna, F.; Soto, Luis A.

    2005-07-01

    Twenty two specimens of vestimentiferan tube worms Riftia pachyptila were collected from Guaymas Basin. The distribution of ten trace metals in trophosome and vestimentum was investigated. Highest mean concentrations of Co, Cu and Fe were detected in the trophosome; while higher mean levels of Cd, Hg, Mn, Ni, Pb and Zn were measured in the vestimentum. However, the t-student test resulted in significant differences (p<0.05) only in the case of Co. Cd and Fe concentrations in vestimentum increased accordingly with the size of specimens. With respect to vent fluids, extreme uptake seems to be a characteristic of R. pachyptila in the case of Cu and Zn but not for the rest of the analyzed metals. Studies concerning accumulation mechanisms of trace metals in R. pachyptila are needed, particularly on the capacity of this organism to tolerate elevated levels of elements considered as non-essential.

  16. Fe-Mn nodules of the Mendeleev Ridge, Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Bazilevskaya, E. S.; Skolotnev, S. G.

    2015-10-01

    The results of study of Fe-Mn crusts from the Mendeleev Ridge in the Arctic Ocean sampled with manipulators from a submarine are presented. In almost all the samples, the ore phase is significantly enriched in some valuable trace elements (Ni, Co, Cu, etc.), the contents of which exceed those in ores from the pelagic zones of other oceans. The high ore potential of the Arctic pelagic zone is stated and substantiated.

  17. Heterotetranuclear oxalato-bridged Re(IV)3M(II) (M = Mn, Fe, Co, Ni, Cu) complexes: a new example of a single-molecule magnet (M = Ni).

    PubMed

    Martínez-Lillo, José; Armentano, Donatella; De Munno, Giovanni; Wernsdorfer, Wolfgang; Clemente-Juan, Juan Modesto; Krzystek, J; Lloret, Francesc; Julve, Miguel; Faus, Juan

    2009-04-06

    The use of the mononuclear species (NBu(4))(2)[Re(IV)Cl(4)(ox)] (NBu(4)(+) = tetra-n-butylammonium cation; ox = oxalate dianion) as a ligand toward fully solvated divalent first-row transition-metal ions affords the tetranuclear complexes (NBu(4))(4)[{Re(IV)Cl(4)(mu-ox)}(3)M(II)] with M = Mn (1), Fe (2), Co (3), Ni (4), and Cu (5). Their structure is made up of discrete [{ReCl(4)(mu-ox)}(3)M](4-) anions and bulky NBu(4)(+) cations. The complexes 2-5 crystallize in the triclinic system with space group P1; 2 and 5 as well as 3 and 4 are isostructural. The Re and M atoms exhibit somewhat distorted ReCl(4)O(2) and MO(6) octahedral surroundings, with the oxalate groups adopting the bis-bidentate bridging mode. Magnetic susceptibility measurements on polycrystalline samples of 1-5 in the temperature range 1.9-300 K show the occurrence of intramolecular antiferromagnetic [J = -1.30 cm(-1) (1)] and ferromagnetic couplings [J = +1.62 (2), +3.0 (3), +16.3 (4), and +4.64 cm(-1) (5)], with the Hamiltonian being defined as H = -J[S(M)(S(Re1) + S(Re2) + S(Re3))]. Compound 4 is the first example of an oxalato-bridged heterometallic species that behaves as a single-molecule magnet with a ground-state spin S = (11)/(2) and D = -0.8(1) cm(-1), as shown by the study of its static and dynamic magnetic properties and a high-frequency electron paramagnetic resonance study on polycrystalline samples together with detailed micro-SQUID measurements on single crystals.

  18. Tough cryogenic alloys from the Fe-Mn and Fe-Mn-Cr systems

    NASA Technical Reports Server (NTRS)

    Schanfein, M. J.; Zackay, V. F.; Morris, J. W., Jr.

    1974-01-01

    By adjusting composition, metastable gamma (austenite) and epsilon (hexagonal) martensite may be retained in Fe-Mn and Fe-Mn-Cr alloys and used to impact toughness through the TRIP mechanism. The resulting alloys have excellent toughness at cryogenic temperatures. The best alloys obtained to date are: Fe-20Mn, with sigma (sub y) = 79ksi and K sub IC = 275ksi square root of (in) at 77 K, and Fc-16Mn-8Cr, with sigma sub y = 85ksi and K sub IC = 72ksi square root of (in) at 77 K.

  19. Spectroscopic and thermal degradation behavior of Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) complexes with thiopental sodium anesthesia drug

    NASA Astrophysics Data System (ADS)

    Refat, Moamen S.

    2013-04-01

    A new series of Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) complexes have been synthesized with thiopental sodium anesthesia drug. The elemental analyses of the complexes are confined to stoichiometry of the formulas [M(TPL)3]ṡnH2O (M = Cr(III) or Fe(III); n = 6 or 5), [M(TPL)2(H2O)2]ṡnH2O (M = Mn(II), Co(II) or Ni(II); n = 0 or 4), and [M(TPL)2] (M = Cu(II) or Zn(II); n = 2 or 0) respectively, where TPL is thiopental chelating agent. Structures have been discussed and suggested upon elemental analyses, infrared, Raman, electronic, electron spin resonance, 1H NMR spectral data and magnetic studies. The X-ray powder diffraction (XRD) was performed of metal complexes. The XRD patterns indicate crystalline nature for the complexes. The measured low molar conductance values in dimethylsulfoxide indicate that the complexes are non-electrolyte nature. Spectroscopic discussion refer that coordination take place through three types: Cdbnd N (pyrimidine moiety) nitrogen and C2sbnd S (2-thiolate group) for Cr(III), Mn(II) and Fe(III), C6dbnd O (amido group) oxygen and C2sbnd S (2-thiolate group) for Co(II) and Ni(II), and Cu(II) and Zn(II) ions coordinated via Cdbnd N (pyrimidine moiety) nitrogen, C2dbnd S (2-thiolate group) and C6dbnd O (amido group) oxygen, respectively. The thermal behavior (TG/DTG/DTA) of the complexes was studied and kinetic parameters were determined by Horowitz-Metzger and Coats-Redfern methods. The thiopental and its complexes have been screened for their antimicrobial (G+ and G-) bacteria (Escherichia coli, Staphylococcus aureus, Bacillus subtilis and Pseudomonas aeruginosa) and fungi (Aspergillus flavus and Candida albicans) activities by minimum inhibitory concentration (MIC) method.

  20. A series of borate-rich metalloborophosphates Na 2[ MIIB 3P 2O 11(OH)]·0.67H 2O ( MII=Mg, Mn, Fe, Co, Ni, Cu, Zn): Synthesis, structure and magnetic susceptibility

    NASA Astrophysics Data System (ADS)

    Yang, Tao; Li, Guobao; Ju, Jing; Liao, Fuhui; Xiong, Ming; Lin, Jianhua

    2006-08-01

    A series of metalloborophosphates Na 2[ MIIB 3P 2O 11(OH)]·0.67H 2O ( MII=Mg, Mn, Fe, Co, Ni, Cu, Zn) have been prepared hydrothermally and their structures have been solved by single-crystal diffraction techniques. They all crystallize in a hexagonal space group P6 3 and form a 3D microporous structure with 12-membered ring channels consisted of octahedral ( MIIO 6), tetrahedral (BO 4, PO 4) and triangular (BO 2(OH)) units, in which the counter Na + cations and water molecules are located. The Na + cations are mobile and can be exchanged by Li + in a melt of LiNO 3. Their open frameworks are thermal stable up to about 500 °C. Completed solid solutions between two different transition metals can also be obtained. Magnetic properties of Na 2[ MIIB 3P 2O 11(OH)]·0.67H 2O ( MII=Mn, Co, Ni, Cu) have been investigated.

  1. Structure and Electrochemistry of LiNi1/3Co1/3-yMyMn1/3O2 (M=Ti, Al, Fe) Positive Electrode Materials

    SciTech Connect

    Wilcox, James; Patoux, Sebastien; Doeff, Marca

    2009-01-14

    A series of materials based on the LiNi1/3Co1/3-yMyMn1/3O2 (M = Ti,Al,Fe) system has been synthesized and examined structurally and electrochemically. It is found that the changes in electrochemical performance depend highly on the nature of the substituting atom and its effect on the crystal structure. Substitution with small amounts of Ti4+ (y = 1/12) leads to the formation of a high-capacity and high-rate positive electrode material. Iron substituted materials suffer from an increased antisite defect concentration and exhibit lower capacities and poor rate capabilities. Single-phase materials are found for LiNi1/3Co1/3-yAlyMn1/3O2 when y<_ 1/4 and all exhibit decreased capacities when cycled to 4.3 V. However, an increase in rate performance and cycle stability upon aluminum substitution is correlated with an improved lamellar structure.

  2. Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) new complexes of 5-aminosalicylic acid: Spectroscopic, thermal characterization and biological activity studies

    NASA Astrophysics Data System (ADS)

    Soliman, Madiha H.; Mohamed, Gehad G.

    2013-04-01

    The complexing behavior of mesalazine (5-aminosalicylic acid; 5-ASA) towards the transition metal ions namely, Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) have been examined by elemental analyses, magnetic measurements, electronic, IR and 1H NMR. Thermal properties and decomposition kinetics of all complexes are investigated. The interpretation, mathematical analyses and evaluation of kinetic parameters of all thermal decomposition stages have been evaluated using Coats-Redfern equation. The free ligand and its metal complexes have been tested in vitro against Aspergillus fumigatus and Candida albicans fungi and Pseudomonas aeruginosa, Escherichia coli, Bacillis subtilies and Staphylococcus aureus bacteria in order to assess their antimicrobial potential. The results indicate that the metal complexes are also found to have more antimicrobial activity than the parent 5-ASA drug.

  3. Effect of heat treatment on structural and Mössbauer spectroscopic properties of coprecipitated Mn{sub 0.5}Ni{sub 0.5}Fe{sub 2}O{sub 4} ferrite nanoparticles

    SciTech Connect

    Srinivas, Ch.; Babu, Ch. Seshu; Tirupanyam, B. V.; Meena, S. S.; Sastry, D. L.

    2015-06-24

    Results obtained in a systamatic study by X-ray diffraction and Mösssbauer spectroscopy on the structural and magnetic properties on Mn{sub 0.5}Ni{sub 0.5}Fe{sub 2}O{sub 4} ferrite nanoparticles heat treated at 200 °C, 500 °C and 800 °C are reported. Average crystallite sizes are estimated to be in the range (2.6nm – 12.8nm). It is observed that crystallite sizes increase with increase in sintering temperature and random variation in lattice parameter was observed. At relatively low sintering temperatures the samples exhibit superparamagnetism and complete ferrite phase was observed at higher heat treatment.

  4. Structural evolution of the double perovskites Sr{sub 2}B'UO{sub 6} (B' = Mn, Fe, Co, Ni, Zn) upon reduction: Magnetic behavior of the uranium cations

    SciTech Connect

    Pinacca, R.M.; Viola, M.C.; Pedregosa, J.C.; Carbonio, R.E.; Lope, M.J. Martinez; Alonso, J.A.

    2011-11-15

    Highlights: {yields} Evolution of the double perovskites Sr{sub 2}B'UO{sub 6} upon reduction were studied by XRPD. {yields} Orthorhombic (Pnma) disordered perovskites SrB'{sub 0.5-x}U{sub 0.5+x}O{sub 3} were obtained at 900 {sup o}C. {yields} U{sup 5+/4+} and Zn{sup 2+} cations are distributed at random over the octahedral positions. {yields} AFM ordering for the perovskite with B' = Zn appears below 30 K. -- Abstract: We describe the preparation of five perovskite oxides obtained upon reduction of Sr{sub 2}B'UO{sub 6} (B' = Mn, Fe, Co, Ni, Zn) with H{sub 2}/N{sub 2} (5%/95%) at 900 {sup o}C during 8 h, and their structural characterization by X-ray powder diffraction (XRPD). During the reduction process there is a partial segregation of the elemental metal when B' = Co, Ni, Fe, and the corresponding B'O oxide when B' = Mn, Zn. Whereas the parent, oxygen stoichiometric double perovskites Sr{sub 2}B'UO{sub 6} are long-range ordered concerning B' and U cations. The crystal structures of the reduced phases, SrB'{sub 0.5-x}U{sub 0.5+x}O{sub 3} with 0.37 < x < 0.27, correspond to simple, disordered perovskites; they are orthorhombic, space group Pnma (No. 62), with a full cationic disorder at the B site. Magnetic measurements performed on the phase with B' = Zn, indicate uncompensated antiferromagnetic ordering of the U{sup 5+}/U{sup 4+} sublattice below 30 K.

  5. Chiral molecular magnets: synthesis, structure, and magnetic behavior of the series [M(L-tart)] (M = Mn(II), Fe(II), Co(II), Ni(II); L-tart = (2R,3R)-(+)-tartrate).

    PubMed

    Coronado, Eugenio; Galán-Mascarós, José R; Gómez-García, Carlos J; Murcia-Martínez, Ana

    2006-04-24

    A new series of layered magnets with the formula [M(L-tartrate)] (M = Mn(II), Co(II), Fe(II), Ni(II); L-tartrate = (2R,3R)-(+)-tartrate) has been prepared. All of these compounds are isostructural and crystallize in the chiral orthorhombic space group I222, as found by X-ray structure analysis. Their structure consists of a three-dimensional polymeric network in which each metal shows distorted octahedral coordination bound to four L-tartrate ligands, two of which chelate through an alcohol and a carboxylate group and the other two bind terminally through a monodentate carboxylate group. The chirality of the ligand imposes a Delta conformation on all metal centers. Magnetically, the paramagnetic metal centers form pseudotetragonal layers in which each metal is surrounded by four other metals, with syn,anti carboxylate bridges. These salts show intralayer antiferromagnetic or ferromagnetic interactions, depending on the electronic configuration of the metal, and weak interlayer antiferromagnetic interaction. In all cases the magnetic properties are strongly affected by the anisotropy of the system, and the presence of magnetic canting has been found. The Mn derivative behaves as a weak ferromagnet with a critical temperature of 3.3 K. The Ni derivative shows very unusual magnetic behavior in that it exhibits antiferromagnetic ordering below 6 K, the onset of spontaneous magnetization arising from spin reorientation into a canted phase below 4.5 K, and a field-induced ferromagnetic state above 0.3 T at 2 K, behavior typical of metamagnets. The Fe and Co derivatives show antiferromagnetic interactions between spin carriers, but do not order above 2 K.

  6. Simultaneous determination of Cd, Pb, Cu, Sb, Bi, Se, Zn, Mn, Ni, Co and Fe in water samples by differential pulse stripping voltammetry at a hanging mercury drop electrode.

    PubMed

    Ghoneim, M M; Hassanein, A M; Hammam, E; Beltagi, A M

    2000-06-01

    A highly sensitive and selective voltammetric procedure is described for the simultaneous determination of eleven elements (Cd, Pb, Cu, Sb, Bi, Se, Zn, Mn, Ni, Co and Fe) in water samples. Firstly, differential pulse anodic stripping voltammetry (DPASV) with a hanging mercury drop electrode (HMDE) is used for the direct simultaneous determination of Cd, Pb, Cu, Sb and Bi in 0.1 M HCI solution (pH = 1) containing 2 M NaCl. Then, differential pulse cathodic stripping voltammetry (DPCSV) is used for the determination of Se in the same solution. Zn is subsequently determined by DPASV after raising the pH of the same solution to pH 4. Next, the pH of the medium is raised to pH 8.5 by adding NH3/NH4Cl buffer solution for the determination of Mn by DPASV. Ni and Co are determined in the same solution by differential pulse adsorptive stripping voltammetry (DPAdSV) after adding DMG (1 x 10(-4) M). Finally, 1 x 10(-5) M 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) is added to the solution for the determination of Fe by DPAdSV. The optimal conditions are described. Relative standard deviations and relative errors are calculated for the eleven elements at three different concentration levels. The lower detection limits for the investigated elements range from 1.11 x 10(-10) to 1.05 x 10(-9)M, depending on the element determined. The proposed analysis scheme was applied for the determination of these eleven elements in some ground water samples.

  7. Domain Structures and Anisotropy in Exchange-coupled [Co/Pd]-NiFe and [Co/Ni]-NiFe Multilayers

    NASA Astrophysics Data System (ADS)

    Tryputen, Larysa; Chung, Sunjae; Mohseni, Majid; Nguyen, T. N. Anh; Åkerman, Johan; Guo, Feng; McMichael, Robert D.; Ross, Caroline A.

    2014-03-01

    Exchange-coupled multilayers [Co/Pd]5-/NiFe and [Co/Ni]4-NiFe with strong perpendicular magnetic anisotropy have been proposed to use in spin-torque switching and oscillators devices with tilted fixed and free layer to improve their functional performance. We present an experimental study of the magnetization behavior of [Co/Pd]5-/NiFe and [Co/Ni]4-NiFe multilayers measured using magnetometry, magnetic force microscopy (MFM) and ferromagnetic resonance (FMR) as a function of the thickness of the top NiFe layer. We varied the thickness of the NiFe layer in [Co/Pd]5-NiFe (t), t = 0 - 80 nm and [Co/Ni]4-NiFe (t), t = 0.5 - 2.5 nm in order to study the interplay between perpendicular magnetization of the Co/Pd or Co/Ni multilayers and in-plane magnetization of the NiFe. Our magnetometry and FMR data suggest that the [Co/Ni]4/NiFe multilayer behaves like a homogeneous ferromagnetic film with anisotropy that reorients towards in-plane as the NiFe thickness increases, whereas the [Co/Pd]5/NiFe multilayer reveals more complex behavior in which the [Co/Pd] layer retains out-of-plane anisotropy while the magnetization of NiFe layer tilts in-plane with increasing thickness. MFM showed that domains with ~0.1 +/-m size were visible in [Co/Pd]-/NiFe with NiFe thickness of 20-80 nm. Multilayers were patterned into sub-100 nm dots using ion beam etching and their magnetization behavior are compared with unpatterned films.

  8. Modeling and Characterization of the Magnetocaloric Effect in Ni2MnGa Materials

    SciTech Connect

    Nicholson, Don M; Odbadrakh, Khorgolkhuu; Rios, Orlando; Hodges, Jason P; Ludtka, Gerard Michael; Porter, Wallace D; Sefat, A. S.; Rusanu, Aurelian; Evans III, Boyd Mccutchen

    2012-01-01

    Magnetic shape memory alloys have great promise as magneto-caloric effect refrigerant materials due to their combined magnetic and structural transitions. Computational and experimental research is reported on the Ni2MnGa material system. The magnetic states of this system have been explored using the Wang-Landau statistical approach in conjunction with the Locally Self-consistent Multiple-Scattering (LSMS) method to explore the magnetic states responsible for the magnet-caloric effect in this material. The effects of alloying agents on the transition temperatures of the Ni2MnGa alloy were investigated using differential scanning calorimetry (DSC) and superconducting quantum interference device (SQUID). Neutron scattering experiments were performed to observe the structural and magnetic phase transformations at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) on alloys of Ni-Mn-Ga and Ni-Mn-Ga-Cu-Fe. Data from the observations are discussed in comparison with the computational studies.

  9. Phase transitions and magnetocaloric effect in MnNiGe 1--xAlx, Ni50Mn35(In1--x Crx)15 and (Mn1--xCrx)NiGe 1.05

    NASA Astrophysics Data System (ADS)

    Quetz, Abdiel

    The magnetocaloric and thermomagnetic properties of the MnNiGe1-xAlx, Ni50Mn35(In 1-xCrx)15 and (Mn1-xCr x)NiGe1.05 systems have been studied by x-ray diffraction, differential scanning calorimetry (DSC), and magnetization measurements. Partial substitution of Al for Ge in MnNiGe1-xAl x results in a first-order magnetostructural transition (MST) from a hexagonal ferromagnetic to an orthorhombic antiferromagnetic phase at 186 K (for x = 0.09). A large magnetic entropy change of ∆SM = -17.6 J/kg K for ∆H = 5 T was observed in the vicinity of T M = 186 K for x = 0.09. This value is comparable to those of well-known giant magnetocaloric materials, such as Gd5Si2Ge 2, MnFeP0.45As0.55, and Ni50Mn 37Sn13 [1]. The values of the latent heat (L = 6.6 J/g) and corresponding total entropy changes (∆ST = 35 J/kg K) have been evaluated for the MST using DSC measurements. Large negative values of ∆S M of -5.8 and -4.8 J/kg K for ∆H = 5 T in the vicinity of T C were observed for x = 0.09 and 0.085, respectively. Partial substitution of Cr for Mn in(Mn1-xCrx)NiGe 1.05 results in a MST from a hexagonal paramagnetic to an orthorhombic paramagnetic phase near TM ~ 380 K (for x = 0.07). Partial substitution of Cr for In in Ni50Mn35(In1-xCr x)15 shifts the magnetostructural transition to a higher temperature (TM ~ 450 K) for x = 0.1. Large magnetic entropy changes of ∆SM = -12 (J/kgK) and ∆S = -11 (J/kgK), both for a magnetic field change of 5 T, were observed in the vicinity of TM for (Mn1-xCrx)NiGe1.05 and Ni 50Mn35(In1-xCrx)15, respectively. The concentration-dependent (T-x) phase diagram of transition temperatures (magnetic, structural, and magnetostructural) has been generated using magnetic, XRD, and DSC data. The role of magnetic and structural changes on transition temperatures are discussed.

  10. Structural ordering tendencies in the new ferromagnetic Ni-Co-Fe-Ga-Zn Heusler alloys

    NASA Astrophysics Data System (ADS)

    Dannenberg, Antje; Siewert, Mario; Gruner, Markus E.; Wuttig, Manfred; Entel, Peter

    In search for new ferromagnetic shape memory alloys (FSMA) we have calculated structural energy differences, magnetic exchange interaction constants and mixing energies of quaternary (X1X2)YZ Heusler alloys with X1,X2,Y =Ni,Co,Fe and Z=Ga, Zn using density functional theory. The comparison of the energy profiles of (NiCo)FeZ, (FeNi)CoZ, and (FeCo)NiZ with Z=Ga and Zn as a function of the tetragonal distortion c / a reveals that the energetically preferred ordering type is (NiCo)FeGa and (NiCo)FeZn which shows that Fe prefers to occupy the same cubic sublattice as Ga or Zn what implies that Fe favors Co and Ni as nearest neighbors, respectively. The Curie temperatures of (NiCo)FeGa and (NiCo)FeZn are high of the order of 600 K. (NiCo)FeGa, which has the same valence electron concentration (e/a=7.5) as Ni2MnGa and also possesses a high martensitic transformation temperature (>500 K), is of interest for future magnetic shape memory devices.

  11. Enhanced Photovoltage Response of Hematite-X-Ferrite Interfaces (X = Cr, Mn, Co, or Ni)

    NASA Astrophysics Data System (ADS)

    Bian, Liang; Li, Hai-long; Li, Yu-jin; Nie, Jia-nan; Dong, Fa-qin; Dong, Hai-liang; Song, Mian-xin; Wang, Li-sheng; Zhou, Tian-liang; Zhang, Xiao-yan; Li, Xin-xi; Xie, Lei

    2017-02-01

    High-fluorescent p-X-ferrites (XFe2O4; XFO; X = Fe, Cr, Mn, Co, or Ni) embedded in n-hematite (Fe2O3) surfaces were successfully fabricated via a facile bio-approach using Shewanella oneidensis MR-1. The results revealed that the X ions with high/low work functions modify the unpaired spin Fe2+-O2- orbitals in the XFe2O4 lattices to become localized paired spin orbitals at the bottom of conduction band, separating the photovoltage response signals (73.36 455.16/-72.63 -32.43 meV). These (Fe2O3)-O-O-(XFe2O4) interfacial coupling behaviors at two fluorescence emission peaks (785/795 nm) are explained via calculating electron-hole effective masses (Fe2O3-FeFe2O4 17.23 × 10-31 kg; Fe2O3-CoFe2O4 3.93 × 10-31 kg; Fe2O3-NiFe2O4 11.59 × 10-31 kg; Fe2O3-CrFe2O4 -4.2 × 10-31 kg; Fe2O3-MnFe2O4 -11.73 × 10-31 kg). Such a system could open up a new idea in the design of photovoltage response biosensors.

  12. Mn deposition on Ni{sub 2}MnGa(100)

    SciTech Connect

    Nayak, J.; Rai, Abhishek; D'Souza, S. W.; Maniraj, M.; Barman, S. R.

    2012-06-05

    We report the study of Mn adlayers on a Mn deficient Ni{sub 2}MnGa(100) surface by using low energy electron diffraction (LEED). The spot profile analysis indicates that after 0.2 monolayer (ML) deposition, the LEED spots become very sharp. This pattern indicates the removal of Mn vacancies formed on the surface due to Mn deficiency. But with further growth of Mn layers on this surface, the LEED spots become broad.

  13. Oxalate-based soluble 2D magnets: the series [K(18-crown-6)]3[M(II)3(H2O)4{M(III)(ox)3}3] (M(III) = Cr, Fe; M(II) = Mn, Fe, Ni, Co, Cu; ox = C2O4(2-); 18-crown-6 = C12H24O6).

    PubMed

    Coronado, Eugenio; Galán-Mascarós, José R; Martí-Gastaldo, Carlos; Waerenborgh, João C; Gaczyński, Piotr

    2008-08-04

    The synthesis and magnetic properties of the oxalate-based molecular soluble magnets with general formula [K(18-crown-6)] 3[M (II) 3(H 2O) 4{M (III)(ox) 3} 3] (M (III) = Cr, Fe; M (II) = Mn, Fe, Ni, Co, Cu; ox = C 2O 4 (2-)) are here described. All the reported compounds are isostructural and built up by 2D bimetallic networks formed by alternating M (III) and M (II) ions connected through oxalate anions. Whereas the Cr (III)M (II) derivatives behave as ferromagnets with critical temperatures up to 8 K, the Fe (III)M (II) present ferri- or weak ferromagnetic ordering up to 26 K.

  14. Development of Fe-Mn-Al-X-C alloys

    NASA Technical Reports Server (NTRS)

    Schuon, S. R.

    1982-01-01

    Development of a low cost Cr-free, iron-base alloy for aerospace applications involves both element substitution and enhancement of microstructural strengthening. When Mn is substituted for Ni and Al or Si is substituted for Cr, large changes occur in the mechanical and thermal stability of austenite in FeMnAlC alloys. The in situ strength of MC or M2C (M = Ti, V, Hf, Ta, or Mo) in FeMnAlC alloys was determined. The high temperature tensile strength depends more on the distribution of carbides than the carbide composition. Precipitation of a high volume percent-ordered phase was achieved in Fe2OMnlONi6Al6Ti (lC) alloys. As case, these alloys have a homogeneous austenitic structure. After solutioning at 1100 C for 5 hr followed by aging at 600 C for 16 hr, gamma prime or a perovskite carbide is precipitated. Overaging occurs at 900 C where eta is precipitated.

  15. Systematic study of electronic and magnetic properties for Cu{sub 12–x}TM{sub x}Sb{sub 4}S{sub 13} (TM = Mn, Fe, Co, Ni, and Zn) tetrahedrite

    SciTech Connect

    Suekuni, K.; Tomizawa, Y.; Ozaki, T.; Koyano, M.

    2014-04-14

    Substitution effects of 3d transition metal (TM) impurities on electronic and magnetic properties for Cu{sub 12}Sb{sub 4}S{sub 13} tetrahedrite are investigated by the combination of low-temperature experiments and first-principles electronic-structure calculations. The electrical resistivity for the cubic phase of Cu{sub 12}Sb{sub 4}S{sub 13} exhibits metallic behavior due to an electron-deficient character of the compound. Whereas that for 0.5 ≤ x ≤ 2.0 of Cu{sub 12−x}Ni{sub x}Sb{sub 4}S{sub 13} exhibits semiconducting behavior. The substituted Ni for Cu is in the divalent ionic state with a spin magnetic moment and creates impurity bands just above the Fermi level at the top of the valence band. Therefore, the semiconducting behavior of the electrical resistivity is attributed to the thermal excitation of electrons from the valence band to the impurity band. The substitution effect of TM on the electronic structure and the valency of TM for Cu{sub 11.0}TM{sub 1.0}Sb{sub 4}S{sub 13} are systematically studied by the calculation. The substituted Mn, Fe, and Co for Cu are found to be in the ionic states with the spin magnetic moments due to the large exchange splitting of the 3d bands between the minority- and majority-spin states.

  16. Crystal structure and dielectric properties of aurivillius phases A 0.5Bi4.5 B 0.5Ti3.5O15 ( A = Na, Ca, Sr, Pb; B = Cr, Co, Ni, Fe, Mn, Ga)

    NASA Astrophysics Data System (ADS)

    Vlasenko, V. G.; Zubkov, S. V.; Shuvaeva, V. A.; Abdulvakhidov, K. G.; Shevtsova, S. I.

    2014-08-01

    New polycrystalline Bi-containing layered perovskite-like oxides having the Aurivillius phase (AP) structure with the general formula A 0.5Bi4.5 B 0.5Ti3.5O15 ( A = Na, Ca, Sr, Pb; B = Cr, Co, Ni, Fe, Mn, Ga) have been synthesized. The unit cell parameters of the synthesized compounds have been determined by X-ray powder diffraction. All studied APs crystallize in the orthorhombic system (space group A21 am (36)). The degree of distortion of AP unit cells has been analyzed based on the obtained structural parameters. The temperature dependences of the permittivity have been measured and the Curie temperatures have been determined for all the samples. The significant difference in the values of the permittivity maxima for APs Sr0.5Bi4.5Co0.5Ti3.5O15 and Sr0.5Bi4.5Ni0.5Ti3.5O15 has been interpreted based on the electron microscopy data and explained by substantial changes in the porosity and crystal grain sizes of these ceramic samples.

  17. A New CuO-Fe2 O3 -Mesocarbon Microbeads Conversion Anode in a High-Performance Lithium-Ion Battery with a Li1.35 Ni0.48 Fe0.1 Mn1.72 O4 Spinel Cathode.

    PubMed

    Di Lecce, Daniele; Verrelli, Roberta; Campanella, Daniele; Marangon, Vittorio; Hassoun, Jusef

    2017-01-10

    A ternary CuO-Fe2 O3 -mesocarbon microbeads (MCMB) conversion anode was characterized and combined with a high-voltage Li1.35 Ni0.48 Fe0.1 Mn1.72 O4 spinel cathode in a lithium-ion battery of relevant performance in terms of cycling stability and rate capability. The CuO-Fe2 O3 -MCMB composite was prepared by using high-energy milling, a low-cost pathway that leads to a crystalline structure and homogeneous submicrometrical morphology as revealed by XRD and electron microscopy. The anode reversibly exchanges lithium ions through the conversion reactions of CuO and Fe2 O3 and by insertion into the MCMB carbon. Electrochemical tests, including impedance spectroscopy, revealed a conductive electrode/electrolyte interface that enabled the anode to achieve a reversible capacity value higher than 500 mAh g(-1) when cycled at a current of 120 mA g(-1) . The remarkable stability of the CuO-Fe2 O3 -MCMB electrode and the suitable characteristics in terms of delivered capacity and voltage-profile retention allowed its use in an efficient full lithium-ion cell with a high-voltage Li1.35 Ni0.48 Fe0.1 Mn1.72 O4 cathode. The cell had a working voltage of 3.6 V and delivered a capacity of 110 mAh gcathode(-1) with a Coulombic efficiency above 99 % after 100 cycles at 148 mA gcathode(-1) . This relevant performances, rarely achieved by lithium-ion systems that use the conversion reaction, are the result of an excellent cell balance in terms of negative-to-positive ratio, favored by the anode composition and electrochemical features.

  18. Spectroscopic and DFT Investigation of [M{HB(3,5-iPr2pz)3}(SC6F5)] (M = Mn, Fe, Co, Ni, Cu, and Zn) Model Complexes: Periodic Trends in Metal-thiolate Bonding

    PubMed Central

    Gorelsky, Serge I.; Basumallick, Lipika; Vura-Weis, Josh; Sarangi, Ritimukta; Hodgson, Keith O.; Hedman, Britt; Fujisawa, Kiyoshi; Solomon, Edward I.

    2008-01-01

    A series of metal-varied model complexes [ML(SC6F5)] (where L = hydrotris(3,5-diisopropyl-1-pyrazolyl)borate and M = Mn, Fe, Co, Ni, Cu, and Zn) related to blue copper proteins has been studied by the combination of absorption, MCD, resonance Raman, and S K-edge X-ray absorption spectroscopies. Density functional calculations have been used to characterize these complexes and calculate their spectra. The observed variations in geometry, spectra, and bond energies are interpreted in terms of changes in the nature of metal-ligand bonding interactions. The metal 3d-ligand orbital interaction, which contributes to the covalent bonding in these complexes, becomes stronger in going from Mn(II) to Co(II) (the σ contribution) and to Cu(II) (the π contribution). This change in the covalency results from the increased effective nuclear charge of the metal atom in going from Mn(II) to Zn(II) and the change in the 3d orbital populations (d5→d10). Ionic bonding also plays an important role in determining the overall strength of the ML+-SC6F5− interaction. However, there is a compensating effect: as the covalent contribution to the metal-ligand bonding increases, the ionic contribution decreases. These results provide insight into the Irving-Williams series, where it is found that the bonding of the ligand being replaced by the thiolate makes a major contribution to the observed order of stability constants over the series of metal ions. PMID:15998022

  19. Effect of sintering temperature on the structural, dielectric and magnetic properties of Ni0.4Zn0.2Mn0.4Fe2O4 potential for radar absorbing

    NASA Astrophysics Data System (ADS)

    Praveena, K.; Sadhana, K.; Matteppanavar, S.; Liu, Hsiang-Lin

    2017-02-01

    Ni0.4Zn0.2Mn0.4Fe2O4 nanopowders were prepared by sol-gel auto-combustion method, densified at different temperatures 400-700 °C/4 h using conventional sintering method. The grain sizes of all the samples vary between 18 nm and 30 nm. The hysteresis loops show high saturation magnetization and low coercivity, indicating magnetically soft behaviour of the material. The real and imaginary parts of permittivity is almost constant upto 1 GHz and increases with further increase of frequency. The permeability is ruled by Snoek's law, the values of μ‧ increases with increase of temperature and the resonance frequency increases with an increase of temperature. The reflection coefficient is however increasing with sintering temperature and the maximum loss is observed in the range of 100 MHz-1 GHz. Sample sintered at 700 °C has shown maximum reflection loss and this loss occurs due to absorption, destructive interference and multiple internal reflections in the sample. Quality factor is constant upto 380 MHz and increases with frequency for all the samples sintered at different temperatures. The TC for all the samples is above 230 °C. The room temperature EPR spectra confirm the oxidation state of Fe3+. The g-factor is in the range of 2.

  20. Evaluation of Mn substitution for Ni in alumina-forming austenitic stainless steels

    SciTech Connect

    Yamamoto, Yukinori; Santella, Michael L; Liu, Chain T; Evans, Neal D; Maziasz, Philip J; Brady, Michael P

    2009-01-01

    There has been increasing interest in the substitution of low-cost Mn for Ni in austenitic stainless steels due to the rising price of Ni. This paper investigates the possibility of such a substitution approach for the recently developed alumina (Al{sub 2}O{sub 3})-forming austenitic (AFA) class of heat-resistant stainless steels. Computational thermodynamic tools were utilized to predict the alloy composition range to maintain an austenitic matrix microstructure when Mn is substituted for Ni in the presence of Al, which is a strong body-centered-cubic (BCC) phase stabilizer. Phase equilibria, oxidation behavior, and creep properties of Fe-(10-14)Cr-(5--15)Mn-(4-12)Ni-(2.5-3)Al-Cu-Nb-C-B (in weight percent) based alloys were studied. The alloys based on Fe-14Cr-2.5Al-(5-9)Mn-(10-12)Ni exhibited the best balance of oxidation and creep resistance, which represents approximately 50% reduction in Ni content compared to previously developed AFA alloys. These low-Ni, high-Mn AFA alloys formed protective Al{sub 2}O{sub 3} scales up to 973-1073 K in air and at 923 K in air with 10% water vapor. Creep-rupture lives of the alloys under a severe screening condition of 1023 K and 100 MPa were in the 7.2 x 10{sup 5}-1.8 x 10{sup 6} s (200-500 h) range, which is comparable to or somewhat improved over that of type 347 stainless steel (Fe-18Cr-11Ni base).

  1. Evolution of structure, magnetic and transport properties of {{Fe}}_{{1-x}}{{Mn}}_{x}{Se}

    NASA Astrophysics Data System (ADS)

    Ingle, Kapil E.; Priolkar, K. R.; Bhobe, P. A.; Nigam, A. K.

    2016-12-01

    The present paper seeks to investigate effect of Mn doping in superconducting FeSe. It is found that over the entire doping range in {{Fe}}1-xMn x Se (0≤slant x≤slant 1), Mn does not substitute Fe in the superconducting tetragonal phase. Instead two impurity phases, NiAs type hexagonal phase and NaCl type cubic phase, grow with increasing Mn content. Initially, hexagonal phase has a higher content than the cubic phase but beyond x = 0.5, the cubic phase grows rapidly and for x≥slant 0.8, the sample is monophasic with cubic NaCl type structure. The superconducting tetragonal phase content steadily decreases with increasing Mn concentration and completely disappears beyond x = 0.5. The premise that Mn never replaces Fe in the superconducting phase is further strengthened by observation of a sharp drop in AC susceptibility akin to superconducting transition at the T c of FeSe up to x = 0.5. EXAFS studies at the Fe K edge also show that the Fe has a four coordinated tetragonal local structure in all compositions below x = 0.5, similar to that in FeSe and it gradually changes to a six coordinated one as is expected for a NaCl type cubic phase for x≥slant 0.5.

  2. Imaging the surface morphology, chemistry and conductivity of LiNi 1/3 Fe 1/3 Mn 4/3 O 4 crystalline facets using scanning transmission X-ray microscopy

    SciTech Connect

    Zhou, Jigang; Wang, Jian; Cutler, Jeffrey; Hu, Enyuan; Yang, Xiao-Qing

    2016-07-26

    We have employed scanning transmission X-ray microscopy (STXM) using the X-ray fluorescence mode in order to elucidate the chemical structures at Ni, Fe, Mn and O sites from the (111) and (100) facets of micron-sized LiNi1/3Fe1/3Mn4/3O4 energy material particles. Furthermore, STXM imaging using electron yield mode has mapped out the surface conductivity of the crystalline particles. Our study presents a novel approach that visualizes local element segregation, chemistry and conductivity variation among different crystal facets, which will assist further tailoring of the morphology and surface structure of this high voltage spinel lithium ion battery cathode material.

  3. Variations on a Theme by Longhi: I, an Analysis of the Thermodynamic Underpinning of Fe, Mn, and Ni Partitioning into Olivine

    NASA Technical Reports Server (NTRS)

    Jones, John H.

    2010-01-01

    Longhi et al. [1] have used the D(Ni) vs. D(Mg) parameterizations of Jones [2, 3] in attempting to explain the Ni systematics of lunar differentiation. A key element of the Jones parameterization and the Longhi et al. models is that, at very high temperatures, Ni may become incompatible in olivine. Unfortunately, there is no actual experimental evidence that this is ever the case [1]. To date, all experiments designed to demonstrate such incompatibility have failed. Here I will investigate the thermodynamic foundations of the D vs. D(Mg) trends for olivine/liquid discovered by [2].

  4. Effects of Fe doping on the structures and properties of hexagonal birnessites - Comparison with Co and Ni doping

    NASA Astrophysics Data System (ADS)

    Yin, Hui; Liu, Fan; Feng, Xionghan; Hu, Tiandou; Zheng, Lirong; Qiu, Guohong; Koopal, Luuk K.; Tan, Wenfeng

    2013-09-01

    Fe-doped hexagonal birnessite was synthesized by adding Fe3+ to the initial reactants, and the effects of Fe doping on the structures and properties of birnessite were investigated and compared with the effects of Co and Ni doping. The underlying mechanisms controlling the incorporation of transition metals (TMs) into the birnessite structure were proposed. Compared to the un-doped control, Fe-doped birnessite has weaker crystallinity, i.e., less stacking of the phyllomanganate sheets in the c direction, and larger surface area. Combination of X-ray photoelectron spectroscopy (XPS) and Mn K-edge XANES and EXAFS spectra demonstrates that Fe doping decreases the Mn average oxidation state (AOS) but has little effect on the basic layer structure and local Mn environments. Fe(III) located in the birnessite layers exhibits high-spin (HS) configuration whereas layer Mn(III) and Co(III) plausibly adopt low-spin (LS) state. The TMs decrease the thickness of birnessite plate crystals along the c axis and affect the unit cell parameter b in the order Fe > Ni > Co. Co and Fe incorporate into the birnessite layers by substitution for Mn(IV) while Ni substitutes for Mn(III). The substitution of TMs into the birnessite layers is governed by the coordination radius (CR), crystal field stabilization energy (CFSE) and oxidation state of the TMs. The variations in potassium contents in doped birnessites together with TM K-edge EXAFS data indicate that most of the Fe (˜81-82%) or Ni (˜66-76%) incorporated into the birnessite structure exists in the interlayer regions, while most of the Co (˜71-80%) occurs in the manganese layers. The compatibility of these TM ions in the birnessite layers is in the order Co > Ni > Fe. The smaller the difference between the CR of Fe, Co or Ni and Mn(IV) or Mn(III), the more dopants are compatible within the Mn layers.

