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Sample records for multilayer interface anisotropy

  1. Magnetic multilayer interface anisotropy

    SciTech Connect

    Pechan, M.J.

    1992-01-01

    Ni/Mo and Ni/V multilayer magnetic anisotropy has been investigated as a function of Ni layer thickness, frequency and temperature. Variable frequency ferromagnetic resonance (FMR) measurements show, for the first time, significant frequency dependence associated with the multilayer magnetic anisotropy. The thickness dependence allows one to extract the interface contribution from the total anisotropy. Temperature dependent FMR (9 GHz) and room temperature magnetization indicate that strain between Ni and the non-magnetic layers is contributing significantly to the source of the interface anisotropy and the state of the interfacial magnetization. In order to examine the interface properties of other transition metal multilayer systems, investigations on Fe/Cu are underway and CoCr/Ag is being proposed. ESR measurements have been reported on Gd substituted YBaCuO superconductors and a novel quasi-equilibrium method has been developed to determine quickly and precisely the ransition temperature.

  2. Magnetic multilayer interface anisotropy. Technical progress report, January 1, 1992--December 31, 1992

    SciTech Connect

    Pechan, M.J.

    1992-12-01

    Ni/Mo and Ni/V multilayer magnetic anisotropy has been investigated as a function of Ni layer thickness, frequency and temperature. Variable frequency ferromagnetic resonance (FMR) measurements show, for the first time, significant frequency dependence associated with the multilayer magnetic anisotropy. The thickness dependence allows one to extract the interface contribution from the total anisotropy. Temperature dependent FMR (9 GHz) and room temperature magnetization indicate that strain between Ni and the non-magnetic layers is contributing significantly to the source of the interface anisotropy and the state of the interfacial magnetization. In order to examine the interface properties of other transition metal multilayer systems, investigations on Fe/Cu are underway and CoCr/Ag is being proposed. ESR measurements have been reported on Gd substituted YBaCuO superconductors and a novel quasi-equilibrium method has been developed to determine quickly and precisely the ransition temperature.

  3. The role of symmetry-breaking-induced interface anisotropy in [Fe/Pt]{sub n} multilayer films

    SciTech Connect

    Li Zhenghua; Xie Hailong; Liu Xi; Bai Jianmin; Wei Fulin; Wei Dan; Yoshimura, S.; Saito, H.; Liu Xiaoxi

    2011-04-01

    The FePt films were deposited with [Fe/Pt]{sub n} multilayer structure on preheated Corning 1737F glass substrate using pure Fe and Pt target in a CMS-18 sputtering system. The dependence of FePt's texture and magnetic properties on the multilayer structure was investigated. The XRD patterns indicate that (111) texture is dominant for all [Fe/Pt]{sub n} (n = 8, 16, 20, 32) multilayer films. However, the measured M-H loops show that the perpendicular anisotropy is greatly enhanced in samples with n = 16, 20, and 32. The origin of the increased perpendicular anisotropy of [Fe/Pt]{sub n} multilayer films is related to the contributions of the interfaces, which will be analyzed using the micromagnetic models, with careful discussions of the crystalline and interface anisotropies. Finally, it is confirmed that the Fe/Pt interfaces favor the perpendicular orientation in the multilayer structure.

  4. Precise control of interface anisotropy during deposition of Co/Pd multilayers

    SciTech Connect

    Barton, C. W. Thomson, T.; Slater, T. J. A.; Haigh, S. J.; Rowan-Robinson, R. M.; Atkinson, D.

    2014-11-28

    We demonstrate the control of perpendicular magnetic anisotropy (PMA) in multilayer films without modification of either the microstructure or saturation magnetization by tuning the Ar{sup +} ion energy using remote plasma sputtering. We show that for [Co/Pd]{sub 8} multilayer films, increasing the Ar{sup +} ion energy results in a strong decrease in PMA through an increase in interfacial roughness determined by X-ray reflectivity measurements. X-ray diffraction and transmission electron microscope image data show that the microstructure is independent of Ar{sup +} energy. This opens a different approach to the in-situ deposition of graded exchange springs and for control of the polarizing layer in hybrid spin transfer torque devices.

  5. Magnetisation reversal in anisotropy graded Co/Pd multilayers

    SciTech Connect

    Barton, C. W. Thomson, T.

    2015-08-14

    We demonstrate high precision controllability of the magnetization reversal nucleation process in [Co/Pd]{sub 8} multilayer films consisting of two sets of bilayers with high and low perpendicular anisotropy, respectively. The anisotropy of the entire film is set by the degree of Co/Pd interfacial mixing during deposition which provides fine control of the anisotropy of an individual bilayer in the multilayer stack. The relative number of each type of bilayer is used to select the magnetisation reversal behavior such that changing one bilayer changes the properties of the entire multilayer through anisotropy averaging. A simple extension to the sputtering protocol would provide multilayer films with fully graded anisotropy, while maintaining a constant saturation magnetization opening new possibilities for the creation of highly engineered multilayer structures for spin torque devices and future magnetic recording media.

  6. Engineering spin-orbit torque in Co/Pt multilayers with perpendicular magnetic anisotropy

    SciTech Connect

    Huang, Kuo-Feng; Wang, Ding-Shuo; Lai, Chih-Huang; Lin, Hsiu-Hau

    2015-12-07

    To address thermal stability issues for spintronic devices with a reduced size, we investigate spin-orbit torque in Co/Pt multilayers with strong perpendicular magnetic anisotropy. Note that the spin-orbit torque arises from the global imbalance of the spin currents from the top and bottom interfaces for each Co layer. By inserting Ta or Cu layers to strengthen the top-down asymmetry, the spin-orbit torque efficiency can be greatly modified without compromised perpendicular magnetic anisotropy. Above all, the efficiency builds up as the number of layers increases, realizing robust thermal stability and high spin-orbit-torque efficiency simultaneously in the multilayers structure.

  7. Perpendicular Magnetic Anisotropy of Tb/Fe and Gd/Fe Multilayers Studied with Torque Magnetometer

    NASA Astrophysics Data System (ADS)

    Chowdhury, Ataur

    Perpendicular magnetic anisotropy (PMA) of multilayers critically depend on the magnetic and structural ordering of the interface. To study the effect of interface on PMA, Tb/Fe and Gd/Fe multilayers with varying Fe (0.8-9.0 nm) and Gd (0.5-2.8 nm) or Tb (0.3-6.3 nm) layer thicknesses were fabricated by planar magnetron sputtering. The magnetometer results of spin orientation clearly reveals that samples with Gd or Tb layer thickness of more than 1.2 nm display no PMA, regardless of the Fe layer thickness. Tb/Fe and Gd/Fe multilayers with thin (<1.2 nm) Tb or Gd layers display large PMA, but no PMA is observed when the Fe layer thickness is increased to 4.0 nm and higher. The bulk magnetization and anisotropy energy constant of the samples are found to increase with increasing Fe layer thickness. Torque measurement also reveals that there are two distinctly different axes of spin alignment at different energy. Tb/Fe and Gd/Fe multilayers with similar composition reveal similar magnetic and structural characteristics, and it may imply that single-ion-anisotropy of rare-earth element, which is quite large for Tb ions and very small for Gd ions, may not be the dominating cause of PMA in Td/Fe and Gd/Fe multilayers. A detailed explanation of the results will be provided based on exchange interaction at the interface.

  8. Effective anisotropy gradient in pressure graded [Co/Pd] multilayers

    SciTech Connect

    Kirby, B. J. Maranville, B. B.; Greene, P. K.; Liu, Kai; Davies, J. E.

    2015-02-14

    We have used polarized neutron reflectometry to show that controlled variation of growth pressure during deposition of Co/Pd multilayers can be used to achieve a significant vertical gradient in the effective anisotropy. This gradient is strongly dependent on deposition order (low to high pressure or vice versa), and is accompanied by a corresponding gradient in saturation magnetization. These results demonstrate pressure-grading as an attractively simple technique for tailoring the anisotropy profile of magnetic media.

  9. Random Field effects in perpendicular-anisotropy multilayer films

    NASA Astrophysics Data System (ADS)

    Xu, Jian; Silevitch, Daniel; Rosenbaum, Thomas

    With the application of a magnetic field transverse to the magnetic easy axis, randomly-distributed 3D collections of dipole-coupled Ising spins form a realization of the Random-Field Ising Model. Tuning the strength of the site-specific random field, and hence the disorder, via the applied transverse field regulates the domain reversal energetics and hence the macroscopic hysteresis loop. We extend this approach to two dimensions, using sputtered Perpendicular Magnetic Anisotropy (PMA) Co/Pt multilayer thin films. We characterize the coercive fields and hysteresis loops at a series of temperatures and transverse fields.

  10. The effect of interfaces on the mechanical behaviour of multilayered metallic laminates

    NASA Astrophysics Data System (ADS)

    Sobie, Cameron; McPhie, Mathieu G.; Capolungo, Laurent; Cherkaoui, Mohammed

    2014-06-01

    The mechanical response of multilayered metallic laminates is dominated by size effects through the confinement of dislocation motion within the layers. We deconvolute the contributions to the plastic behaviour resulting from dislocation-dislocation interactions and dislocation-interface interactions, using discrete dislocation dynamics and atomistic simulations. Upper and lower bounds for the material strength are found by considering two limiting cases for the influence of the interfaces: hard and shearable. Hard interfaces, preserving interfacial dislocations, are shown to significantly increase the strength of the multilayered metallic laminates, whereas a deformable interface results in lesser hardening. Molecular dynamics simulations show that the {1 1 1}Cu ∥ {1 1 0}Nb Cu/Nb interface response lies between these two cases. Additionally, the plastic response of Cu/Nb multilayered metallic laminates is studied and shown to be isotropic due to an effect of averaging among layers, despite the plastic anisotropy of the respective layer materials.

  11. Magnetoelastically induced magnetic anisotropy transition in [CoO5nm/CoPt7nm]5 multilayer films

    NASA Astrophysics Data System (ADS)

    Guo, Lei; Harumoto, Takashi; Sannomiya, Takumi; Muraishi, Shinji; Nakamura, Yoshio; Shi, Ji

    2016-06-01

    The magnetic anisotropy transition of [CoO5nm/CoPt7nm]5 multilayer film with respect to post-annealing has been studied systematically. It undergoes a smooth transition from longitudinal magnetic anisotropy (LMA) to perpendicular magnetic anisotropy (PMA) upon annealing and returns backward to LMA at high temperature of 550 °C. The strongest PMA of [CoO5nm/CoPt7nm]5 is achieved after post-annealing at 300 °C and the tolerable post-annealing temperature with strong PMA is up to 400 °C, which indicates this multilayer film could be a potential candidate for the PMA application at middle-high-temperature-region between 300 °C and 400 °C. The mechanism responsible for the transition of magnetic anisotropy has been investigated by analyzing CoO/CoPt interface and CoPt layer internal stress. It is found the effective PMA energy is proportional to the in-plane tensile stress of CoPt layer but is inversely proportional to the roughness of CoO/CoPt interface. Finally, by means of low temperature experiment we demonstrate the magnetic anisotropy transition observed in [CoO5nm/CoPt7nm]5 multilayer film is mainly attributed to the change of CoPt layer in-plane tensile stress.

  12. Peculiar effective elastic anisotropy of nanometric multilayers studied by surface Brillouin scattering

    NASA Astrophysics Data System (ADS)

    Faurie, D.; Djemia, P.; Castelnau, O.; Brenner, R.; Belliard, L.; Le Bourhis, E.; Goudeau, Ph; Renault, P.-O.