  5. Giant magnetic coercivity in CaCu5-type SmNi3TSi (T=Mn-Cu) solid solutions

    NASA Astrophysics Data System (ADS)

    Yao, Jinlei; Yan, Xu; Morozkin, A. V.

    2015-12-01

    The effects of transition metal substitution for Ni on the magnetic properties of the CaCu5-type SmNi3TSi (T=Mn, Fe, Co, Cu) solid solutions have been investigated. SmNi3MnSi, SmNi3FeSi, SmNi3CoSi and SmNi3CuSi show ferromagnetic ordering at 125 K, 190 K, 46 K and 12 K and field induced transitions at 65 K, 110 K, 30 K and 6 K, respectively. The magnetocaloric effects of SmNi3TSi (T=Mn, Fe, Co, Cu) were calculated in terms of isothermal magnetic entropy change (ΔSm). The magnetic entropy ΔSm reaches value of -1.1 J/kg K at 130 K for SmNi3MnSi, -0.4 J/kg K at 180 K for SmNi3FeSi, -0.37 J/kg K at 45 K for SmNi3CoSi and -0.5 J/kg K at 12 K for SmNi3CuSi in field change of 0-50 kOe around the ferromagnetic ordering temperature. They show positive ΔSm of +2.4 J/kg K at 30 K for SmNi3MnSi, -2.6 J/kg K at 65 K for SmNi3FeSi, +0.73 J/kg K at 15 K for SmNi3CoSi and -0.5 J/kg K at 6 K for SmNi3CuSi in field change of 0-50 kOe around the metamagnetic-like transition temperature. Below the field induced transition temperature, SmNi3TSi (T=Mn, Fe, Co, Cu) exhibits giant magnetic coercivity of 80 kOe at 20 K for SmNi3MnSi, 87 kOe at 40 K for SmNi3FeSi, 27 kOe at 20 K for SmNi3CoSi and 54 kOe at 5 K for SmNi3CuSi. Below the field induced transition temperature, SmNi3TSi (T=Mn, Fe, Co, Cu) exhibits giant magnetic coercivity of 80 kOe at 20 K for SmNi3MnSi, 87 kOe at 40 K for SmNi3FeSi, 27 kOe at 20 K for SmNi3CoSi and 54 kOe at 5 K for SmNi3CuSi.

  6. Interphase evolution at two promising electrode materials for Li-ion batteries: LiFePO4 and LiNi1/2 Mn1/2O2.

    PubMed

    Dupré, Nicolas; Cuisinier, Marine; Martin, Jean-Frederic; Guyomard, Dominique

    2014-07-21

    The present review reports the characterization and control of interfacial processes occurring on olivine LiFePO(4) and layered LiNi(1/2) Mn(1/2)O(2), standing here as model compounds, during storage and electrochemical cycling. The formation and evolution of the interphase created by decomposition of the electrolyte is investigated by using spectroscopic tools such as magic-angle-spinning nuclear magnetic resonance ((7)Li,(19)F and (31)P) and electron energy loss spectroscopy, in parallel to X-ray photoelectron spectroscopy, to quantitatively describe the interphase and unravel its architecture. The influence of the pristine surface chemistry of the active material is carefully examined. The importance of the chemical history of the surface of the electrode material before any electrochemical cycling and the strong correlation between interface phenomena, the formation/evolution of an interphase, and the electrochemical behavior appear clearly from the use of these combined characterization probes. This approach allows identifying interface aging and failure mechanisms. Different types of surface modifications are then investigated, such as intrinsic modifications upon aging in air or methods based on the use of additives in the electrolyte or carbon coatings on the surface of the active materials. In each case, the species detected on the surface of the materials during storage and cycling are correlated with the electrochemical performance of the modified positive electrodes.

  7. [ReCl4(CN)2]2-: a high magnetic anisotropy building unit giving rise to the single-chain magnets (DMF)4MReCl4(CN)2 (M = Mn, Fe, Co, Ni).

    PubMed

    Harris, T David; Bennett, Miriam V; Clérac, Rodolphe; Long, Jeffrey R

    2010-03-24

    An S = 3/2, high-anisotropy building unit, trans-[ReCl(4)(CN)(2)](2-), representing the first paramagnetic complex with a mixture of just cyanide and halide ligands, has been synthesized through the reaction of (Bu(4)N)CN with ReCl(4)(THF)(2). This species is characterized in detail and employed in directing the formation of a series of one-dimensional coordination solids of formula (DMF)(4)MReCl(4)(CN)(2) (M = Mn (2), Fe (3), Co (4), Ni (5)). Variable-temperature dc magnetic susceptibility measurements demonstrate the presence of intrachain antiferromagnetic (2) and ferromagnetic (3-5) exchange coupling within these solids. In addition, probing the ac magnetic susceptibility as a function of both temperature and frequency reveals that all of the chain compounds exhibit slow relaxation of the magnetization. The relaxation time is shown to be thermally activated, with energy barriers to relaxation of Delta(tau) = 31, 56, 17, and 20 cm(-1) for 2-5, respectively. Notably, the field-dependent magnetization of the iron congener exhibits a significant hysteresis effect at low temperature, with a coercive field of H(C) = 1.0 T, thus demonstrating magnetlike behavior in this one-dimensional system. Finally, the magnetization dynamics of all solids occur within the finite-size regime, where the magnetic domain growth is limited due to physical defects along the chains within the crystals.

  8. Influence of the type of tree habitat on the character of co-occurrence of Fe, Mn, Zn, Cu, Pb, Ni, Cr and Co in the soil of the Tatra Mountain National Park.

    PubMed

    Kwapuliński, Jerzy; Paprotny, Łukasz; Paukszto, Andrzej; Kowol, Jolanta; Rochel, Robert; Nogaj, Ewa; Musielińska, Renata; Celiński, Rafał

    2013-01-01

    The objective of the research was to determine the effect of habitat type of selected species of trees on the nature of co-occurrence of Fe, Mn, Zn, Cu, Pb, Cd, Ni, Cr and Co. The presence of speciation forms of these metals was investigated, with reference to the species composition of tree stands in selected areas of the Tatra Mountain National Park (Chochołowska Valley, Strążyska Valley, Kościeliska Valley, as well as Mała Łąka Valley).Contents of selected metals in samples were determined by the flame ASA method, with an accuracy of 0.1 µg/g. In habitats dominated by maples, the Pb content in the Chochołowska Valley, unlike Kościeliska Valley covered with beeches, the Pb content in the form directly bioavailable, was twice as high. This was clearly proved in the case of Strążyska Valley where the soil in beech tree habitats contained larger quantities of exchangeable forms of Pb, than that in the Chochołowska Valley. The soil of the valleys, including the Mała Łąka Valley, showed peculiar characteristic averaging of the contents of selected speciation forms of metals in the soil. Content corresponding to 10 percentile and geometrical average may be regarded as benchmarks in future studies of the Tatra Mountain National Park, or other protected areas.

  9. First principles study of electronic structure for cubane-like and ring-shaped structures of M{sub 4}O{sub 4}, M{sub 4}S{sub 4} clusters (M = Mn, Fe, Co, Ni, Cu)

    SciTech Connect

    Datta, Soumendu; Rahaman, Badiur

    2015-11-15

    Spin-polarized DFT has been used to perform a comparative study of the geometric structures and electronic properties for isolated M{sub 4}X{sub 4} nano clusters between their two stable isomers - a planar rhombus-like 2D structure and a cubane-like 3D structure with M = Mn, Fe, Co, Ni, Cu ; X = O, S. These two structural patterns of the M{sub 4}X{sub 4} clusters are commonly found as building blocks in several poly-nuclear transition metal complexes in inorganic chemistry. The effects of the van der Waals corrections to the physical properties have been considered in the electronic structure calculations employing the empirical Grimme’s correction (DFT+D2). We report here an interesting trend in their relative structural stability - the isolated M{sub 4}O{sub 4} clusters prefer to stabilize more in the planar structure, while the cubane-like 3D structure is more favorable for most of the isolated M{sub 4}S{sub 4} clusters than their planar 2D counterparts. Our study reveals that this contrasting trend in the relative structural stability is expected to be driven by an interesting interplay between the s-d and p-d hybridization effects of the constituents’ valence electrons.

  10. AC Impedance Behavior of LaNi3.55Mn0.4Al0.3Co0.6Fe0.15 Hydrogen-Storage Alloy: Effect of Surface Area

    NASA Astrophysics Data System (ADS)

    Tliha, M.; Khaldi, C.; Lamloumi, J.

    2016-04-01

    The decrease of Cobalt content in alloy is very beneficial to reduce the production cost of the alloy, whereas the effect of Co on cycle life of the AB5-type hydrogen-storage alloys is extremely important. Therefore, it is interesting to investigate low-Co and/or Co-free AB5-type alloys in which Co was substituted by other elements. Iron is a key element in the development of low-Co AB5-type alloys. The aim of this work is to systematically investigate the effect of the real surface area on the all kinetic properties of a low-Co LaNi3.55Mn0.4Al0.3Co0.6Fe0.15 alloy under cycling using electrochemical impedance spectroscopy (EIS) technique. All kinetic properties of the electrode, such as exchange density, limiting current density, high-rate charge/discharge ability, cycle life time, electrocatalytic activity, and diffusion rate are related to the real surface area. During the EIS analysis, interestingly, we found that with increasing number of charge/discharge cycles, the metal hydride alloy powders undergo micro-cracking into smaller particles, and thus the real surface area of the alloy increases, which then influences the kinetic properties of the electrode reactions.

  11. Domain structure and magnetization process of a giant magnetoimpedance geometry FeNi/Cu/FeNi(Cu)FeNi/Cu/FeNi sensitive element

    NASA Astrophysics Data System (ADS)

    Kurlyandskaya, G. V.; Elbaile, L.; Alves, F.; Ahamada, B.; Barrué, R.; Svalov, A. V.; Vas'kovskiy, V. O.

    2004-09-01

    The magnetization process and the magnetic domains of the FeNi (100 nm)/Cu (2.5 nm)/FeNi (100 nm)/Cu (480 nm)/FeNi (100 nm)/Cu (2.5 nm)/FeNi (100 nm) structure were studied. This geometry consists of two FeNi/Cu/FeNi trilayers with a thick in the direction perpendicular to the plane of the sensitive element and narrow in the direction of the flowing current Cu electrode in the centre. Ferromagnet/conductor/ferromagnet is the typical geometry of magnetoimpedance thin-film-based sensitive elements used to detect small magnetic fields. Multilayered structures were prepared by rf-sputtering in a magnetic field of 100 Oe applied perpendicular to the Cu electrode in order to induce transverse magnetic anisotropy. The magnetic measurements and magnetic domain structure observations were made in magnetic fields applied one at a time parallel or perpendicular to the Cu electrode. Different magnetization processes with non-homogeneous rotations in the first case and dominant multiple nucleation and merging of domains in the second one were observed.

  12. Synthesis and Characterization of Poly-phase Waste Form: Gd{sub 3}Fe{sub 5}O{sub 12}+(Ni{sub x}Mn{sub 1-x})(Fe{sub y}Cr{sub 1-y}){sub 2}O{sub 4}

    SciTech Connect

    Chae, S.C.; Jang, Y.N.; Bae, I.K.; Ryu, K.W.

    2006-07-01

    The synthesis of poly-phase waste form, which is an immobilization matrix for the HLW, was performed with the mixed composition of garnet and spinel (Gd{sub 3}Fe{sub 5}O{sub 12}+(Ni{sub x}Mn{sub 1-x})(Fe{sub y}Cr{sub 1-y}){sub 2}O{sub 4}) at temperatures in the range of 1200 deg. C to 1400 deg. C. The phases synthesized from all stoichiometric compositions were garnet, perovskite, and spinel. Especially, garnet was synthesized only in the composition of the highest content of Fe(y=0.9), whereas it was not synthesized in other compositions. This result indicated that the content of Fe was closely related to the formation of garnet. The composition of garnet revealed that the content of Gd was exceeded and that of Fe was depleted. Preferential distribution of elements in the phases can be attributed to the nonstoichiometric composition of garnet. (authors)

  13. A DFT study on the complex formation between desferrithiocin and metal ions (Mg(2+), Al(3+), Ca(2+), Mn(2+), Fe(3+), Co(2+), Ni(2+), Cu(2+), Zn(2+)).

    PubMed

    Kaviani, Sadegh; Izadyar, Mohammad; Housaindokht, Mohammad Reza

    2017-04-01

    In recent years, Metal-chelating compounds, namely siderphores have been considered very much because of their crucial role in various fields of the environmental researches. Their importance lies in the fact that they are able to be bonded to a variety of metals in addition to iron. A theoretical study on the structures of desferrithiocin siderphore coordinated to Mg(2+), Al(3+), Ca(2+), Mn(2+), Fe(3+), Co(2+), Ni(2+), Cu(2+) and Zn(2+) metal ions was carried out, using the CAM-B3LYP/6-31G(d) level of the theory in the water. In order to understand the factors which control the stability, reactivity and the strength of toxic metals excretion as well as microbial uptake of the metal-siderphore complexes, we examined the stability and binding energies of the desferrithiocin and various metal ions with different spin states. The binding affinity of desferrithiocin to Fe(3+) (log β2=23.88) showed that the desferrithiocin can scavenge the excess iron(III) from the labile sources. Also, the binding energy values were well described by addition of the dispersion-corrected D3 functional. Because of the importance of the charge transfer in the complex formation, donor-acceptor interaction energies were evaluated. Based on this analysis, an increase in the effective nuclear charge increases E(2) values. Vibrational analysis showed that the critical bonds (CO stretching and CH bending) are in the range of 1300-1800cm(-1). Finally, some probable correlations between the complexation behavior and quantum chemistry descriptors have been analyzed.

  14. Corrosion behavior of Au and Ag modified Cu-Ni-Mn alloys.

    PubMed

    Wright, S R; Cocks, F H; Gettleman, L

    1980-04-01

    The linear electrochemical polarization method was used to provide quantitative in vitro measurements of corrosion rates as a function of exposure time for Cu-Ni-Mn, Cu-Ni-Mn-Au, Cu-Ni-Mn-Ag, and Cu-Ni-Mn-Au-Ag alloys in artificial saliva. Both Au and Ag additives to dental-cast Cu-Ni-Mn alloys lowered the corrosion rate significantly.

  15. Enhanced Photovoltage Response of Hematite-X-Ferrite Interfaces (X = Cr, Mn, Co, or Ni).

    PubMed

    Bian, Liang; Li, Hai-Long; Li, Yu-Jin; Nie, Jia-Nan; Dong, Fa-Qin; Dong, Hai-Liang; Song, Mian-Xin; Wang, Li-Sheng; Zhou, Tian-Liang; Zhang, Xiao-Yan; Li, Xin-Xi; Xie, Lei

    2017-12-01

    High-fluorescent p-X-ferrites (XFe2O4; XFO; X = Fe, Cr, Mn, Co, or Ni) embedded in n-hematite (Fe2O3) surfaces were successfully fabricated via a facile bio-approach using Shewanella oneidensis MR-1. The results revealed that the X ions with high/low work functions modify the unpaired spin Fe(2+)-O(2-) orbitals in the XFe2O4 lattices to become localized paired spin orbitals at the bottom of conduction band, separating the photovoltage response signals (73.36~455.16/-72.63~-32.43 meV). These (Fe2O3)-O-O-(XFe2O4) interfacial coupling behaviors at two fluorescence emission peaks (785/795 nm) are explained via calculating electron-hole effective masses (Fe2O3-FeFe2O4 17.23 × 10(-31) kg; Fe2O3-CoFe2O4 3.93 × 10(-31) kg; Fe2O3-NiFe2O4 11.59 × 10(-31) kg; Fe2O3-CrFe2O4 -4.2 × 10(-31) kg; Fe2O3-MnFe2O4 -11.73 × 10(-31) kg). Such a system could open up a new idea in the design of photovoltage response biosensors.

  16. The Fe/Mn constraint on precursors of basaltic achondrites

    NASA Technical Reports Server (NTRS)

    Delaney, Jeremy S.; Boesenberg, Joseph S.

    1993-01-01

    Most achondritic meteorites have Fe/Mn ratios that are lower than those of carbonaceous chondrites and of course are lower than the solar system abundance ratio of these elements. Models of the origin of achondritic assemblages must, therefore, account for these ratios. Fe/Mn ratios are suggested to be distinctive for samples from each achondrite parent body and for the Earth and Moon, but the correspondence between the Fe/Mn systematics of achondrites and chondritic precursors is unclear. Most models of achondrite genesis involve magmatic differentiation of chondritic precursors. The Fe/Mn difference between achondrites and chondrites is particularly significant since Fe and Mn are geochemically similar elements with similar partitioning behavior in familiar magmatic systems and are generally coupled during crystal-liquid fractionation. In contrast, however, Mn is more volatile than Fe in a nebular setting. Variation of Fe/Mn ratios based on the relative volatility of these elements in the early nebula provides a constraint for models by which the basaltic achondrites (with Fe/Mn ratios approximately = 25-50) are derived from mixtures of nebular components that were enriched in volatile components such as Mn. However, such volatile enriched components have not been identified in chondrites. When the abundance in achondrites of elements of similar volatility is examined, anomalies appear. For example, Na is massively depleted in basaltic achondrites when compared to Mn. These anomalies might be explained using current models but the alternative hypothesis, that Fe/Mn ratio is controlled not by nebular volatility constraints, but by planetary differentiation should be explored.

  17. Magnetic properties of MnBi based alloys: First-principles calculations for MnBi-Co and MnBi-Co-Fe cases

    SciTech Connect

    Hong, YK; Park, J; Mryasov, ON; Kim, SG; Kim, S; Lee, J; Abo, GS; Choi, CJ; Lee, J

    2013-05-01

    First-principles calculations of fundamental magnetic properties were performed for ordered MnBi, MnBi-Co, and MnBi-Co-Fe alloys to evaluate maximum energy product (BH)(max). Full potential linear-augmented plane wave (FLAPW) and linear-muffin-tin-orbital (LMTO) calculations using density functional theory (DFT) within the local spin density approximation (LSDA) were used and found to give a reasonable description of saturation magnetization (M-s), effective anisotropy constant (K-eff), and Curie temperature (T-c) for NiAs-structured MnBi crystal. We found that upon addition of Co, the M-s and K-eff increased, while T-c reduced. The magnetic anisotropy changed from weak anisotropy easy plane for MnBi to the strong easy axis anisotropy for MnBi-Co and MnBi-Co-Fe. (C) 2013 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.

  18. Fe/Mn in olivine of carbonaceous meteorites

    NASA Technical Reports Server (NTRS)

    Steele, Ian M.

    1993-01-01

    Olivines in primitive meteorites show a range of Fe/Mn both within one grain and among grains suggesting that they have recorded changing conditions during or after growth. Because olivine should be an early forming phase, Fe/Mn is used here to infer these earliest conditions. Initial Fe/Mn in cores of isolated, euhedral forsterite in both C2 and C3 meteorites ranges from 25 to 35 but differs at grain edge. Murchison (C2) forsterites show Fe/Mn approaching 1.0 at the grain edge while Ornans Fe/Mn is near 60 at grain edge. These values are lower than the matrix Fe/Mn for both meteorites and the distinct difference in zoning profile indicates different processes operating during and after grain growth. The Fe/Mn of bulk samples from a particular source such as the Moon is nearly constant. Individual samples show variation suggesting that there is some fractionation of Mn from Fe. Minerals have their individual ranges of Fe/Mn which has been used to recognize different types of olivine within one meteorite. Extreme values of Fe/Mn below 1.0 occur in forsterite from some IDP's, UOC matrix, and C1 meteorites. There are apparently no detailed studies of Fe/Mn variation within single olivine grains. Forsterite grains in C2 and C3 carbonaceous chondrites show complex zoning, and the nearly pure forsterites (Fo greater than approximately 99.5) have high levels of some minor elements including Ti, Al, V, and Sc. There is disagreement on the original source of these grains and both chondrule and vapor growth have been proposed. In addition, there is clear evidence that diffusion has affected the outer margins but in some cases the whole grain. Within the cores, the FeO range is limited, and if growing under constant conditions, the Fe/Mn should be near constant as there is little fractionation of Mn from Fe by forsterite. Additionally, there are apparently no co-crystallizing phases as evidenced by a lack of common inclusions in the forsterites. These observations are now

  19. Systematic study of room-temperature ferromagnetism and the optical response of Zn1-x TM x S/Se (TM  =  Mn, Fe, Co, Ni) ferromagnets: first-principle approach

    NASA Astrophysics Data System (ADS)

    Mahmood, Q.; Hassan, M.; Noor, N. A.

    2016-12-01

    The structural, magnetic and optical characteristics of Zn1-x TM x S/Se (TM  =  Mn, Fe, Co, Ni and x  =  6.25%) have been investigated through the full-potential linearized augmented plane wave method within the framework of density functional theory. The optimized structures have been used to calculate the ferromagnetic and the antiferromagnetic ground-state energies. The stability of the ferromagnetic phase has been confirmed from the formation and the cohesive energies. The Heisenberg model is used to elucidate the Curie temperature (T c) of these alloys. From the band structures and density of states plots, it has been observed that TM-doped ZnS/Se alloys appear to be semiconductors and exhibit ferromagnetism. In addition, the observed ferromagnetism has also been explained in terms of direct exchange energy Δ x (d), exchange splitting energy Δ x (pd), crystal-field energy (E crys), exchange constants (N 0 α and N 0 β) and magnetic moments that shows potential spintronic applications. The optical behaviors of these alloys have been explained in terms of real and imaginary parts of the dielectric constant ɛ(ω), refractive index n(ω), extinction coefficient K(ω), reflectivity R(ω) and absorption coefficient σ(ω), in the energy range 0-25 eV. The calculated static limits of the band gaps and real part of the dielectric constants satisfy the Penn model. The critical limits of the imaginary part of the dielectric constants and absorption coefficients indicate that these alloys can be operated in the visible and the ultraviolet region of the electromagnetic spectrum; therefore, make them important for optoelectronic applications.

  20. The effect of interstitial carbon on the mechanical properties and dislocation substructure evolution in Fe40.4Ni11.3Mn34.8Al7.5Cr6 high entropy alloys

    DOE PAGES

    Wang, Zhangwei; Baker, Ian; Cai, Zhonghou; ...

    2016-09-01

    A systematic study of the effects of up to 1.1 at. % carbon on the mechanical properties and evolution of the dislocation substructure in a series of a high entropy alloys (HEA) based on Fe40.4Ni11.3Mn34.8Al7.5Cr6 is presented. Transmission electron microscopy (TEM), synchrotron X-ray diffraction (XRD) and atom probe tomography (APT) were used to show that all the alloys are single-phase f.c.c. random solid solutions. The lattice constant, determined from synchrotron XRD measurements, increases linearly with increasing carbon concentration, which leads to a linear relationship between the yield strength and the carbon concentration. The dislocation substructures, as determined by a TEM,more » show a transition from wavy slip to planar slip and, at higher strains, and from cell-forming structure (dislocations cells, cell blocks and dense dislocation walls) to non-cell forming structure (Taylor lattice, microbands and domain boundaries) with the addition of carbon, features related to the increase in lattice friction stress. The stacking fault energy (measured via weak-beam imaging of the separation of dislocation partials) decreases with increasing carbon content, which also contributes to the transition from wavy slip to planar slip. The formation of non-cell forming structure induced by carbon leads to a high degree of strain hardening and a substantial increase in the ultimate tensile strength. In conclusion, the consequent postponement of necking due to the high strain hardening, along with the plasticity accommodation arising from the formation of microbands and domain boundaries, result in an increase of ductility due to the carbon addition.« less

  1. Mechanisms of radiation-induced segregation in CrFeCoNi-based single-phase concentrated solid solution alloys

    DOE PAGES

    He, Mo-Rigen; Wang, Shuai; Shi, Shi; ...

    2016-12-31

    Single-phase concentrated solid solution alloys have attracted wide interest due to their superior mechanical properties and enhanced radiation tolerance, which make them promising candidates for the structural applications in next-generation nuclear reactors. However, little has been understood about the intrinsic stability of their as-synthesized, high-entropy configurations against radiation damage. In this paper, we report the element segregation in CrFeCoNi, CrFeCoNiMn, and CrFeCoNiPd equiatomic alloys when subjected to 1250 kV electron irradiations at 400 °C up to a damage level of 1 displacement per atom. Cr/Fe/Mn/Pd can deplete and Co/Ni can accumulate at radiation-induced dislocation loops, while the actively segregating elementsmore » are alloy-specific. Moreover, electron-irradiated matrix of CrFeCoNiMn and CrFeCoNiPd shows L10 (NiMn)-type ordering decomposition and <001>-oriented spinodal decomposition between Co/Ni and Pd, respectively. Finally, these findings are rationalized based on the atomic size difference and enthalpy of mixing between the alloying elements, and identify a new important requirement to the design of radiation-tolerant alloys through modification of the composition.« less

  2. Mechanisms of radiation-induced segregation in CrFeCoNi-based single-phase concentrated solid solution alloys

    SciTech Connect

    He, Mo-Rigen; Wang, Shuai; Shi, Shi; Jin, Ke; Bei, Hongbin; Yasuda, Kazuhiro; Matsumura, Syo; Higashida, Kenji; Robertson, Ian M.

    2016-12-31

    Single-phase concentrated solid solution alloys have attracted wide interest due to their superior mechanical properties and enhanced radiation tolerance, which make them promising candidates for the structural applications in next-generation nuclear reactors. However, little has been understood about the intrinsic stability of their as-synthesized, high-entropy configurations against radiation damage. In this paper, we report the element segregation in CrFeCoNi, CrFeCoNiMn, and CrFeCoNiPd equiatomic alloys when subjected to 1250 kV electron irradiations at 400 °C up to a damage level of 1 displacement per atom. Cr/Fe/Mn/Pd can deplete and Co/Ni can accumulate at radiation-induced dislocation loops, while the actively segregating elements are alloy-specific. Moreover, electron-irradiated matrix of CrFeCoNiMn and CrFeCoNiPd shows L10 (NiMn)-type ordering decomposition and <001>-oriented spinodal decomposition between Co/Ni and Pd, respectively. Finally, these findings are rationalized based on the atomic size difference and enthalpy of mixing between the alloying elements, and identify a new important requirement to the design of radiation-tolerant alloys through modification of the composition.

  3. Canted Antiferromagnetic Structure of M[N(CN)_2]2 (M = Mn, Fe)

    NASA Astrophysics Data System (ADS)

    Kmety, C. R.; Epstein, A. J.; Huang, Q.; Lynn, J. W.; Erwin, R. W.; MLowercaseccall, S.; Crow, J. E.; Manson, J. L.; Miller, Joel S.; Stevenson, K. L.

    2000-03-01

    We report neutron diffraction, magnetic and specific heat studies of the isomorphous M[N(CN)_2]2 (M = Mn, Fe). The crystal structure consists of axially elongated and successively tilted discrete octahedra. There are two antiferromagnetically coupled and spontaneously canted sublattices. The spin orientation is mainly along the a-axis with small uncompensated moments along the b-axis for the Mn compound and in the bc-plane for the Fe compound. Both systems have novel field-induced magnetic phenomena at mK temperatures. Comparisons of the magnetic structures for the isomorphous series M[N(CN)_2]2 (M = Mn, Fe, Co, Ni) suggest that spin direction is stabilized by the crystal fields and spin canting is induced by the successive tilting of the octahedra. We propose that the superexchange interaction is the mechanism responsible for the magnetic ordering in these compounds.

  4. Sharp increase of microwave absorption in nonequilibrium MnZn- and NiZn-nanoferrites

    NASA Astrophysics Data System (ADS)

    Lutsev, Leonid; Shutkevich, Vladimir

    2016-12-01

    We study microwave electromagnetic absorption in films containing (Mn,Zn)Fe2O4 and (Ni,Zn)Fe2O4 spinel nanoparticles in equilibrium and nonequilibrium spin states. The nonequilibrium spin state has been formed by the action of the alternating magnetic field with the frequency of 1 Hz. It is found that in the nonequilibrium state the microwave absorption is strongly enhanced. The microwave losses are increased by 78 times for the film with MnZn-spinel nanoparticles and by 12 times for the film containing NiZn-nanoferrite. The microwave-absorption-increase effect is observed in the central part of the ferromagnetic resonance frequency band. This frequency band of the microwave absorption enhancement is narrower than the ferromagnetic linewidth in the equilibrium state.

  5. Dissimilatory Fe(III) and Mn(IV) reduction.

    PubMed Central

    Lovley, D R

    1991-01-01

    The oxidation of organic matter coupled to the reduction of Fe(III) or Mn(IV) is one of the most important biogeochemical reactions in aquatic sediments, soils, and groundwater. This process, which may have been the first globally significant mechanism for the oxidation of organic matter to carbon dioxide, plays an important role in the oxidation of natural and contaminant organic compounds in a variety of environments and contributes to other phenomena of widespread significance such as the release of metals and nutrients into water supplies, the magnetization of sediments, and the corrosion of metal. Until recently, much of the Fe(III) and Mn(IV) reduction in sedimentary environments was considered to be the result of nonenzymatic processes. However, microorganisms which can effectively couple the oxidation of organic compounds to the reduction of Fe(III) or Mn(IV) have recently been discovered. With Fe(III) or Mn(IV) as the sole electron acceptor, these organisms can completely oxidize fatty acids, hydrogen, or a variety of monoaromatic compounds. This metabolism provides energy to support growth. Sugars and amino acids can be completely oxidized by the cooperative activity of fermentative microorganisms and hydrogen- and fatty-acid-oxidizing Fe(III) and Mn(IV) reducers. This provides a microbial mechanism for the oxidation of the complex assemblage of sedimentary organic matter in Fe(III)- or Mn(IV)-reducing environments. The available evidence indicates that this enzymatic reduction of Fe(III) or Mn(IV) accounts for most of the oxidation of organic matter coupled to reduction of Fe(III) and Mn(IV) in sedimentary environments. Little is known about the diversity and ecology of the microorganisms responsible for Fe(III) and Mn(IV) reduction, and only preliminary studies have been conducted on the physiology and biochemistry of this process. PMID:1886521

  6. Spin-dependent electron momentum density in the Ni2MnSn Heusler alloy

    NASA Astrophysics Data System (ADS)

    Deb, Aniruddha; Hiraoka, N.; Itou, M.; Sakurai, Y.; Onodera, M.; Sakai, N.

    2001-05-01

    The spin-dependent electron momentum distribution in Ni2MnSn Heusler alloy single crystals was studied using 270 keV circularly polarized synchrotron radiation, through magnetic Compton profile measurements, on the high energy inelastic scattering beamline at SPring-8. The experiments were carried out for the three principal crystallographic directions [100], [110], and [111] at 10 K. The results show that the conduction electrons have a negative spin polarization of 0.34μB the 3d spin moment on the nickel site was found to be negligible. A band structure calculation was performed including a hyperfine field study using the full potential linearized augmented plane wave (FLAPW) method, with the generalized gradient approximation (GGA) for the electronic exchange and correlation. The spin moment on the Mn site at 10 K was observed as 4.39μB. The spin-dependent Compton profiles for the [100], [110], and [111] directions reported here show anisotropy in the momentum density, which is in good agreement with the FLAPW-GGA results, based on a ferromagnetic ground state. The hyperfine fields calculated were compared with previously calculated hyperfine field of Cu2MnAl and Co2FeGa Heusler alloys. From the comparison it is seen that the value of Hval (valence contribution to the hyperfine field) is roughly proportional to the spin polarization (ms) of the s electrons at the X (Ni,Cu,Co) and Y (Mn of Ni2MnSn and Cu2MnAl, Fe of Co2FeGa) atom positions.

  7. Magnetic properties of Mn1-xAl1-yNi alloys in the B2 (CsCl-type) structure

    NASA Astrophysics Data System (ADS)

    Paduani, C.; Schaf, J.; Ardisson, J. D.; Takeuchi, A. Y.

    2010-02-01

    In this work is investigated structural and magnetic properties of ferromagnetic Mn1-xAl1-yNi alloys in the κ phase which has a B2 (CsCl-type) structure. The Curie temperatures are above room temperature and decrease with the substitution of Ni for Mn. The magnetic measurements indicate the existence of ferrimagnetism originated from Mn atoms which carry unequal and opposite magnetic moments in different sublattices. A larger average magnetic moment is observed in the Ni-doped system, as compared to the Fe-system, which is due to the formation of larger moment on Mn atoms at the cube corners.

  8. Spin transport through the metallic antiferromagnet FeMn

    NASA Astrophysics Data System (ADS)

    Saglam, H.; Zhang, W.; Jungfleisch, M. B.; Sklenar, J.; Pearson, J. E.; Ketterson, J. B.; Hoffmann, A.

    2016-10-01

    We investigate spin transport through metallic antiferromagnets using measurements based on spin pumping combined with inverse spin Hall effects in N i80F e20/FeMn /W trilayers. The relatively large magnitude and opposite sign of spin Hall effects in W compared to FeMn enable an unambiguous detection of spin currents transmitted through the entire FeMn layer thickness. Using this approach we can detect two distinctively different spin transport regimes, which we associate with electronic and magnonic spin currents, respectively. The latter can extend to relatively large distances (≈9 nm) and is enhanced when the antiferromagnetic ordering temperature is close to the measurement temperature.

  9. Metal elution from Ni- and Fe-based alloy reactors under hydrothermal conditions.

    PubMed

    Faisal, Muhammad; Quitain, Armando T; Urano, Shin-Ya; Daimon, Hiroyuki; Fujie, Koichi

    2004-05-20

    Elution of metals from Ni- and Fe-based alloy (i.e. Inconel 625 and SUS 316) under hydrothermal conditions was investigated. Results showed that metals could be eluted even in a short contact time. At subcritical conditions, a significant amount of Cr was extracted from SUS 316, while only traces of Ni, Fe, Mo, and Mn were eluted. In contrast, Ni was removed in significant amounts compared to Cr when Inconel 625 was tested. Several factors including temperature and contact time were found to affect elution behavior. The presence of air in the fluid even promoted elution under subcritical conditions.

  10. Corrosion Behavior of Thermally Sprayed NiCrBSi Coating on 16MnR Low-Alloy Steel in KOH Solution

    NASA Astrophysics Data System (ADS)

    Zeng, Q.; Sun, J.; Emori, W.; Jiang, S. L.

    2016-05-01

    NiCrBSi coatings were selected as protective material and air plasma-sprayed on 16MnR low-alloy steel substrates. Corrosion behavior of 16MnR substrates and NiCrBSi coatings in KOH solution were evaluated by polarization resistance ( R p), potentiodynamic polarization curves, electrochemical impedance spectroscopy, and immersion corrosion tests. Electrolytes were solutions with different KOH concentrations. NiCrBSi coating showed superior corrosion resistance in KOH solution compared with the 16MnR. Corrosion current density of 16MnR substrate was 1.7-13.0 times that of NiCrBSi coating in the given concentration of KOH solution. By contrast, R p of NiCrBSi coating was 1.2-8.0 times that of the substrate, indicating that the corrosion rate of NiCrBSi coating was much lower than that of 16MnR substrate. Capacitance and total impedance value of NiCrBSi coating were much higher than those of 16MnR substrate in the same condition. This result indicates that corrosion resistance of NiCrBSi coating was better than that of 16MnR substrate, in accordance with polarization results. NiCrBSi coatings provided good protection for 16MnR substrate in KOH solution. Corrosion products were mainly Ni/Fe/Cr oxides.

  11. Giant magnetic coercivity in YNi4B-type SmNi3TB (T=Mn-Cu) solid solutions

    NASA Astrophysics Data System (ADS)

    Yao, Jinlei; Yan, Chang; Yapaskurt, V. O.; Morozkin, A. V.

    2016-12-01

    The effects of transition metal substitution for Ni on the magnetic properties of the YNi4B-type SmNi4B via SmNi3TB (T=Mn, Fe, Co, Cu) solid solutions have been investigated. SmNi4B, SmNi3MnB, SmNi3FeB, SmNi3CoB and SmNi3CuB show ferromagnetic ordering at 40 K, 210 K, 322 K, 90 K and 57 K and field sensitive metamagnetic-like transitions at 15 K, 100 K, 185 K, 55 K and 15 K in a magnetic field of 10 kOe, respectively. The magnetocaloric effects of SmNi3TB (T=Mn-Cu) were calculated in terms of isothermal magnetic entropy change (ΔSm). The magnetic entropy ΔSm reaches value of -0.94 J/kg K at 40 K for SmNi4B, -1.5 J/kg K at 205 K for SmNi3MnB, -0.54 J/kg K at 320 K for SmNi3FeB, -0.49 J/kg K at 90 K for SmNi3CoB and -0.54 J/kg K at 60 K for SmNi3CuB in field change of 0-50 kOe around the Curie temperature. They show positive ΔSm of +0.71 J/kg K at ~10 K for SmNi4B, +1.69 J/kg K at 30 K for SmNi3MnB, +0.89 J/kg K at 110 K for SmNi3FeB, +1.08 J/kg K at 25 K for SmNi3CoB and +1.12 J/kg K at 10 K for SmNi3CuB in field change of 0-50 kOe around the low temperature metamagnetic-like transition. Below the field induced transition temperature (change of magnetic structure), SmNi3TB (T=Mn-Cu) exhibits giant magnetic coercivity of 74 kOe at 5 K for SmNi4B, 69 kOe at 20 K (90 kOe at 10 K) for SmNi3MnB, 77 kOe at 60 K for SmNi3FeB, 88 kOe at 20 K for SmNi3CoB and 52 kOe at 5 K for SmNi3CuB.

  12. Influence of Zn on magnetocaloric effect in (0.95)La{sub 0.7}Sr{sub 0.3}MnO{sub 3}/Ni{sub 1−x}Zn{sub x}Fe{sub 2}O{sub 4} ceramic composites

    SciTech Connect

    Anwar, M.S.; Khan, Azmat Ali; Park, K.Y.; Lee, Seung Rok; Ahmed, Faheem; Koo, Bon Heun

    2015-09-15

    Highlights: • Synthesis of magnetic ceramic composites. • Magnetization of dual phase ceramics. • Magnetic entropy change in (0.95)La{sub 0.7}Sr{sub 0.3}MnO{sub 3}/(0.05)Ni{sub 1−x}Zn{sub x}Fe{sub 2}O{sub 4} solid solution. - Abstract: We report the magnetic and magnetocaloric properties of (0.95)La{sub 0.7}Sr{sub 0.3}MnO{sub 3}/(0.05)Ni{sub 1−x}Zn{sub x}Fe{sub 2}O{sub 4} (x = 0.0, 0.1, 0.3, and 0.5) ceramic composites. The composite samples with nominal compositions were prepared using the conventional solid-state reaction method. The phase purity and structure were confirmed by using X-ray diffraction. Temperature dependent magnetization measurements and Arrott analysis reveal second order of magnetic phase transition in the composite samples. A maximum in magnetic entropy change of ∼0.75 J/kg K at 1 T has been observed in (0.95)La{sub 0.7}Sr{sub 0.3}MnO{sub 3}/(0.05)NiFe{sub 2}O{sub 4} sample. The values of magnetic entropy change of these composites make them attractive for potential applications. These composite samples may consider as potential material for magnetic refrigeration near room temperature.

  13. Critical evaluation of sequential leaching procedures for the determination of Ni and Mn species in welding fumes.

    PubMed

    Berlinger, B; Náray, M; Sajó, I; Záray, G

    2009-06-01

    corrosion-resistant steel and unalloyed structural steel, respectively. According to the results of the leaching procedures, GMAW fumes are rich in oxidic Ni (79%), while Ni compounds in welding fumes generated during MMAW are mainly in easily soluble form (44%). The crystalline phases were identified in each welding fume by X-ray powder diffraction (XRPD) technique as well. From the XRPD spectra, it is clear that GMAW fumes contain predominantly magnetite (FeFe(2)O(4)). In case of structural steel welding, there was a little amount of ferrite (alpha-Fe) also found. Welding fume generated during MMAW of structural steel contained a complex alkali-alkali earth fluoride phase (KCaF(3)-CaF(2)) and some magnetite and jakobsite (MnFe(2)O(4)). The XRPD results did not fully confirm the ones obtained from the extraction experiments. However, some results, for example the rate of soluble Ni and Mn compounds compared to the total, can be useful for further investigations of welding fumes.