    2015-12-01

    We show in this paper by using a two-scale transition model that the elastic anisotropy of a thin film specimen can be tuned by appropriate stacking design. The anisotropic behaviour is illustrated for two monophase thin films, namely W which is perfectly elastically isotropic and Au which is strongly elastically anisotropic, and for a nanometric W/Au multilayers. The experimental measurements show that the model capture the elastic anisotropy rather well even for a nanometric multilayer stacking (period of 12 nm) and that the elastic anisotropy of W/Au multilayer is more pronounced than the ones of the two components for a fraction of 50%. This enhanced anisotropy is discussed in view of the multilayer microstructure.

  13. Interfacial electronic structure-modulated magnetic anisotropy in Ta/CoFeB/MgO/Ta multilayers

    SciTech Connect

    Chen, Xi; Jiang, Shao Long; Yang, Guang; Liu, Yang; Teng, Jiao; Yu, Guang Hua; Wang, Kai You; Wu, Zheng Long

    2014-09-01

    We have observed several unexpected phenomena when a trace amount of Fe atoms is deposited onto the CoFeB/MgO interface in Ta/CoFeB/MgO/Ta multilayers. With the nominal thickness of the introduced Fe atoms (t{sub Fe}) varying from 0 to 0.1 Å, the effective magnetic anisotropy energy (K{sub eff}) of annealed multilayers is remarkably enhanced from 1.28 × 10{sup 6 }erg/cm{sup 3} to 2.14 × 10{sup 6 }erg/cm{sup 3}. As t{sub Fe} further increasing, the K{sub eff} decreases and even becomes negative when t{sub Fe} > 1 Å, indicating the change from perpendicular magnetic anisotropy to in-plane magnetic anisotropy. The analysis by X-ray photoelectron spectrometer reveals that the Fe atoms at annealed CoFeB/MgO interface show different electronic structures as t{sub Fe} increasing, which combine with O atoms to form FeO{sub x} (x < 1), Fe{sub 2}O{sub 3}, and Fe{sub 3}O{sub 4}, respectively, leading to modulation of Fe 3d-O 2p orbital hybridization and thus the K{sub eff}. On the other hand, we find that the introduction of Fe atoms also helps to reduce the multilayers' magnetic damping.

  14. Constraints on Multilayered Anisotropy beneath Ocean Islands from Harmonic Decomposition of Receiver Functions

    NASA Astrophysics Data System (ADS)

    Park, J. J.; Olugboji, T. M.

    2013-12-01

    Receiver functions have been used to provide, with improved resolution, velocity structure in the crust and upper mantle for oceans and continents. For oceanic regions, receiver function results are only possible were there is station coverage - ocean island stations and ocean bottom seismometers. Receiver function studies of oceanic crustal and upper mantle structure have provided constraints on Moho depth, lithosphere-asthenosphere boundary depth, and show evidence for magmatic underplating. Until recently, these receiver functions have focused on the radial RFs, neglecting information available from transverse RFs. We provide new results that suggest the prevalence of multi-layered crustal anisotropy using azimuthal variation in the amplitudes of radial and transverse receiver functions, reconstructed via harmonic decomposition. The harmonic components give information on the dip and trend of the axis of symmetry within the anisotropic layers above and below interfaces that generate Ps converted waves. Information from preliminary study of ten ocean island stations shows that azimuthal RF variation is largely two-lobed for most of the ocean-island stations, consistent with anisotropy with a tilted symmetry axis in the oceanic crust, including the underplated layers. Using sequential H-K stacks to model the isotropic velocity and the number of layers, we can guide harmonic decomposition to specify the presence and orientation of anisotropy within the specific layers. We will use this to evaluate hypothetical models for ocean-island crustal fabric.

  15. Anisotropies and spin dynamics in ultrathin magnetic multilayer structures

    NASA Astrophysics Data System (ADS)

    Kardasz, Bartlomiej

    High quality magnetic films were prepared by Molecular Beam Epitaxy (MBE) using Thermal Deposition (TD) and Pulse Laser Deposition (PLD) techniques. Ferromagnetic Resonance (FMR) and Mossbauer studies have shown that the Fe films prepared by PLD exhibited a more intermixed interface lattice structure than those prepared by TD. Dramatic decrease of the in-plane interface uniaxial anisotropy for the PLD films compared to those prepared by TD has shown that the in-plane uniaxial anisotropy is caused by magnetoelasticity driven by the Fe/GaAs(001) interface lattice shear. Magnetization dynamics of the ultrathin Fe/Au,Ag/Fe films was studied using Time-Resolved Magneto-Optical Kerr Effect (TRMOKE) and FMR in the frequency range from 1 to 73 GHz. The Gilbert damping was studied in the Au/Fe/GaAs(001) structures as a function of the Fe and Au layer thickness, respectively. The observed increase in magnetic damping in the Fe film covered with thick Au capping layers was explained by spin pumping at the Fe/Au interface accompanied by spin relaxation and diffusion of the accumulated spin density in the Au layer. The spin diffusion length in Au was found to be 34 nm at room temperature. Significant increase of the Gilbert damping was observed in the Au/Fe/GaAs structures with decreasing Fe film thickness. Its origin lies in the additional damping at the Fe/GaAs interface. Direct detection of the spin current propagating across the Ag spacer in Fe/Ag,Au/Fe/GaAs(001) structures was carried out with stroboscopic TRMOKE measurements. The Fe layer grown on GaAs served as a spin pumping source and the Fe layer grown on the Au,Ag spacer was used as a probe for detection of the spin current propagating across the Au and Ag spacers. The experimental results were interpreted using selfconsistent solution of the Landau Lifshitz Gilbert (LLG) equations of motion with the spin diffusion equation for the accumulated spin density in the Au and Ag spacers. The spin diffusion length in Ag was

  16. Corrosion protected, multi-layer fuel cell interface

    DOEpatents

    Feigenbaum, Haim; Pudick, Sheldon; Wang, Chiu L.

    1986-01-01

    An improved interface configuration for use between adjacent elements of a fuel cell stack. The interface is impervious to gas and liquid and provides resistance to corrosion by the electrolyte of the fuel cell. The multi-layer configuration for the interface comprises a non-cupreous metal-coated metallic element to which is film-bonded a conductive layer by hot pressing a resin therebetween. The multi-layer arrangement provides bridging electrical contact.

  17. Impact of buffer layer and Pt thickness on the interface structure and magnetic properties in (Co/Pt) multilayers.

    PubMed

    Bersweiler, M; Dumesnil, K; Lacour, D; Hehn, M

    2016-08-24

    The influence of Pt thickness on the interface structure (roughness / intermixing) and magnetic properties has been investigated for (Co / Pt) multilayers sputtered on a Pt or a thin oxide (MgO or AlO x ) buffer layer. When Pt thickness increases from 1.2 nm-2.2 nm, we observe that the effective anisotropy increases with the Pt thickness, simultaneously with the decrease of roughness, i.e. the occurrence of sharper interfaces. Perpendicular magnetic anisotropy (PMA) is still achieved on the oxide buffer layers, but with a lower effective anisotropy correlated to more perturbed interfaces. The detailed analysis of the saturation magnetization shows that: (i) M s is significantly enhanced in the case of rough/intermixed interfaces, which is attributed to and discussed in the framework of Pt induced polarization, (ii) the change in volume dipolar anisotropy is the main factor responsible for the reduction of K eff for systems grown on oxides. Beyond the major role of volume dipolar contribution that reduces PMA, a supplemental positive contribution promoting PMA can be invoked for rough interfaces and large M s (deposit on oxide). This contribution is consistent with a dipolar surface anisotropy term and increases for rough interfaces, in contrast to the Néel surface anisotropy. These opposite variations may interestingly lead to an enhanced anisotropy in (Co / Pt) stackings grown on oxides compared to systems deposited on Pt, i.e. with sharper interfaces. PMID:27351776

  18. Impact of buffer layer and Pt thickness on the interface structure and magnetic properties in (Co/Pt) multilayers

    NASA Astrophysics Data System (ADS)

    Bersweiler, M.; Dumesnil, K.; Lacour, D.; Hehn, M.

    2016-08-01

    The influence of Pt thickness on the interface structure (roughness / intermixing) and magnetic properties has been investigated for (Co / Pt) multilayers sputtered on a Pt or a thin oxide (MgO or AlO x ) buffer layer. When Pt thickness increases from 1.2 nm–2.2 nm, we observe that the effective anisotropy increases with the Pt thickness, simultaneously with the decrease of roughness, i.e. the occurrence of sharper interfaces. Perpendicular magnetic anisotropy (PMA) is still achieved on the oxide buffer layers, but with a lower effective anisotropy correlated to more perturbed interfaces. The detailed analysis of the saturation magnetization shows that: (i) M s is significantly enhanced in the case of rough/intermixed interfaces, which is attributed to and discussed in the framework of Pt induced polarization, (ii) the change in volume dipolar anisotropy is the main factor responsible for the reduction of K eff for systems grown on oxides. Beyond the major role of volume dipolar contribution that reduces PMA, a supplemental positive contribution promoting PMA can be invoked for rough interfaces and large M s (deposit on oxide). This contribution is consistent with a dipolar surface anisotropy term and increases for rough interfaces, in contrast to the Néel surface anisotropy. These opposite variations may interestingly lead to an enhanced anisotropy in (Co / Pt) stackings grown on oxides compared to systems deposited on Pt, i.e. with sharper interfaces.

  19. Field-induced domain wall motion of amorphous [CoSiB/Pt]{sub N} multilayers with perpendicular anisotropy

    SciTech Connect

    Choi, Y. H.; Lee, K. J.; Jung, M. H.; Yoon, J. B.; Cho, J. H.; You, C.-Y.; Kim, T. W.

    2014-05-14

    Amorphous CoSiB/Pt multilayer is a perpendicular magnetic anisotropy material to achieve high squareness, low coercivity, strong anisotropy, and smooth domain wall (DW) motion, because of the smoother interface compared with crystalline multilayers. For [CoSiB(6 Å)/Pt (14 Å)]{sub N} multilayers with N = 3, 6, and 9, we studied the field-induced DW dynamics. The effective anisotropy constant K{sub 1}{sup eff} is 1.5 × 10{sup 6} erg/cm{sup 3} for all the N values, and the linear increment of coercive field H{sub c} with N gives constant exchange coupling J. By analyzing the field dependence of DW images at room temperature, a clear creep motion with the exponent μ = 1/4 could be observed. Even though the pinning field H{sub dep} slightly increases with N, the pinning potential energy U{sub c} is constant (=35 k{sub B}T) for all the N values. These results imply that the amorphous [CoSiB/Pt]{sub N} multilayers are inherently homogeneous compared to crystalline multilayers. For N ≤ 6, the pinning site density ρ{sub pin} is less than 1000/μm{sup 2}, which is about 1 pinning site per the typical device junction size of 30 × 30 nm{sup 2}. Also, the exchange stiffness constant A{sub ex} is obtained to be 0.48 × 10{sup −6} erg/cm, and the domain wall width is expected to be smaller than 5.5 nm. These results may be applicable for spin-transfer-torque magnetic random access memory and DW logic device applications.