  14. Magnetic properties of CaCu{sub 5}-type RNi{sub 3}TSi (R=Gd and Tb, T=Mn, Fe, Co and Cu) compounds

    SciTech Connect

    Morozkin, A.V.; Knotko, A.V.; Yapaskurt, V.O.; Yao, Jinlei; Yuan, Fang; Mozharivskyj, Y.; Nirmala, R.; Quezado, S.; Malik, S.K.

    2015-12-15

    Magnetic properties and magnetocaloric effect of CaCu{sub 5}-type RNi{sub 3}TSi (R=Gd and Tb, T=Mn, Fe, Co and Cu) compounds have been investigated. Magnetic measurements of RNi{sub 3}TSi display the increasing of Curie temperature and the decreasing of magnetocaloric effect and saturated magnetic moment in the row of ‘RNi{sub 3}CuSi–RNi{sub 3}NiSi–RNi{sub 3}CoSi–RNi{sub 3}MnSi–RNi{sub 3}FeSi’. In contrast to GdNi{sub 3}{Mn, Fe, Co}Si, TbNi{sub 3}{Mn, Fe, Co}Si exhibit significant magnetic hysteresis. The coercive field increases from TbNi{sub 4}Si (~0.5 kOe) to TbNi{sub 3}CoSi (4 kOe), TbNi{sub 3}MnSi (13 kOe) and TbNi{sub 3}FeSi (16 kOe) in field of 50 kOe at 5 K, whereas TbNi{sub 3}CuSi exhibits a negligible coercive field. - Graphical abstract: Magnetic measurements of RNi{sub 3}TSi show the increasing of Curie temperature and the decreasing of magnetocaloric effect and saturated magnetic moment in the row of 'RNi{sub 3}CuSi–RNi{sub 3}NiSi–RNi{sub 3}CoSi–RNi{sub 3}MnSi–RNi{sub 3}FeSi'. In contrast to GdNi{sub 3}{Mn, Fe, Co}Si, TbNi{sub 3}{Mn, Fe, Co}Si exhibit significant magnetic hysteresis. The coercive field increases from TbNi{sub 4}Si (~0.5 kOe) to TbNi{sub 3}CoSi (4 kOe), TbNi{sub 3}MnSi (13 kOe) and TbNi{sub 3}FeSi (16 kOe) in field of 50 kOe at 5 K, whereas TbNi{sub 3}CuSi exhibits a negligible coercive field. - Highlights: • CaCu{sub 5}-type RNi{sub 3}TSi show ferromagnetic ordering (R=Gd, Tb, T=Mn–Co, Cu). • Curie point increases in ‘RNi{sub 3}CuSi–RNi{sub 3}NiSi–RNi{sub 3}CoSi–RNi{sub 3}MnSi–RNi{sub 3}FeSi’ row. • MCE decreases in ‘RNi{sub 3}CuSi–RNi{sub 3}NiSi–RNi{sub 3}CoSi–RNi{sub 3}MnSi–RNi{sub 3}FeSi’ row. • TbNi{sub 3}{Mn, Fe, Co}Si exhibit significant magnetic hysteresis. • The coercive field of TbNi{sub 3}MnSi and TbNi{sub 3}FeSi reach 13 kOe and 16 kOe at 5 K.

  15. H+-induced irradiation damage resistance in Fe- and Ni-based metallic glass

    NASA Astrophysics Data System (ADS)

    Zhang, Hongran; Mei, Xianxiu; Zhang, Xiaonan; Li, Xiaona; Wang, Yingmin; Sun, Jianrong; Wang, Younian

    2016-05-01

    In this study, use of 40-keV H+ ion for irradiating metallic glass Fe80Si7.43B12.57 and Ni62Ta38 as well as metallic tungsten (W) at fluences of 1 × 1018 and 3 × 1018 ions/cm2, respectively, was investigated. At the fluence of 1 × 1018 ions/cm2, a crystalline layer appeared in metallic glass Fe80Si7.43B12.57, with α-Fe as the major crystalline phase, coupled with a little Fe2B, Fe3B, and metastable β-Mn-type phase. Fe80Si7.43B12.57 exhibited good soft magnetic properties after irradiation. At the fluence of 3 × 1018 ions/cm2, Ni62Ta38 was found to be amorphous-based, with a little μ-NiTa and Ni3Ta phases. No significant irradiation damage phenomenon appeared in metallic glasses Fe80Si7.43B12.57 and Ni62Ta38. Blistering, flaking, and other damage occurred on the surface of metallic W, and the root-mean-square (RMS) roughness increased with the increase of fluence. Metallic glass Ni62Ta38 exhibited better resistance to H+ irradiation than Fe80Si7.43B12.57, both of which were superior to the metallic W.

  16. First principle-based AKMC modelling of the formation and medium-term evolution of point defect and solute-rich clusters in a neutron irradiated complex Fe-CuMnNiSiP alloy representative of reactor pressure vessel steels

    NASA Astrophysics Data System (ADS)

    Ngayam-Happy, R.; Becquart, C. S.; Domain, C.

    2013-09-01

    The formation and medium-term evolution of point defect and solute-rich clusters under neutron irradiation have been modelled in a complex Fe-CuMnNiSiP alloy representative of RPV steels, by means of first principle-based atomistic kinetic Monte Carlo simulations. The results obtained reproduce most features observed in available experimental studies, highlighting the very good agreement between both series. According to simulation, solute-rich clusters form and develop via an induced segregation mechanism on either the vacancy or interstitial clusters, and these point defect clusters are efficiently generated only in cascade debris and not Frenkel pair flux. The results have revealed the existence of two distinct populations of clusters with different characteristic features. Solute-rich clusters in the first group are bound essentially to interstitial clusters and they are enriched in Mn mostly, but also Ni to a lesser extent. Over the low dose regime, their density increases in the alloy as a result of the accumulation of highly stable interstitial clusters. In the second group, the solute-rich clusters are merged with vacancy clusters, and they contain mostly Cu and Si, but also substantial amount of Mn and Ni. The formation of a sub-population of pure solute clusters has been observed, which results from annihilation of the low stable vacancy clusters on sinks. The results indicate finally that the Mn content in clusters is up to 50%, Cu, Si, and Ni sharing the other half in more or less equivalent amounts. This composition has not demonstrated any noticeable modification with increasing dose over irradiation.

  17. Correlation of martensitic transformation temperatures of Ni- Mn-Ga/Al-X alloys to non-bonding electron concentration

    NASA Astrophysics Data System (ADS)

    Ramudu, M.; Satish Kumar, A.; Seshubai, V.; Rajasekharan, T.

    2015-02-01

    The martensitic transformation TM of the alloys of Ni-Mn-Ga and Ni-Mn-Al show a general trend of increase with electron per atom ratio (e/a) calculated from the total number of electrons outside the rare gas shell of the atoms. However prediction of TM fails among iron substituted Ni-Mn-Ga alloys and those with In doped for Ga, due to the absence of a useful trend. A scheme of computing modified electron concentration is presented considering only the non-bonding electrons per atom Ne/a of the compounds, based on Pauling's ideas on the electronic structure of metallic elements. Systematic variation of TM with Ne/a is reproduced for a large number of alloys of Ni-Mn-Ga and the anomaly observed for Fe containing alloys with e/a disappears. The non-bonding electron concentration is thus demonstrated to be effective in predicting TM of shape memory alloys of Ni-Mn-Ga-X system including the isoelectronic compounds of Ni-Mn-Ga-In.

  18. Strength of "Light" Ferritic and Austenitic Steels Based on the Fe - Mn - Al - C System

    NASA Astrophysics Data System (ADS)

    Kaputkina, L. M.; Svyazhin, A. G.; Smarygina, I. V.; Kindop, V. E.

    2017-01-01

    The phase composition, the hardness, the mechanical properties at room temperature, and the resistance to hot (950 - 1000°C) and warm (550°C) deformation are studied for cast deformable "light" ferritic and austenitic steels of the Fe - (12 - 25)% Mn - (0 - 15)% Al - (0 - 2)% C system alloyed additionally with about 5% Ni. The high-aluminum high-manganese low-carbon and carbonless ferritic steels at a temperature of about 0.5 T melt have a specific strength close to that of the austenitic steels and may be used as weldable scale-resistant and wear-resistant materials. The high-carbon Fe - (20 - 24)% Mn - (5 - 9)% Al - 5% Ni - 1.5% C austenitic steels may be applied as light high-strength materials operating at cryogenic temperatures after a solution treatment and as scale- and heat-resistant materials in an aged condition.

  19. Study of Magnetic Behavior of Mn1-xNixFe2O4 Nanoparticles

    NASA Astrophysics Data System (ADS)

    Kumar, E. Ranjith; Kumar, Sanjay; Kojima, Toshinori; Jayaprakash, R.

    The nano crystalline manganese nickel cobalt ferrite is synthesized by a simple technique of thermal evaporation with the help of egg white and its magnetic behaviour is analyzed for different annealing temperature. The saturation magnetization for MnNiFe2O4 at different annealing temperature has been recorded and also the influence of particle size in magnetic properties is analyzed. The FT-IR spectra of the sample reveal the common feature of ferrites like high frequency band to the tetrahedral and low frequency band to the octahedral stretching vibrations. The presence of constituent phases in MnNiFe2O4 is confirmed by X-Ray Diffraction. The particle size, morphology and percentage of composition elements are measured by employing Transmission Electron Microscopy (TEM),

  20. Magnetic properties of CaCu5-type RNi3TSi (R=Gd and Tb, T=Mn, Fe, Co and Cu) compounds

    NASA Astrophysics Data System (ADS)

    Morozkin, A. V.; Knotko, A. V.; Yapaskurt, V. O.; Yao, Jinlei; Yuan, Fang; Mozharivskyj, Y.; Nirmala, R.; Quezado, S.; Malik, S. K.

    2015-12-01

    Magnetic properties and magnetocaloric effect of CaCu5-type RNi3TSi (R=Gd and Tb, T=Mn, Fe, Co and Cu) compounds have been investigated. Magnetic measurements of RNi3TSi display the increasing of Curie temperature and the decreasing of magnetocaloric effect and saturated magnetic moment in the row of 'RNi3CuSi-RNi3NiSi-RNi3CoSi-RNi3MnSi-RNi3FeSi'. In contrast to GdNi3{Mn, Fe, Co}Si, TbNi3{Mn, Fe, Co}Si exhibit significant magnetic hysteresis. The coercive field increases from TbNi4Si ( 0.5 kOe) to TbNi3CoSi (4 kOe), TbNi3MnSi (13 kOe) and TbNi3FeSi (16 kOe) in field of 50 kOe at 5 K, whereas TbNi3CuSi exhibits a negligible coercive field.

  1. The effect of carbon on the microstructures, mechanical properties, and deformation mechanisms of thermo-mechanically treated Fe40.4Ni11.3Mn34.8Al7.5Cr6 high entropy alloys

    DOE PAGES

    Wang, Zhangwei; Baker, Ian; Guo, Wei; ...

    2017-03-01

    We investigated the effects of cold rolling followed by annealing on the mechanical properties and dislocation substructure evolution of undoped and 1.1 at. % carbon-doped Fe40.4Ni11.3Mn34.8Al7.5Cr6 high entropy alloys (HEAs). X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atom probe tomography (APT) were employed to characterize the microstructures. The as-cast HEAs were coarse-grained and single phase f.c.c., whereas the thermo-mechanical treatment caused recrystallization (to fine grain sizes) and precipitation (a B2 phase for the undoped HEA; and a B2 phase, and M23C6 and M7C3 carbides for the C-doped HEA). Carbon, which was found to have segregated tomore » the grain boundaries using APT, retarded recrystallization. The reduction in grain size resulted in a sharp increase in strength, while the precipitation, which produced only a small increase in strength, probably accounted for the small decrease in ductility for both undoped and C-doped HEAs. For both undoped and C-doped HEAs, the smaller grain-sized material initially exhibited higher strain hardening than the coarse-grained material but showed a much lower strain hardening at large tensile strains. Wavy slip in the undoped HEAs and planar slip in C-doped HEAs were found at the early stages of deformation irrespective of grain size. At higher strains, dislocation cell structures formed in the 19 μm grain-sized undoped HEA, while microbands formed in the 23 μm grain-sized C-doped HEA. Conversely, localized dislocation clusters were found in both HEAs at the finest grain sizes (5 μm). The inhibition of grain subdivision by the grain boundaries and precipitates lead to the transformation from regular dislocation configurations consisting of dislocation-cells and microbands to irregular dislocation configurations consisting of localized dislocation clusters, which further account for the decrease in ductility. Our investigation of the formation mechanism

  2. Molecular orbital (SCF-X-α-SW) theory of Fe2+-Mn3+, Fe3+-Mn2+, and Fe3+-Mn3+ charge transfer and magnetic exchange in oxides and silicates

    USGS Publications Warehouse

    Sherman, David M.

    1990-01-01

    Metal-metal charge-transfer and magnetic exchange interactions have important effects on the optical spectra, crystal chemistry, and physics of minerals. Previous molecular orbital calculations have provided insight on the nature of Fe2+-Fe3+ and Fe2+-Ti4+ charge-transfer transitions in oxides and silicates. In this work, spin-unrestricted molecular orbital calculations on (FeMnO10) clusters are used to study the nature of magnetic exchange and electron delocalization (charge transfer) associated with Fe3+-Mn2+, Fe3+-Mn3+, and Fe2+-Mn3+ interactions in oxides and silicates. 

  3. Mechanisms of Formation and Transformation of Ni-Fe Hydroxycarbonates

    SciTech Connect

    Refait, Ph.; Jeannin, M.; Reffass, M.; Drissi, S.H.; Abdelmoula, M.; Genin, J.-M.R.

    2005-04-26

    The mechanisms of the transformation of (Ni,Fe)(OH)2 precipitates in carbonated aqueous solutions were studied. The reactions were monitored by measuring the redox potential of the aqueous suspension, and end products were studied by Moessbauer spectroscopy, X-ray diffraction and Raman spectroscopy. The oxidation processes were compared to those occurring without Ni, that is when the initial hydroxide is Fe(OH)2. Schematically, the oxidation of Fe(OH)2 involves two intermediate compounds, the carbonated GR of formula Fe{sup II}{sub 4}Fe{sup III}{sub 2}(OH){sub 12}CO{sub 3} {center_dot} 2H{sub 2}O, and ferrihydrite, before to lead finally to goethite {alpha}-FeOOH. It proved possible to prepare Ni(II)-Fe(III) hydroxycarbonates with ratios Fe/Ni from 1/6 to 1/3. When the Fe/Ni ratio is larger than 1/3, a two stage oxidation process takes place. The first stage leads to a Ni(II)-Fe(II)-Fe(III) hydroxycarbonate. The second stage corresponds to the oxidation of the Fe(II) remaining inside the hydroxycarbonate and leads to a mixture of Ni(II)-Fe(III) hydroxycarbonate with ferrihydrite. The main effect of Ni is then to stop the reaction at an intermediate stage, as Ni(II) is not oxidised by O2, leaving unchanged the main features of the mechanisms of transformation.

  4. Fe-Ni composition dependence of magnetic anisotropy in artificially fabricated L1 0-ordered FeNi films.

    PubMed

    Kojima, Takayuki; Ogiwara, Misako; Mizuguchi, Masaki; Kotsugi, Masato; Koganezawa, Tomoyuki; Ohtsuki, Takumi; Tashiro, Taka-Yuki; Takanashi, Koki

    2014-02-12

    We prepared L10-ordered FeNi alloy films by alternate deposition of Fe and Ni monatomic layers, and investigated their magnetic anisotropy. We employed a non-ferromagnetic Au-Cu-Ni buffer layer with a flat surface and good lattice matching to L10-FeNi. An L10-FeNi film grown on Au6Cu51Ni43 showed a large uniaxial magnetic anisotropy energy (Ku = 7.0 × 10(6) erg cm(-)3). Ku monotonically increased with the long-range order parameter (S) of the L10 phase. We investigated the Fe-Ni composition dependence by alternating the deposition of Fe 1 − x and Ni 1 + x monatomic layers (− 0.4 < x < 0.4). Saturation magnetization (Ms) and Ku showed maxima (Ms = 1470 emu cm(-3), Ku = 9.3 × 10(6) erg cm(-3)) for Fe60Ni40 (x = -0.2) while S showed a maximum at the stoichiometric composition (x = 0). The change in the ratio of lattice parameters (c/a) was small for all compositions. We found that enrichment of Fe is very effective to enhance Ku. The large Ms and Ku of Fe60Ni40 indicate that Fe-rich L10-FeNi is promising as a rare-earth-free permanent magnet.

  5. Ferromagnetism of Fe86Mn14-yCuy alloys

    NASA Astrophysics Data System (ADS)

    França, F.; Paduani, C.; Krause, J. C.; Ardisson, J. D.; Yoshida, M. I.; Schaf, J.

    2007-01-01

    The magnetic properties of disordered Fe86Mn14-yCuy alloys were investigated with several experimental techniques. The results of X-ray diffraction showed that these alloys are single phase with the A2 (BCC) structure. These are ferromagnetic alloys at room temperature, and the Curie temperature decreases with the increase of the Cu content. An abrupt loss of magnetization was observed below TC at a temperature which increases with the reduction of the Mn content in the alloys. The addition of manganese enhances the solubility of copper in iron matrix and retains the BCC structure in iron-rich alloys. The behavior of the magnetization with temperature and its composition dependence indicate that an antiferromagnetic coupling is expected between the Fe and Mn atoms. The magnetic moments of both Fe and Mn atoms are expected to vary strongly with composition in these alloys.

  6. Resolving and modeling the effects of Fe and Mn redox cycling on trace metal behavior in a seasonally anoxic lake

    NASA Astrophysics Data System (ADS)

    Hamilton-Taylor, J.; Smith, E. J.; Davison, W.; Sugiyama, M.

    2005-04-01

    Vertical profiles of the dissolved and particulate (>0.45 μm) concentrations of Fe, Mn, Co, Ni, Cu, Pb, Al and Ba were determined on two occasions (14 and 22 August 1996) during summer stratification in a seasonally anoxic lake (Esthwaite Water, UK). The results were combined with contemporaneous in situ measurements of water-column remobilization of the metals from settling particles at the base of the suboxic zone and other ancillary measurements. The combined data were interpreted with the aid of an equilibrium speciation model (WHAM6), incorporating metal-humic interactions and a surface-complexation description of binding to Fe and Mn oxides. The behavior of all the metals was related in different ways to the position of the O 2-H 2S interface and to Fe and Mn redox cycling. In the region of the O 2-H 2S interface the behavior of Co and to a lesser degree Ni was dominated by Mn redox cycling. Ba behavior was dominated by the biogenic precipitation and dissolution of barite and to a lesser degree by Mn redox cycling. The behavior of Al was linked to both Mn and Fe redox cycling, although the extent of binding to the oxides and to humic substances was poised with respect to pH. Unlike the other metals, the profiles of Pb and Cu showed little variation above the dissolved sulfide maximum, but modeling indicated that binding of Pb was significant to both Mn and Fe oxides. The featureless nature of the Cu profiles in the upper part of the water column was linked to its overriding association with dissolved humic substances. Below the dissolved sulfide maximum, Co, Ni, Ba, Cu, Pb and Mn were all affected by sulfide precipitation, probably through a common association with FeS. In the case of Co, Ni, Cu and Pb, inverse relationships between the measured dissolved and particulate concentrations were attributed to the coexistence of both filterable and nonfilterable FeS particles and associated mass balance effects. The observed behavior of the metals in relation to

  7. Dislocation Mechanism of Twinning in Ni-Mn-Ga

    NASA Astrophysics Data System (ADS)

    Zárubová, N.; Ge, Y.; Gemperlová, J.; Gemperle, A.; Hannula, S.-P.

    2012-03-01

    Tensile tests were performed in situ in a transmission electron microscope to investigate the twinning mechanism in non-modulated Ni-Mn-Ga martensite. The reorientation of the twin variants occurs via twinning dislocations. Their generation and movement were followed; the glide plane and Burgers vector were verified. Individual twinning dislocations were visualized.

  8. Synthesis and properties of A{sub 6}B{sub 2}(OH){sub 16}Cl{sub 2}.4H{sub 2}O (A = Mg, Ni, Zn, Co, Mn and B = Al, Fe) materials for environmental applications

    SciTech Connect

    Dias, Anderson; Cunha, Lumena; Vieira, Andiara C.

    2011-09-15

    Highlights: {yields} A{sub 6}B{sub 2}(OH){sub 16}Cl{sub 2}.4H{sub 2}O (A = Mg, Ni, Zn, Co, Mn and B = Al, Fe) materials were synthesized. {yields} Chemical synthesis produced different levels of crystallinity and ordering degree. {yields} Structural investigation by Raman scattering revealed a complex band structure. {yields} A strong correlation between band structure and ionic radius was determined. -- Abstract: Double layered hydroxide materials of composition A{sub 6}B{sub 2}(OH){sub 16}Cl{sub 2}.4H{sub 2}O (A = Mg, Ni, Zn, Co, Mn and B = Al, Fe) were synthesized by chemical precipitation at 60 {sup o}C. Different levels of crystallinity and ordering degree were observed depending upon the chemical environment or the combination between divalent and trivalent cations. The results from high-resolution transmission electron microscopy revealed that nanostructured layered samples were obtained with interplanar spacing compatible with previous literature. Raman scattering was employed to investigate the complex band structure observed, particularly the lattice vibrations at lower frequencies, which is intimately correlated to the cationic radius of both divalent and trivalent ions. The results showed that strongly coordinated water and chloride ions besides highly structured hydroxide layers have a direct influence on the stability of the hydrotalcites. It was observed that transition and decomposition temperatures varied largely for different chemical compositions.

  9. Mn-Fe base and Mn-Cr-Fe base austenitic alloys

    DOEpatents

    Brager, Howard R.; Garner, Francis A.

    1987-01-01

    Manganese-iron base and manganese-chromium-iron base austenitic alloys designed to have resistance to neutron irradiation induced swelling and low activation have the following compositions (in weight percent): 20 to 40 Mn; up to about 15 Cr; about 0.4 to about 3.0 Si; an austenite stabilizing element selected from C and N, alone or in combination with each other, and in an amount effective to substantially stabilize the austenite phase, but less than about 0.7 C, and less than about 0.3 N; up to about 2.5 V; up to about 0.1 P; up to about 0.01 B; up to about 3.0 Al; up to about 0.5 Ni; up to about 2.0 W; up to about 1.0 Ti; up to about 1.0 Ta; and with the remainder of the alloy being essentially iron.

  10. Mn-Fe base and Mn-Cr-Fe base austenitic alloys

    DOEpatents

    Brager, Howard R.; Garner, Francis A.

    1987-09-01

    Manganese-iron base and manganese-chromium-iron base austenitic alloys designed to have resistance to neutron irradiation induced swelling and low activation have the following compositions (in weight percent): 20 to 40 Mn; up to about 15 Cr; about 0.4 to about 3.0 Si; an austenite stabilizing element selected from C and N, alone or in combination with each other, and in an amount effective to substantially stabilize the austenite phase, but less than about 0.7 C, and less than about 0.3 N; up to about 2.5 V; up to about 0.1 P; up to about 0.01 B; up to about 3.0 Al; up to about 0.5 Ni; up to about 2.0 W; up to about 1.0 Ti; up to about 1.0 Ta; and with the remainder of the alloy being essentially iron.

  11. Diffusion Quantum Monte Carlo predictions for bulk MnNiO3

    NASA Astrophysics Data System (ADS)

    Mitra, Chandrima; Krogel, Jaron; Reboredo, Fernando A.

    MnNiO3 is a strongly correlated transition metal oxide that has recently been investigated theoretically for its potential application as an oxygen-evolution photo-catalyst. However, there is no experimental report on critical quantities like its band gap or its bulk modulus. Recent theoretical predictions with standard functionals, such as PBE +U and HSE show large discrepancies in the band-gaps (about 1.23 eV), depending on the nature of the functional used. Hence, there is clearly a need for an accurate quantitative prediction of the band-gap in order to decide its usefulness as a photo-catalyst. In this work, we present Diffusion Quantum Monte Carlo (DMC) study of the bulk properties of MnNiO3. This includes the quasiparticle band gap for the two spin channels, the equilibrium lattice parameter and the bulk modulus. The DMC approach has already been shown to achieve excellent agreement with experimental results for other oxides such as ZnO NiO and Fe2O3. To our knowledge, MnNiO3 is the first case where this theory is applied before experiments are done. This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.

  12. Euhedral metallic-Fe-Ni grains in extraterrestrial samples

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.

    1993-01-01

    Metallic Fe-Ni is rare in terrestrial rocks, being largely restricted to serpentinized peridotites and volcanic rocks that assimilated carbonaceous material. In contrast, metallic Fe-Ni is nearly ubiquitous among extraterrestrial samples (i.e., meteorites, lunar rocks, and interplanetary dust particles). Anhedral grains are common. For example, in eucrites and lunar basalts, most of the metallic Fe-Ni occurs interstitially between silicate grains and thus tends to have irregular morphologies. In many porphyritic chondrules, metallic Fe-Ni and troilite form rounded blebs in the mesostasis because their precursors were immiscible droplets. In metamorphosed ordinary chondrites, metallic Fe-Ni and troilite form coarse anhedral grains. Some of the metallic Fe-Ni and troilite grains has also been mobilized and injected into fractures in adjacent silicate grains where local shock-reheating temperatures reached the Fe-FeS eutectic (988 C). In interplanetary dust particles metallic Fe-Ni most commonly occurs along with sulfide as spheroids and fragments. Euhedral metallic Fe-Ni grains are extremely rare. Several conditions must be met before such grains can form: (1) grain growth must occur at free surfaces, restricting euhedral metallic Fe-Ni grains to systems that are igneous or undergoing vapor-deposition; (2) the metal (+/-) sulfide assemblage must have an appropriate bulk composition so that taenite is the liquidus phase in igneous systems or the stable condensate phase in vapor-deposition systems; and (3) metallic Fe-Ni grains must remain underformed during subsequent compaction, thermal metamorphism, and shock. Because of these restrictions, the occurrence of euhedral metallic Fe-Ni grains in an object can potentially provide important petrogenetic information. Despite its rarity, euhedral metallic Fe-Ni occurs in a wide variety of extraterrestrial materials. Some of these materials formed in the solar nebula; others formed on parent body surfaces by meteoroid

  13. Martensitic transformation of FeNi nanofilm induced by interfacial stress generated in FeNi/V nanomultilayered structure

    NASA Astrophysics Data System (ADS)

    Li, Wei; Liu, Ping; Zhang, Ke; Ma, Fengcang; Liu, Xinkuan; Chen, Xiaohong; He, Daihua

    2014-08-01

    FeNi/V nanomultilayered films with different V layer thicknesses were synthesized by magnetron sputtering. By adjusting the thickness of the V layer, different interfacial compressive stress were imposed on FeNi layers and the effect of interfacial stress on martensitic transformation of the FeNi film was investigated. Without insertion of V layers, the FeNi film exhibits a face-centered cubic (fcc) structure. With the thickness of V inserted layers up to 1.5 nm, under the coherent growth structure in FeNi/V nanomultilayered films, FeNi layers bear interfacial compressive stress due to the larger lattice parameter relative to V, which induces the martensitic transformation of the FeNi film. As the V layer thickness increases to 2.0 nm, V layers cannot keep the coherent growth structure with FeNi layers, leading to the disappearance of interfacial compressive stress and termination of the martensitic transformation in the FeNi film. The interfacial compressive stress-induced martensitic transformation of the FeNi nanofilm is verified through experiment. The method of imposing and modulating the interfacial stress through the epitaxial growth structure in the nanomultilayered films should be noticed and utilized.

  14. Martensitic transformation of FeNi nanofilm induced by interfacial stress generated in FeNi/V nanomultilayered structure

    PubMed Central

    2014-01-01

    FeNi/V nanomultilayered films with different V layer thicknesses were synthesized by magnetron sputtering. By adjusting the thickness of the V layer, different interfacial compressive stress were imposed on FeNi layers and the effect of interfacial stress on martensitic transformation of the FeNi film was investigated. Without insertion of V layers, the FeNi film exhibits a face-centered cubic (fcc) structure. With the thickness of V inserted layers up to 1.5 nm, under the coherent growth structure in FeNi/V nanomultilayered films, FeNi layers bear interfacial compressive stress due to the larger lattice parameter relative to V, which induces the martensitic transformation of the FeNi film. As the V layer thickness increases to 2.0 nm, V layers cannot keep the coherent growth structure with FeNi layers, leading to the disappearance of interfacial compressive stress and termination of the martensitic transformation in the FeNi film. The interfacial compressive stress-induced martensitic transformation of the FeNi nanofilm is verified through experiment. The method of imposing and modulating the interfacial stress through the epitaxial growth structure in the nanomultilayered films should be noticed and utilized. PMID:25232296

  15. Martensitic transformation of FeNi nanofilm induced by interfacial stress generated in FeNi/V nanomultilayered structure.

    PubMed

    Li, Wei; Liu, Ping; Zhang, Ke; Ma, Fengcang; Liu, Xinkuan; Chen, Xiaohong; He, Daihua

    2014-01-01

    FeNi/V nanomultilayered films with different V layer thicknesses were synthesized by magnetron sputtering. By adjusting the thickness of the V layer, different interfacial compressive stress were imposed on FeNi layers and the effect of interfacial stress on martensitic transformation of the FeNi film was investigated. Without insertion of V layers, the FeNi film exhibits a face-centered cubic (fcc) structure. With the thickness of V inserted layers up to 1.5 nm, under the coherent growth structure in FeNi/V nanomultilayered films, FeNi layers bear interfacial compressive stress due to the larger lattice parameter relative to V, which induces the martensitic transformation of the FeNi film. As the V layer thickness increases to 2.0 nm, V layers cannot keep the coherent growth structure with FeNi layers, leading to the disappearance of interfacial compressive stress and termination of the martensitic transformation in the FeNi film. The interfacial compressive stress-induced martensitic transformation of the FeNi nanofilm is verified through experiment. The method of imposing and modulating the interfacial stress through the epitaxial growth structure in the nanomultilayered films should be noticed and utilized.

  16. [FeFe]- and [NiFe]-hydrogenase diversity, mechanism, and maturation.

    PubMed

    Peters, John W; Schut, Gerrit J; Boyd, Eric S; Mulder, David W; Shepard, Eric M; Broderick, Joan B; King, Paul W; Adams, Michael W W

    2015-06-01

    The [FeFe]- and [NiFe]-hydrogenases catalyze the formal interconversion between hydrogen and protons and electrons, possess characteristic non-protein ligands at their catalytic sites and thus share common mechanistic features. Despite the similarities between these two types of hydrogenases, they clearly have distinct evolutionary origins and likely emerged from different selective pressures. [FeFe]-hydrogenases are widely distributed in fermentative anaerobic microorganisms and likely evolved under selective pressure to couple hydrogen production to the recycling of electron carriers that accumulate during anaerobic metabolism. In contrast, many [NiFe]-hydrogenases catalyze hydrogen oxidation as part of energy metabolism and were likely key enzymes in early life and arguably represent the predecessors of modern respiratory metabolism. Although the reversible combination of protons and electrons to generate hydrogen gas is the simplest of chemical reactions, the [FeFe]- and [NiFe]-hydrogenases have distinct mechanisms and differ in the fundamental chemistry associated with proton transfer and control of electron flow that also help to define catalytic bias. A unifying feature of these enzymes is that hydrogen activation itself has been restricted to one solution involving diatomic ligands (carbon monoxide and cyanide) bound to an Fe ion. On the other hand, and quite remarkably, the biosynthetic mechanisms to produce these ligands are exclusive to each type of enzyme. Furthermore, these mechanisms represent two independent solutions to the formation of complex bioinorganic active sites for catalyzing the simplest of chemical reactions, reversible hydrogen oxidation. As such, the [FeFe]- and [NiFe]-hydrogenases are arguably the most profound case of convergent evolution. This article is part of a Special Issue entitled: Fe/S proteins: Analysis, structure, function, biogenesis and diseases.

  17. The Effect of Metal Composition on Fe-Ni Partition Behavior between Olivine and FeNi-Metal, FeNi-Carbide, FeNi-Sulfide at Elevated Pressure

    NASA Technical Reports Server (NTRS)

    Holzheid, Astrid; Grove, Timothy L.

    2005-01-01

    Metal-olivine Fe-Ni exchange distribution coefficients were determined at 1500 C over the pressure range of 1 to 9 GPa for solid and liquid alloy compositions. The metal alloy composition was varied with respect to the Fe/Ni ratio and the amount of dissolved carbon and sulfur. The Fe/Ni ratio of the metal phase exercises an important control on the abundance of Ni in the olivine. The Ni abundance in the olivine decreases as the Fe/Ni ratio of the coexisting metal increases. The presence of carbon (up to approx. 3.5 wt.%) and sulfur (up to approx. 7.5 wt.%) in solution in the liquid Fe-Ni-metal phase has a minor effect on the partitioning of Fe and Ni between metal and olivine phases. No pressure dependence of the Fe-Ni-metal-olivine exchange behavior in carbon- and sulfur-free and carbon- and sulfur-containing systems was found within the investigated pressure range. To match the Ni abundance in terrestrial mantle olivine, assuming an equilibrium metal-olivine distribution, a sub-chondritic Fe/Ni-metal ratio that is a factor of 17 to 27 lower than the Fe/Ni ratios in estimated Earth core compositions would be required, implying higher Fe concentrations in the core forming metal phase. A simple metal-olivine equilibrium distribution does not seem to be feasible to explain the Ni abundances in the Earth's mantle. An equilibrium between metal and olivine does not exercise a control on the problem of Ni overabundance in the Earth's mantle. The experimental results do not contradict the presence of a magma ocean at the time of terrestrial core formation, if olivine was present in only minor amounts at the time of metal segregation.

  18. Fate of half-metallicity near interfaces: the case of NiMnSb/MgO and NiMnSi/MgO.

    PubMed

    Zhang, Rui-Jing; Eckern, Ulrich; Schwingenschlögl, Udo

    2014-08-27

    The electronic and magnetic properties of the interfaces between the half-metallic Heusler alloys NiMnSb, NiMnSi, and MgO have been investigated using first-principles density-functional calculations with projector augmented wave potentials generated in the generalized gradient approximation. In the case of the NiMnSb/MgO (100) interface, the half-metallicity is lost, whereas the MnSb/MgO contact in the NiMnSb/MgO (100) interface maintains a substantial degree of spin polarization at the Fermi level (∼60%). Remarkably, the NiMnSi/MgO (111) interface shows 100% spin polarization at the Fermi level, despite considerable distortions at the interface, as well as rather short Si/O bonds after full structural optimization. This behavior markedly distinguishes NiMnSi/MgO (111) from the corresponding NiMnSb/CdS and NiMnSb/InP interfaces.

  19. FeNi-based magnetoimpedance multilayers: Tailoring of the softness by magnetic spacers

    NASA Astrophysics Data System (ADS)

    Svalov, A. V.; Fernandez, E.; Garcia-Arribas, A.; Alonso, J.; Fdez-Gubieda, M. L.; Kurlyandskaya, G. V.

    2012-04-01

    The microstructure and magnetic properties of sputtered permalloy films and FeNi(170 nm)/X/FeNi(170 nm) (X = Co, Fe, Gd, Gd-Co) sandwiches were studied. Laminating of the thick FeNi film with various spacers was done in order to control the magnetic softness of FeNi-based multilayers. In contrast to the Co and Fe spacers, Gd and Gd-Co magnetic spacers improved the softness of the FeNi/X/FeNi sandwiches. The magnetoimpedance responses were measured for [FeNi/Ti(6 nm)]2/FeNi and [FeNi/Gd(2 nm)]2/FeNi multilayers in a frequency range of 1-500 MHz: for all frequencies under consideration the highest magnetoimpedance variation was observed for [FeNi/Gd(2 nm)]2/FeNi multilayers.

  20. Shape-Memory Effect and Pseudoelasticity in Fe-Mn-Based Alloys

    NASA Astrophysics Data System (ADS)

    La Roca, P.; Baruj, A.; Sade, M.

    2017-03-01

    Several Fe-based alloys are being considered as potential candidates for applications which require shape-memory behavior or superelastic properties. The possibility of using fabrication methods which are well known in the steel industry is very attractive and encourages a large amount of research in the field. In the present article, Fe-Mn-based alloys are mainly addressed. On the one hand, attention is paid to the shape-memory effect where the alloys contain (a) a maximum amount of Mn up to around 30 wt%, (b) several possible substitutional elements like Si, Cr, Ni, Co, and Nb and (c) some possible interstitial elements like C. On the other hand, superelastic alloys are analyzed, mainly the Fe-Mn-Al-Ni system discovered a few years ago. The most noticeable properties resulting from the martensitic transformations which are responsible for the mentioned properties, i.e., the fcc-hcp in the first case and the bcc-fcc in the latter are discussed. Selected potential applications are also analyzed.

  1. Shape-Memory Effect and Pseudoelasticity in Fe-Mn-Based Alloys

    NASA Astrophysics Data System (ADS)

    La Roca, P.; Baruj, A.; Sade, M.

    2016-12-01

    Several Fe-based alloys are being considered as potential candidates for applications which require shape-memory behavior or superelastic properties. The possibility of using fabrication methods which are well known in the steel industry is very attractive and encourages a large amount of research in the field. In the present article, Fe-Mn-based alloys are mainly addressed. On the one hand, attention is paid to the shape-memory effect where the alloys contain (a) a maximum amount of Mn up to around 30 wt%, (b) several possible substitutional elements like Si, Cr, Ni, Co, and Nb and (c) some possible interstitial elements like C. On the other hand, superelastic alloys are analyzed, mainly the Fe-Mn-Al-Ni system discovered a few years ago. The most noticeable properties resulting from the martensitic transformations which are responsible for the mentioned properties, i.e., the fcc-hcp in the first case and the bcc-fcc in the latter are discussed. Selected potential applications are also analyzed.

  2. Study of intergranular embrittlement in Fe-12Mn alloys

    SciTech Connect

    Lee, H.J.

    1982-06-01

    A high resolution scanning Auger microscopic study has been performed on the intergranular fracture surfaces of Fe-12Mn steels in the as-austenitized condition. Fracture mode below the ductile-brittle transition temperature was intergranular whenever the alloy was quenched from the austenite field. The intergranular fracture surface failed to reveal any consistent segregation of P, S, As, O, or N. The occasional appearance of S or O on the fracture surface was found to be due to a low density precipitation of MnS and MnO/sub 2/ along the prior austenite boundaries. An AES study with Ar/sup +/ ion-sputtering showed no evidence of manganese enrichment along the prior austenite boundaries, but a slight segregation of carbon which does not appear to be implicated in the tendency toward intergranular fracture. Addition of 0.002% B with a 1000/sup 0/C/1h/WQ treatment yielded a high Charpy impact energy at liquid nitrogen temperature, preventing the intergranular fracture. High resolution AES studies showed that 3 at. % B on the prior austenite grain boundaries is most effective in increasing the grain boundary cohesive strength in an Fe-12Mn alloy. Trace additions of Mg, Zr, or V had negligible effects on the intergranular embrittlement. A 450/sup 0/C temper of the boron-modified alloys was found to cause tempered martensite embrittlement, leading to intergranular fracture. The embrittling treatment of the Fe-12Mn alloys with and without boron additions raised the ductile-brittle transition by 150/sup 0/C. This tempered martensite embrittlement was found to be due to the Mn enrichment of the fracture surface to 32 at. % Mn in the boron-modified alloy and 38 at. % Mn in the unmodified alloy. The Mn-enriched region along the prior austenite grain boundaries upon further tempering is believed to cause nucleation of austenite and to change the chemistry of the intergranular fracture surfaces. 61 figures.

  3. Research on pulse electrodeposition of Fe-Ni alloy

    SciTech Connect

    Peng, Yongsen; Zhu, Zengwei Ren, Jianhua; Chen, Jiangbo; Han, Taojie

    2014-03-15

    Fe-Ni alloys were fabricated on steel substrates by means of pulse electrodeposition in sulfate solutions. The layers were electrodeposited using different peak current densities, duty cycles and frequencies. Fe contents, microhardnesses and crystalline phases were examined systematically. The Fe content in the deposit decreased and the microhardness increased with increasing duty cycle and peak current density. The pulse frequency had little effect on Fe content but led to a slight decrease in microhardness. X-ray diffraction patterns show that the crystalline phases vary with changes in peak current density and duty cycle but are barely influenced by frequency. When the peak current density or duty cycle is relatively low, crystalline Fe-Ni alloy and pure Fe phases coexist; the pure Fe phases disappear as the peak current density or duty cycle increases. At still larger peak current densities or duty cycles, crystalline Fe-Ni alloy and pure Ni phases coexist.