  20. Characterization of ultra smooth interfaces in Mo/Si-multilayers.

    PubMed

    Dietsch, R; Holz, T; Hopfe, S; Mai, H; Scholz, R; Schöneich, B; Wendrock, H

    1995-10-01

    The interface structure of Mo/Si-multilayers prepared by Pulsed Laser Deposition (PLD) on Si substrates at room temperature has been investigated. Already the in-situ ellipsometer data acquired during film growth indicate a particular behaviour of this material system that is caused by reaction/diffusion processes of the condensing atoms. MoSi(x) interlayers are formed both at the Mo on Si- and at the Si on Mo-interfaces. The results of multilayer characterization carried out by SNMS and RBS show similar concentration profiles for both types of the interlayers. More detailed information about interface structure and morphology can be provided by HREM investigations. In the TEM micrographs of various multilayers prepared for different laser light wavelengths an improvement of layer stack quality, i.e. formation of abrupt interfaces, with increasing photon energy is observed. Layer stacks having almost ideally smooth interfaces were synthesized by UV-photon ablation. HREM micrographs of these multilayers show a pronounced separation of spacer and absorber layers. The roughness sigma(R) of the interfaces between the amorphous Si- and MoSi(x)-layers was determined by image analysis. On the average a level sigma(R) approximately 0.1 nm is found. There is no indication for roughness replication or amplification from interface to interface as it is known from the appropriate products of conventional thin film technologies. PMID:15048504

  1. Perpendicular magnetic anisotropy in Ta/Co2FeAl/MgO multilayers

    NASA Astrophysics Data System (ADS)

    Gabor, M. S.; Petrisor, T.; Tiusan, C.; Petrisor, T.

    2013-08-01

    In this paper, we demonstrate the stabilization of perpendicular magnetic anisotropy (PMA) in Ta/Co2FeAl/MgO multilayers sputtered on thermally oxidized Si(100) substrates. The magnetic analysis points out that these films show significant interfacial anisotropy even in the as-deposited state, KS=0.67 erg/cm2, enough to provide PMA for the as-deposited films with thicknesses below 1.5 nm. Moreover, the interfacial anisotropy is enhanced by thermal annealing up to 300 °C. The presence of a magnetic dead layer, whose thickness increases with annealing temperature, was also identified.

  2. Magnetic structure and anisotropy of [Co/Pd ] 5/NiFe multilayers

    NASA Astrophysics Data System (ADS)

    Tryputen, Larysa; Guo, Feng; Liu, Frank; Nguyen, T. N. Anh; Mohseni, Majid S.; Chung, Sunjae; Fang, Yeyu; Ã kerman, Johan; McMichael, R. D.; Ross, Caroline A.

    2015-01-01

    The magnetization behavior, magnetic anisotropy, and domain configurations of Co/Pd multilayers with perpendicular magnetic anisotropy capped with permalloy is investigated using magnetometry, magnetic force microscopy, and ferromagnetic resonance. The thickness of the Ni80Fe20 layer in [Co/Pd ] 5/NiFe (t ) was varied from t =0 to 80 nm in order to study the interplay between the anisotropy and magnetization directions of Co/Pd and NiFe. By varying the thickness of the NiFe layer, the net anisotropy changes sign, but domains with plane-normal magnetization are present even for the thickest NiFe. Ferromagnetic resonance measurements show a decrease in damping with increasing NiFe thickness. The results demonstrate how the magnetic behavior of mixed-anisotropy thin films can be controlled.

  3. Strain-assisted magnetization reversal in Co/Ni multilayers with perpendicular magnetic anisotropy.

    PubMed

    Gopman, D B; Dennis, C L; Chen, P J; Iunin, Y L; Finkel, P; Staruch, M; Shull, R D

    2016-01-01

    Multifunctional materials composed of ultrathin magnetic films with perpendicular magnetic anisotropy combined with ferroelectric substrates represent a new approach toward low power, fast, high density spintronics. Here we demonstrate Co/Ni multilayered films with tunable saturation magnetization and perpendicular anisotropy grown directly on ferroelectric PZT [Pb(Zr0.52Ti0.48)O3] substrate plates. Electric fields up to ±2 MV/m expand the PZT by 0.1% and generate at least 0.02% in-plane compression in the Co/Ni multilayered film. Modifying the strain with a voltage can reduce the coercive field by over 30%. We also demonstrate that alternating in-plane tensile and compressive strains (less than 0.01%) can be used to propagate magnetic domain walls. This ability to manipulate high anisotropy magnetic thin films could prove useful for lowering the switching energy for magnetic elements in future voltage-controlled spintronic devices. PMID:27297638

  4. Strain-assisted magnetization reversal in Co/Ni multilayers with perpendicular magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Gopman, D. B.; Dennis, C. L.; Chen, P. J.; Iunin, Y. L.; Finkel, P.; Staruch, M.; Shull, R. D.

    2016-06-01

    Multifunctional materials composed of ultrathin magnetic films with perpendicular magnetic anisotropy combined with ferroelectric substrates represent a new approach toward low power, fast, high density spintronics. Here we demonstrate Co/Ni multilayered films with tunable saturation magnetization and perpendicular anisotropy grown directly on ferroelectric PZT [Pb(Zr0.52Ti0.48)O3] substrate plates. Electric fields up to ±2 MV/m expand the PZT by 0.1% and generate at least 0.02% in-plane compression in the Co/Ni multilayered film. Modifying the strain with a voltage can reduce the coercive field by over 30%. We also demonstrate that alternating in-plane tensile and compressive strains (less than 0.01%) can be used to propagate magnetic domain walls. This ability to manipulate high anisotropy magnetic thin films could prove useful for lowering the switching energy for magnetic elements in future voltage-controlled spintronic devices.

  5. Strain-assisted magnetization reversal in Co/Ni multilayers with perpendicular magnetic anisotropy

    PubMed Central

    Gopman, D. B.; Dennis, C. L.; Chen, P. J.; Iunin, Y. L.; Finkel, P.; Staruch, M.; Shull, R. D.