  4. On the Tendency of the Co-, Ni-, and Fe-Based Melts to the Bulk Amorphization

    NASA Astrophysics Data System (ADS)

    Sterkhova, Irina V.; Lad'yanov, Vladimir I.; Kamaeva, Larisa V.; Umnova, Nadezhda V.; Umnov, Pavel P.

    2016-11-01

    In this article, the influence of the liquid phase state on the glass-forming ability and solidification processes of the Co65.5Fe6.5Si18B10, Ni64.4Fe4Cr4.9Mn2B16.2C0.5Si8, and Fe50Cr15Mo14C15B6 alloys was studied. It was shown that in conditions of quenching from the melt at ~103 K/s, the largest fraction of the amorphous phase is achieved by cooling from a narrow temperature range near 1573 K (1300 °C) for Co65.5Fe6.5Si18B10, 1503 K (1230 °C) for Ni64.4Fe4Cr4.9Mn2B16.2C0.5Si8, and 1653 K (1380 °C) for Fe50Cr15Mo14C15B6. It was found that at these temperatures, there are anomalies in the viscosity and undercooling polytherms caused by changes in short-range ordering in these melts. Overheating the Co65.5Fe6.5Si18B10, Ni64.4Fe4Cr4.9Mn2B16.2C0.5Si8, and Fe50Cr15Mo14C15B6 melts above these temperatures is accompanied by changing the nature of their crystallization. It was shown that the analysis of the temperature dependences of undercooling and kinematic viscosity can be used to determine the optimum temperatures of the melts quenching to achieve their best bulk amorphization.

  5. Electronic structure of disordered α-FeMn alloys

    NASA Astrophysics Data System (ADS)

    Paduani, C.; da Silva, E. G.

    1996-08-01

    Cluster calculations were performed with the first-principles discrete variational method, in the LSD approximation and spin-polarized case, to investigate the electronic structure of the ferromagnetic disordered α-FeMn alloys. We investigated the effect on the local magnetic properties at iron sites of the introduction of Mn atoms in their first and second neighborhoods. The calculated magnetic moment and hyperfine magnetic field ( Hc) for an isolated Mn atom in a bcc iron host were obtained as -3.15 μB and -230 kG, respectively, in good agreement with experimental results.

  6. Exchange bias magnetism in films of NiFe/(Ni,Fe)O nanocrystallite dispersions

    SciTech Connect

    Hsiao, C.-H.; Chi, C.-C.; Wang, S.; Ouyang, H.; Desautels, R. D.; Lierop, J. van; Lin, K.-W.; Lin, T.-L.

    2014-05-07

    Ni{sub 3}Fe/(Ni,Fe)O thin films having a nanocrystallite dispersion morphology were prepared by a reactive ion beam-assisted deposition technique. The crystallite sizes of these dispersion-based films were observed to decrease from 8.4 ± 0.3 nm to 3.4 ± 0.3 nm as the deposition flow-rate increased from 2.78% to 7.89% O{sub 2}/Ar. Thin film composition was determined using selective area electron diffraction images and Multislice simulations. Through a detailed analysis of high resolution transmission electron microscopy images, the nanocrystallites were determined to be Ni{sub 3}Fe (a ferromagnet), NiO, and FeO (both antiferromagnets). It was determined that the interfacial molar Ni{sub 3}Fe ratio in the nanocrystallite dispersions increased slightly at first, then decreased as the oxygen content was increased; at 7.89% O{sub 2}/Ar, the interfacial molar ratio was essentially zero (only NiO and FeO remained). For nanocrystallite dispersion films grown with O{sub 2}/Ar flow-rate greater than 7.89%, no interfacial (intermixed) Ni{sub 3}Fe phase was detected, which resulted in no measurable exchange bias. Comparing the exchange bias field between the nanocrystallite dispersion films at 5 K, we observed a decrease in the magnitude of the exchange bias field as the nanocrystallite size decreased. The exchange bias coupling for all samples measured set in at essentially the same temperature (i.e., the exchange bias blocking temperature). Since the ferromagnetic/anti-ferromagnetic (FM/AFM) contact area in the nanocrystallite dispersion films increased as the nanocrystallite size decreased, the increase in the magnitude of the exchange bias could be attributed to larger regions of defects (vacancies and bond distortions) which occupied a significant portion of the FM/AFM interfaces in the nanocrystallite dispersion films.

  7. Microstructural Development and Ternary Interdiffusion in Ni-Mn-Ga Alloys

    NASA Astrophysics Data System (ADS)

    Zhou, Le; Kammerer, Catherine; Giri, Anit; Cho, Kyu; Sohn, Yongho

    2015-12-01

    NiMnGa alloys functioning as either ferromagnetic shape memory alloys or magnetocaloric materials have both practical applications and fundamental research value. In this study, solid-to-solid diffusion couple experiments were carried out to investigate the phase equilibria, microstructural development, and interdiffusion behavior in Ni-Mn-Ga ternary alloys. Selected diffusion couples between pure Ni, Ni25Mn75 and four ternary off-stoichiometric NiMnGa alloys ( i.e., Ni52Mn18Ga30, Ni46Mn30Ga24, Ni52Mn30Ga18, Ni58Mn18Ga24) were assembled and annealed at 1073 K, 1123 K, and 1173 K (800 °C, 850 °C, and 900 °C) for 480, 240, and 120 hours, respectively. At these high temperatures, the β NiMnGa phase has a B2 crystal structure. The microstructure of the interdiffusion zone was examined by scanning electron microscopy and transmission electron microscopy. Concentration profiles across the interdiffusion zone were determined by electron probe micro analysis. Solubility values obtained for various phases were mostly consistent with the existing isothermal phase diagrams, but the phase boundary of the γ(Mn) + β two-phase region was slightly modified. In addition, equilibrium compositions for the γ(Ni) and α' phases at 1173 K (900 °C) were also determined for the respective two-phase region. Both austenitic and martensitic phases were found at room temperature in each diffusion couple with a clear boundary. The compositions at the interfaces corresponded close to valence electron concentration (e/a) of 7.6, but trended to lower values when Mn increased to more than 35 at. pct. Average effective interdiffusion coefficients for the β phase over different compositional ranges were determined and reported in the light of temperature-dependence. Ternary interdiffusion coefficients were also determined and examined to assess the ternary diffusional interactions among Ni, Mn, and Ga. Ni was observed to interdiffuse the fastest, followed by Mn then Ga. Interdiffusion flux

  8. Structural and magnetic studies on Mn-doped Ni-Zn ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Ramesh, S.; Dhanalakshmi, B.; Chandra Sekhar, B.; Subba Rao, P. S. V.; Parvatheeswara Rao, B.

    2016-11-01

    Ni-Zn ferrite nanoparticles with manganese substitutions, Ni0.4Zn0.6- x Mn x Fe2O4, where x varies from 0.00 to 0.25 in steps of 0.05, were prepared using sol-gel autocombustion method. The resultant nanoparticles were analyzed using X-ray diffractometry, transmission electron microscopy, thermogravimetry and vibrating sample magnetometer measurements. X-ray diffraction patterns confirm single-phase cubic spinel structures with crystallite sizes in the range from 25.43 to 37.23 nm. Particle sizes obtained from transmission electron micrographs were also in good agreement with the crystallite sizes obtained from the X-ray data. Saturation magnetization and coercivity data for all the samples obtained from the corresponding M-H loops suggest a sinusoidal variations with Mn concentration ( x) implying that the substitution of Mn in the given nano-sized Ni-Zn ferrite system seems to have brought in a profound influence not only on the site preferences of other cations in the system but also in bringing about modifications in its own site preferences. The results are analyzed in terms of the compositional and structural modifications, and it was found that the observed magnetic variation was governed by the crystallite size and the corresponding change in cationic preferences in these materials.

  9. Magneto Caloric Effect in Ni-Mn-Ga alloys: First Principles and Experimental studies

    NASA Astrophysics Data System (ADS)

    Odbadrakh, Khorgolkhuu; Nicholson, Don; Brown, Gregory; Rusanu, Aurelian; Rios, Orlando; Hodges, Jason; Safa-Sefat, Athena; Ludtka, Gerard; Eisenbach, Markus; Evans, Boyd

    2012-02-01

    Understanding the Magneto-Caloric Effect (MCE) in alloys with real technological potential is important to the development of viable MCE based products. We report results of computational and experimental investigation of a candidate MCE materials Ni-Mn-Ga alloys. The Wang-Landau statistical method is used in tandem with Locally Self-consistent Multiple Scattering (LSMS) method to explore magnetic states of the system. A classical Heisenberg Hamiltonian is parametrized based on these states and used in obtaining the density of magnetic states. The Currie temperature, isothermal entropy change, and adiabatic temperature change are then calculated from the density of states. Experiments to observe the structural and magnetic phase transformations were performed at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) on alloys of Ni-Mn-Ga and Fe-Ni-Mn-Ga-Cu. Data from the observations are discussed in comparison with the computational studies. This work was sponsored by the Laboratory Directed Research and Development Program (ORNL), by the Mathematical, Information, and Computational Sciences Division; Office of Advanced Scientific Computing Research (US DOE), and by the Materials Sciences and Engineering Division; Office of Basic Energy Sciences (US DOE).

  10. Giant exchange bias in Mn2FeGa with hexagonal structure

    NASA Astrophysics Data System (ADS)

    Liu, Z. H.; Zhang, Y. J.; Zhang, H. G.; Zhang, X. J.; Ma, X. Q.

    2016-07-01

    In this study, we present the experimental observation that polycrystalline Mn2+xFe1-xGa (x = -0.2, 0, 0.2, 0.4) compounds can be synthesized to be D019-type (Ni3Sn-type) hexagonal structure with space group P63/mmc. A giant exchange bias field up to 1.32 kOe was achieved in hexagonal Mn2FeGa alloy at 5 K. A cluster glass state is confirmed by ac susceptibility measurement under different driving frequencies. Interestingly, robust horizontal and vertical shifts in magnetic hysteresis loop were simultaneously observed at 5 K under high cooling field up to 90 kOe. The large exchange bias is originated from the large exchange anisotropy between cluster glass phase and ferrimagnetic matrix. The vertical shift is thought to be attributed to the incomplete reversal of frozen cluster spins.

  11. Structure and function of [NiFe] hydrogenases.

    PubMed

    Ogata, Hideaki; Lubitz, Wolfgang; Higuchi, Yoshiki

    2016-11-01

    Hydrogenases catalyze the reversible conversion of molecular hydrogen to protons and electrons via a heterolytic splitting mechanism. The active sites of [NiFe] hydrogenases comprise a dinuclear Ni-Fe center carrying CO and CN(-) ligands. The catalytic activity of the standard (O2-sensitive) [NiFe] hydrogenases vanishes under aerobic conditions. The O2-tolerant [NiFe] hydrogenases can sustain H2 oxidation activity under atmospheric conditions. These hydrogenases have very similar active site structures that change the ligand sphere during the activation/catalytic process. An important structural difference between these hydrogenases has been found for the proximal iron-sulphur cluster located in the vicinity of the active site. This unprecedented [4Fe-3S]-6Cys cluster can supply two electrons, which lead to rapid recovery of the O2 inactivation, to the [NiFe] active site.

  12. Transformation behavior of Ni Mn Ga thin films

    NASA Astrophysics Data System (ADS)

    Chernenko, V. A.; Ohtsuka, M.; Kohl, M.; Khovailo, V. V.; Takagi, T.

    2005-10-01

    The transformation behavior of Ni-Mn-Ga submicron polycrystalline thin films was investigated with respect to target composition, different substrates, annealing temperature and film thickness. Two series of thin films (A and B) with thicknesses ranging from 0.1 to 5 µm were deposited onto alumina ceramic, poly-vinyl alcohol (PVA), quartz and glass by the RF magnetron sputtering technique. The use of the targets of Ni49.5Mn28.0Ga22.5 and Ni52Mn24Ga24 facilitated the formation of 10M and 14M martensitic structures for heat treated films A and B, respectively. Magnetization curves and temperature dependences of resistivity demonstrated anomalies and features typical for the bulk Heusler alloys exhibiting both martensitic and ferromagnetic transformations. The transformation temperatures and distribution of magnetic moments were found to be dependent on the film thickness. A magnetoresistance ratio of 1.5% was achieved at a maximum field of 1.5 T at room temperature.

  13. Self-current induced spin-orbit torque in FeMn/Pt multilayers

    PubMed Central

    Xu, Yanjun; Yang, Yumeng; Yao, Kui; Xu, Baoxi; Wu, Yihong

    2016-01-01

    Extensive efforts have been devoted to the study of spin-orbit torque in ferromagnetic metal/heavy metal bilayers and exploitation of it for magnetization switching using an in-plane current. As the spin-orbit torque is inversely proportional to the thickness of the ferromagnetic layer, sizable effect has only been realized in bilayers with an ultrathin ferromagnetic layer. Here we demonstrate that, by stacking ultrathin Pt and FeMn alternately, both ferromagnetic properties and current induced spin-orbit torque can be achieved in FeMn/Pt multilayers without any constraint on its total thickness. The critical behavior of these multilayers follows closely three-dimensional Heisenberg model with a finite Curie temperature distribution. The spin torque effective field is about 4 times larger than that of NiFe/Pt bilayer with a same equivalent NiFe thickness. The self-current generated spin torque is able to switch the magnetization reversibly without the need for an external field or a thick heavy metal layer. The removal of both thickness constraint and necessity of using an adjacent heavy metal layer opens new possibilities for exploiting spin-orbit torque for practical applications. PMID:27185656

  14. Self-current induced spin-orbit torque in FeMn/Pt multilayers

    NASA Astrophysics Data System (ADS)

    Xu, Yanjun; Yang, Yumeng; Yao, Kui; Xu, Baoxi; Wu, Yihong

    2016-05-01

    Extensive efforts have been devoted to the study of spin-orbit torque in ferromagnetic metal/heavy metal bilayers and exploitation of it for magnetization switching using an in-plane current. As the spin-orbit torque is inversely proportional to the thickness of the ferromagnetic layer, sizable effect has only been realized in bilayers with an ultrathin ferromagnetic layer. Here we demonstrate that, by stacking ultrathin Pt and FeMn alternately, both ferromagnetic properties and current induced spin-orbit torque can be achieved in FeMn/Pt multilayers without any constraint on its total thickness. The critical behavior of these multilayers follows closely three-dimensional Heisenberg model with a finite Curie temperature distribution. The spin torque effective field is about 4 times larger than that of NiFe/Pt bilayer with a same equivalent NiFe thickness. The self-current generated spin torque is able to switch the magnetization reversibly without the need for an external field or a thick heavy metal layer. The removal of both thickness constraint and necessity of using an adjacent heavy metal layer opens new possibilities for exploiting spin-orbit torque for practical applications.

  15. Magnetic properties and electronic structure of Mn-Ni-Ga magnetic shape memory alloys.

    PubMed

    D'Souza, Sunil Wilfred; Roy, Tufan; Barman, Sudipta Roy; Chakrabarti, Aparna

    2014-12-17

    Influence of disorder, antisite defects, martensite transition and compositional variation on the magnetic properties and electronic structure of Mn(2)NiGa and Mn(1+x)Ni(2-x)Ga magnetic shape memory alloys have been studied by using full potential spin-polarized scalar relativistic Korringa-Kohn-Rostocker (FP-SPRKKR) method. Mn(2)NiGa is ferrimagnetic and its total spin moment increases when disorder in the occupancy of MnNi (Mn atom in Ni position) is considered. The moment further increases when Mn-Ga antisite defect [1] is included in the calculation. A reasonable estimate of TC for Mn(2)NiGa is obtained from the exchange parameters for the disordered structure. Disorder influences the electronic structure of Mn(2)NiGa through overall broadening of the density of states and a decrease in the exchange splitting. Inclusion of antisite defects marginally broaden the minority spin partial DOS (PDOS), while the majority spin PDOS is hardly affected. For Mn(1+x)Ni(2-x)Ga where 1 ⩾ x ⩾ 0, as x decreases, Mn(Mn) moment increases while Mn(Ni) moment decreases in both austenite and martensite phases. For x ⩾ 0.25, the total moment of the martensite phase is smaller compared to the austenite phase, which indicates possible occurrence of inverse magnetocaloric effect. We find that the redistribution of Ni 3d- Mn(Ni) 3d minority spin electron states close to the Fermi level is primarily responsible for the stability of the martensite phase in Mn-Ni-Ga.

  16. Replacement of Ni by Mn in High-Ni-Containing Austenitic Cast Steels used for Turbo-Charger Application

    NASA Astrophysics Data System (ADS)

    Jung, Seungmun; Jo, Yong Hee; Jeon, Changwoo; Choi, Won-Mi; Lee, Byeong-Joo; Oh, Yong-Jun; Kim, Gi-Yong; Jang, Seongsik; Lee, Sunghak

    2017-02-01

    High-temperature tensile properties of austenitic cast steels fabricated by replacing Ni by Mn in a 20 wt pct Ni-containing steel were investigated. In a steel where 8 wt pct Ni was replaced by 9.2 wt pct of Mn, 17.4 and 9.8 pct of ferrite existed in equilibrium phase diagrams and actual microstructures, respectively, because a role of Mn as an austenite stabilizer decreased, and led to deterioration of high-temperature properties. When 2 to 6 wt pct Ni was replaced by 2.3 to 6.9 wt pct Mn, high-temperature properties were comparable to those of the 20 wt pct Ni-containing steel because ferrites were absent, which indicated the successful replacement of 6 wt pct Ni by Mn, with cost reduction of 27 pct.

  17. Rapidly solidified NiAl and FeAl

    NASA Technical Reports Server (NTRS)

    Gaydosh, D. J.; Crimp, M. A.

    1984-01-01

    Melt spinning was used to produce rapidly solidified ribbons of the B2 intermetallics NiAl and FeAl. Both Fe-40Al and Fe-45Al possessed some bend ductility in the as spun condition. The bend ductility of Fe-40Al, Fe-45Al, and equiatomic NiAl increased with subsequent heat treatment. Heat treatment at approximately 0.85 T (sub m) resulted in significant grain growth in equiatomic FeAl and in all the NiAl compositions. Low bend ductility in both FeAl and NiAl generally coincided with intergranular failure, while increased bend ductility was characterized by increasing amounts of transgranular cleavage fracture.

  18. Low temperature diffusion coefficients in the Fe-Ni and FeNiP systems: Application to meteorite cooling rates

    NASA Technical Reports Server (NTRS)

    Dean, D. C.; Goldstein, J. I.

    1984-01-01

    The interdiffusion coefficient of FeNi in fcc taenite (gamma) of Fe-Ni and Fe-Ni-0.2 P alloys was measured as a function of temperature between 600 and 900 C. This temperature range is directly applicable to the nucleation and growth of the Widmanstatten pattern in iron meteorites and metal regions of stony and stony-iron meteorites. Diffusion couples were made from FeNi or FeNiP alloys which ensured that the couples were in the taenite phase at the diffusion temperature. The presence or absence of grain boundary diffusion was determined by measuring the Ni profile normal to the existing grain boundaries with the AEM. Ignoring any variation of interdiffusion coefficient with composition, the measured data was plotted versus the reciprocal of the diffusion temperature. The FeNi data generally follow the extrapolated Goldstein, et al. (1965) data from high temperatures. The FeNiP data indicates that small additions of P (0.2 wt%) cause a 3 to 10 fold increase in the FeNi interdifussion coefficient increasing with decreasing temperature. This increase is about the same as that predicted by Narayan and Goldstein (1983) at the Widmanstatten growth temperature.

  19. A comparative study of magnetic behaviors in TbNi{sub 2}, TbMn{sub 2} and TbNi{sub 2}Mn

    SciTech Connect

    Wang, J. L.; Md Din, M. F.; Hong, F.; Cheng, Z. X.; Dou, S. X.; Kennedy, S. J.; Studer, A. J.; Campbell, S. J.; Wu, G. H.

    2014-05-07

    All TbNi{sub 2}, TbMn{sub 2}, and TbNi{sub 2}Mn compounds exhibit the cubic Laves phase with AB{sub 2}-type structure in spite of the fact that the ratio of the Tb to transition-metal components in TbNi{sub 2}Mn is 1:3. Rietveld refinement indicates that in TbNi{sub 2}Mn the Mn atoms are distributed on both the A (8a) and B (16d) sites. The values of the lattice constants were measured to be a = 14.348 Å (space group F-43 m), 7.618 Å, and 7.158 Å (space group Fd-3 m) for TbNi{sub 2}, TbMn{sub 2}, and TbNi{sub 2}Mn, respectively. The magnetic transition temperatures T{sub C} were found to be T{sub C} = 38 K and T{sub C} = 148 K for TbNi{sub 2} and TbNi{sub 2}Mn, respectively, while two magnetic phase transitions are detected for TbMn{sub 2} at T{sub 1} = 20 K and T{sub 2} = 49 K. Clear magnetic history effects in a low magnetic field are observed in TbMn{sub 2} and TbNi{sub 2}Mn. The magnetic entropy changes have been obtained.

  20. Coercive force reduction effect in FeCoV and FeNi films due to ultrathin FeNiMo layer

    NASA Astrophysics Data System (ADS)

    Nozawa, T.; Nouchi, N.; Morimoto, F.; Otani, A.

    2003-01-01

    The mechanism of the drastic coercive force reduction effect in essentially semi-hard FeCoV and FeNi films due to ultrathin FeNiMo layer has been examined. It is noted experimentally that a kind of a coupling of magnetic moments existing between ultrathin FeNiMo layer with anisotropic magnetization and semi-hard magnetic layer with anisotropic magnetization contributes to this drastic coercive force reducing effect.

  1. Analyzing the magnetic profile in NiFe/NiO bilayers

    NASA Astrophysics Data System (ADS)

    Tafur, Miguel; Nascimento, V. P.; Alayo, W.; Xing, Y. T.; Baggio-Saitovitch, E.

    2017-04-01

    The magnetic profile of the Si(100)/NiO(35 nm)/NiFe(10 nm)/Ta(1 nm) sample has been obtained by X-ray absorption spectroscopy (XAS) and the X-ray magnetic circular dichroism (XMCD). Two experimental procedures were used. In the procedure 1, the magnetic depth profile has been determines using samples deposited with different NiFe thicknesses, Si(100)/NiO(35 nm)/NiFe(t)/Ta(1 nm), t = 1 , 3 , 5 , 7 , 10 nm . In procedure 2, the sample (NiFe=10 nm), was thinned by several in situ sputtering cycles with Ar+ ions, followed by XAS and XMCD analysis. In both procedures, the calculated magnetic moments values tend to decrease close to interface with the NiO antiferromagnetic (AF) layer, however, this decreasement is more evidenced in the sputtered sample. There is no charge transfer between Ni and Fe in the inner part of the NiFe layer, a reduction of the morb /mspineff has been found at the NiFe/NiO interface. Procedure 1 emerged as the most indicated to analyse the interface region.

  2. CASSCF/CI calculations for first row transition metal hydrides - The TiH(4-phi), VH(5-delta), CrH(6-sigma-plus), MnH(7-sigma-plus), FeH(4,6-delta) and NiH(2-delta) states

    NASA Technical Reports Server (NTRS)

    Walch, S. P.; Bauschlicher, C. W., Jr.

    1983-01-01

    Calculations are performed for the predicted ground states of TiH(4-phi), VH(5-delta), CrH(6-sigma-plus), MnH(7-sigma-plus), Fett(4,6-delta) and NiH(2-delta). For FeH both the 6-delta and 4-delta states are studied, since both are likely candidates for the ground state. The ground state symmetries are predicted based on a combination of atomic coupling arguments and coupling of 4s(2)3d(n) and 4s(1)3d(n+1) terms in the molecular system. Electron correlation is included by a CASSCF/CI (SD) treatment. The CASSCF includes near-degeneracy effects, while correlation of the 3d electrons in included at the CI level.

  3. Exchange Coupling in an Isostructural Series of Face-Sharing Bioctahedral Complexes [LM(II)(&mgr;-X)(3)M(II)L]BPh(4) (M = Mn, Fe, Co, Ni, Zn; X = Cl, Br; L = 1,4,7-Trimethyl-1,4,7-triazacyclononane).

    PubMed

    Bossek, Ursula; Nühlen, Daniela; Bill, Eckhard; Glaser, Thorsten; Krebs, Carsten; Weyhermüller, Thomas; Wieghardt, Karl; Lengen, Marek; Trautwein, A. X.

    1997-06-18

    The reaction of the divalent metal halides ZnCl(2), ZnBr(2), MnCl(2).4CH(3)CN, MnBr(2), FeCl(2).4CH(3)CN, CoCl(2).4CH(3)CN, CoBr(2), NiCl(2).6H(2)O, and NiBr(2), respectively, with the macrocycle 1,4,7-trimethyl-1,4,7-triazacyclononane (L) (1:1) in anhydrous acetonitrile, acetone, chloroform, or ethanol affords upon additon of NaBPh(4) the isomorphous series of complexes [LM(II)(&mgr;-X)(3)M(II)L]BPh(4): 1, M = Zn, X = Cl; 2, Zn, Br; 3, Mn, Cl; 4, Mn, Br; 5, Fe, Cl; 6, Co, Cl; 7, Co, Br; 8, Ni, Cl; 9, Ni, Br. Six of these complexes have been structurally characterized by single-crystal X-ray crystallography; they crystallize in the triclinic space group P&onemacr; (No. 2) with Z = 4. Crystal data are as follows 1, a = 16.654(1), b = 17.042(1), c = 17.684(1) Å, alpha = 97.30(1), beta = 93.58(1), gamma = 117.46(1) degrees; 3, a = 16.632(8), b = 17.012(8), c = 17.855(5) Å, alpha = 97.16(3), beta = 93.37(3), gamma = 117.24(3) degrees; 5, a = 16.658(3), b = 17.064(3), c = 17.741(4) Å, alpha = 97.32(3), beta = 93.47(3), gamma = 117.36(3) degrees; 6, a = 16.640(3), b = 17.040(3), c = 17.686(4) Å, alpha = 97.39(3), beta = 93.58(3), gamma = 117.39(3) degrees; 8, a = 16.608(3), b = 16.995(3), c = 17.555(3) Å, alpha = 97.36(1), beta = 93.52(1), gamma = 117.52(1) degrees; 9, a = 16.680(3), b = 17.016(2), c = 17.715(3)Å, alpha = 96.99(1), beta = 93.70(1), gamma = 117.42(1) degrees. All complexes consist of a dinuclear, face-sharing bioctahedral monocation with three &mgr;(2)-Cl or &mgr;(2)-Br bridging ligands and two LM fragments and well-separated tetraphenylborate anions (1:1). The cations cocrystallize in two different forms: an enantiomeric form with (lambdalambdalambda) (or (deltadeltadelta)) conformation at both LM fragments and a meso form with an (lambdalambdalambda) conformation at one LM fragment and (deltadeltadelta) at the other (ratio 1:1). From temperature-dependent magnetic susceptibility measurements (2-293 K) it was established that the spins of the

  4. Effect of mono- and bimetallic nanoparticles Fe, Ni, & Fe/Ni based on carbon nanocomposites on electrocatalytic properties of anodes

    NASA Astrophysics Data System (ADS)

    Ranabhat, K.; Pylinina, A. I.; Skripkin, K. S.; Sofronova, E. A.; Revina, A. A.; Kasatkin, V. E.; Patrikeev, L. N.; Lapshinsky, V. A.

    2016-10-01

    The optical properties of metallic Fe nanoparticles (NPs), Ni NPs and bimetallic Fe/Ni NPs produced under radiolysis in anaerobic condition based on a chemical reduction in the presence of oxygen and quercetin in reversed micellar solutions, and electrokinetic properties of nanoparticles carbon-based nanocomposites were studied. The possibility of the preparation of coating using different nanocomposites with anomalous electrocatalytic is addressed.

  5. Electromagnetic properties of Fe53Ni47 and Fe53Ni47/Cu granular composite materials in the microwave range

    NASA Astrophysics Data System (ADS)

    Massango, Herieta; Tsutaoka, Takanori; Kasagi, Teruhiro

    2016-09-01

    The electromagnetic proprieties of Fe53Ni47 granular composite materials and Fe53Ni47/Cu hybrid granular composites have been studied by measuring the relative complex permeability and permittivity spectra as well as the ac electrical conductivity. In the Fe53Ni47 composite, the variation of the ac conductivity at 1 kHz with the particle volume content shows an insulator-metal transition at the percolation threshold at 61 vol% particle content. A negative permeability spectrum due to the magnetic resonance in Fe53Ni47 particles was observed in the 85 vol% composite. Meanwhile, the negative permittivity spectrum caused by the plasmoinc state of the percolated Fe53Ni47 particle clusters appears at 90 vol%. The Fe53Ni47/Cu hybrid composite containing 85 vol% of Fe53Ni47/Cu hybrid particle as filers shows the percolative metallic properties; the ac conductivity increases with increasing the Cu particle volume fraction in the Fe53Ni47/Cu particle system. The negative permittivity spectrum appears above the Cu particle volume fraction of 0.16; the double negative characteristic was observed at that of 0.20 and 0.24 hybrid composites in the frequency range from 300 MHz to 1.8 GHz in the absence of the external magnetic field.

  6. Magnetoresistance behavior of Ni80Fe20/Ru/Ni80Fe20 nanostripes

    NASA Astrophysics Data System (ADS)

    Lupo, P.; Liu, X. M.; Adeyeye, A. O.

    2015-07-01

    We present a systematic investigation on the effects of interlayer coupling on the magnetoresistance (MR) behavior of Ni80Fe20/Ru(/Ni80Fe20 trilayer nanostripes (NSs) as a function of temperature T . By changing from 0.8 nm to 1.7 nm, either a ferromagnetic or an antiferromagnetic (AFM) type of interlayer coupling was achieved, leading to a markedly different MR behavior. We observed that the MR response is a superimposition of AMR and GMR effects, and it is significantly dependent on temperature. For AFM coupled NSs, there is a transition from a pure AFM state to a reversed spin-flop phase due to enhanced ferromagnetic pin-hole coupling at low T. Our experimental results are in good agreement with micromagnetic simulations.

  7. Magnetic properties and atomic ordering of BCC Heusler alloy Fe2MnGa ribbons

    NASA Astrophysics Data System (ADS)

    Xin, Yuepeng; Ma, Yuexing; Luo, Hongzhi; Meng, Fanbin; Liu, Heyan

    2016-05-01

    The electronic structure, atomic disorder and magnetic properties of the Heusler alloy Fe2MnGa have been investigated experimentally and theoretically. BCC Fe2MnGa ribbon samples were prepared. Experimentally, a saturation magnetic moment (3.68 μB at 5 K) much larger than the theoretical value (2.04 μB) has been reported. First-principles calculations indicate that the difference is related to the Fe-Mn disorder between A, B sites, as can also be deduced from the XRD pattern. L21 type Fe2MnGa is a ferrimagnet with antiparallel Fe and Mn spin moments. However, when Fe-Mn disorder occurs, part of Mn moments will be parallel to Fe moments, and the Fe moments also clearly increase simultaneously. All this results in a total moment of 3.74 μB, close to the experimental value.

  8. Electronic structure and ferromagnetism in the martensitic-transformation material Ni2FeGa

    NASA Astrophysics Data System (ADS)

    Liu, Z. H.; Hu, H. N.; Liu, G. D.; Cui, Y. T.; Zhang, M.; Chen, J. L.; Wu, G. H.; Xiao, Gang

    2004-04-01

    We calculated the electronic structures of the Heusler alloy Ni2FeGa for both the cubic and the orthorhombic structures by self-consistent full-potential linearized-augmented plane-wave method. The localized moment of Fe atom is interpreted based on the electronic structure and the popular explanation of the localized moment of Mn in Heusler alloy X2MnY. Comparing the density of states of cubic and orthorhombic structures, we observed that a Ni peak near the density of states of d band for the cubic structure splits for the orthorhombic structure, indicating a band Jahn-Teller mechanism should be responsible for the structural transition. Accompanied by this transformation, an increase of Ni moment and magnetization redistribution occurred. Temperature-dependence anisotropy field shows an evidence of martensitic transformation between 125 and 190 K. The magnetic behavior seems to contain a transition from Heisenberg-like at temperature below 70 K to itinerant magnetism at temperature higher than 160 K upon martensitic transformation. Temperature dependence of saturation magnetization reveals the spontaneous magnetization at martensite and parent phase are 3.170μB and 3.035μB, respectively. The calculated magnetic moment at martensite is 3.171μB, which is quite consistent with the experimental value. The magnetic moment of Fe and Ni atom in Heusler alloy Ni2FeGa is analyzed based on the computational results and the experimental magnetization curves. It is found that the magnetic moment of Fe atoms is about 10 43% larger than that of α-Fe.

  9. Nanostructurization of Fe-Ni Alloy

    NASA Astrophysics Data System (ADS)

    Danilhenko, Vitaliy E.

    2017-03-01

    Data about an effect of cyclic γ-α-γ martensitic transformations on the structure state of reverted austenite Fe-31.7 wt.% Ni-0.06 wt.% C alloy are presented. The effect of multiple direct γ-α and reverse α-γ martensitic transformations on fragmentation of austenitic grains has been investigated by electron microscopy and X-ray diffraction methods. An ultrafine structure has been formed by nanofragmentation inside the initial austenite grains due to the successive misorientation of their crystal lattice. Austenite was nanofragmented as a result of multiple γ-α-γ martensitic transformations. Slow heating of the nanofragmented alloy at a rate below 2 °C/s results in nanograin refinement of the structure by multiplication of the reverted γ-phase orientations. The conditions of structure refinement up to ultrafine and nanocrystalline levels as a result of both shear and diffusion mechanisms of reverse α-γ transformation are determined.

  10. Spectral and thermodynamic properties of Ag(I), Au(III), Cd(II), Co(II), Fe(III), Hg(II), Mn(II), Ni(II), Pb(II), U(IV), and Zn(II) binding by methanobactin from Methylosinus trichosporium OB3b.

    PubMed

    Choi, Dong W; Do, Young S; Zea, Corbin J; McEllistrem, Marcus T; Lee, Sung-W; Semrau, Jeremy D; Pohl, Nicola L; Kisting, Clint J; Scardino, Lori L; Hartsel, Scott C; Boyd, Eric S; Geesey, Gill G; Riedel, Theran P; Shafe, Peter H; Kranski, Kim A; Tritsch, John R; Antholine, William E; DiSpirito, Alan A

    2006-12-01

    Methanobactin (mb) is a novel chromopeptide that appears to function as the extracellular component of a copper acquisition system in methanotrophic bacteria. To examine this potential physiological role, and to distinguish it from iron binding siderophores, the spectral (UV-visible absorption, circular dichroism, fluorescence, and X-ray photoelectron) and thermodynamic properties of metal binding by mb were examined. In the absence of Cu(II) or Cu(I), mb will bind Ag(I), Au(III), Co(II), Cd(II), Fe(III), Hg(II), Mn(II), Ni(II), Pb(II), U(VI), or Zn(II), but not Ba(II), Ca(II), La(II), Mg(II), and Sr(II). The results suggest metals such as Ag(I), Au(III), Hg(II), Pb(II) and possibly U(VI) are bound by a mechanism similar to Cu, whereas the coordination of Co(II), Cd(II), Fe(III), Mn(II), Ni(II) and Zn(II) by mb differs from Cu(II). Consistent with its role as a copper-binding compound or chalkophore, the binding constants of all the metals examined were less than those observed with Cu(II) and copper displaced other metals except Ag(I) and Au(III) bound to mb. However, the binding of different metals by mb suggests that methanotrophic activity also may play a role in either the solubilization or immobilization of many metals in situ.

  11. Effect of Ti content on the microstructure and mechanical behavior of (Fe36Ni18Mn33Al13)100–xTix high entropy alloys

    SciTech Connect

    Wang, Zhangwei; Wu, Margaret; Cai, Zhonghou; Chen, Si; Baker, Ian

    2016-06-13

    The microstructure and mechanical properties studies of a series of two-phase f.c.c./B2 (ordered b.c.c.) lamellar-structured, high entropy alloys (HEA) Fe36Ni18Mn33Al13Tix with x up to 6 at. % Ti have been investigated. X-ray microanalysis in a TEM showed that the Ti resided mostly in the B2 phase. The lamellar spacing decreased significantly with increasing Ti content from 1.56 μm for the undoped alloy to 155 nm with an addition of 4 at. % Ti, leading to a sharp increase in room-temperature yield strength,σy, from 270 MPa to 953 MPa, but with a concomitant decrease in ductility from 22% elongation to 2.3%. Annealing at 1173 K for 20 h greatly increased the lamellar spacing of Fe36Ni18Mn33Al13Ti4 to 577 nm, producing a corresponding decrease in σy to 511 MPa. The yield strengths of all the doped alloys decreased significantly when tensile tested at 973 K with a concomitant increase in ductility due to softening of the B2 phase. The fracture mode changed from cleavage at room temperature to a ductile dimple-type rupture at 973 K. Lastly, the results are discussed in terms of the Hall-Petch-type relationship.

  12. Angular dependent FORC and FMR of exchange-biased NiFe multilayer films

    NASA Astrophysics Data System (ADS)

    Gallardo, R. A.; Khanal, S.; Vargas, J. M.; Spinu, L.; Ross, C. A.; Garcia, C.

    2017-02-01

    Dynamic ferromagnetic resonance (FMR, X-band 9.8 GHz) and static first-order reversal curve (FORC) techniques are combined to study the intrinsic exchange-bias distribution via measurements of in-plane angular variation in (FeNi/IrMn)n multilayers. The angular dependence of the exchange bias field was qualitatively and quantitatively investigated using both methods, which are sensitive to different couplings between the ferromagnetic layers. We have used the analysis of the angular dependence of first-order reversal curve (AFORC) data, extracted from FORC curves measured from {{0}\\circ} up to {{360}\\circ} in {{10}\\circ} steps. In addition, its counterpart angular dependence of FMR (AFMR) measurements were carried out and correlated with the AFORC results. The AFORC proved to be useful for simultaneously studying the magnetization reversal processes and magnetic interactions between the layers of the (FeNi/IrMn)n. These interactions are related to the structure and interfaces in the (FeNi/IrMn), and the results obtained by AFMR and AFORC are contrasted with a modified theoretical model for domain-wall formation.

  13. Enhancement of ferromagnetism by Cr doping in Ni-Mn-Cr-Sb Heusler alloys

    NASA Astrophysics Data System (ADS)

    Khan, Mahmud; Dubenko, Igor; Stadler, Shane; Jung, J.; Stoyko, S. S.; Mar, Arthur; Quetz, Abdiel; Samanta, Tapas; Ali, Naushad; Chow, K. H.

    2013-03-01

    A series of Mn rich Ni50Mn37-xCrxSb13 Heusler alloys have been investigated by dc magnetization and electrical resistivity measurements. Due to the weakening of the Ni-Mn hybridization, the martensitic transition shifts to lower temperatures with increasing Cr concentration, while the saturation magnetization at 5 K increases. The magnetoresistance and exchange bias properties are dramatically suppressed with increasing Cr concentration. The observed behaviors suggest that substitution of Cr for Mn in Ni50Mn37-xCrxSb13 Heusler alloys not only destabilizes the martensitic phase but also enhances ferromagnetism in the system. The possible mechanisms responsible for the observed behavior are discussed.

  14. Strain mediated coupling in magnetron sputtered multiferroic PZT/Ni-Mn-In/Si thin film heterostructure

    SciTech Connect

    Singh, Kirandeep; Kaur, Davinder; Singh, Sushil Kumar

    2014-09-21

    The strain mediated electrical and magnetic properties were investigated in PZT/Ni-Mn-In heterostructure deposited on Si (100) by dc/rf magnetron sputtering. X-ray diffraction pattern revealed that (220) orientation of Ni-Mn-In facilitate the (110) oriented tertragonal phase growth of PZT layer in PZT/Ni-Mn-In heterostructure. A distinctive peak in dielectric constant versus temperature plots around martensitic phase transformation temperature of Ni-Mn-In showed a strain mediated coupling between Ni-Mn-In and PZT layers. The ferroelectric measurement taken at different temperatures exhibits a well saturated and temperature dependent P-E loops with a highest value of P{sub sat}~55 μC/cm² obtained during martensite-austenite transition temperature region of Ni-Mn-In. The stress induced by Ni-Mn-In layer on upper PZT film due to structural transformation from martensite to austenite resulted in temperature modulated Tunability of PZT/Ni-Mn-In heterostructure. A tunability of 42% was achieved at 290 K (structural transition region of Ni-Mn-In) in these heterostructures. I-V measurements taken at different temperatures indicated that ohmic conduction was the main conduction mechanism over a large electric field range in these heterostructures. Magnetic measurement revealed that heterostructure was ferromagnetic at room temperature with a saturation magnetization of ~123 emu/cm³. Such multiferroic heterostructures exhibits promising applications in various microelectromechanical systems.

  15. Environmentally assisted cracking of two-phase Fe-Mn-Al alloys in NaCl solution

    NASA Astrophysics Data System (ADS)

    Shih, S.-T.; Tsu, I.-F.; Perng, T.-P.

    1993-02-01

    Three two-phase Fe-Mn-Al alloys with nominal compositions, Fe-24Mn-9Al, Fe-27Mn-9Al-3Cr,. and Fe-27Mn-9Al-6Cr, were prepared in the solution-treated and cold-rolled conditions. The fractions of ferrite in the solution-treated condition were controlled at 46 to 60 pct, mainly by adjusting the carbon content and the relative amounts of Mn and Al. The ferrite fractions were reduced to 30 to 37 pct after 75 pct deformation by cold-rolling. Specimens were tensile tested at open circuit in aerated 3.5 pct NaCl solution at slow strain rates ranging from 4 × 10-7 to 4 × 10-5 s-1 at room temperature. All of the alloys were quite susceptible to environmentally assisted cracking (EAC). The deformed specimens showed less susceptibility, presumably because the plasticity was already too limited. The EAC appeared to occur at or after the onset of plastic deformation. In this alloy system, the ferritic phase was less resistant to EAC than the austenitic phase, in contrast to the Fe-Cr-Ni stainless steels. The crack propagated preferentially through the ferrite grains or along the ferrite/austenite grain boundaries. The addition of up to 6 pct Cr did not improve the EAC resistance.

  16. β decay of 61Mn to levels in 61Fe

    NASA Astrophysics Data System (ADS)

    Radulov, D.; Chiara, C. J.; Darby, I. G.; De Witte, H.; Diriken, J.; Fedorov, D. V.; Fedosseev, V. N.; Fraile, L. M.; Huyse, M.; Köster, U.; Marsh, B. A.; Pauwels, D.; Popescu, L.; Seliverstov, M. D.; Sjödin, A. M.; Van den Bergh, P.; Van Duppen, P.; Venhart, M.; Walters, W. B.; Wimmer, K.

    2013-07-01

    A detailed β-decay study of 61Mn is presented, yielding extended information on the level structure of 61Fe. Pure beams were obtained at ISOLDE, CERN, after selective laser ionization and mass separation of fission products from the bombardment of a UCx target by 1.4-GeV protons. The β and γ information was detected by two MiniBall clusters and three ΔE plastic scintillators. The new 61Mn decay scheme reveals 48 γ transitions, distributed over 20 excited states. A comparison to the decay scheme of 59Mn and excited states in 59Fe is made. Shell-model calculations with two different interactions are performed in order to compare the nuclear structure of the two neighboring odd-A iron isotopes. Tentative spin and parities of several excited states in 61Fe are assigned on the basis of β-decay feeding patterns in both 59,61Fe and of results from the theoretical shell-model calculations.

  17. Surface chemistry, friction and wear of Ni-Zn and Mn-Zn ferrites in contact with metals

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1982-01-01

    X-ray photoelectron and Auger electron spectroscopy analysis were used in sliding friction experiments. These experiments were conducted with hot-pressed polycrystalline Ni-Zn and Mn-Zn ferrites, and single-crystal Mn-Zn ferrite in contact with various transition metals at room temperature in both vacuum and argon. The results indicate that Ni2O3 and Fe3O4 were present on the Ni-Zn ferrite surface in addition to the nominal bulk constituents, while MnO2 and Fe3O4 were present on the Mn-Zn ferrite surface in addition to the nominal bulk constituents. The coefficients of friction for the ferrites in contact with metals were related to the relative chemical activity of these metals. The more active the metal, the higher is the coefficient of friction. The coefficients of friction for the ferrites were correlated with the free energy of formation of the lowest metal oxide. The interfacial bond can be regarded as a chemical bond between the metal atoms and the oxygen anions in the ferrite surfaces. The adsorption of oxygen on clean metal and ferrite does strengthen the metal-ferrite contact and increase the friction. The ferrites exhibit local cracking and fracture with sliding under adhesive conditions. All the metals transferred to he surfaces of the ferrites in sliding.

  18. Surface chemistry, friction, and wear of Ni-Zn and Mn-Zn ferrites in contact with metals

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1983-01-01

    X-ray photoelectron and Auger electron spectroscopy analysis were used in sliding friction experiments. These experiments were conducted with hot-pressed polycrystalline Ni-Zn and Mn-Zn ferrites, and single-crystal Mn-Zn ferrite in contact with various transition metals at room temperature in both vacuum and argon. The results indicate that Ni2O3 and Fe3O4 were present on the Ni-Zn ferrite surface in addition to the nominal bulk constituents, while MnO2 and Fe3O4 were present on the Mn-Zn ferrite surface in addition to the nominal bulk constituents. The coefficients of friction for the ferrites in contact with metals were related to the relative chemical activity of these metals. The more active the metal, the higher is the coefficient of friction. The coefficients of friction for the ferrites were correlated with the free energy of formation of the lowest metal oxide. The interfacial bond can be regarded as a chemical bond between the metal atoms and the oxygen anions in the ferrite surfaces. The adsorption of oxygen on clean metal and ferrite does strengthen the metal-ferrite contact and increase the friction. The ferrites exhibit local cracking and fracture with sliding under adhesive conditions. All the metals transferred to the surfaces of the ferrites in sliding. Previously announced in STAR as N83-19901

  19. Magnetism of hexagonal Mn{sub 1.5}X{sub 0.5}Sn (X = Cr, Mn, Fe, Co) nanomaterials

    SciTech Connect

    Fuglsby, R.; Kharel, P.; Zhang, W.; Sellmyer, D. J.; Valloppilly, S.; Huh, Y.

    2015-05-07

    Mn{sub 1.5}X{sub 0.5}Sn (X = Cr, Mn, Fe, Co) nanomaterials in the hexagonal Ni{sub 2}In-type crystal structure have been prepared using arc-melting and melt spinning. All the rapidly quenched Mn{sub 1.5}X{sub 0.5}Sn alloys show moderate saturation magnetizations with the highest value of 458 emu/cm{sup 3} for Mn{sub 1.5}Fe{sub 0.5}Sn, but their Curie temperatures are less than 300 K. All samples except the Cr containing one show spin-glass-like behavior at low temperature. The magnetic anisotropy constants calculated from the high-field magnetization curves at 100 K are on the order of 1 Merg/cm{sup 3}. The vacuum annealing of the ribbons at 550 °C significantly improved their magnetic properties with the Curie temperature increasing from 206 K to 273 K for Mn{sub 1.5}Fe{sub 0.5}Sn.

  20. The ferromagnetic shape-memory effect in Ni Mn Ga

    NASA Astrophysics Data System (ADS)

    Marioni, M. A.; O'Handley, R. C.; Allen, S. M.; Hall, S. R.; Paul, D. I.; Richard, M. L.; Feuchtwanger, J.; Peterson, B. W.; Chambers, J. M.; Techapiesancharoenkij, R.

    2005-04-01

    Active materials have long been used in the construction of sensors and devices. Examples are piezo-electric ceramics and shape memory alloys. The more recently developed ferromagnetic shape-memory alloys (FSMAs) have received considerable attention due to their large magnetic field-induced, reversible strains (up to 10%). In this article, we review the basic physical characteristics of the FSMA Ni-Mn-Ga (crystallography, thermal, mechanical and magnetic behavior). Also, we present some of the works currently under way in the areas of pulse-field and acoustic-assisted actuation, and vibration energy absorption.

  1. Lattice dynamics of Ni-Mn-Al Heusler alloys

    SciTech Connect

    Moya, Xavier; Manosa, Lluis; Planes, A.; Krenke, T.; Acet, Mehmet; Wassermann, E. F.; Morin, M.; Garlea, Vasile O; Lograsso, Tom; Zarestky, Jerel L.

    2008-01-01

    We have studied the lattice dynamics of a Ni54Mn23Al23 (at.%) Heusler single-crystalline alloy by means of neutron scattering and ultrasonic techniques. Results show the existence of a number of precursor phenomena. We have found an anomaly (dip) in the low TA2 phonon branch at the wave number 0.33 (in reciprocal lattice units) that becomes more pronounced (phonon softening) with decreasing temperature. We have also observed softening of the associated shear elastic constant (C ) with decreasing temperature. Ultrasonic measurements under applied magnetic field, both isothermally and varying the temperature show that the values of elastic constants depend on magnetic order thus evidencing magnetoelastic coupling.

  2. Low-cost Fe--Ni--Cr alloys for high temperature valve applications

    DOEpatents

    Muralidharan, Govindarajan

    2017-03-28

    An Fe--Ni--Cr alloy is composed essentially of, in terms of weight percent: 1 to 3.5 Al, up to 2 Co, 15 to 19.5 Cr, up to 2 Cu, 23 to 40 Fe, up to 0.3 Hf, up to 4 Mn, 0.15 to 2 Mo, up to 0.15 Si, up to 1.05 Ta, 2.8 to 4.3 Ti, up to 0.5 W, up to 0.06 Zr, 0.02 to 0.15 C, 0.0001 to 0.007 N, balance Ni, wherein, in terms of atomic percent: 6.5.ltoreq.Al+Ti+Zr+Hf+Ta.ltoreq.10, 0.33.ltoreq.Al/(Al+Ti+Zr+Hf+Ta).ltoreq.0.065, 4.ltoreq.(Fe+Cr)/(Al+Ti+Zr+Hf+Ta).ltoreq.10, the alloy being essentially free of Nb and V.

  3. Positron Annihilation Spectroscopy and Small Angle Neutron Scattering Characterization of Nanostructural Features in Irradiated Fe-Cu-Mn Alloys

    SciTech Connect

    Wirth, B D; Asoka-Kumar, P; Howell, R H; Odette, G R; Sterne, P A

    2001-01-01

    Radiation embrittlement of nuclear reactor pressure vessel steels results from a high number density of nanometer sized Cu-Mn-Ni rich precipitates (CRPs) and sub-nanometer matrix features, thought to be vacancy-solute cluster complexes (VSC). However, questions exist regarding both the composition of the precipitates and the defect character and composition of the matrix features. We present results of positron annihilation spectroscopy (PAS) and small angle neutron scattering (SANS) characterization of irradiated and thermally aged Fe-Cu and Fe-Cu-Mn alloys. These complementary techniques provide insight into the composition and character of both types of nanoscale features. The SANS measurements indicate populations of CRPs and VSCs in both alloys. The CRPs are coarser in the Fe-Cu alloy and the number densities of CRP and VSC increase with the addition of Mn. The PAS involved measuring both the positron lifetimes and the Doppler broadened annihilation spectra in the high momentum region to provide elemental sensitivity at the annihilation site. The spectra in Fe-Cu-Mn specimens thermally aged to peak hardness at 450 C and irradiated at 288 C are nearly identical to elemental Cu. Positron lifetime and spectrum measurements in Fe-Cu specimens irradiated at 288 C clearly show the existence of long lifetime ({approx}500 ps) open volume defects, which also contain Cu. Thus the SANS and PAS provide a self-consistent picture of nanostructures composed of CRPs and VSCs and tend to discount high Fe concentrations in the CRPs.

  4. Temperature-induced variations of magnetization kinetics of FeNi in the FM/SC and FM/AFM heterostructures

    NASA Astrophysics Data System (ADS)

    Uspenskaya, L. S.; Egorov, S. V.

    2009-03-01

    Remagnetization kinetics of the bilayer ferromagnetic/superconductor (FeNi/Nb) and ferromagnetic/antiferromagnetic (FeNi/FeMn) ultra-thin films is investigated. Experimental results are obtained by direct observation of domain structure using the magneto-optic visualization technique in a wide temperature range. It is found that proximity of a second layer varies drastically the FeNi magnetic properties, such as domain and domain boundary structures, domain boundary mobility, coercivity. Moreover, the mechanism of magnetization is found to be temperature dependent. The effect of temperature becomes especially pronounced below 50 K.

  5. Strong anisotropy and magnetostriction in the two-dimensional Stoner ferromagnet Fe>3mn>GeTe>2mn>

    SciTech Connect

    Zhuang, Houlong L.; Kent, P. R. C.; Hennig, Richard G.

    2016-04-06

    Computationally characterizing magnetic properies of novel two-dimensional (2D) materials serves as an important first step of exploring possible applications. Using density-functional theory, we show that single-layer Fe>3mn>GeTe>2mn> is a potential 2D material with sufficiently low formation energy to be synthesized by mechanical exfoliation from the bulk phase with a van der Waals layered structure. In addition, we calculated the phonon dispersion demonstrating that single-layer Fe>3mn>GeTe>2mn>is dynamically stable. Furthermore, we find that similar to the bulk phase, 2D Fe>3mn>GeTe>2mn> exhibits amagnetic moment that originates from a Stoner instability. In contrast to other 2D materials, we find that single-layer Fe>3mn>GeTe>2mn> exhibits a significant uniaxial magnetocrystalline anisotropy energy of 920μ eV per Fe atom originating from spin-orbit coupling. In conclusion, we show that applying biaxial tensile strains enhances the anisotropy energy, which reveals strong magnetostriction in single-layer Fe>3mn>GeTe>2mn> with a sizable magneostrictive coefficient. Our results indicate that single-layer Fe>3mn>GeTe>2mn> is potentially useful for magnetic storage applications.

  6. Photoelectrochemical Performance Observed in Mn-Doped BiFeO3 Heterostructured Thin Films

    PubMed Central

    Xu, Hao-Min; Wang, Huanchun; Shi, Ji; Lin, Yuanhua; Nan, Cewen

    2016-01-01

    Pure BiFeO3 and heterostructured BiFeO3/BiFe0.95Mn0.05O3 (5% Mn-doped BiFeO3) thin films have been prepared by a chemical deposition method. The band structures and photosensitive properties of these films have been investigated elaborately. Pure BiFeO3 films showed stable and strong response to photo illumination (open circuit potential kept −0.18 V, short circuit photocurrent density was −0.023 mA·cm−2). By Mn doping, the energy band positions shifted, resulting in a smaller band gap of BiFe0.95Mn0.05O3 layer and an internal field being built in the BiFeO3/BiFe0.95Mn0.05O3 interface. BiFeO3/BiFe0.95Mn0.05O3 and BiFe0.95Mn0.05O3 thin films demonstrated poor photo activity compared with pure BiFeO3 films, which can be explained by the fact that Mn doping brought in a large amount of defects in the BiFe0.95Mn0.05O3 layers, causing higher carrier combination and correspondingly suppressing the photo response, and this negative influence was more considerable than the positive effects provided by the band modulation. PMID:28335343

  7. Low temperature selective catalytic reduction (SCR) of NO with NH3 over Fe-Mn based catalysts.

    PubMed

    Long, Richard Q; Yang, Ralph T; Chang, Ramsay

    2002-03-07

    Fe-Mn based transition metal oxides (Fe-Mn, Fe-Mn-Zr and Fe-Mn-Ti) show nearly 100% NO conversion at 100-180 degrees C for selective catalytic reduction of NO with NH3 under the applied conditions with a space velocity of 15,000 h-1.

  8. Prototypical topological orbital ferromagnet γ-FeMn.

    PubMed

    Hanke, Jan-Philipp; Freimuth, Frank; Blügel, Stefan; Mokrousov, Yuriy

    2017-01-20

    We predict from first principles an entirely topological orbital magnetization in the noncoplanar bulk antiferromagnet γ-FeMn originating in the nontrivial topology of the underlying spin structure, without any reference to spin-orbit interaction. Studying the influence of strain, composition ratio, and spin texture on the topological orbital magnetization and the accompanying topological Hall effect, we promote the scalar spin chirality as key mechanism lifting the orbital degeneracy. The system is thus a prototypical topological orbital ferromagnet, the macroscopic orbital magnetization of which is prominent even without spin-orbit coupling. One of the remarkable features of γ-FeMn is the possibility for pronounced orbital magnetostriction mediated by the complex spin topology in real space.

  9. Prototypical topological orbital ferromagnet γ-FeMn

    NASA Astrophysics Data System (ADS)

    Hanke, Jan-Philipp; Freimuth, Frank; Blügel, Stefan; Mokrousov, Yuriy

    2017-01-01

    We predict from first principles an entirely topological orbital magnetization in the noncoplanar bulk antiferromagnet γ-FeMn originating in the nontrivial topology of the underlying spin structure, without any reference to spin-orbit interaction. Studying the influence of strain, composition ratio, and spin texture on the topological orbital magnetization and the accompanying topological Hall effect, we promote the scalar spin chirality as key mechanism lifting the orbital degeneracy. The system is thus a prototypical topological orbital ferromagnet, the macroscopic orbital magnetization of which is prominent even without spin-orbit coupling. One of the remarkable features of γ-FeMn is the possibility for pronounced orbital magnetostriction mediated by the complex spin topology in real space.

  10. Prototypical topological orbital ferromagnet γ-FeMn

    PubMed Central

    Hanke, Jan-Philipp; Freimuth, Frank; Blügel, Stefan; Mokrousov, Yuriy

    2017-01-01

    We predict from first principles an entirely topological orbital magnetization in the noncoplanar bulk antiferromagnet γ-FeMn originating in the nontrivial topology of the underlying spin structure, without any reference to spin-orbit interaction. Studying the influence of strain, composition ratio, and spin texture on the topological orbital magnetization and the accompanying topological Hall effect, we promote the scalar spin chirality as key mechanism lifting the orbital degeneracy. The system is thus a prototypical topological orbital ferromagnet, the macroscopic orbital magnetization of which is prominent even without spin-orbit coupling. One of the remarkable features of γ-FeMn is the possibility for pronounced orbital magnetostriction mediated by the complex spin topology in real space. PMID:28106133

  11. Micromagnetism of MnBi:FeCo thin films

    NASA Astrophysics Data System (ADS)

    Rana, T. H.; Manchanda, P.; Balamurugan, B.; Kashyap, A.; Gao, T. R.; Takeuchi, I.; Cun, J.; Biswas, S.; Sabirianov, R. F.; Sellmyer, D. J.; Skomski, R.

    2016-02-01

    MnBi:FeCo hard-soft bilayers are investigated using micromagnetic simulations with open boundary conditions and two-dimensional (2D) periodic boundary conditions (PBC). Open and PBC yield similar coercivities of about 1.01 T, in agreement with experiment, but the hysteresis-loop shape is very different in the two theoretical approaches. The difference is ascribed to edge effects, which occur in open boundary conditions but not in PBC and experiment. Near the nucleation field, a curling or vortex mode develops in dots with circular cross sections. The curling mode, which is caused by magnetostatic self-interaction, does not negatively affect the high coercivity of 1.01 T. The magnetostatic self-interaction contributes to the favorable second-quadrant behavior of the MnBi:FeCo thin films.

  12. Delocalization and hybridization enhance the magnetocaloric effect in Ni2Mn0.75Cu0.25Ga

    SciTech Connect

    Roy, Sujoy; Blackburn, E.; Valvidares, S. M.; Fitzsimmons, M. R.; Vogel, Sven C.; Khan, M.; Dubenko, I.; Stadler, S.; Ali, N.; Sinha, S. K.; Kortright, J. B.

    2008-11-26

    In view of the looming energy crisis facing our planet, attention increasingly focuses on materials potentially useful as a basis for energy saving technologies. The discovery of giant magnetocaloric (GMC) compounds - materials that exhibit especially large changes in temperature as the externally applied magnetic field is varied - is one such compound 1. These materials have potential for use in solid state cooling technology as a viable alternative to existing gas based refrigeration technologies that use choro-fluoro - and hydro-fluoro-carbon chemicals known to have a severe detrimental effect on human health and environment 2,3. Examples of GMC compounds include Gd5(SiGe)4 4, MnFeP1-xAsx 5 and Ni-Mn-Ga shape memory alloy based compounds 6-8. Here we explain how the properties of one of these compounds (Ni2MnGa) can be tuned as a function of temperature by adding dopants. By altering the free energy such that the structural and magnetic transitions coincide, a GMC compound that operates at just the right temperature for human requirements can be obtained 9. We show how Cu, substituted for Mn, pulls the magnetic transition downwards in temperature and also, counterintuitively, increases the delocalization of the Mn magnetism. At the same time, this reinforces the Ni-Ga chemical bond, raising the temperature of the martensite-austenite transition. At 25percent doping, the two transitions coincide at 317 K.

  13. Correlation between bias fields and magnetoresistance in CoPt biased FeNi/Ta/FeNi GMR heterosystems

    NASA Astrophysics Data System (ADS)

    Wang, Yi; Sahoo, S.; Echtenkamp, W.; Binek, Ch.

    2009-03-01

    Exchange coupled magnetic hard layer (HL)/ soft layer (SL) thin films show SL biasing in close analogy to conventional exchange bias systems with antiferromagnetic pinning.^1 Here we study CoPt(35nm)/FeNi450nm/Ta(d)/FeNi450nm heterostructures with d between 0.7 and 5nm. The CoPt films have in-plane magnetic anisotropy and pin the adjacent FeNi SL films. The latter are exchange coupled from top via Ta spacer layers with FeNi in a GMR-type architecture. We use AGFM and SQUID magnetometry to study the FeNi magnetization reversal with (CoPt) and without (vacuum) pinning layer proximity. The two minor FeNi hysteresis loops of the GMR trilayer reveal different biasing effects due to the distinct exchange interaction at the respective interfaces. The FeNi/CoPt coupling is systematically tuned via a series of set fields which allow partial demagnetization of the pinning layer. Moreover we study the correlation between the overall and minor magnetization reversals and the corresponding magnetoresistance effects for various temperature between T=20 and 400K. ^1Ch. Binek, S. Polisetty, Xi He and A. Berger, Phys. Rev. Lett. 96, 067201 (2006). Financial support by NSF through Career DMR-0547887, MRSEC DMR-0820521 and the NRI.

  14. Positive exchange bias in a Ni 80Fe 20/Ni xFe 1-xO thin-film bilayer

    NASA Astrophysics Data System (ADS)

    Lin, K.-W.; Tzeng, Y.-M.; Guo, Z.-Y.; Liu, C.-Y.; van Lierop, J.

    2006-09-01

    We have measured positive exchange bias in a Ni 80Fe 20/Ni xFe 1-xO thin-film nanocrystallite system. A series of solid solution Ni xFe 1-xO 40 nm thick films capped with 25 nm thick Ni 80Fe 20 were deposited using a range of %O 2/Ar bombardment energies (i.e. End-Hall voltages). Proper tuning of the deposition conditions results in a Ni 80Fe 20/Ni xFe 1-xO (30%O 2/Ar) based bilayer that exhibits a positive exchange bias loop shift of Hex˜60 Oe at 150 K.

  15. Towards a Superplastic Forming of Fe-Mn-Al Alloys

    SciTech Connect

    Guanabara, Paulo Jr.; Bueno, Levi de O.; Ferreira Batalha, Gilmar

    2011-01-17

    The aim is to study the characteristics of superplasticity, mostly on non qualified materials, such as austenitic steel of the Fe-Mn-Al alloy, which has some of the specific material parameters closely related to microstructural mechanisms. These parameters are used as indicators of material superplastic potentiality. The material was submitted to hot tensile testing, within a temperature range from 600 deg. C to 1000 deg. C and strain-rates varying from 10{sup -6} to 1 s{sup -1}. The strain rate sensitivity parameter (m) and observed maximum elongation until rupture ({epsilon}{sub r}) could be determined and also obtained from the hot tensile test. The experiments stated a possibility of superplastic behaviour in a Fe-Mn-Al alloy within a temperature range from 700 deg. C to 900 deg. C with grain size around 3 {mu}m (ASTM grain size 12) and average strain rate sensitivity of m {approx} 0.54, as well as a maximum elongation at rupture around 600%. The results are based on a more enhanced research from the authors; however, this paper has focused just on the hot tensile test, as further creep tests results are not available herein. There are rare examples of superplasticity study of an austenitic steel Fe-Mn-Al alloy, thus this work showed some possibility of exploring the potential use of such materials in this regime at temperatures {>=}700 deg. C.

  16. Preparation of melt textured Ni-Mn-Ga

    NASA Astrophysics Data System (ADS)

    Pötschke, Martin; Gaitzsch, Uwe; Roth, Stefan; Rellinghaus, Bernd; Schultz, Ludwig

    2007-09-01

    Ni-Mn-Ga alloys are the best-known group of magnetically active alloys, which show magnetic field-induced strain (MFIS) via twin boundary motion. This phenomenon is often referred to as the magnetic shape memory effect. In single crystals, strains of up to 10% have been achieved that way. Up to now, no systematic study of this effect in polycrystals is available. In order to obtain this effect also in polycrystals, stationary casting is employed to achieve coarse-grained, textured samples. Therefore, a hot ceramic mold is mounted on a cold copper plate. Thus, a unidirectional heat flow along the sample axis is realized. The direction of heat flow coincides with the growth direction, which is preferentially [1 0 0]. After solidification, the samples were annealed at high temperature (1000 °C) to ensure chemical homogeneity on a local scale. The samples were cut by spark erosion. In order to allow for a direct investigation of the resulting microstructure by electron backscatter diffraction (EBSD) measurements, an alloy composition with a martensitic transformation below room temperature was chosen (Ni 48Mn 30Ga 22). The transformation temperature was checked by differential scanning calometry (DSC). The orientation of the grains and the preferred growth direction was analyzed using EBSD.

  17. Pressure dependence on the remanent magnetization of Fe-Ni alloys and Ni metal

    NASA Astrophysics Data System (ADS)

    Wei, Qingguo; Gilder, Stuart Alan; Maier, Bernd

    2014-10-01

    We measured the acquisition of magnetic remanence of iron-nickel alloys (Fe64Ni36, Fe58Ni42, and Fe50Ni50) and pure Ni under pressures up to 23 GPa at room temperature. Magnetization decreases markedly for Fe64Ni36 between 5 and 7 GPa yet remains ferromagnetic until at least 16 GPa. Magnetization rises by a factor of 2-3 for the other compositions during compression to the highest applied pressures. Immediately upon decompression, magnetic remanence increases for all Fe-Ni alloys while magnetic coercivity remains fairly constant at relatively low values (5-20 mT). The amount of magnetization gained upon complete decompression correlates with the maximum pressure experienced by the sample. Martensitic effects best explain the increase in remanence rather than grain-size reduction, as the creation of single domain sized grains would raise the coercivity. The magnetic remanence of low Ni Invar alloys increases faster with pressure than for other body-centered-cubic compositions due to the higher magnetostriction of the low Ni Invar metals. Thermal demagnetization spectra of Fe64Ni36 measured after pressure release broaden as a function of peak pressure, with a systematic decrease in Curie temperature. Irreversible strain accumulation from the martensitic transition likely explains the broadening of the Curie temperature spectra, consistent with our x-ray diffraction analyses.

  18. Influence of Co substitution for Ni and Mn on the structural and electrochemical characteristics of LiNi 0.5Mn 1.5O 4

    NASA Astrophysics Data System (ADS)

    Ito, Atsushi; Li, Decheng; Lee, Yunsung; Kobayakawa, Koichi; Sato, Yuichi

    LiNi 0.5- xCo 2 xMn 1.5- xO 4 (0 ≤ 2 x ≤ 0.2) was prepared by spray drying, then re-annealing in O 2. Their structural and electrochemical properties were studied by ex-situ XRD, GITT, and charge-discharge testing. The substitution of cobalt for Ni and Mn in the LiNi 0.5Mn 1.5O 4 resulted in significant structural and electrochemical variations, such as the change in structural transformation with lithium extraction, the increase in the lithium diffusion coefficient and the decrease in the area specific impedance. Moreover, the improved kinetic properties caused by the Co substitution for Ni and Mn result in an improved cyclic performance at a high rate and at elevated temperature as well as the rate capability.

  19. Morphological evolution and strengthening behavior of α-Al(Fe,Mn)Si in Al-6Si-2Fe-xMn alloys

    NASA Astrophysics Data System (ADS)

    Gao, Tong; Hu, Kaiqi; Wang, Longshuai; Zhang, Bangran; Liu, Xiangfa

    β-Al5FeSi is preferred to form in Al-Si-Fe alloys, normally exhibiting needlelike, which is harmful for the mechanical properties. In this paper, with the addition of 1%, 1.5% and 3% Mn into an Al-6Si-2Fe alloy, β-Al5FeSi phase was found to transform to skeleton, flower-like and coarse dendritic α-Al(Fe,Mn)Si, respectively. The novel flower-like α-Al(Fe,Mn)Si crystals contain developed branches with the average diameter of ∼200 nm, performing strengthening effect on the tensile property. Detailed morphologies of α-Al(Fe,Mn)Si phase and the formation mechanism were discussed.

  20. Influence of site occupancy on the structure, microstructure and magnetic properties of ternary and quasi-ternary alloys of Ni-Mn-Ga

    NASA Astrophysics Data System (ADS)

    Seshubai, V.; Kumar, A. Satish; Ramudu, M.

    2012-07-01

    A systematic study of the effect of cobalt, selectively substituted for Ni and Mn, in the modulated orthorhombic (7M) Ni50Mn29Ga21 alloy has led to interesting correlations between the resultant structure and microstructure. Substitution of Co for Mn resulted in the stabilization of a non-modulated tetragonal (NM) phase at higher Co content and caused suppression of long-range twin deformation leading to sporadic islands within which twin variants were confined. On the other hand, substitution of Co for Ni does not to alter either the superstructural ordering or the long-range twin deformation. A study of the compositional dependence of saturation magnetization measured at 5 K is shown to throw light on the site preference of cobalt and iron atoms substituted in Mn-rich alloys of quasi-ternary Ni-Mn-Ga-(Fe,Co) system. The study reveals that the dopant atoms occupy the regular Mn site, rather than the vacant Ga site, with ferromagnetic exchange relative to the moments on Ni and Mn sub-lattices. These effects are attributed to have their origin in minimizing the stresses generated by the corresponding atomic volume changes incorporated by doping.

  1. Remarkably Improved Electrochemical Performance of Li- and Mn-Rich Cathodes upon Substitution of Mn with Ni.

    PubMed

    Kumar Nayak, Prasant; Grinblat, Judith; Levi, Elena; Penki, Tirupathi Rao; Levi, Mikhael; Sun, Yang-Kook; Markovsky, Boris; Aurbach, Doron

    2017-02-08

    Li- and Mn-rich transition-metal oxides of layered structure are promising cathodes for Li-ion batteries because of their high capacity values, ≥250 mAh g(-1). These cathodes suffer from capacity fading and discharge voltage decay upon prolonged cycling to potential higher than 4.5 V. Most of these Li- and Mn-rich cathodes contain Ni in a 2+ oxidation state. The fine details of the composition of these materials may be critically important in determining their performance. In the present study, we used Li1.2Ni0.13Mn0.54Co0.13O2 as the reference cathode composition in which Mn ions are substituted by Ni ions so that their average oxidation state in Li1.2Ni0.27Mn0.4Co0.13O2 could change from 2+ to 3+. Upon substitution of Mn with Ni, the specific capacity decreases but, in turn, an impressive stability was gained, about 95% capacity retention after 150 cycles, compared to 77% capacity retention for Li1.2Ni0.13Mn0.54Co0.13O2 cathodes when cycled at a C/5 rate. Also, a higher average discharge voltage of 3.7 V is obtained for Li1.2Ni0.27Mn0.4Co0.13O2 cathodes, which decreases to 3.5 V after 150 cycles, while the voltage fading of cathodes comprising the reference material is more pronounced. The Li1.2Ni0.27Mn0.4Co0.13O2 cathodes also demonstrate higher rate capability compared to the reference Li1.2Ni0.13Mn0.54Co0.13O2 cathodes. These results clearly indicate the importance of the fine composition of cathode materials containing the five elements Li, Mn, Ni, Co, and O. The present study should encourage rigorous optimization efforts related to the fine composition of these cathode materials, before external means such as doping and coating are applied.

  2. Isotopic fractionation associated with [NiFe]- and [FeFe]-hydrogenases

    SciTech Connect

    Yang, Hui; Gandhi, Hasand; Cornish, Adam J.; Moran, James J.; Kreuzer, Helen W.; Ostrom, Nathaniel; Hegg, Eric L.

    2016-01-30

    Hydrogenases catalyze the reversible formation of H2 from electrons and protons with high efficiency. Understanding the relationships between H2 production, H2 uptake, and H2-H2O exchange can provide insight into the metabolism of microbial communities in which H2 is an essential component in energy cycling. In this manuscript, we used stable H isotopes (1H and 2H) to probe the isotope effects associated with three [FeFe]-hydrogenases and three [NiFe]-hydrogenases. All six hydrogenases displayed fractionation factors for H2 formation that were significantly less than 1, producing H2 that was severely depleted in 2H relative to the substrate, water. Consistent with differences in their active site structure, the fractionation factors for each class appear to cluster, with the three [NiFe]-hydrogenases (α = 0.27-0.40) generally having smaller values than the three [FeFe]-hydrogenases (α = 0.41-0.55). We also obtained isotopic fractionation factors associated with H2 uptake and H2-H2O exchange under conditions similar to those utilized for H2 production, providing us with a more complete picture of the three reactions catalyzed by hydrogenases. The fractionation factors determined in our studies can be used as signatures for different hydrogenases to probe their activity under different growth conditions and to ascertain which hydrogenases are most responsible for H2 production and/or uptake in complex microbial communities.

  3. An x-ray absorption spectroscopy study of Ni-Mn-Ga shape memory alloys.

    PubMed

    Sathe, V G; Dubey, Aditi; Banik, Soma; Barman, S R; Olivi, L

    2013-01-30

    The austenite to martensite phase transition in Ni-Mn-Ga ferromagnetic shape memory alloys was studied by extended x-ray absorption fine structure (EXAFS) and x-ray absorption near-edge structure (XANES) spectroscopy. The spectra at all the three elements', namely, Mn, Ga and Ni, K-edges in several Ni-Mn-Ga samples (with both Ni and Mn excess) were analyzed at room temperature and low temperatures. The EXAFS analysis suggested a displacement of Mn and Ga atoms in opposite direction with respect to the Ni atoms when the compound transforms from the austenite phase to the martensite phase. The first coordination distances around the Mn and Ga atoms remained undisturbed on transition, while the second and subsequent shells showed dramatic changes indicating the presence of a modulated structure. The Mn rich compounds showed the presence of antisite disorder of Mn and Ga. The XANES results showed remarkable changes in the unoccupied partial density of states corresponding to Mn and Ni, while the electronic structure of Ga remained unperturbed across the martensite transition. The post-edge features in the Mn K-edge XANES spectra changed from a double peak like structure to a flat peak like structure upon phase transition. The study establishes strong correlation between the crystal structure and the unoccupied electronic structure in these shape memory alloys.

  4. Magnetoimpedance of FeNi-based asymmetric sensitive elements

    NASA Astrophysics Data System (ADS)

    Chlenova, A. A.; Svalov, A. V.; Kurlyandskaya, G. V.; Volchkov, S. O.

    2016-10-01

    [Ti/FeNi]5/Ti/Cu/Ti/[FeNi/Ti]x (x=0-5) multilayers were prepared by sputtering. Their magnetic properties and magnetoimpedance were studied focusing on future technological applications. Both (ΔZ/Z)max and (ΔR/R)max values showed a tendency to decrease with a decrease of the number of magnetic layers of the top multilayer. Such a parameter as an even or odd number of layers is important for the MI value. In the field interval of technological interest all [Ti/FeNi]5/Ti/Cu/Ti/[FeNi/Ti]x structures show similar sensitivities of about 70%/Oe for ΔR/R ratios but the lower the number of magnetic layers in the top multilayer, the higher the operating frequency.

  5. Interdiffusion in nanometric Fe/Ni multilayer films

    SciTech Connect

    Liu, JX; Barmak, K

    2015-03-01

    Fe (3.1 nm)/Ni (3.3 nm)](20) multilayer films were prepared by DC magnetron sputtering onto oxidized Si(100) substrates. The Fe and Ni layers were shown to both be face-centered cubic by x-ray diffraction. Interdiffusion of the Fe and Ni layers in the temperature range of 300-430 degrees C was studied by x-ray reflectivity. From the decay of the integral intensity of the superlattice peak, the activation energy and the pre-exponential term for the effective interdiffusion coefficient were determined as to 1.06 +/- 0.07 eV and 5 x 10(-10) cm(2)/s, respectively. The relevance of the measured interdiffusion coefficient to the laboratory timescale synthesis of L1(0) ordered FeNi as a rare-earth free permanent magnet is discussed. (C) 2015 American Vacuum Society.

  6. Insulating 'nanocables': Invar Fe Ni alloy nanorods inside BN nanotubes

    NASA Astrophysics Data System (ADS)

    Bando, Y.; Ogawa, K.; Golberg, D.

    2001-10-01

    Here we present the results on synthesis, structural and chemical analysis of insulating boron nitride (BN) nanotubes (NTs) which have been filled with conducting Invar Fe-Ni alloy (˜60 at.% Fe; ˜40 at.% Ni) nanorods. The result was accomplished by a two-step process: (i) carbon (C) NTs containing Invar alloy nanoparticles placed at the tube tips were synthesized by plasma-assisted chemical vapor deposition (CVD) on an Invar Fe-Ni alloy substrate; and (ii) the material was heated to the melting point of the alloy (1723 K) in a flow of B 2O 3 and N 2 gases and held for 30 min. During this second stage, simultaneous filling of NTs with the Fe-Ni melt through capillarity and chemical modification of C tubular shells to form BN tubules occurred.

  7. Low-frequency creep in CoNiFe films.

    NASA Technical Reports Server (NTRS)

    Bartran, D. S.; Bourne, H. C., Jr.; Chow, L. G.

    1972-01-01

    Domain wall motion excited by slow rise-time, bipolar, hard-axis pulses in vacuum deposited CoNiFe films from 1500 to 2000 A thick is studied. The results are consistent with those of comparable NiFe films. Furthermore, the wall coercivity is found to be the most significant sample property correlated to the low-frequency creep properties of all the samples.

  8. Ferromagnetic resonance in FeCoNi electroplated wires

    NASA Astrophysics Data System (ADS)

    García-Miquel, H.; Bhagat, S. M.; Lofland, S. E.; Kurlyandskaya, G. V.; Svalov, A. V.

    2003-08-01

    We have investigated the microwave properties (ferromagnetic resonance and ferromagnetic antiresonance) of FeCoNi magnetic tubes created by electroplating on CuBe wire. Important parameters such as the g factor, magnetization, anisotropy field, and damping parameter were obtained from the measurements. One sample, prepared by a method which entails rf-sputtering deposition of an additional FeNi layer, shows a clear ferromagnetic antiresonance.

  9. Anodic vacuum arc developed nanocrystalline Cu-Ni and Fe-Ni thin film thermocouples

    SciTech Connect

    Mukherjee, S. K.; Sinha, M. K.; Pathak, B.; Rout, S. K.; Barhai, P. K.

    2009-12-01

    This paper deals with the development of nanocrystalline Cu-Ni and Fe-Ni thin film thermocouples (TFTCs) by using ion-assisted anodic vacuum arc deposition technique. The crystallographic structure and surface morphology of individual layer films have been studied by x-ray diffraction and scanning electron microscopy, respectively. The resistivity, temperature coefficient of resistance, and thermoelectric power of as deposited and annealed films have been measured. The observed departure of these transport parameters from their respective bulk values can be understood in terms of intrinsic scattering due to enhanced crystallite boundaries. From the measured values of thermoelectric power and the corresponding temperature coefficient of resistance of annealed Cu, Ni, and Fe films, the calculated values of log derivative of the mean free path of conduction electrons at the Fermi surface with respect to energy (U) are found to be -0.51, 3.22, and -8.39, respectively. The thermoelectric response of annealed Cu-Ni and Fe-Ni TFTCs has been studied up to a maximum temperature difference of 300 deg. C. Reproducibility of TFTCs has been examined in terms of the standard deviation in thermoelectric response of 16 test samples for each pair. Cu-Ni and Fe-Ni TFTCs agree well with their wire thermocouple equivalents. The thermoelectric power values of Cu-Ni and Fe-Ni TFTCs at 300 deg. C are found to be 0.0178 and 0.0279 mV/ deg. C, respectively.

  10. Anodic vacuum arc developed nanocrystalline Cu-Ni and Fe-Ni thin film thermocouples

    NASA Astrophysics Data System (ADS)

    Mukherjee, S. K.; Sinha, M. K.; Pathak, B.; Rout, S. K.; Barhai, P. K.

    2009-12-01

    This paper deals with the development of nanocrystalline Cu-Ni and Fe-Ni thin film thermocouples (TFTCs) by using ion-assisted anodic vacuum arc deposition technique. The crystallographic structure and surface morphology of individual layer films have been studied by x-ray diffraction and scanning electron microscopy, respectively. The resistivity, temperature coefficient of resistance, and thermoelectric power of as deposited and annealed films have been measured. The observed departure of these transport parameters from their respective bulk values can be understood in terms of intrinsic scattering due to enhanced crystallite boundaries. From the measured values of thermoelectric power and the corresponding temperature coefficient of resistance of annealed Cu, Ni, and Fe films, the calculated values of log derivative of the mean free path of conduction electrons at the Fermi surface with respect to energy (U) are found to be -0.51, 3.22, and -8.39, respectively. The thermoelectric response of annealed Cu-Ni and Fe-Ni TFTCs has been studied up to a maximum temperature difference of 300°C. Reproducibility of TFTCs has been examined in terms of the standard deviation in thermoelectric response of 16 test samples for each pair. Cu-Ni and Fe-Ni TFTCs agree well with their wire thermocouple equivalents. The thermoelectric power values of Cu-Ni and Fe-Ni TFTCs at 300°C are found to be 0.0178 and 0.0279mV/°C, respectively.