    2016-01-01

    Multifunctional materials composed of ultrathin magnetic films with perpendicular magnetic anisotropy combined with ferroelectric substrates represent a new approach toward low power, fast, high density spintronics. Here we demonstrate Co/Ni multilayered films with tunable saturation magnetization and perpendicular anisotropy grown directly on ferroelectric PZT [Pb(Zr0.52Ti0.48)O3] substrate plates. Electric fields up to ±2 MV/m expand the PZT by 0.1% and generate at least 0.02% in-plane compression in the Co/Ni multilayered film. Modifying the strain with a voltage can reduce the coercive field by over 30%. We also demonstrate that alternating in-plane tensile and compressive strains (less than 0.01%) can be used to propagate magnetic domain walls. This ability to manipulate high anisotropy magnetic thin films could prove useful for lowering the switching energy for magnetic elements in future voltage-controlled spintronic devices. PMID:27297638

  6. Anisotropy of heat conduction in Mo/Si multilayers

    SciTech Connect

    Medvedev, V. V.; Yakshin, A. E.; Kruijs, R. W. E. van de; Bijkerk, F.; Yang, J.; Schmidt, A. J.; Zoethout, E.

    2015-08-28

    This paper reports on the studies of anisotropic heat conduction phenomena in Mo/Si multilayers with individual layer thicknesses selected to be smaller than the mean free path of heat carriers. We applied the frequency-domain thermoreflectance technique to characterize the thermal conductivity tensor. While the mechanisms of the cross-plane heat conduction were studied in detail previously, here we focus on the in-plane heat conduction. To analyze the relative contribution of electron transport to the in-plane heat conduction, we applied sheet-resistance measurements. Results of Mo/Si multilayers with variable thickness of the Mo layers indicate that the net in-plane thermal conductivity depends on the microstructure of the Mo layers.

  7. Magnetoelastically induced perpendicular magnetic anisotropy and perpendicular exchange bias of CoO/CoPt multilayer films

    NASA Astrophysics Data System (ADS)

    Guo, Lei; Wang, Yue; Wang, Jian; Muraishi, Shinji; Sannomiya, Takumi; Nakamura, Yoshio; Shi, Ji

    2015-11-01

    The effects of magnetoelastically induced perpendicular magnetic anisotropy (PMA) on perpendicular exchange bias (PEB) have been studied in [CoO5nm/CoPt5nm]5 multilayer films. After deposition at room temperature, [CoO5nm/CoPt5nm]5 multilayer films were post-annealed at 100 °C, 250 °C, 300 °C and 375 °C for 3 h. In-plane tensile stress of CoPt layer was calculated by sin2 φ method, and we found it increased gradually upon annealing from 0.99 GPa (as-deposited) up to 3.02 GPa (300 °C-annealed). As to the magnetic property, significant enhancement of PMA was achieved in [CoO5nm/CoPt5nm]5 multilayer films after annealing due to the increase of CoPt layer in-plane tensile stress. With the enhancement of magnetoelastically induced PMA, great improvement of PEB was also achieved in [CoO5nm/CoPt5nm]5 multilayer films, which increased from 130 Oe (as-deposited) up to 1060 Oe (300 °C-annealed), showing the same change tendency as PMA and the strong correlation with CoPt layer in-plane tensile stress. We consider it is the increase of CoPt layer in-plane tensile stress that leads to the enhancement of CoPt layer PMA, which is favorable for the spins in CoPt layer aligning to a more perpendicular direction. And thus the enhanced PMA with more perpendicular spins alignment in CoPt layer results in the improved PEB in [CoO5nm/CoPt5nm]5 multilayer films through enhanced perpendicular spins coupling at CoO/CoPt interfaces.

  8. Co2FeAl films with perpendicular magnetic anisotropy in multilayer structure

    NASA Astrophysics Data System (ADS)

    Li, X. Q.; Xu, X. G.; Yin, S. Q.; Zhang, D. L.; Miao, J.; Jiang, Y.

    2011-01-01

    We have fabricated Co2FeAl (CFA) films with perpendicular magnetic anisotropy (PMA) in a (Co2FeAl/Ni)6 multilayer structure. The effects of underlayer Cu thickness (tCu), Co2FeAl thickness (tCFA) and Ni thickness (tNi) on the magnetic properties have been studied. The PMA is realized with a large anisotropy energy density K = 3.7×106 ergs/cm3, a high squareness Mr/Ms = 1 and a small perpendicular coercivity Hc = 60 Oe, while tCu, tCFA and tNi are 9 nm, 0.2 nm and 0.6 nm respectively. The PMA remains after 300 °C annealing, which demonstrates better thermal stability of the (Co2FeAl/Ni)6 multilayer than that of (Co/Ni)n.

  9. Exchange coupling and magnetic anisotropy at Fe/FePt interfaces

    NASA Astrophysics Data System (ADS)

    Aas, C. J.; Hasnip, P. J.; Cuadrado, R.; Plotnikova, E. M.; Szunyogh, L.; Udvardi, L.; Chantrell, R. W.

    2013-11-01

    We perform fully relativistic first-principles calculations of the exchange interactions and the magnetocrystalline anisotropy energy (MAE) in an Fe/FePt/Fe sandwich system in order to elucidate how the presence of Fe/FePt (soft/hard magnetic) interfaces impacts on the magnetic properties of Fe/FePt/Fe multilayers. Throughout our study we make comparisons between a geometrically unrelaxed system and a geometrically relaxed system. We observe that the Fe layer at the Fe/FePt interface plays a crucial role inasmuch as its (isotropic) exchange coupling to the soft (Fe) phase of the system is substantially reduced. Moreover, this interfacial Fe layer has a substantial impact on the MAE of the system. We show that the MAE of the FePt slab, including the contribution from the Fe/FePt interface, is dominated by anisotropic intersite exchange interactions. Our calculations indicate that the change in the MAE of the FePt slab with respect to the corresponding bulk value is negative, i.e., the presence of Fe/FePt interfaces appears to reduce the perpendicular MAE of the Fe/FePt/Fe system. However, for the relaxed system, this reduction is marginal. It is also shown that the relaxed system exhibits a reduced interfacial exchange. Using a simple linear chain model, we demonstrate that the reduced exchange leads to a discontinuity in the magnetization structure at the interface.