  11. Effectiveness of hypolimnetic oxygenation for preventing accumulation of Fe and Mn in a drinking water reservoir.

    PubMed

    Munger, Zackary W; Carey, Cayelan C; Gerling, Alexandra B; Hamre, Kathleen D; Doubek, Jonathan P; Klepatzki, Spencer D; McClure, Ryan P; Schreiber, Madeline E

    2016-12-01

    The accumulation of Fe and Mn in seasonally stratified drinking water reservoirs adversely impacts water quality. To control issues with Fe and Mn at the source, some drinking water utilities have deployed hypolimnetic oxygenation systems to create well-oxygenated conditions in the water column that are favorable for the oxidation, and thus removal, of Fe and Mn. However, in addition to being controlled by dissolved oxygen (DO), Fe and Mn concentrations are also influenced by pH and metal-oxidizing microorganisms. We studied the response of Fe and Mn concentrations to hypolimnetic oxygenation in a shallow drinking water reservoir in Vinton, Virginia, USA by sequentially activating and deactivating an oxygenation system over two summers. We found that maintaining well-oxygenated conditions effectively prevented the accumulation of soluble Fe in the hypolimnion. However, while the rate of Mn oxidation increased under well-oxygenated conditions, soluble Mn still accumulated in the slightly acidic to neutral (pH 5.6 to 7.5) hypolimnion. In parallel, we conducted laboratory incubation experiments, which showed that the presence of Mn-oxidizing microorganisms increased the rate of Mn oxidation in comparison with rates under oxic, abiotic conditions. Combined, our field and laboratory results demonstrate that increasing DO concentrations in the water column is important for stimulating the oxidation of Fe and Mn, but that the successful management of Mn is also tied to the activity of Mn-oxidizing organisms in the water column and favorable (neutral to alkaline) pH.

  12. Effect of NiO spin orientation on the magnetic anisotropy of the Fe film in epitaxially grown Fe/NiO/Ag(001) and Fe/NiO/MgO(001)

    SciTech Connect

    Kim, W.; Jin, E.; Wu, J.; Park, J.; Arenholz, E.; Scholl, A.; Hwang, C.; Qiu, Z.

    2010-02-10

    Single crystalline Fe/NiO bilayers were epitaxially grown on Ag(001) and on MgO(001), and investigated by Low Energy Electron Diffraction (LEED), Magneto-Optic Kerr Effect (MOKE), and X-ray Magnetic Linear Dichroism (XMLD). We find that while the Fe film has an in-plane magnetization in both Fe/NiO/Ag(001) and Fe/NiO/MgO(001) systems, the NiO spin orientation changes from in-plane direction in Fe/NiO/Ag(001) to out-of-plane direction in Fe/NiO/MgO(001). These two different NiO spin orientations generate remarkable different effects that the NiO induced magnetic anisotropy in the Fe film is much greater in Fe/NiO/Ag(001) than in Fe/NiO/MgO(001). XMLD measurement shows that the much greater magnetic anisotropy in Fe/NiO/Ag(001) is due to a 90{sup o}-coupling between the in-plane NiO spins and the in-plane Fe spins.

  13. Study of Fe-12Cr-20Mn-W-C austenitic steels irradiated in the SM-2 reactor

    NASA Astrophysics Data System (ADS)

    Shamardin, V. K.; Bulanova, T. M.; Neustroyev, V. S.; Ostrovsky, Z. E.; Kosenkov, V. M.; Ivanov, L. I.; Djomina, E. V.

    1992-09-01

    A comparison has been made between the mechanical properties and swelling of austenitic stainless steels EP-838 (Fe-Cr-Mn) and 316SS (Fe-Cr-Ni) irradiated in the mixed-neutron spectrum of the SM-2 reactor in the temperature range 400-800°C (every 100°C) to 16 dpa dose with 1000 and 3000 appm helium generation correspondingly, determined by nickel content. EP-838 exhibited less susceptibility to void swelling and radiation hardening. Fe-12Cr-20Mn-W-0.1C steel without nickel irradiated at 100°C to 21 dpa exhibited significant radiation hardening accompanied by α-phase formation in the steel structure.

  14. Origin of concretionary Mn-Fe-oxides in stream sediments of Maine, U.S.A.

    USGS Publications Warehouse

    Nowlan, G.A.; McHugh, J.B.; Hessin, T.D.

    1983-01-01

    Studies of stream and sediment-pore waters largely explain the genesis of concretionary Mn-Fe-oxides in Maine. Waters of two small streams near Jackman, Maine, were studied in terms of pH, Eh, dissolved oxygen, dissolved organic carbon, dissolved Mn, total dissolved Fe, and ferrous and ferric Fe. Pyrite Creek has profuse concretions and coatings of Mn-Fe-oxides, whereas West Pyrite Creek has only sparse Mn-Fe-oxide stains. Pyrite Creek drains boggy terrain and West Pyrite Creek drains well-drained terrain. In West Pyrite Creek, stream and subjacent pore waters have chemical characteristics that do not differ greatly. However, dissolved Mn, ferrous Fe, dissolved oxygen, and in situ Eh measurements show that a steep Eh gradient exists between stream and subjacent pore waters of Pyrite Creek. The steep Eh gradient is manifested by the common zonation of coatings and stains on rocks in stream sediment. The bottom zone has no deposition of oxides, the middle zone is red and consists mostly of Fe-oxides, and the upper zone is black or dark-brown and consists of Mn-oxides with varying amounts of Fe-oxides. The zonation agrees with theoretical predictions of oxide stability as one moves from a reducing to an oxidizing environment. At locations where concretionary Mn-Fe-oxides form, pore waters are depleted of oxygen because of abundant decaying organic material in the stream sediment. The pore waters are charged with dissolved Mn and Fe because mechanically deposited Mn-Fe-oxides are remobilized due to the low-Eh conditions. Groundwaters also contribute dissolved Mn and Fe. Stream waters, on the other hand, are oxygenated and the high-Eh conditions result in low concentrations of dissolved Mn and Fe in stream waters because of the insolubility of Mn-Fe-oxides in high-Eh environments. Therefore, concretionary Mn-Fe-oxides form at the interface between pore and stream waters because Mn- and Fe-rich pore waters, which are undersaturated with respect to Mn-Fe-oxides, mix with

  15. Unique coordination of pyrazine in T[Ni(CN){sub 4}].2pyz with T=Mn, Zn, Cd

    SciTech Connect

    Lemus-Santana, A.A.; Rodriguez-Hernandez, J.; Castillo, L.F. del; Basterrechea, M.; Reguera, E.

    2009-04-15

    The materials under study, T[Ni(CN){sub 4}].2pyz with T=Mn, Zn, Cd, were prepared by separation of T[Ni(CN){sub 4}] layers in citrate aqueous solution to allow the intercalation of the pyrazine molecules. The obtained solids were characterized from chemical analyses, X-ray diffraction, infrared, Raman, thermogravimetry, UV-Vis, magnetic and adsorption data. Their crystal structure was solved from ab initio using direct methods and then refined by the Rietveld method. A unique coordination for pyrazine to metal centers at neighboring layers was observed. The pyrazine molecule is found forming a bridge between Ni and T atoms, quite different from the proposed structures for T=Fe, Ni where it remains coordinated to two T atoms to form a vertical pillar between neighboring layers. The coordination of pyrazine to both Ni and T atoms minimizes the material free volume and leads to form a hydrophobic framework. On heating the solids remain stable up to 140 deg. C. No CO{sub 2} and H{sub 2} adsorption was observed in the small free spaces of their frameworks. - Graphical abstract: Framework for T[Ni(CN){sub 4}].2pyz with T=Mn, Zn, Cd.

  16. BiMnFe(2)O(6) a Polysynthetically Twinned hcp MO Structure

    SciTech Connect

    T Yang; A Abakumov; J Hadermann; G Van Tendeloo; I Nowik; P Stephens; J Hemberger; A Tsirlin; K Ramanujachary; et al.

    2011-12-31

    The most efficient use of spatial volume and the lowest potential energies in the metal oxide structures are based on cubic close packing (ccp) or hexagonal close packing (hcp) of anions with cations occupying the interstices. A promising way to tune the composition of close packed oxides and design new compounds is related to fragmenting the parent structure into modules by periodically spaced planar interfaces, such as twin planes at the unit cell scale. The unique crystal chemistry properties of cations with a lone electron pair, such as Bi{sup 3+} or Pb{sup 2+}, when located at interfaces, enables them to act as 'chemical scissors', to help relieve configurational strain. With this approach, we synthesized a new oxide, BiMnFe{sub 2}O{sub 6}, where fragments of the hypothetical hcp oxygen-based MO structure (the NiAs structure type), for the first time, serve as the building modules in a complex transition metal oxide. Mn{sup 3+} and Fe{sup 3+} ions are randomly distributed in two crystallographically independent sites (M1 and M2). The structure consists of quasi two-dimensional blocks of the 2H hexagonal close packed MO structure cut along the (114) crystal plane of the hcp lattice and stacked along the c axis. The blocks are related by a mirror operation that allows BiMnFe{sub 2}O{sub 6} to be considered as a polysynthetically twinned 2H hcp MO structure. The transition to an AFM state with an incommensurate spin configuration at {approx}212 K is established by {sup 57}Fe Moessbauer spectroscopy, magnetic susceptibility, specific heat and low temperature powder neutron diffraction.

  17. BiMnFe2O6 a Polysynthetically Twinned hcp MO Structure

    SciTech Connect

    T Yang; A Abakumov; J Hadermann; G Van Tendeloo; I Nowik; P Stephens; J Hemberger; M Croft; A Ignatov; et al.

    2011-12-31

    The most efficient use of spatial volume and the lowest potential energies in the metal oxide structures are based on cubic close packing (ccp) or hexagonal close packing (hcp) of anions with cations occupying the interstices. A promising way to tune the composition of close packed oxides and design new compounds is related to fragmenting the parent structure into modules by periodically spaced planar interfaces, such as twin planes at the unit cell scale. The unique crystal chemistry properties of cations with a lone electron pair, such as Bi{sup 3+} or Pb{sup 2+}, when located at interfaces, enables them to act as 'chemical scissors', to help relieve configurational strain. With this approach, we synthesized a new oxide, BiMnFe{sub 2}O{sub 6}, where fragments of the hypothetical hcp oxygen-based MO structure (the NiAs structure type), for the first time, serve as the building modules in a complex transition metal oxide. Mn{sup 3+} and Fe{sup 3+} ions are randomly distributed in two crystallographically independent sites (M1 and M2). The structure consists of quasi two-dimensional blocks of the 2H hexagonal close packed MO structure cut along the (114) crystal plane of the hcp lattice and stacked along the c axis. The blocks are related by a mirror operation that allows BiMnFe{sub 2}O{sub 6} to be considered as a polysynthetically twinned 2H hcp MO structure. The transition to an AFM state with an incommensurate spin configuration at {approx}212 K is established by {sup 57}Fe Moessbauer spectroscopy, magnetic susceptibility, specific heat and low temperature powder neutron diffraction.

  18. Close correlation between magnetic properties and the soft phonon mode of the structural transition in BaFe>2mn>As>2mn> and SrFe>2mn>As>2mn>

    SciTech Connect

    Parshall, D.; Pintschovius, L.; Niedziela, Jennifer L.; Castellan, J. -P.; Lamago, D.; Mittal, R.; Wolf, Th.; Reznik, Dmitry

    2015-04-27

    Parent compounds of Fe-based superconductors undergo a structural phase transition from a tetragonal to an orthorhombic structure. We investigated the temperature dependence of the frequencies of TA phonons that extrapolate to the shear vibrational mode at the zone center, which corresponds to the orthorhombic deformation of the crystal structure at low temperatures in BaFe>2mn>As>2mn> and SrFe>2mn>As>2mn>. We found that acoustic phonons at small wave vectors soften gradually towards the transition from high temperatures, tracking the increase of the size of slowly fluctuating magnetic domains. On cooling below the transition to base temperature the phonons harden, following the square of the magnetic moment (which we find is proportional to the anisotropy gap). Finally, our results provide evidence for close correlation between magnetic and phonon properties in Fe-based superconductors.

  19. Impact of Mn(II)-Manganese Oxide Reactions on Ni and Zn Speciation.

    PubMed

    Hinkle, Margaret A G; Dye, Katherine G; Catalano, Jeffrey G

    2017-03-01

    Layered Mn oxide minerals (phyllomanganates) often control trace metal fate in natural systems. The strong uptake of metals such as Ni and Zn by phyllomanganates results from adsorption on or incorporation into vacancy sites. Mn(II) also binds to vacancies and subsequent comproportionation with structural Mn(IV) may alter sheet structures by forming larger and distorted Mn(III)O6 octahedra. Such Mn(II)-phyllomanganate reactions may thus alter metal uptake by blocking key reactive sites. Here we investigate the effect of Mn(II) on Ni and Zn binding to phyllomanganates of varying initial vacancy content (δ-MnO2, hexagonal birnessite, and triclinic birnessite) at pH 4 and 7 under anaerobic conditions. Dissolved Mn(II) decreases macroscopic Ni and Zn uptake at pH 4 but not pH 7. Extended X-ray absorption fine structure spectroscopy demonstrates that decreased uptake at pH 4 corresponds with altered Ni and Zn adsorption mechanisms. These metals transition from binding in the interlayer to sheet edges, with Zn increasing its tetrahedrally coordinated fraction. These effects on metal uptake and binding correlate with Mn(II)-induced structural changes, which are more substantial at pH 4 than 7. Through these structural effects and the pH-dependence of Mn(II)-metal competitive adsorption, system pH largely controls metal binding to phyllomanganates in the presence of dissolved Mn(II).

  20. Magnetic domains in Ni Mn Ga martensitic thin films

    NASA Astrophysics Data System (ADS)

    Chernenko, V. A.; Lopez Anton, R.; Kohl, M.; Ohtsuka, M.; Orue, I.; Barandiaran, J. M.

    2005-08-01

    A series of martensitic Ni52Mn24Ga24 thin films deposited on alumina ceramic substrates has been prepared by using RF (radio-frequency) magnetron sputtering. The film thickness, d, varies from 0.1 to 5.0 µm. Magnetic domain patterns have been imaged by the MFM (magnetic force microscopy) technique. A maze domain structure is found for all studied films. MFM shows a large out-of-plane magnetization component and a rather uniform domain width for each film thickness. The domain width, δ, depends on the film thickness as \\delta \\sim \\sqrt {d} in the whole studied range of film thickness. This dependence is the expected one for magnetic anisotropy and magnetostatic contributions in a perpendicular magnetic domain configuration. The proportionality coefficient is also consistent with the values of saturation magnetization and magnetic anisotropy determined in the samples.

  1. Structural and DC resistivity behaviour of Li-Mn-Ni ferrites substituted with trace amount of Co 2+

    NASA Astrophysics Data System (ADS)

    Maisnam, Mamata; Phanjoubam, Sumitra; Sarma, H. N. K.; Prakash, Chandra; Radhapiyari Devi, L.; Thakur, O. P.

    2005-12-01

    This paper reports the influence of Co 2+ substitution on the structural parameters and DC resistivity of Li-Mn-Ni ferrites. Samples having the compositional formula Li 0.45-x/2Ni 0.1Mn 0.1Co xFe 2.35-x/2O 4, with x ranging from 0 to 0.01 in steps of 0.002, were prepared by the conventional ceramic technique. X-ray diffraction has confirmed the single-phase spinel structure of the samples. The lattice parameter and theoretical density of the samples were determined and the latter compared with the experimental density measured by Archimedes Principle. Porosity was found to decrease with substitution. The temperature dependence of DC resistivity shows the semiconducting nature. The resistivity and activation energies increase with the increase of substitution level.

  2. Determination of the deformation mechanism of Fe-Mn alloys

    NASA Astrophysics Data System (ADS)

    Jo, Minho; Koo, Yang Mo; Kwon, Se Kyun

    2015-03-01

    The energy parameters of planar defects are decisive for understanding the deformation mechanisms of metals. The stacking fault energy has been regarded as a key parameter to determine the activation of the deformation mechanisms of the face-centered cubic metals and alloys. However, it is still under a long debate why the stacking fault energy can be treated to be such an exclusive parameter among the general planar fault energies. We have employed molecular dynamics method to examine the effects of Mn alloying on the deformation behavior of austenitic Fe-Mn systems. The energies of stable and unstable states are calculated by sliding the (111) plane and are analyzed in two different schemes, stacking fault energy and energy barriers, which leads to a contradiction between them. We show that a linear relationship can be identified among the energy barriers. This finding is used to identify the activated deformation mechanism. A new parameter is also suggested to characterize the material deformation.

  3. Magnetic properties and thermal stability of MnBi/NdFeB hybrid bonded magnets

    NASA Astrophysics Data System (ADS)

    Cao, S.; Yue, M.; Yang, Y. X.; Zhang, D. T.; Liu, W. Q.; Zhang, J. X.; Guo, Z. H.; Li, W.

    2011-04-01

    Magnetic properties and thermal stability were investigated for the MnBi/NdFeB (MnBi = 0, 20, 40, 60, 80, and 100 wt.%) bonded hybrid magnets prepared by spark plasma sintering (SPS) technique. Effect of MnBi content on the magnetic properties of the hybrid magnets was studied. With increasing MnBi content, the coercivity of the MnBi/NdFeB hybrid magnets increases rapidly, while the remanence and maximum energy product drops simultaneously. Thermal stability measurement on MnBi magnet, NdFeB magnet, and the hybrid magnet with 20 wt.% MnBi indicates that both the NdFeB magnet and the MnBi/NdFeB hybrid magnet have a negative temperature coefficient of coercivity, while the MnBi magnet has a positive one. The (BH)max of the MnBi/NdFeB magnet (MnBi = 20 wt.%) is 5.71 MGOe at 423 K, which is much higher than 3.67 MGOe of the NdFeB magnet, indicating a remarkable improvement of thermal stability.

  4. Critical Evaluations and Thermodynamic Optimizations of the MnO-Mn2 O3 -SiO2 and FeO-Fe2 O3 -MnO-Mn2 O3 -SiO2 Systems

    NASA Astrophysics Data System (ADS)

    Kang, Youn-Bae; Jung, In-Ho

    2017-03-01

    A critical evaluation and thermodynamic modeling for thermodynamic properties of all oxide phases and phase diagrams in the Fe-Mn-Si-O system (MnO-Mn2 O3 -SiO2 and FeO-Fe2 O3 -MnO-Mn2 O3 -SiO2 systems) are presented. Optimized Gibbs energy parameters for the thermodynamic models of the oxide phases were obtained which reproduce all available and reliable experimental data within error limits from 298 K (25°C) to above the liquidus temperatures at all compositions covering from known oxide phases, and oxygen partial pressure from metal saturation to 0.21 bar. The optimized thermodynamic properties and phase diagrams are believed to be the best estimates presently available. Slag (molten oxide) was modeled using the modified quasichemical model in the pair approximation. Olivine (Fe2 SiO4 -Mn2 SiO4 ) was modeled using two-sublattice model in the framework of the compound energy formalism (CEF), while rhodonite (MnSiO3 -FeSiO3 ) and braunite (Mn7 SiO_{12} with excess Mn2 O3 ) were modeled as simple Henrian solutions. It is shown that the already developed models and databases of two spinel phases (cubic- and tetragonal-(Fe, Mn)3 O4 ) using CEF [Kang and Jung, J. Phys. Chem. Solids (2016), vol. 98, pp. 237-246] can successfully be integrated into a larger thermodynamic database to be used in practically important higher order system such as silicate. The database of the model parameters can be used along with a software for Gibbs energy minimization in order to calculate any type of phase diagram section and thermodynamic properties.

  5. Nickel recovery from electronic waste II electrodeposition of Ni and Ni-Fe alloys from diluted sulfate solutions.

    PubMed

    Robotin, B; Ispas, A; Coman, V; Bund, A; Ilea, P

    2013-11-01

    This study focuses on the electrodeposition of Ni and Ni-Fe alloys from synthetic solutions similar to those obtained by the dissolution of electron gun (an electrical component of cathode ray tubes) waste. The influence of various parameters (pH, electrolyte composition, Ni(2+)/Fe(2+) ratio, current density) on the electrodeposition process was investigated. Scanning electron microscopy (SEM) and X-ray fluorescence analysis (XRFA) were used to provide information about the obtained deposits' thickness, morphology, and elemental composition. By controlling the experimental parameters, the composition of the Ni-Fe alloys can be tailored towards specific applications. Complementarily, the differences in the nucleation mechanisms for Ni, Fe and Ni-Fe deposition from sulfate solutions have been evaluated and discussed using cyclic voltammetry and potential step chronoamperometry. The obtained results suggest a progressive nucleation mechanism for Ni, while for Fe and Ni-Fe, the obtained data points are best fitted to an instantaneous nucleation model.

  6. Mechanical characteristics and swelling of austenitic Fe-Cr-Mn steels irradiated in the SM-2 and BOR-60 reactors

    NASA Astrophysics Data System (ADS)

    Shamardin, V. K.; Bulanova, T. M.; Neustroev, V. S.; Ivanov, L. I.; Djomina, E. V.; Platov, Yu. M.

    1991-03-01

    Three types of austenitic Fe-Cr-Mn stainless steels were irradiated simultaneously with Fe-Cr-Ni austenitic steel at temperatures from 400 to 800°C in the mixed spectrum of the high flux SM-2 reactor to 10 dpa and 700 appm of He and in the BOR-60 reactor to 60 dpa without He generation. The paper presents the swelling and mechanical properties of steels irradiated in the BOR-60 and SM-2 as a function of the concentration of transmuted He and the value of atomic displacement.

  7. Crystal Structures at Atomic Resolution of the Perovskite-Related GdBaMnFeO5 and Its Oxidized GdBaMnFeO6.

    PubMed

    García-Martín, Susana; Manabe, Keisuke; Urones-Garrote, Esteban; Ávila-Brande, David; Ichikawa, Noriya; Shimakawa, Yuichi

    2017-02-06

    Perovskite-related GdBaMnFeO5 and the corresponding oxidized phase GdBaMnFeO6, with long-range layered-type ordering of the Ba and Gd atoms have been synthesized. Oxidation retains the cation ordering but drives a modulation of the crystal structure associated with the incorporation of the oxygen atoms between the Gd layers. Oxidation of GdBaMnFeO5 increases the oxidation state of Mn from 2+ to 4+, while the oxidation state of Fe remains 3+. Determination of the crystal structure of both GdBaMnFeO5 and GdBaMnFeO6 is carried out at atomic resolution by means of a combination of advanced transmission electron microscopy techniques. Crystal structure refinements from synchrotron X-ray diffraction data support the structural models proposed from the TEM data. The oxidation states of the Mn and Fe atoms are evaluated by means of EELS and Mössbauer spectroscopy, which also reveals the different magnetic behavior of these oxides.

  8. Effect of Fe substitution on the structure and magnetocaloric effect of Mn5-xFexGeSi2 alloys

    NASA Astrophysics Data System (ADS)

    Sun, Y. W.; Yan, J. L.; Feng, E. L.; Tang, G. W.; Zhou, K. W.

    2017-01-01

    The structure and magnetocaloric effect of Mn5-xFexGeSi2 compounds were studied. Analysis of X-ray powder diffraction and energy dispersive X-Ray spectroscopy revealed that Mn5-xFexGeSi2 alloys with x<1 crystallize in the Mn5Si3-type structure (space group P63/mcm), maintaining the structure of Mn5Ge3; and alloys with x=1.5 and 2 consist of the major Mn5Si3-type phase and the minor Ni2In-type phase (space group P63/mmc). The results of Rietveld refinement showed that the cell parameters for the Mn5Si3-type phase decrease with increasing Fe content. The positive slopes in Arrott plots indicate that a second-order ferromagnetic to paramagnetic transition occurs. The Curie temperature increases with increasing Fe content from 182 K for x=0.6 to 224 K for x=2. The maximum magnetic entropy change of 3.7 J/(kg K) for x=0.8 was found under a magnetic field change of 0-20 kOe.

  9. Magnetic epoxy nanocomposites with superparamagnetic MnFe2O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Huang, Jiangnan; Cao, Yonghai; Zhang, Xi; Li, Yutong; Guo, Jiang; Wei, Suying; Peng, Xiangfang; Shen, Tong D.; Guo, Zhanhu

    2015-09-01

    Manganese iron oxide (MnFe2O4) nanoparticles successfully served as nanofillers for obtaining magnetic epoxy nanocomposites. The viscosities of MnFe2O4/epoxy resin liquid suspensions increased with increasing the nanoparticles loading except the suspension with 5.0 and 1.0 wt% loading, whose viscosities were lower than that of pure epoxy. The introduction of MnFe2O4 nanoparticles showed a lower onset decomposition temperature and glass transition temperature (Tg), which decreased with increasing the nanoparticles loading. The storage modulus and tensile strength of 1.0 wt% MnFe2O4/epoxy were a little higher than that of pure epoxy. The coercivity of MnFe2O4/epoxy nanocomposites with 5.0 wt% (44.7 Oe) and 10.0 wt% (43.9 Oe) displayed much higher than that of pure MnFe2O4 nanoparticles (14.94 Oe). The magnetic moment (m) of nanocomposites (1.354 μB for 10 wt% MnFe2O4/epoxy) are higher than that of pure MnFe2O4 nanoparticles (1.244 μB). The increased real permittivity observed in the nanocomposites was attributed to the interfacial polarization. The intrinsic permittivity of the MnFe2O4 nanoparticles was also calculated.

  10. The design of an Fe-12Mn-O.2Ti alloy steel for low temperature use

    NASA Technical Reports Server (NTRS)

    Hwang, S. K.; Morris, J. W., Jr.

    1977-01-01

    An investigation was made to improve the low temperature mechanical properties of Fe-8 approximately 12% Mn-O 2Ti alloy steels. A two-phase(alpha + gamma) tempering in combination with cold working or hot working was identified as an effective treatment. A potential application as a Ni-free cryogenic steel was shown for this alloy. It was also shown that an Fe-8Mn steel could be grain-refined by a purely thermal treatment because of its dislocated martensitic structure and absence of epsilon phase. A significant reduction of the ductile-brittle transition temperature was obtained in this alloy. The nature and origin of brittle fracture in Fe-Mn alloys were also investigated. Two embrittling regions were found in a cooling curve of an Fe-12Mn-O 2Ti steel which was shown to be responsible for intergranular fracture. Auger electron spectroscopy identified no segregation during solution-annealing treatment. Avoiding the embrittling zones by controlled cooling led to a high cryogenic toughness in a solution-annealed condition.

  11. Structural analysis of ferromagnetic Ni-Mn-Sn thin films fabricated by co-sputter deposition

    NASA Astrophysics Data System (ADS)

    Guvenc, Sema; Yumak, Mehmet; Nedelcos, A. Quintana; Llamazares, J. L. Sanchez; Garcia, Carlos Garcia

    2015-03-01

    Ferromagnetic Ni-Mn-X (Sn, In) alloys are predicted as potential candidates for energy efficient Magnetocaloric Effect (MCE) technologies. The MCE is the basis of magnetic refrigeration and it leads to a groundbreaking progress on conventional refrigeration methods. In our research, Ni-Mn-Sn thin films were fabricated by co-sputter deposition method. The Mn losses due to the high Mn vapor pressure produce a deviation from the desired Ni50Mn37Sn13 composition, which are partially compensated by increasing power of the Mn target gun. A systematic study of thin film co-sputter fabrication was divided into three stages; i) a Ni-Mn-Sn target was evaporated at different temperatures in order to study the grain size temperature dependence, ii) the nominal chemical composition (Ni50Mn37Sn13) was reached by controlling the power value applied to the Mn target, iii) the dependence of the phase transformation temperature with the grain size of the thin film alloys was studied. Grain size can be controlled by modifying the substrate temperature (Ts) .

  12. Magnetocaloric effect with low magnetic hysteresis loss in ferromagnetic Ni-Mn-Sb-Si alloys

    NASA Astrophysics Data System (ADS)

    Zhang, Ruochen; Qian, Mingfang; Zhang, Xuexi; Qin, Faxiang; Wei, Longsha; Xing, Dawei; Cui, Xiping; Sun, Jianfei; Geng, Lin; Peng, Huaxin

    2017-04-01

    Giant magnetocaloric effect in Ni-Mn-X (X=In, Sn, Sb) Heusler alloys has been revealed due to the significant shift of the martensite transformation temperatures under a bias magnetic field. However, the magnetic hysteresis during the magnetization and demagnetization cycles creates a large hysteresis loss and reduces the refrigeration capacity. Here we demonstrated that the magnetic hysteresis loss in Ni-Mn-Sb alloys was effectively reduced by Si-doping. The quaternary Ni49.0Mn38.4Sb11.7Si0.9 alloy exhibited martensite and magnetic transitions around room temperature. Maximum magnetic entropy change ΔSm 9.4 J/kg K and working temperature interval 7.0 K were achieved attributed to the martensite transformation under a magnetic field of 5 T. Meanwhile, the average magnetic hysteresis loss for Ni49.0Mn38.4Sb11.7Si0.9 alloy was 2.1 J/kg, much smaller than that for Ni49.0Mn38.5Sb12.5 alloy, 11.4 J/kg. As a result, a refrigeration capacity of 50.2 J/kg was obtained in the Ni49.0Mn38.4Sb11.7Si0.9 alloy. This result shows that Si-doped Ni-Mn-Sb alloys may act as a potential material system for magnetic refrigeration.

  13. Magnetization reversal of uncompensated Fe moments in exchangebiased Ni/FeF2 bilayers

    SciTech Connect

    Arenholz, Elke; Liu, Kai; Li, Zhipan; Schuller, Ivan K.

    2006-01-01

    The magnetization reversal of uncompensated Fe moments in exchange biased Ni/FeF{sub 2} bilayers was determined using soft x-ray magnetic circular and linear dichroism. The hysteresis loops resulting from the Fe moments are almost identical to those of the ferromagnetic Ni layer. However, a vertical loop shift indicates that some Fe moments are pinned in the antiferromagnetically ordered FeF{sub 2}. The pinned moments are oriented antiparallel to small cooling fields leading to negative exchange bias, but parallel to large cooling fields resulting in positive exchange bias. No indication for the formation of a parallel antiferromagnetic domain wall in the FeF{sub 2} layer upon magnetization reversal in the Ni layer was found.

  14. Fermi surfaces and phase stability of Ba( Fe>1mn>-xMx)<mn>2mn> As<mn>2mn> ( M=Co,Ni,Cu,Zn )

    SciTech Connect

    Khan, S. N.; Alam, Aftab; Johnson, Duane D.

    2014-05-01

    BaFe2As2 with transition-metal doping exhibits a variety of rich phenomena from the coupling of structure, magnetism, and superconductivity. Using density functional theory, we systematically compare the Fermi surfaces (FSs), formation energies (ΔEf), and densities of states (DOSs) of electron-doped Ba(Fe1-xMx)2As2 with M={Co,Ni,Cu,Zn} in tetragonal (I4/mmm) and orthorhombic (Fmmm) structures in nonmagnetic, antiferromagnetic, and paramagnetic (disordered local moment) states. We explain changes to the phase stability (ΔEf) and Fermi surfaces (and nesting) due to chemical and magnetic disorder. We compare our results to observed/assessed properties and contrast alloy theory with the results expected from the rigid-band model. Finally, with alloying, the DOS changes from common band (Co,Ni) to split band (Cu,Zn), which dictates ΔEf and can overwhelm FS-nesting instabilities, as for the Cu and Zn cases.

  15. Effects of Mn doping on temperature-dependent magnetic properties of L10 FeMnPt

    NASA Astrophysics Data System (ADS)

    Xu, D. B.; Chen, J. S.; Zhou, T. J.; Chow, G. M.

    2011-04-01

    We report the effect of Mn doping on temperature-dependent magnetic properties of L10 FeMnPt (001) epitaxial films. (001) textured L10 Fe50-xMnxPt50 (x = 0, 5, 10, 15, 20 at. %) films were prepared by cosputtering Fe, Pt, and Mn onto MgO single crystal substrates at 550 °C. θ-2θ XRD scans indicated the lattice parameter c increased whereas the ordering parameter S decreased with Mn doping. The thermal magnetic properties measured using a superconducting quantum interference device showed that Curie temperature TC could be reduced to 500 K with 15 at. % Mn doping, but Ku was decreased to 1.6 × 107 erg/cm3. The relation of temperature-dependent anisotropy and saturation magnetization showed that it did not obey the Callen-Callen theory.

  16. NiMnGa/Si Shape Memory Bimorph Nanoactuation

    NASA Astrophysics Data System (ADS)

    Lambrecht, Franziska; Lay, Christian; Aseguinolaza, Iván R.; Chernenko, Volodymyr; Kohl, Manfred

    2016-12-01

    The size dependences of thermal bimorph and shape memory effect of nanoscale shape memory alloy (SMA)/Si bimorph actuators are investigated in situ in a scanning electron microscope and by finite element simulations. By combining silicon nanomachining and magnetron sputtering, freestanding NiMnGa/Si bimorph cantilever structures with film/substrate thickness of 200/250 nm and decreasing lateral dimensions are fabricated. Electrical resistance and mechanical beam bending tests upon direct Joule heating demonstrate martensitic phase transformation and reversible thermal bimorph effect, respectively. Corresponding characteristics are strongly affected by the large temperature gradient in the order of 50 K/µm forming along the nano bimorph cantilever upon electro-thermal actuation, which, in addition, depends on the size-dependent heat conductivity in the Si nano layer. Furthermore, the martensitic transformation temperatures show a size-dependent decrease by about 40 K for decreasing lateral dimensions down to 200 nm. The effects of heating temperature and stress distribution on the nanoactuation performance are analyzed by finite element simulations revealing thickness ratio of SMA/Si of 90/250 nm to achieve an optimum SME. Differential thermal expansion and thermo-elastic effects are discriminated by comparative measurements and simulations on Ni/Si bimorph reference actuators.

  17. Controllable synthesis and enhanced microwave absorbing properties of Fe3O4/NiFe2O4/Ni heterostructure porous rods

    NASA Astrophysics Data System (ADS)

    Li, Yana; Wu, Tong; Jin, Keying; Qian, Yao; Qian, Naxin; Jiang, Kedan; Wu, Wenhua; Tong, Guoxiu

    2016-11-01

    We developed a coordinated self-assembly/precipitate transfer/sintering method that allows the controllable synthesis of Fe3O4/NiFe2O4/Ni heterostructure porous rods (HPRs). A series of characterizations confirms that changing [Ni2+] can effectively control the crystal size, internal strain, composition, textural characteristics, and properties of HPRs. Molar percentages of Ni and NiFe2O4 in HPRs increase with [Ni2+] in various Boltzmann function modes. Saturation magnetization Ms and coercivity Hc show U-shaped change trends because of crystal size, composition, and interface magnetic coupling. High magnetic loss is maintained after decorating NiFe2O4 and Ni on the surface of Fe3O4 PRs. Controlling the NiFe2O4 interface layers and Ni content can improve impedance matching and dielectric losses, thereby leading to lighter weight, stronger absorption, and broader absorption band of Fe3O4/NiFe2O4/Ni HPRs than Fe3O4 PRs. An optimum EM wave absorbing property was exhibited by Fe3O4/NiFe2O4/Ni HPRs formed at [Ni2+] = 0.05 M. The maximum reflection loss (RL) reaches -58.4 dB at 13.68 GHz, which corresponds to a 2.1 mm matching thickness. The absorbing bandwidth (RL ≤ -20 dB) reaches 14.4 GHz with the sample thickness at 1.6-2.4 and 2.8-10.0 mm. These excellent properties verify that Fe3O4/NiFe2O4/Ni HPRs are promising candidates for new and effective absorptive materials.

  18. Synthesis and characterization of perovskite-type Sr{sub x}Y{sub 1−x}FeO{sub 3−δ} (0.63≤x<1.0) and Sr{sub 0.75}Y{sub 0.25}Fe{sub 1−y}M{sub y}O{sub 3−δ} (M=Cr, Mn, Ni), (y=0.2, 0.33, 0.5)

    SciTech Connect

    Biendicho, J.J.; Shafeie, S.; Frenck, L.; Gavrilova, D.; Böhme, S.; Bettanini, A.M.; Svedlindh, P.; Hull, S.; Zhao, Z.; Istomin, S.Ya.; Grins, J.; Svensson, G.

    2013-04-15

    Oxygen-deficient ferrates with the cubic perovskite structure Sr{sub x}Y{sub 1−x}FeO{sub 3−δ} were prepared in air (0.71≤x≤0.91) as well as in N{sub 2} (x=0.75 and 0.79) at 1573 K. The oxygen content of the compounds prepared in air increases with increasing strontium content from 3−δ=2.79(2) for x=0.75 to 3−δ=2.83(2) for x=0.91. Refinement of the crystal structure of Sr{sub 0.75}Y{sub 0.25}FeO{sub 2.79} using TOF neutron powder diffraction (NPD) data shows high anisotropic atomic displacement parameter (ADP) for the oxygen atom resulting from a substantial cation and anion disorder. Electron diffraction (ED) and high-resolution electron microscopy (HREM) studies of Sr{sub 0.75}Y{sub 0.25}FeO{sub 2.79} reveal a modulation along 〈1 0 0〉{sub p} with G± ∼0.4〈1 0 0〉{sub p} indicating a local ordering of oxygen vacancies. Magnetic susceptibility measurements at 5–390 K show spin-glass behaviour with dominating antiferromagnetic coupling between the magnetic moments of Fe cations. Among the studied compositions, Sr{sub 0.75}Y{sub 0.25}FeO{sub 2.79} shows the lowest thermal expansion coefficient (TEC) of 10.5 ppm/K in air at 298–673 K. At 773–1173 K TEC increases up to 17.2 ppm/K due to substantial reduction of oxygen content. The latter also results in a dramatic decrease of the electrical conductivity in air above 673 K. Partial substitution of Fe by Cr, Mn and Ni according to the formula Sr{sub 0.75}Y{sub 0.25}Fe{sub 1−y}M{sub y}O{sub 3−δ} (y=0.2, 0.33, 0.5) leads to cubic perovskites for all substituents with y=0.2. Their TECs are higher in comparison with un-doped Sr{sub 0.75}Y{sub 0.25}FeO{sub 2.79}. Only M=Ni has increased electrical conductivity compared to un-doped Sr{sub 0.75}Y{sub 0.25}FeO{sub 2.79}. - Graphical abstract: Oxygen-deficient ferrates with the cubic perovskite structure Sr{sub x}Y{sub 1−x}FeO{sub 3−δ} were prepared both in air (0.71≤x≤0.91) and N{sub 2} (x=0.75 and 0.79) at 1573 K. Refinement of the

  19. Reduction of nitrate by NaY zeolite supported Fe, Cu/Fe and Mn/Fe nanoparticles.

    PubMed

    Zeng, Yubin; Walker, Harold; Zhu, Qingzhi

    2017-02-15

    Nano particles Fe, Cu/Fe and Mn/Fe supported on NaY zeolite (F@Y, CF@Y, and MF@Y) were prepared by two-step processes consisting of ion exchange and liquid-phase reduction. The characterization by XRD, SEM-EDX and BET-N2 adsorption demonstrated that Fe, Cu/Fe and Mn/Fe nano particles were successfully loaded onto NaY zeolite and exhibited larger BET surface area compared to nano-Fe(0) (nZVI). Laboratory experiments showed that nitrate removal by metals@Y in unbuffered conditions reached nearly 100% at a dosage of 4g/L after 6h of reaction. Moreover, the nitrate removal was not sensitive to the initial solution pH. Even at a high pH of 9.0, metals@Y exhibited nitrate reduction above 94%. CF@Y demonstrated high N2 selectivity, due to the high content of Cu (20wt%) and Fe (41wt%) in CF@Y and the highly active metallic sites on its surface with positive charge. Kinetic data showed a good fit to a first-order kinetic model during early reaction times. A close fit to both a second-order and an nth-order kinetic model was shown for the whole of the reaction period. The data suggest that both liquid phase mass transfer and the intrinsic reaction rate control the process of nitrate reduction by metals@Y.

  20. Complexes of MN2S2·Fe(η(5)-C5R5)(CO) as platform for exploring cooperative heterobimetallic effects in HER electrocatalysis.

    PubMed

    Ghosh, Pokhraj; Quiroz, Manuel; Wang, Ning; Bhuvanesh, Nattamai; Darensbourg, Marcetta Y

    2017-02-08

    The control of aggregation at sulfur by metallodithiolates (MN2S2) has made them prime candidates as building blocks for the synthesis of biomimetics of various bimetallic enzyme active sites, with reactivity consequences implicating redox control by both metal centers. Recent studies of MN2S2 (M = Ni(2+), Fe(NO)(2+)) bound to [(η(5)-C5H5)Fe(CO)](+) as electrocatalysts for proton reduction, the hydrogen evolution reaction, demonstrated reduction-induced hemi-lability of the bridging cis-dithiolates as a key step in the electrochemical proton reduction process (Ding, et al., J. Am. Chem. Soc., 2016, 138, 12920-12927). The MN2S2·Fe(η(5)-C5R5)(CO) platform offers numerous possibilities for tuning the electronic character of the M(μ-S2)Fe core. As well as modifying M within the metallodithiolate ligand, replacing H by CH3 at the η(5)-C5R5 moiety increases the electron density at the Fe center, which might facilitate the reductive Fe-S bond cleavage. Although release of a free thiolate in these hemi-labile ligands creates a needed internal pendant base, this benefit might be countered by the increase in over-potential for addition of the first electron. Herein we report the preparation and characterization of four bimetallic aggregates with the (η(5)-C5R5)Fe(CO) (R = H, CH3; Fe' or Fe*', respectively) or the dicarbonyl (η(5)-C5R5)Fe(CO)2 scaffold (R = H, CH3; Fe'' or Fe*'', respectively) bound to redox active MN2S2 ligands (M = Ni(2+), Co(NO)(2+); N2S2 = bismercaptoethane diazacycloheptane) Co-Fe*', Ni-Fe*', Co-Fe' and Co-Fe*'' complexes. The bidentate complexes were found to be electrocatalysts for proton reduction, although at high over-potential, especially for the derivatives of the electron-rich (η(5)-C5(CH3)5)Fe(CO)(+). The turnover (TON) and turnover frequencies (TOF) were determined and found to be comparable to the previously reported MN2S2·Fe(η(5)-C5H5)(CO)(+) analogues.

  1. Increasing magnetoplasticity in polycrystalline Ni-Mn-Ga by reducing internal constraints through porosity.

    PubMed

    Boonyongmaneerat, Yuttanant; Chmielus, Markus; Dunand, David C; Müllner, Peter

    2007-12-14

    Foams with 55% and 76% open porosity were produced from a Ni-Mn-Ga magnetic shape-memory alloy by replication casting. These polycrystalline martensitic foams display a fully reversible magnetic-field-induced strain of up to 0.115% without bias stress, which is about 50 times larger than nonporous, fine-grained Ni-Mn-Ga. This very large improvement is attributed to the bamboolike structure of grains in the foam struts which, due to reduced internal constraints, deform by magnetic-field-induced twinning more easily than equiaxed grains in nonporous Ni-Mn-Ga.

  2. Increasing Magnetoplasticity in Polycrystalline Ni-Mn-Ga by Reducing Internal Constraints through Porosity

    NASA Astrophysics Data System (ADS)

    Boonyongmaneerat, Yuttanant; Chmielus, Markus; Dunand, David C.; Müllner, Peter

    2007-12-01

    Foams with 55% and 76% open porosity were produced from a Ni-Mn-Ga magnetic shape-memory alloy by replication casting. These polycrystalline martensitic foams display a fully reversible magnetic-field-induced strain of up to 0.115% without bias stress, which is about 50 times larger than nonporous, fine-grained Ni-Mn-Ga. This very large improvement is attributed to the bamboolike structure of grains in the foam struts which, due to reduced internal constraints, deform by magnetic-field-induced twinning more easily than equiaxed grains in nonporous Ni-Mn-Ga.

  3. Structural and magnetic properties of Ni/Mn codoped ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Vijayaprasath, G.; Murugan, R.; Asaithambi, S.; Sakthivel, P.; Mahalingam, T.; Ravi, G.

    2016-05-01

    We report systematic studies of the magnetic properties of Ni and Mn co-doped ZnO nanoparticles prepared by co-precipitation method. Structural characterization reveals that Ni and Mn ions substituted into ZnO lattices without any secondary phases formation. Photoluminescence and Raman spectra shows that the Ni/Mn were doped into the ZnO lattice resulting slight shift in near-band-edge emission. Moreover, the novel Raman peak at 586 cm-1 indicates two kinds of cations via doping that could affect the local polarizability. Magnetic measurements of the nanoparticles exhibits ferromagnetic behavior at room-temperature.

  4. Modulated exchange bias in NiFe/CoO/α-Fe2O3 trilayers and NiFe/CoO bilayers

    NASA Astrophysics Data System (ADS)

    Li, X.; Lin, K.-W.; Yeh, W.-C.; Desautels, R. D.; van Lierop, J.; Pong, Philip W. T.

    2017-02-01

    While the exchange bias in ferromagnetic/antiferromagnetic (FM/AF) bilayer and FM1/AF/FM2 trilayer configurations has been widely investigated, the role of an AF2 layer in FM/AF1/AF2 trilayer configurations is still not well understood. In this work, the magnetic properties of NiFe/CoO, NiFe/α-Fe2O3 bilayers, and NiFe/CoO/α-Fe2O3 trilayer were studied comparatively. The microstructure and chemical composition were characterized. Temperature dependent magnetometry reveals increased irreversibility temperature in NiFe/CoO/α-Fe2O3 trilayer compared with NiFe/CoO bilayer. The magnetic hysteresis loops show that the exchange bias (Hex) and coercivity (Hc) depend strongly on the anisotropy of AF layer (CoO, α-Fe2O3 and CoO/α-Fe2O3). Our work shows that the AF1/AF2 interfacial interactions can be used effectively for tuning the exchange bias in FM/AF1/AF2 trilayers.

  5. Evaporative segregation in 80% Ni-20% Cr and 60% Fe-40% Ni alloys

    NASA Technical Reports Server (NTRS)

    Gupta, K. P.; Mukherjee, J. L.; Li, C. H.

    1974-01-01

    An analytical approach is outlined to calculate the evaporative segregation behavior in metallic alloys. The theoretical predictions are based on a 'normal' evaporation model and have been examined for Fe-Ni and Ni-Cr alloys. A fairly good agreement has been found between the predicted values and the experimental results found in the literature.

  6. Nanocrystalline spinel ferrite (MFe{sub 2}O{sub 4}, M = Ni, Co, Mn, Mg, Zn) powders prepared by a simple aloe vera plant-extracted solution hydrothermal route

    SciTech Connect

    Phumying, Santi; Labuayai, Sarawuth; Swatsitang, Ekaphan; Amornkitbamrung, Vittaya; Maensiri, Santi

    2013-06-01

    Graphical abstract: This figure shows the specific magnetization curves of the as-prepared MFe{sub 2}O{sub 4} (M = Ni, Co, Mn, Mg, Zn) powders obtained from room temperature VSM measurement. These curves are typical for a soft magnetic material and indicate hysteresis ferromagnetism in the field ranges of ±500 Oe, ±1000 Oe, and ±2000 Oe for the CoFe{sub 2}O{sub 4}, MgFe{sub 2}O{sub 4} and MnFe{sub 2}O{sub 4} respectively, whereas the samples of NiFe{sub 2}O{sub 4} and ZnFe{sub 2}O{sub 4} show a superparamagnetic behavior. Highlights: ► Nanocrystalline MFe{sub 2}O{sub 4} powders were synthesized by a novel hydrothermal method. ► Metal acetylacetonates and aloe vera plant-extracted solution are used. ► This biosynthetic route is very simple and provides high-yield oxide nanomaterials. ► XRD and TEM results indicate that the prepared samples have only spinel structure. ► The maximum M{sub s} of 68.9 emu/g at 10 kOe were observed for the samples of MnFe{sub 2}O{sub 4}. - Abstract: Nanocrystalline spinel ferrite MFe{sub 2}O{sub 4} (M = Ni, Co, Mn, Mg, Zn) powders were synthesized by a novel hydrothermal method using Fe(acac){sub 3}, M(acac){sub 3} (M = Ni, Co, Mn, Mg, Zn) and aloe vera plant extracted solution. The X-ray diffraction and selected-area electron diffraction results indicate that the synthesized nanocrystalline have only spinel structure without the presence of other phase impurities. The crystal structure and morphology of the spinel ferrite powders, as revealed by TEM, show that the NiFe{sub 2}O{sub 4} and CoFe{sub 2}O{sub 4} samples contain nanoparticles, whereas the MnFe{sub 2}O{sub 4} and MgFe{sub 2}O{sub 4} samples consist of many nanoplatelets and nanoparticles. Interestingly, the ZnFe{sub 2}O{sub 4} sample contains plate-like structure of networked nanocrystalline particles. Room temperature magnetization results show a ferromagnetic behavior of the CoFe{sub 2}O{sub 4}, MnFe{sub 2}O{sub 4} and MgFe{sub 2}O{sub 4} samples, whereas the

  7. Temperature dependence of elastic properties of Ni2+xMn1-xGa and Ni2Mn(Ga1-xAlx) from first principles

    NASA Astrophysics Data System (ADS)

    Li, Chun-Mei; Luo, Hu-Bin; Hu, Qing-Miao; Yang, Rui; Johansson, Börje; Vitos, Levente

    2011-11-01

    The temperature dependence of the elastic properties of Ni2+xMn1-xGa and Ni2Mn(Ga1-xAlx) (x=0.0, 0.1, and 0.2) random alloys are investigated by using the first-principles exact muffin-tin orbitals method. At 0 K, the calculated equilibrium parameters in both cubic L21 and nonmodulated tetragonal β'''-Ni2MnGa are in good agreement with the available experimental data and other theoretical results. Separating the thermal effects into single electron excitation, volume expansion, phonon smearing, and magnetic terms, we find that phonon smearing gives the dominating positive tetragonal elastic constant (C') versus temperature (T) slope for the cubic phase. For Ni2+xMn1-xGa, the competition between the negative alloying effect (∂C'/∂x<0) and the positive temperature effect (∂C'/∂T>0) leads to nearly constant C'[x,TM(x)] at the martensitic transition temperature TM(x). For Ni2Mn(Ga1-xAlx), where both ∂C'/∂x and ∂C'/∂T are positive, however, due to the significantly decrease of TM(x), the critical C'[x,TM(x)] slightly decreases with Al doping. Furthermore, it is demonstrated that both the composition and the temperature dependence of C' are indispensable to get a reasonable theoretical TM(x).

  8. Cu-Mn-Fe alloys and Mn-rich amphiboles in ancient copper slags from the Jabal Samran area, Saudi Arabia: With synopsis on chemistry of Fe-Mn(III) oxyhydroxides in alteration zones

    NASA Astrophysics Data System (ADS)

    Surour, Adel A.

    2015-01-01

    In the Jabal Samran area (western Saudi Arabia), secondary copper mineralization in a NE-trending shear zone in which the arc metavolcanic host rocks (dacite-rhyodacite) show conjugate fractures and extensive hydrothermal alteration and bleaching. The zones contain frequent Fe-Mn(III) oxyhydroxides (FeOH-MnOH) that resulted from oxidation of pyrite and Mn-bearing silicates. In the bleached part, the groundmass is represented by Fe-bearing interstratified illite-smectite with up to 4.02 wt% FeOt. FeOH-MnOH are pre-weathering phases formed by hydrothermal alteration in a submarine environment prior to uplifting. Five varieties of FeOH are distinguished, four of them are exclusively hydrothermal with ∼20 wt% H2O whereas the fifth contains ∼31-33 wt% H2O and might represent reworking of earlier hydrothermal FeOH phases by weathering. FeOH fills thin fractures in the form of veinlets and crenulated laminae or as a pseudomorph for pyrite, goethite and finally ferrihydrite, and this oxyhydroxide is characterized by positive correlation of Fe2O3 with SiO2 and Al2O3. On the other hand, MOH shows positive correlation between MnO2 and Al2O3 whereas it is negative between Fe2O3 and SiO2. Paratacamite is the most common secondary copper mineral that fills fractures and post-dates FeOH and MnOH. It is believed that Cl- in the structure of paratacamite represents inherited marine storage rather than from surfacial evaporates or meteoric water. The mineralogy of slags suggests a complicated mineral assemblage that includes native Cu prills, synthetic spinifixed Mn-rich amphiboles with 16.73 wt% MnO, brown glass and Ca-Mn-Fe phase close to the olivine structure. EMPA indicate that the some Cu prills have either grey discontinuous boarder zone of S-rich Mn-Cu alloy (with up to 21.95 wt% S and 19.45 wt% Mn) or grey Cu-Mn-Fe alloy (with up to 15.9 wt% Cu, 39. 12 wt% Mn and 61.64 wt% Fe). Mn in the Cu prills is expelled inward as Cu-Mn-Fe alloy inclusions whereas S is expelled

  9. Natural speciation of Mn, Ni and Zn at a micrometer scale in aclayey paddy soil using X-ray fluorescence, absorption anddiffraction

    SciTech Connect

    Manceau, Alain; Tommaseo, Caterina; Rihs, Sophie; Geoffroy,Nicolas; Chateigner, Daniel; Schlegel, Michel; Tisserand, Delphine; Marcus, Matthew A.; Tamura, Nobumichi; Chen, Zueng-Sang

    2005-08-29

    The natural speciation of Mn (0.19 g/kg), Ni (46 mg/kg), and Zn (42 mg/kg) in the argillic horizon (120 cm depth, pH = 5.6) of an Ultisol from a paddy soil in northern Taiwan was investigated by advanced X-ray synchrotron techniques. Microchemical associations were imaged by synchrotron-based X-ray microfluorescence, host minerals were identified by standard and micrometer-resolved X-ray diffraction, and the local coordination environment of Mn, Ni, and Zn was probed using extended X-ray absorption fine structure (EXAFS) spectroscopy on a powdered sample and a soil thin section, and polarized EXAFS spectroscopy on a highly textured self-supporting clay film from the <2 mu m fraction of the soil. Manganese was concentrated in Fe-Mn soft mottles (44.4 g/kg) as turbostratic hexagonal birnessite and lithiophorite having Mn3+/Mn4+atomic ratios of {approx} 20 percent and 50 percent, respectively. Quantitative analysis of high-order scattering paths of the EXAFS spectrum for natural and synthetic (Al0.67Li0.32)(Mn0.684+Mn0.323+)O2(OH)2 lithiophorite revealed that Mn3+ and Mn4+ are ordered in the[(Mn0.684+Mn0.323+)O2]0.32- layer. A structural model is proposed, in which Mn4+ and Mn3+ are ordered similarly to Al and Li in the [(Al0.673+Li0.32+)(OH)2]0.32- layer, with Mn3+ cations being surrounded by six Mn4+, and Mn4+ cations by three Mn3+ and three Mn4+. Similar cation ordering in the manganese and aluminum layers likely provides a more homogeneous local balance of the excess and deficit of charges in each layer and increases the stability of lithiophorite. Ni (r = 0.70Angstrom) substitutes for Mn(r(Mn4+) = 0.54 Angstrom, r(Mn3+) = 0.65Angstrom) in the manganese layer in the natural lithiophorite. In contrast, Zn(r = 0.74 Angstrom) fills vacant sites in the gibbsitic layer of natural lithiophorite, in a similar manner as lithium (r = 0.74) Angstrom in synthetic lithiophorite. The partitioning of Ni and Zn between the two layers is a result of the general preference of Ni

  10. Entropic and magnetic properties of Ni-Mn-In magnetocaloric materials

    NASA Astrophysics Data System (ADS)

    Chen, Jing-Han; Bruno, Nickolaus; Karaman, Ibrahim; Huang, Yujin; Li, Jianguo; Ross, Joseph H., Jr.

    2015-03-01

    We report magnetization and field-dependent calorimetry studies of phase transitions in Ni-Mn-In. Off-stoichiometric alloys based on NiMnIn have drawn attention due to the coupled first order magnetic and structural transformation, and the large magnetocaloric entropy associated with this martensitic transformation. We have analyzed materials with compositions NiMnIn, NiMnInand NiMnIn, which differ in that the former exhibits a paramagnetic to antiferromagnetic transition, while the others exhibit an additional ferromagnetic transition. Our results show that in the Nimaterials, the total entropy change at the phase transition can be modeled solely according to a magnetic contribution due to local moments on the Mn sites. On the other hand, NiMnInincludes a larger contribution which can be described in terms of a magneto-elastic coupling. This we will discuss in terms of the Bean-Rodbell model and a renomalization of the Debye temperature coupled with magnetism. We will also discuss the low-temperature properties, which show divergent behavior including antiferromagnetic, ferrimagnetic and superparamagnetic behavior. We gratefully acknowledge the support from NSF-DMR and the Robert A. Welch Foundation.

  11. Excess Ni-doping induced enhanced room temperature magneto-functionality in Ni-Mn-Sn based shape memory alloy

    SciTech Connect

    Pramanick, S.; Giri, S.; Majumdar, S.; Chatterjee, S.

    2014-09-15

    Present work reports on the observation of large magnetoresistance (∼−30% at 80 kOe) and magnetocaloric effect (∼12 J·kg{sup −1}·K{sup −1} for 0–50 kOe) near room temperature (∼290 K) on the Ni-excess ferromagnetic shape memory alloy Ni{sub 2.04}Mn{sub 1.4}Sn{sub 0.56}. The sample can be thought of being derived from the parent Ni{sub 2}Mn{sub 1.4}Sn{sub 0.6} alloy, where excess Ni was doped at the expense of Sn. Such Ni doping enhances the martensitic transition temperature and for the Ni{sub 2.04}Mn{sub 1.4}Sn{sub 0.56} it is found to be optimum (288 K). The doped alloy shows enhanced magneto-functional properties as well as reduced saturation magnetization as compared to the undoped counterpart at low temperature. A probable increment of antiferromagnetic correlation between Mn-atoms on Ni substitution can be accounted for the enhanced magneto-functional properties as well as reduction in saturation moment.

  12. Synthesis and properties of Fe/Ni nanotubes

    NASA Astrophysics Data System (ADS)

    Kozlovskiy, A. L.; Zdorovets, M. V.; Kadyrzhanov, K. K.

    2016-09-01

    Fe/Ni nanotubes were formed in pores of polyethylenterephtalate-based template matrices by electrochemical deposition. The inner diameter, wall height, and thickness of the nanostructures, as well as the elemental and phase compositions, can be controlled by varying the deposition conditions. The volume deposition rate constants have been determined for each potential difference, due to which the nanostructure growth could be controlled. An X-ray diffraction analysis of the samples obtained at a potential difference of 1-1.6 V has revealed their composition to correspond to the substitutional solid solution, with an iron atom replaced by a nickel atom and dominance of the bcc a-Fe phase. The samples obtained at a potential difference of 1.8-2 V contain the bcc a-Fe phase and fcc Ni phase; the fcc phase dominates in the sample obtained at a potential difference of 2 V, which can be related to the high Ni content in nanotubes.

  13. Bimetallic Fe-Ni Oxygen Carriers for Chemical Looping Combustion

    SciTech Connect

    Bhavsar, Saurabh; Veser, Goetz

    2013-11-06

    The relative abundance, low cost, and low toxicity of iron make Fe-based oxygen carriers of great interest for chemical looping combustion (CLC), an emerging technology for clean and efficient combustion of fossil and renewable fuels. However, Fe also shows much lower reactivity than other metals (such as Ni and Cu). Here, we demonstrate strong improvement of Fe-based carriers by alloying the metal phase with Ni. Through a combination of carrier synthesis and characterization with thermogravimetric and fixed-bed reactor studies, we demonstrate that the addition of Ni results in a significant enhancement in activity as well as an increase in selectivity for total oxidation. Furthermore, comparing alumina and ceria as support materials highlights the fact that reducible supports can result in a strong increase in oxygen carrier utilization.

  14. Cu(II), Co(II), Ni(II), Mn(II), and Fe(II) metal complexes containing N,N'-(3,4-diaminobenzophenon)-3,5-Bu t2-salicylaldimine ligand: Synthesis, structural characterization, thermal properties, electrochemistry, and spectroelectrochemistry

    NASA Astrophysics Data System (ADS)

    Tas, E.; Kilic, A.; Durgun, M.; Küpecik, L.; Yilmaz, I.; Arslan, S.

    2010-02-01

    The synthesis, structure, spectroscopic and electro-spectrochemical properties of steric hindered Schiff-base ligand [ N,N'-(3,4-benzophenon)-3,5-Bu t2-salicylaldimine (LH 2)] and its mononuclear Cu(II), Co(II), Ni(II), Mn(II) and Fe(II) complexes are described in this work. The new dissymmetric steric hindered Schiff-base ligand containing a donor set of NONO was prepared through reaction of 3,4-diaminobenzophenon with 3,5-Bu t2-salicylaldehyde. Certain metal complexes of this ligand were synthesized by treating an ethanolic solution of the ligand with an equimolar amount of metal salts. The ligand and its complexes were characterized by FT-IR, UV-vis, 1H NMR, elemental analysis, molar conductivity and thermal analysis methods in addition to magnetic susceptibility, electrochemistry and spectroelectrochemistry techniques. The tetradentate and mononuclear metal complexes were obtained by reacting N,N'-(3,4-benzophenon)-3,5-Bu t2-salicylaldimine (LH 2) with some metal acetate in a 1:1 mole ratio. The molar conductance data suggest metal complexes to be non-electrolytes.

  15. Scrutinizing Al-like 10+51V, 11+53Cr, 12+55Mn, 13+57Fe, 14+59Co, 15+61Ni, and 16+63Cu 1ions for atomic clocks with uncertainties below the 10-19 level

    NASA Astrophysics Data System (ADS)

    Yu, Yan-mei; Sahoo, B. K.

    2016-12-01

    We investigate the transition between the fine structure levels of the ground state, 3 p 2P1 /2→3 p 2P3 /2 , of the highly charged Al-like 10+51V, 11+53Cr, 12+55Mn, 13+57Fe, 14+59Co, 15+61Ni, and 16+63Cu ions for frequency standards. To comprehend them as prospective atomic clocks, we determine their transition wavelengths, quality factors, and various plausible systematics during the measurements. Since most of these ions have nuclear spin I =3 /2 , uncertainties due to dominant quadrupole shifts can be evaded in the F =0 hyperfine level of the 3 p 2P3 /2 state. Other dominant systematics such as quadratic Stark and black-body radiation shifts have been evaluated precisely demonstrating the feasibility of achieving high accuracy, below 10-19 fractional uncertainty, atomic clocks using the above transitions. Moreover, relativistic sensitivity coefficients are determined to find out the aptness of these proposed clocks to investigate possible temporal variation of the fine structure constant. To carry out these analysis, a relativistic coupled-cluster method considering Dirac-Coulomb-Breit Hamiltonian along with lower-order quantum electrodynamics interactions is employed and many spectroscopic properties are evaluated. These properties are also of immense interest for astrophysical studies.

  16. The improvement of cryogenic mechanical properties of Fe-12 Mn and Fe-8 Mn alloy steels through thermal/mechanical treatments

    NASA Technical Reports Server (NTRS)

    Hwang, S. K.; Morris, J. W., Jr.

    1979-01-01

    An investigation has been made to improve the low temperature mechanical properties of Fe-8Mn and Fe-12Mn-0.2 Ti alloy steels. A reversion annealing heat treatment in the two-phase (alpha + gamma) region following cold working has been identified as an effective treatment. In an Fe-12Mn-0.2Ti alloy a promising combination of low temperature (-196 C) fracture toughness and yield strength was obtained by this method. The improvement of properties was attributed to the refinement of grain size and to the introduction of a uniform distribution of retained austenite (gamma). It was also shown that an Fe-8Mn steel could be grain-refined by a purely thermal treatment because of its dislocated alpha-prime martensitic structure and absence of epsilon martensite. As a result, a significant reduction of ductile to brittle transition temperature was obtained.

  17. Enhanced magnetic refrigeration properties in Mn-rich Ni-Mn-Sn ribbons by optimal annealing

    PubMed Central

    Zhang, Yu; Zhang, Linlin; Zheng, Qiang; Zheng, Xinqi; Li, Ming; Du, Juan; Yan, Aru

    2015-01-01

    The influence of annealing time on temperature range of martensitic phase transition (ΔTA-M), thermal hysteresis (ΔThys), magnetic hysteresis loss (ΔMhys), magnetic entropy change (ΔSM) and relative refrigeration capacity (RC) of the Mn-rich Ni43Mn46Sn11 melt spun ribbons have been systematically studied. By optimal annealing, an extremely large ΔSM of 43.2 J.kg−1K−1 and a maximum RC of 221.0 J.kg−1 could be obtained respectively in a field change of 5 T. Both ΔTA-M and ΔThys decreases after annealing, while ΔMhys and ΔSM first dramatically increase to a maximum then degenerates as increase of annealing time. A large effective cooling capacity (RCeff) of 115.4 J.kg−1 was achieved in 60 min annealed ribbons, which increased 75% compared with that unannealed ribbons. The evolution of magnetic properties and magnetocaloric effect has been discussed and proved by atomic ordering degree, microstructure and composition analysis. PMID:26055884

  18. Low temperature magneto-structural transitions in Mn3Ni20P6

    NASA Astrophysics Data System (ADS)

    Cedervall, Johan; Beran, Premysl; Vennström, Marie; Danielsson, Therese; Ronneteg, Sabina; Höglin, Viktor; Lindell, David; Eriksson, Olle; André, Gilles; Andersson, Yvonne; Nordblad, Per; Sahlberg, Martin

    2016-05-01

    X-ray and neutron powder diffraction has been used to determine the crystal and magnetic structure of Mn3Ni20P6. The crystal structure can be described as cubic with space group Fm 3 barm (225) without any nuclear phase transformation within studied temperature interval from room temperature down to 4 K. The magnetic structure of Mn3Ni20P6 is complex with two independent magnetic positions for the Mn atoms and the compound passes three successive magnetic phase transitions during cooling. At 30 K the spins of the Mn atoms on the Wyckoff 4a site (Mn1) order to form a primitive cubic antiferromagnetic structure with propagation vector k=(0 0 1). Between 29 and 26 K the Mn atoms on the Wyckoff 8c site (Mn2) order independently on already ordered Mn1 magnetic structure forming a commensurate antiferromagnetic structure with propagation vector k=(0 0 ½) and below 26 K, both Mn positions order to form an incommensurate helical structure with propagation vector k=(0 0 ~0.45). Magnetization vs. temperature curve of Mn3Ni20P6 shows a steep increase indicating some magnetic ordering below 230 K and a sharp field dependent anomaly in a narrow temperature range around 30 K.

  19. Possible martensitic transformation and ferrimagnetic properties in Heusler alloy Mn2NiSn

    NASA Astrophysics Data System (ADS)

    Duan, Ying-Ni; Fan, Xiao-Xi; Kutluk, Abdugheni; Du, Xiu-Juan; Zhang, Zheng-Wei; Song, Yu-Ling

    2015-07-01

    The electronic structure and magnetic properties of Hg2CuTi-type Mn2NiSn have been studied by performing the first-principle calculations. It is found that the phase transformation from the cubic to the tetragonal structure reduces the total energy, indicating that the martensitic phase is more stable and the phase transition from austenite to martensite may happen at low temperature for Hg2CuTi-type Mn2NiSn. Concerning the magnetism of Hg2CuTi-type Mn2NiSn, both austenitic and martensitic phases are suggested to be ferrimagnets. Furthermore, martensitic transformation decreases the magnetic moment per formula unit compared with austenitic phase. The results are helpful to accelerate the use of Mn2NiSn alloys in the series for magnetic shape memory applications.

  20. Nonreciprocal spin wave spectroscopy of thin Ni-Fe stripes

    NASA Astrophysics Data System (ADS)

    Khalili Amiri, Pedram; Rejaei, Behzad; Vroubel, Marina; Zhuang, Yan

    2007-08-01

    The authors report on the observation of nonreciprocal spin wave propagation in a thin (˜200nm) patterned Ni-Fe stripe. The spin wave transmission spectrum is measured using a pair of microstrip lines as antennas. The nonreciprocity of surface wave dispersion brought about by an adjacent aluminum ground leads to a nonreciprocal coupling of the antennas. The effects of Ni-Fe film conductivity, thickness, and reflections caused by the lateral confinement of the magnetic stripe are discussed. The nonreciprocity observed in this structure can potentially be used to realize nonreciprocal microwave devices on silicon.

  1. Structural, magnetic and dielectric properties of polyaniline/MnCoFe2O4 nanocomposites

    NASA Astrophysics Data System (ADS)

    Chitra, Palanisamy; Muthusamy, Athianna; Jayaprakash, Rajan

    2015-12-01

    Ferromagnetic PANI containing MnCoFe2O4 nanocomposites were synthesized by in-situ chemical polymerization of aniline incorporated MnCoFe2O4 nanoparticles (20%, 10% w/w of fine powders) with and without ultrasonic treatment. The MnCoFe2O4 nanoparticles were synthesized by auto combustion method. The PANI/MnCoFe2O4 nanocomposites were characterized with Fourier transform infrared (FTIR), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The average particle size of the resulting PANI/MnCoFe2O4 nanocomposites was confirmed from the TEM and XRD analysis. The structure and morphology of the composites were confirmed by FT-IR spectroscopy, XRD and SEM. In addition, the electrical and magnetic properties of the nanocomposites were investigated. The PANI/MnCoFe2O4 nanocomposites under applied magnetic field exhibited the hysteresis loops of ferromagnetic nature at room temperature. The variation of Dielectric constant, Dielectric loss, and AC conductivity of PANI/MnCoFe2O4 nanocomposites at room temperature as a function of frequency in the range 50 Hz-5 MHz has been studied. Effect of ultrasonication on the PANI/MnCoFe2O4 nanocomposites was also investigated.

  2. Imaging the antiparallel magnetic alignment of adjacent Fe and MnAs thin films

    NASA Astrophysics Data System (ADS)

    Breitwieser, R.; Marangolo, M.; Lüning, J.; Jaouen, N.; Joly, L.; Eddrief, M.; Etgens, V. H.; Sacchi, M.

    2008-09-01

    The magnetic coupling between iron and α-MnAs in the epitaxial system Fe/MnAs/GaAs(001) has been studied at the submicron scale, using element-selective x-ray photoemission electron microscopy. At room temperature, MnAs layers display ridges and grooves, alternating α (magnetic) and β (nonmagnetic) phases. The self-organized microstructure of MnAs and the stray fields that it generates govern the local alignment between the Fe and α-MnAs magnetization directions, which is mostly antiparallel with a marked dependence upon the magnetic domain size.

  3. Synthesis and consolidation of γ-Ni-Fe nanoalloy powder

    NASA Astrophysics Data System (ADS)

    Lee, J. S.; Nam, J. G.; Knorr, P.

    1999-04-01

    The present work studies the synthesis and consolidation of γ-Ni-Fe nanoalloy powder by the mechano-chemical process comprising high-energy ball-milling of NiO-Fe2O3 powder and a subsequent hydrogen reduction process. To examine the formation mechanism of the nanoalloy powder, the effect of the oxide powder char-acteristics on the reduction process and alloying was investigated by varying the ball-milling time. The reduction process and the alloying of the γ-Ni-Fe phase proved to accelerate as the ball-milling time increased. However, prolonged milling (for 30 hours) retarded the reduction of Fe2O3 as well as the alloying process. The densification process of the Ni-Fe nanoalloy powder strongly depended on the degree of agglomeration which results in enhancing homogeneous sintering. The limited densification of the nanoalloy powder originates from the high degree of particle agglomeration. While intra-agglomerate porosity is easily eliminated in the course of sintering, it is found to resist densification. The limitation of the sintered density could be overcome by increasing the green density of the powder compacts. Full density was achieved by starting with a green density of 72% theoretical density.

  4. [Effect of Fe-Mn-Si on the biomass structure of Eichhornia crassipes].

    PubMed

    Wu, Shao-Wei; Zhu, Duan-Wei; Zhou, Wen-Bing; Deng, Li

    2011-04-01

    Eichhornia crassipes (water hyacinth) was cultivated under different iron (Fe), manganese (Mn) and silicon (Si) nutrient treatments for its biomass characteristics research which was determined by various items including nutrient element content (Fe, Mn and Si), adsorption sites and active function groups. The results show that Mn and Si can enhance acidic sites of the plant, in which Mn plays a great role, but Fe reduces the acidic sites. The sequence of acidic sites' amount among three parts of the plant is root > stem > leaf, in the treatment of Fe, Mn and their combination, and leaf > stem > root in Si treatment. The amount of alkaline sites is less than that of acidic sites, and the difference in their distributions among three parts of the plant is not great. Mn and Si treated Eichhornia crassipes stalks have more amorphous material, such as lignin, pectin and xylan (hemicellulose), which have more functional groups of -OH, -COOH and acidic sites.

  5. Fe-Ni-bearing serpentines from the saprolite horizon of Caribbean Ni-laterite deposits: new insights from thermodynamic calculations

    NASA Astrophysics Data System (ADS)

    Villanova-de-Benavent, Cristina; Domènech, Cristina; Tauler, Esperança; Galí, Salvador; Tassara, Santiago; Proenza, Joaquín A.

    2016-10-01

    Fe-Ni-bearing serpentine from the saprolite horizon is the main Ni ores in hydrous silicate-type Ni laterites and formed by chemical weathering of partially serpentinized ultramafic rocks under tropical conditions. During lateritization, Mg, Si, and Ni are leached from the surface and transported downwards. Fe2+ is oxidized to Fe3+ and fixed as insoluble Fe-oxyhydroxides (mostly goethite) that incorporate Ni. This Ni is later leached from goethite and incorporated in secondary serpentine and garnierite. As a result, a serpentine-dominated saprolite horizon forms over the ultramafic protolith, overlapped by a Fe-oxyhydroxide-dominated limonite horizon. The serpentine from the protolith (serpentine I) is of hydrothermal origin and yields similar Ni (0.10-0.62 wt.% NiO) and lower Fe (mostly 1.37-5.81 wt.% FeO) concentrations than the primary olivine. In contrast, Fe-Ni-bearing serpentine from the saprolite (serpentine II) shows significantly higher and variable Fe and Ni contents, typically ranging from 2.23 to 15.59 wt.% Fe2O3 and from 1.30 to 7.67 wt.% NiO, suggesting that serpentine get enriched in Fe and Ni under supergene conditions. This study presents detailed mineralogical, textural, and chemical data on this serpentine II, as well as new insights by thermodynamic calculations assuming ideal solution between Fe-, Ni- and Mg-pure serpentines. The aim is to assess if at atmospheric pressure and temperature Fe-Ni-bearing serpentine can be formed by precipitation. Results indicate that the formation of serpentine II under atmospheric pressure and temperature is thermodynamically supported, and pH, Eh, and the equilibrium constant of the reaction are the parameters that affect the results more significantly.

  6. Effects of two-temperature model on cascade evolution in Ni and NiFe

    DOE PAGES

    Samolyuk, German D.; Xue, Haizhou; Bei, Hongbin; ...

    2016-07-05

    We perform molecular dynamics simulations of Ni ion cascades in Ni and equiatomic NiFe under the following conditions: (a) classical molecular dynamics (MD) simulations without consideration of electronic energy loss, (b) classical MD simulations with the electronic stopping included, and (c) using the coupled two-temperature MD (2T-MD) model that incorporates both the electronic stopping and the electron-phonon interactions. Our results indicate that the electronic effects are more profound in the higher-energy cascades, and that the 2T-MD model results in a smaller amount of surviving damage and smaller defect clusters, while less damage is produced in NiFe than in Ni.

  7. Tuning of interlayer exchange coupling in Ni80Fe20/Ru/Ni80Fe20 nanowires

    NASA Astrophysics Data System (ADS)

    Liu, X. M.; Lupo, P.; Cottam, M. G.; Adeyeye, A. O.

    2015-09-01

    In this work, we demonstrate how the static and dynamic properties of Ni80Fe20/Ru/Ni80Fe20 nanowires can be tuned by varying the Ru spacer layer thickness. Specifically, changing the Ru thickness we have tuned the Ruderman-Kittel-Kasuya-Yosida exchange interaction, and thus the antiferromagnetic (AFM) strength between the Ni80Fe20 layers. We show that there is a strong correlation between the interlayer coupling and features in ferromagnetic resonance (FMR) modes. We found different mode-softening degree of the FMR curves as function of the strength of AFM coupling, together with a clear frequency gap at around zero field. These experimental results are in qualitative agreement with presented micromagnetic simulations that also include biquadratic interface exchange. Understanding these characteristics may offer insights for reconfigurable vertical magnetic logic devices and microwave filters.

  8. Stripe-to-bubble transition of magnetic domains at the spin reorientation of (Fe/Ni)/Cu/Ni/Cu(001)

    SciTech Connect

    Wu, J.; Choi, J.; Won, C.; Wu, Y. Z.; Scholl, A.; Doran, A.; Hwang, Chanyong; Qiu, Z.

    2010-06-09

    Magnetic domain evolution at the spin reorientation transition (SRT) of (Fe/Ni)/Cu/Ni/Cu(001) is investigated using photoemission electron microscopy. While the (Fe/Ni) layer exhibits the SRT, the interlayer coupling of the perpendicularly magnetized Ni layer to the (Fe/Ni) layer serves as a virtual perpendicular magnetic field exerted on the (Fe/Ni) layer. We find that the perpendicular virtual magnetic field breaks the up-down symmetry of the (Fe/Ni) stripe domains to induce a net magnetization in the normal direction of the film. Moreover, as the virtual magnetic field increases to exceed a critical field, the stripe domain phase evolves into a bubble domain phase. Although the critical field depends on the Fe film thickness, we show that the area fraction of the minority domain exhibits a universal value that determines the stripe-to-bubble phase transition.

  9. Application of damping mechanism model and stacking fault probability in Fe-Mn alloy

    SciTech Connect

    Huang, S.K.; Wen, Y.H.; Li, N. Teng, J.; Ding, S.; Xu, Y.G.

    2008-06-15

    In this paper, the damping mechanism model of Fe-Mn alloy was analyzed using dislocation theory. Moreover, as an important parameter in Fe-Mn based alloy, the effect of stacking fault probability on the damping capacity of Fe-19.35Mn alloy after deep-cooling or tensile deformation was also studied. The damping capacity was measured using reversal torsion pendulum. The stacking fault probability of {gamma}-austenite and {epsilon}-martensite was determined by means of X-ray diffraction (XRD) profile analysis. The microstructure was observed using scanning electronic microscope (SEM). The results indicated that with the strain amplitude increasing above a critical value, the damping capacity of Fe-19.35Mn alloy increased rapidly which could be explained using the breakaway model of Shockley partial dislocations. Deep-cooling and suitable tensile deformation could improve the damping capacity owning to the increasing of stacking fault probability of Fe-19.35Mn alloy.

  10. Effect of phosphate and sulfate on Ni repartitioning during Fe(II)-catalyzed Fe(III) oxide mineral recrystallization

    NASA Astrophysics Data System (ADS)

    Hinkle, Margaret A. G.; Catalano, Jeffrey G.

    2015-09-01

    Dissolved Fe(II) activates coupled oxidative growth and reductive dissolution of Fe(III) oxide minerals, causing recrystallization and the repartitioning of structurally-compatible trace metals. Phosphate and sulfate, two ligands common to natural aquatic systems, alter Fe(II) adsorption onto Fe(III) oxides and affect Fe(III) oxide dissolution and precipitation. However, the effect of these oxoanions on trace metal repartitioning during Fe(II)-catalyzed Fe(III) oxide recrystallization is unclear. The effects of phosphate and sulfate on Ni adsorption and Ni repartitioning during Fe(II)-catalyzed Fe(III) oxide recrystallization were investigated as such repartitioning may be affected by both Fe(II)-oxoanion and metal-oxoanion interactions. In most systems examined, phosphate alters Ni repartitioning during Fe(II)-catalyzed recrystallization to a larger extent than sulfate. Phosphate substantially enhances Ni adsorption onto hematite but decreases (nearly inhibiting) Fe(II)-catalyzed Ni incorporation into and release from this mineral. In the goethite system, however, phosphate suppresses Ni release but enhances Ni incorporation in the presence of aqueous Fe(II). In contrast, sulfate has little effect on macroscopic Ni adsorption and release of Ni from Fe(III) oxides, but substantially enhances Ni incorporation into goethite. This demonstrates that phosphate and sulfate have unique, mineral-specific interactions with Ni during Fe(II)-catalyzed Fe(III) oxide recrystallization. This research suggests that micronutrient bioavailability at redox interfaces in hematite-dominated systems may be especially suppressed by phosphate, while both oxoanions likely have limited effects in goethite-rich soils or sediments. Phosphate may also exert a large control on contaminant fate at redox interfaces, increasing Ni retention on iron oxide surfaces. These results further indicate that trace metal retention by iron oxides during lithification and later repartitioning during

  11. Origin of spontaneous exchange bias in Co/NiMn bilayer structure

    NASA Astrophysics Data System (ADS)

    Akbulut, A.; Akbulut, S.; Yildiz, F.