  10. Magneto-transport anisotropy in epitaxially grown hybrid MnAs/GaAs multilayer

    SciTech Connect

    Song, J. H.; Cui, Y.; Lee, J. J.; Ketterson, J. B.

    2015-05-07

    Using molecular-beam epitaxy, we grew a MnAs/GaAs multilayer on a GaAs(100) substrate and compared its magneto-transport characteristics to those of a single-layer MnAs thin film. The crystal orientation of the MnAs layers in both samples was type-B. M–H measurements revealed two-fold symmetric magnetic anisotropy on the surface with the easy and hard direction of magnetization. When the current flowed along the hard direction, the MnAs/GaAs multilayer exhibited negative magnetoresistance below Curie temperature; when the current flowed along the easy direction, it turned positive. We suggest that this peculiar anisotropic magneto-transport behavior in the multilayer originated from two-dimensional carrier confinement and spin-orbit coupling.

  11. Spin-triplet supercurrent in Co/Ni multilayer Josephson junctions with perpendicular anisotropy

    NASA Astrophysics Data System (ADS)

    Gingrich, E. C.; Quarterman, P.; Wang, Yixing; Loloee, R.; Pratt, W. P., Jr.; Birge, Norman O.

    2012-12-01

    We have measured spin-triplet supercurrent in Josephson junctions of the form S/F'/F/F'/S, where S is superconducting Nb, F' is a thin Ni layer with in-plane magnetization, and F is a Ni/[Co/Ni]n multilayer with out-of-plane magnetization. The supercurrent in these junctions decays very slowly with F-layer thickness and is much larger than in similar junctions not containing the two F' layers. Those two features are the characteristic signatures of spin-triplet supercurrent, which is maximized by the orthogonality of the magnetizations in the F and F' layers. Magnetic measurements confirm the out-of-plane anisotropy of the Co/Ni multilayers. These samples have their critical current optimized in the as-prepared state, which will be useful for future applications.

  12. Assessment of Layer Thickness and Interface Quality in CoP Electrodeposited Multilayers.

    PubMed

    Lucas, Irene; Ciudad, David; Plaza, Manuel; Ruiz-Gómez, Sandra; Aroca, Claudio; Pérez, Lucas

    2016-07-27

    The magnetic properties of CoP electrodeposited alloys can be easily controlled by layering the alloys and modulating the P content of the different layers by using pulse plating in the electrodeposition process. However, because of its amorphous nature, the study of the interface quality, which is a limitation for the optimization of the soft magnetic properties of these alloys, becomes a complex task. In this work, we use Rutherford backscattering spectroscopy (RBS) to determine that electrodeposited Co0.74P0.26/Co0.83P0.17 amorphous multilayers with layers down to 20 nm-thick are composed by well-defined layers with interfacial roughness below 3 nm. We have also determined, using magnetostriction measurements, that 4 nm is the lower limitation for the layer thickness. Below this thickness, the layers are mixed and the magnetic behavior of the multilayered films is similar to that shown by single layers, thus going from in-plane to out-of-plane magnetic anisotropy. Therefore, these results establish the range in which the magnetic properties of these alloys can be controlled by layering. PMID:27381897

  13. Interface Roughness Evolution in Sputtered WSi2/Si Multilayers

    SciTech Connect

    Wang,Y.; Zhou, H.; Zhou, L.; Headrick, R.; Macrander, A.; Ozcan, A.

    2007-01-01

    We report on the growth of WSi{sub 2} and Si amorphous thin films by dc magnetron sputtering. In situ synchrotron x-ray scattering with high temporal resolution has been employed to probe the surface and interface roughness during film deposition. It is found that the WSi{sub 2}/Si multilayer surface alternately roughens and smoothes during deposition; while the Si layer roughness monotonically, the WSi{sub 2} layer is observed to smooth out when deposited on an initially rough surface. Subsequent deposition of the next layer effectively freezes in the surface morphology of the previous layer in each case. Energetic neutrals and ions assisting the growth may play a role in inducing this pronounced alternating pattern in the roughness.

  14. Perpendicular magnetic anisotropy in granular multilayers of CoPd alloyed nanoparticles

    NASA Astrophysics Data System (ADS)

    Vivas, L. G.; Rubín, J.; Figueroa, A. I.; Bartolomé, F.; García, L. M.; Deranlot, C.; Petroff, F.; Ruiz, L.; González-Calbet, J. M.; Pascarelli, S.; Brookes, N. B.; Wilhelm, F.; Chorro, M.; Rogalev, A.; Bartolomé, J.

    2016-05-01

    Co-Pd multilayers obtained by Pd capping of pre-deposited Co nanoparticles on amorphous alumina are systematically studied by means of high-resolution transmission electron microscopy, x-ray diffraction, extended x-ray absorption fine structure, SQUID-based magnetometry, and x-ray magnetic circular dichroism. The films are formed by CoPd alloyed nanoparticles self-organized across the layers, with the interspace between the nanoparticles filled by the non-alloyed Pd metal. The nanoparticles show atomic arrangements compatible with short-range chemical order of L 10 strucure type. The collective magnetic behavior is that of ferromagnetically coupled particles with perpendicular magnetic anisotropy, irrespective of the amount of deposited Pd. For increasing temperature three magnetic phases are identified: hard ferromagnetic with strong coercive field, soft-ferromagnetic as in an amorphous asperomagnet, and superparamagnetic. Increasing the amount of Pd in the system leads to both magnetic hardness increment and higher transition temperatures. Magnetic total moments of 1.77(4) μB and 0.45(4) μB are found at Co and Pd sites, respectively, where the orbital moment of Co, 0.40(2) μB, is high, while that of Pd is negligible. The effective magnetic anisotropy is the largest in the capping metal series (Pd, Pt, W, Cu, Ag, Au), which is attributed to the interparticle interaction between de nanoparticles, in addition to the intraparticle anisotropy arising from hybridization between the 3 d -4 d bands associated to the Co and Pd chemical arrangement in a L 10 structure type.