    2016-11-01

    Spontaneous exchange bias (EB) is reported for as deposited Si/Pt(tPt)/Ni45Mn55(tAFM/Co(tFM)/Pt(30 Å) thin film system without requiring any post annealing, deposition with field or field cooling procedures. Magnetic properties of this system were investigated with respect to thicknesses of buffer Pt layer (tPt), antiferromagnetic NiMn layer (tAFM) and ferromagnetic Co layer (tFM). Exchange coupling between NiMn and Co layers enhanced considerably by increasing tPt. In order to observe a spontaneous EB in the system, Pt buffer layer must be thicker than a certain thickness, and NiMn layer must be grown directly on the buffer layer. On the other hand, significant increments in the coercive fields (HC) were reported for thinner Pt buffer layers. The thickness ranges for Co and NiMn layers were also determined to obtain spontaneous EB. This spontaneous EB is discussed to be a result of NiMn (111) texture which is induced by Pt buffer layer. Greater EB fields (HEB) are measured for the samples in the negative field direction by the effect of annealing and field cooling (from 400 K to 300 K at 2 kOe).

  12. Prolidase-Associated Trace Elements (Mn, Zn, Co, and Ni) in the Patients with Parkinson's Disease.

    PubMed

    Verma, Akhilesh Kumar; Keshari, Anand Kumar; Raj, Janak; Kumari, Renu; Kumar, Tarun; Sharma, Vivek; Singh, Tej Bali; Srivastava, Shalabh; Srivastava, Ragini

    2016-05-01

    Micronutrients and trace elements have been identified to play an important role in the development of Parkinson's disease (PD). In our previous study, we observed that prolidase activity is associated with oxidative stress and progression of PD. In present study, we aimed to study the association of prolidase-associated trace elements, such as Co, Mn, Ni, and Zn in the plasma of patients with PD by inductively coupled plasma spectrometry. Plasma levels of Co, Mn, and Ni were significantly increased, whereas plasma levels of Zn was significantly decreased (all P < 0.05) in the patients with PD than healthy controls. Plasma prolidase activity was not correlated to its associated trace elements in PD. A positive, linear, and significant correlation was observed between age and Co, and Mn, and Ni while negative and non-significant between age and status of Zn in the patients. Co, Mn, and Ni were continually elevated with increase in age as well as duration of disease in the patients with PD, whereas status of Zn was continually decreased. Thus, the study concluded that trace elements Co, Ni, and Mn status were increased and Zn status was decreased in the plasma of patients with PD. It is also concluded that elevated Co, Mn, and Ni has been associated with progression of Parkinson's disease.

  13. First-principles computation of structural, elastic and magnetic properties of Ni2FeGa across the martensitic transformation

    NASA Astrophysics Data System (ADS)

    Sahariah, Munima B.; Ghosh, Subhradip; Singh, Chabungbam S.; Gowtham, S.; Pandey, Ravindra

    2013-01-01

    The structural stabilities, elastic, electronic and magnetic properties of the Heusler-type shape memory alloy Ni2FeGa are calculated using density functional theory. The volume conserving tetragonal distortion of the austenite Ni2FeGa find an energy minimum at c/a = 1.33. Metastable behaviour of the high temperature cubic austenite phase is predicted due to elastic softening in the [110] direction. Calculations of the total and partial magnetic moments show a dominant contribution from Fe atoms of the alloy. The calculated density of states shows a depression in the minority spin channel of the cubic Ni2FeGa just above the Fermi level which gets partially filled up in the tetragonal phase. In contrast to Ni2MnGa, the transition metal spin-down states show partial hybridization in Ni2FeGa and there is a relatively high electron density of states near the Fermi level in both phases.

  14. First-principles computation of structural, elastic and magnetic properties of Ni2FeGa across the martensitic transformation.

    PubMed

    Sahariah, Munima B; Ghosh, Subhradip; Singh, Chabungbam S; Gowtham, S; Pandey, Ravindra

    2013-01-16

    The structural stabilities, elastic, electronic and magnetic properties of the Heusler-type shape memory alloy Ni(2)FeGa are calculated using density functional theory. The volume conserving tetragonal distortion of the austenite Ni(2)FeGa find an energy minimum at c/a = 1.33. Metastable behaviour of the high temperature cubic austenite phase is predicted due to elastic softening in the [110] direction. Calculations of the total and partial magnetic moments show a dominant contribution from Fe atoms of the alloy. The calculated density of states shows a depression in the minority spin channel of the cubic Ni(2)FeGa just above the Fermi level which gets partially filled up in the tetragonal phase. In contrast to Ni(2)MnGa, the transition metal spin-down states show partial hybridization in Ni(2)FeGa and there is a relatively high electron density of states near the Fermi level in both phases.

  15. Ferromagnetic shape memory in the NiMnGa system

    SciTech Connect

    Tickle, R.; James, R.D.; Shield, T.; Wuttig, M.; Kokorin, V.V.

    1999-09-01

    Strain versus field measurements for a ferromagnetic shape memory alloy in the NiMnGa system demonstrate the largest magnetostrictive strains to date of nearly 1.3%. These strains are achieved in the martensitic state through field-induced variant rearrangement. An experimental apparatus is described that provides biaxial magnetic fields and uniaxial compressive prestress with temperature control while recording microstructural changes with optical microscopy. The magnetostrictive response is found to be sensitive to the initial state induced by stress-biasing the martensitic variant structure, and exhibits rate effects related to twin boundary mobility. Experiments performed with constant stress demonstrate work output capacity. Experimental results are interpreted by using a theory based on minimization of a micromagnetic energy functional that includes applied field, stress, and demagnetization energies. It is found that the theory provides a good qualitative description of material behavior, but significantly overpredicts the amount of strain produced. Issues concerning the martensitic magnetic anisotropy and variant nucleation are discussed with regard to this discrepancy.

  16. Growth in solution of hooked Ni-Fe fibers by oriented rotation and attachment approaches

    NASA Astrophysics Data System (ADS)

    Zhang, Yong; Liu, Fang; Zhang, Wei-ze

    2016-04-01

    Inspired by the curved branches of fractal trees, hooked Ni-Fe fibers were grown in situ in Ni-Fe composite coatings on a spheroidal graphite cast iron substrate. These hooked Ni-Fe fibers exhibited inclination angles of about 39°, which was in accordance with the theoretical prediction of 37°. Ni-Fe nanostructures self-assembled to form dendrites and evolved into hooked fibers by an oriented attachment reaction. The orientation rotation of Ni-Fe nanostructures played an important role in the growth of curved hooked Ni-Fe fibers. During sliding wear tests, the volume loss of the spheroidal graphite cast iron substrate was 2.2 times as large as that of the Ni-Fe coating reinforced by hooked fibers. The good load-transferring ability of hooked Ni-Fe fibers led to an improvement in their wear properties during wear tests.

  17. Investigation of the structural, electronic, and magnetic properties of Ni-based Heusler alloys from first principles

    NASA Astrophysics Data System (ADS)

    Qawasmeh, Yasmeen; Hamad, Bothina

    2012-02-01

    Density functional theory (DFT) calculations are performed to investigate the structural, electronic, magnetic, and elastic properties of Ni2MnZ (Z = B, Al, Ga, In) and Ni2FeZ (Z = Al, Ga) full Heusler alloys. The alloys are found to be metallic ferromagnets with total magnetic moments of about 4μB/f.u. and 3μB/f.u for Ni2MnZ and Ni2FeZ alloys, respectively. The Ni2MnAl and Ni2MnIn alloys are found to be stable at L21 phase, while the other alloys are more stable in the tetragonal phase with c/a ratios of 1.38 and 1.27 for Ni2MnB and Ni2MnGa, respectively and 1.35 for both Ni2FeAl and Ni2FeGa. The Ni2MnB alloy exhibits the highest electron spin polarization in its tetragonal phase, which is about 88% greater than that of L21 structure. However, the Ni2MnGa, Ni2FeAl, and Ni2FeGa alloys exhibit lower spin polarizations in their tetragonal phase than those at the L21. The most contribution of the total magnetic moments comes from Mn or Fe atoms, whereas Ni atoms exhibit much smaller magnetic moments. However, Z atoms have small induced magnetic moments, which are coupled antiferromagnetically with Ni, Mn and Fe.

  18. Phase relationships in the iron-rich Fe-Cr-Ni-C system at solidification temperatures

    NASA Astrophysics Data System (ADS)

    Kundrat, D. M.; Elliott, J. F.

    1986-08-01

    The phase relationships between the liquid phase and the primary solid phases were investigated in the iron-rich comer of the Fe-Cr-Ni-C system as part of a larger study of the Fe-Cr-Mn-Ni-C system. The investigation consisted of measurements of tie-lines for the liquid-delta (bcc) and the liquid-gamma (fcc) equilibria in the iron-rich corner of the Gibbs tetrahedron bounded by 0 to 25 wt Pct Cr, 0 to 25 wt Pct Ni, and 1.2 wt Pct C (bal. Fe). The temperature ranged from 1811 to 1750 K. Compositions for the tie-lines were obtained from liquid-solid equilibrium couples and the temperatures of the equilibrium, by differential thermal analysis (DTA). A mathematical procedure was employed on the experimental data to obtain parameters for a thermodynamic model of the alloy system. This involved minimization of an error function. The details of this analysis are discussed fully in this paper. Calculations by the model employing the “best-set” parameters are in good agreement with the experimental results. The usefulness of the model is demonstrated by calculation of the three-phase equilibrium in the quaternary system as a function of temperature.

  19. Exchange bias of Ni nanoparticles embedded in an antiferromagnetic IrMn matrix.

    PubMed

    Kuerbanjiang, Balati; Wiedwald, Ulf; Haering, Felix; Biskupek, Johannes; Kaiser, Ute; Ziemann, Paul; Herr, Ulrich

    2013-11-15

    The magnetic properties of Ni nanoparticles (Ni-NPs) embedded in an antiferromagnetic IrMn matrix were investigated. The Ni-NPs of 8.4 nm mean diameter were synthesized by inert gas aggregation. In a second processing step, the Ni-NPs were in situ embedded in IrMn films or SiOx films under ultrahigh vacuum (UHV) conditions. Findings showed that Ni-NPs embedded in IrMn have an exchange bias field HEB = 821 Oe at 10 K, and 50 Oe at 300 K. The extracted value of the exchange energy density is 0.06 mJ m(-2) at 10 K, which is in good accordance with the results from multilayered thin film systems. The Ni-NPs embedded in SiOx did not show exchange bias. As expected for this particle size, they are superparamagnetic at T = 300 K. A direct comparison of the Ni-NPs embedded in IrMn or SiOx reveals an increase of the blocking temperature from 210 K to around 400 K. The coercivity of the Ni-NPs exchange coupled to the IrMn matrix at 10 K is 8 times larger than the value for Ni-NPs embedded in SiOx. We studied time-dependent remanent magnetization at different temperatures. The relaxation behavior is described by a magnetic viscosity model which reflects a rather flat distribution of energy barriers. Furthermore, we investigated the effects of different field cooling processes on the magnetic properties of the embedded Ni-NPs. Exchange bias values fit to model calculations which correlate the contribution of the antiferromagnetic IrMn matrix to its grain size.

  20. Impact of Mn3+ upon structure and magnetism of the perovskite derivative Pb(2-x)Ba(x)FeMnO5 (x ∼ 0.7).

    PubMed

    Barrier, N; Lebedev, O I; Seikh, Md Motin; Porcher, F; Raveau, B

    2013-05-20

    On the basis of the Mn(3+) for Fe(3+) substitution in Pb(2-x)Ba(x)Fe2O5, a novel oxide Pb1.3Ba0.7MnFeO5 has been synthesized at normal pressure. Though it belongs to the same structural family, the mixed "MnFe" oxide exhibits a very different structural distortion of its framework compared to the pure "Fe2" oxide, due to the Jahn-Teller effect of Mn(3+). Combined neutron diffraction, high resolution electron microscopy/high angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) investigations allow the origin of this difference to be determined. Here we show that the MO6 octahedra of the double perovskite layers in the "MnFe" structure exhibit a strong tetragonal pyramidal distortion "5 + 1", whereas the "Fe2" structure shows a tetrahedral distortion "4 + 2" of the FeO6 octahedra. Similarly, the MO5 polyhedra of the "MnFe" structure tend toward a tetragonal pyramid, whereas the FeO5 polyhedra of the "Fe2" structure are closer to a trigonal bipyramid. Differently from the oxide Pb(2-x)Ba(x)Fe2O5, which is antiferromagnetic, the oxide Pb1.3Ba0.7MnFeO5 exhibits a spin glass behavior with Tg ∼ 50 K in agreement with the disordered distribution of the Mn(3+) and Fe(3+) species.

  1. The effect of deposition temperature on the intermixing and microstructure of Fe/Ni thin film

    NASA Astrophysics Data System (ADS)

    Chen, Shang-Da; Wang, Tao; Zheng, De-Li; Zhou, Yi-Chun

    2010-12-01

    The physical vapour deposition of Ni atoms on α-Fe(001) surface under different deposition temperatures were simulated by molecular dynamics to study the intermixing and microstructure of the interfacial region. The results indicate that Ni atoms hardly penetrate into Fe substrate while Fe atoms easily diffuse into Ni deposition layers. The thickness of the intermixing region is temperature-dependent, with high temperatures yielding larger thicknesses. The deposited layers are mainly composed of amorphous phase due to the abnormal deposition behaviour of Ni and Fe. In the deposited Ni-rich phase, the relatively stable metallic compound B2 structured FeNi is found under high deposition temperature conditions.

  2. Magnetic studies of spin wave excitations in Fe/Mn multilayers

    NASA Astrophysics Data System (ADS)

    Salhi, H.; Moubah, R.; El Bahoui, A.; Lassri, H.

    2017-04-01

    The structural and magnetic properties of Fe/Mn multilayers grown by thermal evaporation technique were investigated by transmission electron microscopy, vibrating sample magnetometer and spin wave theory. Transmission electron microscopy shows that the Fe and Mn layers are continuous with a significant interfacial roughness. The magnetic properties of Fe/Mn multilayers were studied for various Fe thicknesses (tFe). The change of magnetization as a function of temperature is well depicted by a T3/2 law. The Fe spin-wave constant was extracted and found to be larger than that reported for bulk Fe, which we attribute to the fluctuation of magnetic moments at the interface, due to the interfacial roughness. The experimental M (T) data were satisfactory fitted for multilayers with different Fe thicknesses; and several exchange interactions were extracted.

  3. Magnetic Properties of FeNi-Based Thin Film Materials with Different Additives.

    PubMed

    Liang, Cai; Gooneratne, Chinthaka P; Wang, Qing Xiao; Liu, Yang; Gianchandani, Yogesh; Kosel, Jurgen

    2014-09-01

    This paper presents a study of FeNi-based thin film materials deposited with Mo, Al and B using a co-sputtering process. The existence of soft magnetic properties in combination with strong magneto-mechanical coupling makes these materials attractive for sensor applications. Our findings show that FeNi deposited with Mo or Al yields magnetically soft materials and that depositing with B further increases the softness. The out-of-plane magnetic anisotropy of FeNi thin films is reduced by depositing with Al and completely removed by depositing with B. The effect of depositing with Mo is dependent on the Mo concentration. The coercivity of FeNiMo and FeNiAl is reduced to less than a half of that of FeNi, and a value as low as 40 A/m is obtained for FeNiB. The surfaces of the obtained FeNiMo, FeNiAl and FeNiB thin films reveal very different morphologies. The surface of FeNiMo shows nano-cracks, while the FeNiAl films show large clusters and fewer nano-cracks. When FeNi is deposited with B, a very smooth morphology is obtained. The crystal structure of FeNiMo strongly depends on the depositant concentration and changes into an amorphous structure at a higher Mo level. FeNiAl thin films remain polycrystalline, even at a very high concentration of Al, and FeNiB films are amorphous, even at a very low concentration of B.

  4. Magnetic Properties of FeNi-Based Thin Film Materials with Different Additives

    PubMed Central

    Liang, Cai; Gooneratne, Chinthaka P.; Wang, Qing Xiao; Liu, Yang; Gianchandani, Yogesh; Kosel, Jurgen

    2014-01-01

    This paper presents a study of FeNi-based thin film materials deposited with Mo, Al and B using a co-sputtering process. The existence of soft magnetic properties in combination with strong magneto-mechanical coupling makes these materials attractive for sensor applications. Our findings show that FeNi deposited with Mo or Al yields magnetically soft materials and that depositing with B further increases the softness. The out-of-plane magnetic anisotropy of FeNi thin films is reduced by depositing with Al and completely removed by depositing with B. The effect of depositing with Mo is dependent on the Mo concentration. The coercivity of FeNiMo and FeNiAl is reduced to less than a half of that of FeNi, and a value as low as 40 A/m is obtained for FeNiB. The surfaces of the obtained FeNiMo, FeNiAl and FeNiB thin films reveal very different morphologies. The surface of FeNiMo shows nano-cracks, while the FeNiAl films show large clusters and fewer nano-cracks. When FeNi is deposited with B, a very smooth morphology is obtained. The crystal structure of FeNiMo strongly depends on the depositant concentration and changes into an amorphous structure at a higher Mo level. FeNiAl thin films remain polycrystalline, even at a very high concentration of Al, and FeNiB films are amorphous, even at a very low concentration of B. PMID:25587418

  5. Biocorrosion investigation of two shape memory nickel based alloys: Ni-Mn-Ga and thin film NiTi.

    PubMed

    Stepan, L L; Levi, D S; Gans, E; Mohanchandra, K P; Ujihara, M; Carman, G P

    2007-09-01

    Thin film nitinol and single crystal Ni-Mn-Ga represent two new shape memory materials with potential to be used as percutaneously placed implant devices. However, the biocompatibility of these materials has not been adequately assessed. Immersion tests were conducted on both thin film nitinol and single crystal Ni-Mn-Ga in Hank's balanced salt solution at 37 degrees C and pH 7.4. After 12 h, large pits were found on the Ni-Mn-Ga samples while thin film nitinol displayed no signs of corrosion. Further electrochemical tests on thin film nitinol samples revealed breakdown potentials superior to a mechanically polished nitinol disc. These results suggest that passivation or electropolishing of thin film nitinol maybe unnecessary to promote corrosion resistance.

  6. Sulfur evolution in chemical looping combustion of coal with MnFe2O4 oxygen carrier.

    PubMed

    Wang, Baowen; Gao, Chuchang; Wang, Weishu; Zhao, Haibo; Zheng, Chuguang

    2014-05-01

    Chemical looping combustion (CLC) of coal has gained increasing attention as a novel combustion technology for its advantages in CO2 capture. Sulfur evolution from coal causes great harm from either the CLC operational or environmental perspective. In this research, a combined MnFe2O4 oxygen carrier (OC) was synthesized and its reaction with a typical Chinese high sulfur coal, Liuzhi (LZ) bituminous coal, was performed in a thermogravimetric analyzer (TGA)-Fourier transform infrared (FT-IR) spectrometer. Evolution of sulfur species during reaction of LZ coal with MnFe2O4 OC was systematically investigated through experimental means combined with thermodynamic simulation. TGA-FTIR analysis of the LZ reaction with MnFe2O4 indicated MnFe2O4 exhibited the desired superior reactivity compared to the single reference oxides Mn3O4 or Fe2O3, and SO2 produced was mainly related to oxidization of H2S by MnFe2O4. Experimental analysis of the LZ coal reaction with MnFe2O4, including X-ray diffraction and X-ray photoelectron spectroscopy analysis, verified that the main reduced counterparts of MnFe2O4 were Fe3O4 and MnO, in good agreement with the related thermodynamic simulation. The obtained MnO was beneficial to stabilize the reduced MnFe2O4 and avoid serious sintering, although the oxygen in MnO was not fully utilized. Meanwhile, most sulfur present in LZ coal was converted to solid MnS during LZ reaction with MnFe2O4, which was further oxidized to MnSO4. Finally, the formation of both MnS and such manganese silicates as Mn2SiO4 and MnSiO3 should be addressed to ensure the full regeneration of the reduced MnFe2O4.

  7. Anomalous Dilatometric Response in Fe-Mn-Al-Si Steel

    NASA Astrophysics Data System (ADS)

    Ghosh, S. K.

    2012-04-01

    The present study deals with the transformation of an aggregate consisting of ferrite and pearlite into austenite in a Fe-0.36C-1.98Mn-1.97Al-0.30Si (wt%) steel. The transformation phenomenon has been studied using dilatometry which confirms that austenite starts to nucleate due to dissolution of ferrite and pearlite and subsequently it commences to grow when the appropriate elevated temperature is reached. The austenite formation has been accompanied with the formation of a hump in the dilatation curve which is different with respect to the results reported earlier. The non-conventional behaviour associated with the austenite formation has been explained using the X-ray diffraction data, microstructural investigation and also with MT-DATA theoretical calculations.

  8. Interdiffusion in nanometric Fe/Ni multilayer films

    SciTech Connect

    Liu, Jiaxing Barmak, Katayun

    2015-03-15

    [Fe (3.1 nm)/Ni (3.3 nm)]{sub 20} multilayer films were prepared by DC magnetron sputtering onto oxidized Si(100) substrates. The Fe and Ni layers were shown to both be face-centered cubic by x-ray diffraction. Interdiffusion of the Fe and Ni layers in the temperature range of 300–430 °C was studied by x-ray reflectivity. From the decay of the integral intensity of the superlattice peak, the activation energy and the pre-exponential term for the effective interdiffusion coefficient were determined as to 1.06 ± 0.07 eV and 5 × 10{sup −10} cm{sup 2}/s, respectively. The relevance of the measured interdiffusion coefficient to the laboratory timescale synthesis of L1{sub 0} ordered FeNi as a rare-earth free permanent magnet is discussed.

  9. Mesoporous MFe{sub 2}O{sub 4} (M = Mn, Co, and Ni) for anode materials of lithium-ion batteries: Synthesis and electrochemical properties

    SciTech Connect

    Duan, Lianfeng; Wang, Yuanxin; Wang, Linan; Zhang, Feifei; Wang, Limin

    2015-01-15

    Highlights: • MFe{sub 2}O{sub 4} (M = Mn, Co, and Ni) are synthesized by a template-free hydrothermal method. • The mesoporous morphology is formed by self-assembly of crystal nucleus. • The mesporous MnFe{sub 2}O{sub 4} have the active phase and the synergy for Li-ion storage. - Abstract: The MFe{sub 2}O{sub 4} (M = Mn, Co, and Ni) mesoporous spheres with an average diameter of 250 nm were synthesized through a template-free hydrothermal method. The mesoporous MnFe{sub 2}O{sub 4} with a large surface area of 87.5 m{sup 2}/g and an average pore size of 27.52 nm were obtained. As the anode materials for Li-ion batteries, the mesoporous MnFe{sub 2}O{sub 4} exhibits excellent initial charge and discharge capacities of 1010 and 642.5 mA h/g. After 50 cycles, the discharge capacity could still remain at 379 mA h/g. The results showed that the active phase and the synergy between different metal oxides greatly improved the electrochemical performance, and the mesoporous composite could stabilize the structure of the electrodes.

  10. Solid-state synthesis and phase transformations in Ni/Fe films: Structural and magnetic studies

    NASA Astrophysics Data System (ADS)

    Myagkov, V. G.; Zhigalov, V. C.; Bykova, L. E.; Bondarenko, G. N.

    2006-10-01

    We have used X-ray diffraction, volume magnetocrystalline anisotropy constant and resistance measurements to study solid-state synthesis in Ni(0 0 1)/Fe(0 0 1), Ni/Fe(0 0 1) and Ni/Fe thin films with the atomic ratio between Fe and Ni of 1:1 (1Fe:1Ni), and 3:1 (3Fe:1Ni). We have found that the formation of Ni 3Fe and NiFe phases in the 1Fe:1Ni films takes place at temperatures ˜620 and ˜720 K, correspondingly. In the case of the 3Fe:1Ni films the solid-state synthesis starts with Ni 3Fe and NiFe phase formation at the same temperatures as for the 1Fe:1Ni films. The increasing of annealing temperature above 820 K leads to the nucleation of a paramagnetic γpar phase at the FeNi/Fe interface. The final products of solid-state synthesis in the Ni(0 0 1)/Fe(0 0 1) thin films are crystallites which consist of the epitaxially intergrown NiFe and γpar phases according to the [1 0 0](0 0 1)NiFe||[1 0 0](0 0 1) γpar orientation relationship. The crystalline perfection and epitaxial growth of the (NiFe+ γpar) crystallites on the MgO(0 0 1) surface allow to distinguish (0 0 2) γpar and (0 0 2)NiFe X-ray peaks (the cell parameters are: a( γpar)=0.3600±0.0005 nm and a(NiFe)=0.3578±0.0005 nm, correspondingly). At low temperatures the paramagnetic γpar phase undergoes the martensite γ→α' phase transition which can be hindered by thermal and epitaxial strains and epitaxial clamping with a MgO substrate. On the basis of the studies of the thin-film solid-state synthesis we predict the existence of two novel structural phase transformations at the temperatures of about 720 and 820 K for alloys of the invar region of the Fe-Ni system.

  11. A study of Fe2+xMn1-xAl alloys: Structural and magnetic properties

    NASA Astrophysics Data System (ADS)

    Paduani, C.; Migliavacca, A.; Pöttker, W. E.; Schaf, J.; Krause, J. C.; Ardisson, J. D.; Samudio Pérez, C. A.; Takeuchi, A. Y.; Yoshida, M. I.

    2007-08-01

    The Fe2+xMn1-xAl alloys were studied experimentally to assess the effect of variations of composition around stoichiometric on the structural and magnetic properties of this system. The results indicate that the ordered L21(X2YZ) structure of full Heusler alloys can be stabilized with small deviations of composition from the stoichiometric 2:1:1. The saturation magnetization is strongly composition dependent and decreases with the increase of the Mn concentration, in spite of the fact that the Mn atoms carry the largest moment in the ordered phase. The highest Curie temperature was observed for the Fe-richer alloy. Magnetic measurements suggest that atomic disorder and competition of the antiferromagnetic Fe-Mn and Mn-Mn interactions with the ferromagnetic Fe-Fe, Mn-Mn and Fe-Mn interactions lead to a frustrated couplings ending in a reentrant spin-glass behavior at low temperature.

  12. Synthesis of Mn1-xZnxFe2O4 ferrite powder by co-precipitation method

    NASA Astrophysics Data System (ADS)

    Irfan, Salma; Ajaz-un-Nabi, M.; Jamil, Yasir; Amin, Nasir

    2014-06-01

    Ferrimagnetic substances referred to as ferrites are ionic crystals whose chemical composition is of the form XFe2 O4 where X signifies a divalent metal. Magnetic Nano sized ferrites have found a significant potential in many applications, such as magnetic recording media, Ferro fluids and radar absorbing coating. Ferrites are widely used in many industrial applications due to their spontaneous magnetization. Soft ferrites of Mn-Zn, Ni-Zn and Mg-Mn are well known for their high magnetic permeability. In the present research work we have prepared fine Mn1-xZnxFe2O4 ferrite powder with varying x concentrations (0.25-0.75) by metal chloride precursors through a co-precipitation technique by pipette drop method using aqueous NaOH solution for comparing their spontaneous magnetization and particle size. The co-precipitation technique is a high way to produce chemically homogeneous powder with fine particle size in nanometers (22.5nm-74.5nm).The effect of x-concentration on the particle size of the Mn(1-x) Zn(x) ferrite has been discussed on the basis of XRD. The crystalline phases have been identified by X-ray diffraction with Cu-Kα radiations. The XRD patterns have verified that the specimen has spinal type structure. The observable peaks are broad since the size of the particles is small. We have concluded that at constants temperature particle size increases with increasing x-concentrations. Effect of different concentrations of x (Zn+2) on the spontaneous magnetization of different Mn(1-x) Zn(x) Fe2O4 sample is determined. We have reached the conclusion that all the samples of Mn(1-x) Zn(x) Fe2 O4 ferrites were magnetic either of low or high magnetization. The maximum spontaneous magnetization and minimum particle size is obtained at x=0.25 (at digestion temperature=65°C).

  13. Natural speciation of Mn, Ni, and Zn at the micrometer scale in a clayey paddy soil using X-ray fluorescence, absorption, and diffraction

    NASA Astrophysics Data System (ADS)

    Manceau, Alain; Tommaseo, Caterina; Rihs, Sophie; Geoffroy, Nicolas; Chateigner, Daniel; Schlegel, Michel; Tisserand, Delphine; Marcus, Matthew A.; Tamura, Nobumichi; Chen, Zueng-Sang

    2005-08-01

    The natural speciation of Mn (0.19 g/kg), Ni (46 mg/kg), and Zn (42 mg/kg) in the argillic horizon (120 cm depth, pH = 5.6) of an Ultisol from a paddy soil in northern Taiwan was investigated by advanced X-ray synchrotron techniques. Microchemical associations were imaged by synchrotron-based X-ray microfluorescence, host minerals were identified by standard and micrometer-resolved X-ray diffraction, and the local coordination environment of Mn, Ni, and Zn was probed using extended X-ray absorption fine structure (EXAFS) spectroscopy on a powdered sample and a soil thin section, and polarized EXAFS spectroscopy on a highly textured self-supporting clay film from the <2 μm fraction of the soil. Manganese was concentrated in Fe-Mn soft mottles (44.4 g/kg) as turbostratic hexagonal birnessite and lithiophorite having Mn 3+/Mn 4+ atomic ratios of ˜20% and 50%, respectively. Quantitative analysis of high-order scattering paths of the EXAFS spectrum for natural and synthetic (AlLi)(Mn0.684+Mn0.323+)O( lithiophorite revealed that Mn 3+ and Mn 4+ are ordered in the [ layer. A structural model is proposed, in which Mn 4+ and Mn 3+ are ordered similarly to Al and Li in the [ layer, with Mn 3+ cations being surrounded by six Mn 4+, and Mn 4+ cations by three Mn 3+ and three Mn 4+. Similar cation ordering in the manganese and aluminum layers likely provides a more homogeneous local balance of the excess and deficit of charges in each layer and increases the stability of lithiophorite. Ni ( r = 0.70 Å) substitutes for Mn (r(Mn 4+) = 0.54 Å, r(Mn 3+) = 0.65 Å) in the manganese layer in the natural lithiophorite. In contrast, Zn ( r = 0.74 Å) fills vacant sites in the gibbsitic layer of natural lithiophorite, in a similar manner as lithium ( r = 0.74 Å) in synthetic lithiophorite. The partitioning of Ni and Zn between the two layers is a result of the general preference of Ni, whose size is intermediate between those of Mn 3+ and Li +, for slightly smaller sites. In

  14. Dilute ferrimagnetism of ilmenites Mn3FeTiSbO9 and Mn4FeTi2SbO12

    NASA Astrophysics Data System (ADS)

    Bazuev, G. V.; Korolev, A. V.; Golovkin, B. G.

    2016-07-01

    Metastable solid solutions (SS) Mn3FeTiSbO9 and Mn4FeTi2SbO12 with the ilmenite structure (space group R bar 3) have been prepared by quenching at normal conditions. The compositions of the compounds have been justified using EDX spectroscopy and X-ray diffraction. The magnetic properties of SSs have been analyzed by comparison with ferrimagnetic ilmenite Mn2FeSbO6 ( T N = 269 K) as a natural mineral and ceramics obtained at high pressure and high temperature. The solid solutions have been characterized as dilute magnetic systems formed as a result of substitution of nonmagnetic cations Ti4+ for a part of Fe3+ and Sb5+ cations. Mn3FeTiSbO9 is considered as a ferromagnetic with T N = 171 K and Mn4FeTi2SbO12 as a magnetic with the concentration of magnetic clusters below the percolation threshold.

  15. Liquid flow deposited spinel (Ni,Mn)3O4 thin films for microbolometer applications

    NASA Astrophysics Data System (ADS)

    Le, Duc Thang; Jeon, Chang Jun; Lee, Kui Woong; Jeong, Young Hun; Yun, Ji Sun; Yoon, Dae Ho; Cho, Jeong Ho

    2015-03-01

    A liquid flow deposition (LFD) technique was initially used for the fabrication of single-component Mn3O4 thin films onto Si wafer substrates at a range of substrate temperatures of 30-80 °C, with the introduction of an oxidizing reagent (H2O2). As a result, solid thin films were well formed from an aqueous solution. An X-ray diffraction (XRD) analysis showed typical characteristics of hausmannite Mn3O4 with a spinel tetragonal phase. Field-emission scanning electron microscopy (FE-SEM) observations revealed nano-sized grains arranged uniformly on a dense and smooth surface for all of the as-deposited films. On the other hand, the LFD method was then extended to prepare two-component nickel-manganite films according to the binary chemical composition of NixMn3-xO4 with x = 0.02-0.2. The as-grown nickel-manganite films showed a surface with a good quality with a spherical bead-like architecture when x ≤ 0.10, while a conversion from spherical grains into highly porous nanowalls in the microstructure was noted in films when x ≥ 0.12. These results signify that it is possible to fabricate various multi-component manganite-oxide thin films at a low temperature. In addition, the dependences of the room-temperature electrical resistivity (ρ) and the temperature coefficient of resistance (TCR) on the Ni substitution level (x) were investigated on films annealed at 400 °C.

  16. Defect controlled magnetism in FeP/graphene/Ni(111)

    PubMed Central

    Bhandary, Sumanta; Eriksson, Olle; Sanyal, Biplab

    2013-01-01

    Spin switching of organometallic complexes by ferromagnetic surfaces is an important topic in the area of molecular nanospintronics. Moreover, graphene has been shown as a 2D surface for physisorption of molecular magnets and strain engineering on graphene can tune the spin state of an iron porphyrin (FeP) molecule from S = 1 to S = 2. Our ab initio density functional calculations suggest that a pristine graphene layer placed between a Ni(111) surface and FeP yields an extremely weak exchange interaction between FeP and Ni whereas the introduction of defects in graphene shows a variety of ferromagnetic and antiferromagnetic exchange interactions. Moreover, these defects control the easy axes of magnetization, strengths of magnetic anisotropy energies and spin-dipolar contributions. Our study suggests a new way of manipulating molecular magnetism by defects in graphene and hence has the potential to be explored in designing spin qubits to realize logic operations in molecular nanospintronics. PMID:24296980

  17. Local structure study of Fe dopants in Ni-deficit Ni3Al alloys

    DOE PAGES

    V. N. Ivanovski; Umicevic, A.; Belosevic-Cavor, J.; ...

    2015-08-24

    We found that the local electronic and magnetic structure, hyperfine interactions, and phase composition of polycrystalline Ni–deficient Ni 3-x FexAl (x = 0.18 and 0.36) were investigated by means of 57 Fe Mössbauer spectroscopy. The samples were characterized by X–ray diffraction and magnetization measurements. The ab initio calculations performed with the projector augmented wave method and the calculations of the energies of iron point defects were done to elucidate the electronic structure and site preference of Fe doped Ni 3 Al. Moreover, the value of calculated electric field gradient tensor Vzz=1.6 1021Vm-2 matches well with the results of Mössbauer spectroscopymore » and indicates that the Fe atoms occupy Ni sites.« less

  18. Effect of Ni content on microwave absorbing properties of MnAl powder

    NASA Astrophysics Data System (ADS)

    Wang, Zhen-zhong; Lin, Pei-hao; Huang, Wei-chao; Pan, Shun-kang; Liu, Ye; Wang, Lei

    2016-09-01

    MnAlNi powder was prepared by the process of vacuum levitation melting and high-energy ball milling, The morphology and phase structure of the powder were analyzed by Scanning Electron Microscope(SEM), X-ray diffraction(XRD) and the effect of the Ni content on microwave absorbing properties of MnAl powder was investigated by an vector network analyzer. The addition of Ni, which improved the microwave absorbing properties of MnAl powder but not changed the composition of Al8Mn5 alloy. The minimum reflectivity of (Al8Mn5)0.95Ni0.05 powder with a coating thickness (d) of 1.8 mm was about -40.8 dB and has better bandwidth effect, the absorbing mechanism of AlMnNi powders on the electromagnetic was related to the electromagnetic loss within the absorbing coatings and the effect of coating thickness on the interference loss of electromagnetic wave.

  19. Room temperature ferromagnetism in Mn-doped NiO nanoparticles

    NASA Astrophysics Data System (ADS)

    Layek, Samar; Verma, H. C.

    2016-01-01

    Mn-doped NiO nanoparticles of the series Ni1-xMnxO (x=0.00, 0.02, 0.04 and 0.06) are successfully synthesized using a low temperature hydrothermal method. Samples up to 6% Mn-doping are single phase in nature as observed from powder x-ray diffraction (XRD) studies. Rietveld refinement of the XRD data shows that all the single phase samples crystallize in the NaCl like fcc structure with space group Fm-3m. Unit cell volume decreases with increasing Mn-doping. Pure NiO nanoparticles show weak ferromagnetism, may be due to nanosize nature. Introduction of Mn within NiO lattice improves the magnetic properties significantly. Room temperature ferromagnetism is found in all the doped samples whereas the magnetization is highest for 2% Mn-doping and then decreases with further doping. The ZFC and FC branches in the temperature dependent magnetization separate well above 350 K indicating transition temperature well above room temperature for 2% Mn-doped NiO Nanoparticle. The ferromagnetic Curie temperature is found to be 653 K for the same sample as measured by temperature dependent magnetization study using vibrating sample magnetometer (VSM) in high vacuum.

  20. Application of atomic Hirshfeld surface analysis to intermetallic systems: is Mn in cubic CeMnNi4 a thermoelectric rattler atom?

    PubMed

    Jørgensen, Mads R V; Skovsen, Iben; Clausen, Henrik F; Mi, Jian-Li; Christensen, Mogens; Nishibori, Eiji; Spackman, Mark A; Iversen, Bo B

    2012-02-06

    The Mn atom in the cubic polymorph of CeMnNi(4) appears to be located in an oversized cage-like structure, and anomalously large atomic displacement parameters (ADPs) for the Mn atom indicate that it is a potential "rattler" atom. Here, multitemperature synchrotron powder X-ray diffraction data measured between 110 and 900 K are used to estimate ADPs for the Mn "guest" atom and the "host" structure atoms in cubic CeMnNi(4). The ADPs are subsequently fitted with Debye and Einstein models, giving Θ(D) = 301(2) K for the "host" structure and Θ(E) = 165(2) K for the Mn atom. This is higher than typical Einstein temperatures for rattlers in thermoelectric skutterudites and clathrates (Θ(E) = 50-80 K), indicating that the Mn atom in cubic CeMnNi(4) is more strongly bonded. In order to probe the chemical interactions of the potential Mn rattler atom, atomic Hirshfeld surface (AHS) analysis is carried out and compared with AHS analysis of well-established guest atom rattlers in archetypical skutterudites, MCoSb(3). Surprisingly, the skutterudite rattlers have more deformed AHSs than the Mn atom in cubic CeMnNi(4). This is related to the highly ionic nature of the skutterudite rattlers, which is not taken into account in the neutral spherical atom approach of the AHS. Additionally, visualization of void spaces in the two materials using the procrystal electron density shows that while the Mn atom is tightly fitting in the CeMnNi(4) structure then the La atom in the skutterudite is truly situated in an oversized cage of the host structure. Overall, we conclude that the Mn atom in cubic CeMnNi(4) cannot be coined a rattler.

  1. Influence of substrate rocks on Fe-Mn crust composition

    USGS Publications Warehouse

    Hein, J.R.; Morgan, C.L.

    1999-01-01

    Principal Component and other statistical analyses of chemical and mineralogical data of Fe-Mn oxyhydroxide crusts and their underlying rock substrates in the central Pacific indicate that substrate rocks do not influence crust composition. Two ridges near Johnston Atoll were dredged repetitively and up to seven substrate rock types were recovered from small areas of similar water depths. Crusts were analyzed mineralogically and chemically for 24 elements, and substrates were analyzed mineralogically and chemically for the 10 major oxides. Compositions of crusts on phosphatized substrates are distinctly different from crusts on substrates containing no phosphorite. However, that relationship only indicates that the episodes of phosphatization that mineralized the substrate rocks also mineralized the crusts that grew on them. A two-fold increase in copper contents in crusts that grew on phosphatized clastic substrate rocks, relative to crusts on other substrate rock types, is also associated with phosphatization and must have resulted from chemical reorganization during diagenesis. Phosphatized crusts show increases in Sr, Zn, Ca, Ba, Cu, Ce, V, and Mo contents and decreases in Fe, Si, and As contents relative to non-phosphatized crusts. Our statistical results support previous studies which show that crust compositions reflect predominantly direct precipitation from seawater (hydrogenetic), and to lesser extents reflect detrital input and diagenetic replacement of parts of the older crust generation by carbonate fluorapatite.