  15. 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.

  16. Strong Perpendicular Magnetic Anisotropy at Co(111)/α-Cr2O3(0001) Interface

    NASA Astrophysics Data System (ADS)

    Shiratsuchi, Yu; Oikawa, Hiroto; Kawahara, Shin-ichi; Takechi, Yuichiro; Fujita, Toshiaki; Nakatani, Ryoichi

    2012-04-01

    We have investigated the perpendicular magnetic anisotropy (PMA) at the ferromagnetic/antiferromagnetic interface using [Pt/Co]n/α-Cr2O3 superlattices. By changing the number of stacking periods, the contributions of the Co/α-Cr2O3 and Pt/Co interfaces to the PMA are separately estimated. The results indicate that the strong PMA is induced at the Co/α-Cr2O3 interface as well as at the Pt/Co interface. The change in the interface magnetic anisotropy energy density with the ferromagnetic layer composition supports the PMA at the Co/α-Cr2O3 interface. To the best of our knowledge, this is the first demonstration of PMA at the ferromagnetic/antiferromagnetic interface.

  17. Strong interface in CMCs, a condition for efficient multilayered interphases

    SciTech Connect

    Droillard, C.; Lamon, J.; Bourrat, X.

    1995-10-01

    A fiber treatment was used to change the bonding strength of the Nicalon NLM 202 SiC fiber from weak to strong, in a series of 2D-SiC/SiC composites with multilayered interphases. The materials with the pre-treated fibers were compared to the same materials but reinforced with as received fibers. The stress-strain behavior and the fracture toughness were examined as a function of rack patterns identified by TEM. All the materials could be grouped into two distinct families: (1) materials reinforced with untreated fibers have a weak fiber bonding and are characterized by a low strength and a low toughness and (2) materials with the pre-treated fibers have a strong fiber bonding and are characterized by a high strength and a high toughness. This latter behavior is identified by TEM. It corresponds to a new interfacial behavior with a cohesive mode of interfacial cracking, involving branching and deflection by the successive interfaces. In the former family, the adhesive interfacial failure mode corresponds to the classical debond/sliding mechanism.

  18. Perpendicular magnetic anisotropy in ultrathin Co|Ni multilayer films studied with ferromagnetic resonance and magnetic x-ray microspectroscopy

    NASA Astrophysics Data System (ADS)

    Macià, F.; Warnicke, P.; Bedau, D.; Im, M.-Y.; Fischer, P.; Arena, D. A.; Kent, A. D.

    2012-11-01

    Ferromagnetic resonance (FMR) spectroscopy, x-ray magnetic circular dichroism (XMCD) spectroscopy and magnetic transmission soft x-ray microscopy (MTXM) experiments have been performed to gain insight into the magnetic anisotropy and domain structure of ultrathin Co|Ni multilayer films with a thin permalloy layer underneath. MTXM images with a spatial resolution better than 25 nm were obtained at the Co L3 edge down to an equivalent thickness of Co of only 1 nm, which establishes a new lower boundary on the sensitivity limit of MTXM. Domain sizes are shown to be strong functions of the anisotropy and thickness of the film.

  19. Multilayer FeRh/MgO: controllable magnetocrystalline anisotropy for an antiferromagnetic system

    NASA Astrophysics Data System (ADS)

    Zheng, Guohui; Dorj, Odkhuu; Ke, Sanhuang; Ramesh, Rammoorthy; Miao, Maosheng; Kioussis, Nickolas

    2015-03-01

    Controlling the magnetocrystalline anisotropy (MCA) of ferromagnetic (FM) thin films by tunable strain and electric field has been pursued as an effective method of achieving low-power and highly scalable memory. Comparing with FM materials, AFM are much less sensitive to external magnetic field, a substantial advantage for memory devices. Inspired by recent work on AFM memory resistors based on FeRh, we carried out a systematic first principles study of the MCA of multi-layer FeRh, either stand alone, or combined with MgO layers. FeRh is a unique material that undergoes a transition from AFM (type-II) to FM at elevated temperature of 370 K. Our calculations for thin films of FeRh from 5-15 atomic layers reveal that AFM is always the most stable configuration for Fe terminated films; while for Rh terminated films, there is a transition from FM to a configuration featured AFM at the center layers and FM at the surface layers (reconstructed). While applying the spin-orbit interactions (SOI) for the valence electrons, we found Fe-terminated films exhibit a relatively small MCA that varies and may change sign with film thickness, substrate and strain, providing a possibility of spin reorientation via the control of strain and electric field. The k-resolved MCA values reveals that the region around Gamma point adds the major contribution to the MCA.

  20. Interface Morphology During Crystal Growth: Effects of Anisotropy and Fluid Flow

    NASA Technical Reports Server (NTRS)

    Coriell, S. R.; Murray, B. T.; Chernov, A. A.; McFadden, G. B.

    1996-01-01

    The effect of a parallel shear flow and anisotropic interface kinetics on the onset of instability during growth from a supersaturated solution is analyzed. The model used for anisotropy is based on the microscopic picture of step motion. A shear flow (linear Couette flow or asymptotic suction profile) parallel to the crystal solution interface in the same direction as the step motion decreases interface stability. A shear flow counter to the step motion enhances stability and for sufficiently large shear rates the interface is absolutely morphologically stable. For large wave numbers, the perturbed flow field can be neglected and a simple analytic approximation for the stability-instability demarcation is found.

  1. Enhanced perfume surface delivery to interfaces using surfactant surface multilayer structures.

    PubMed

    Brabury, Robert; Penfold, Jeffrey; Thomas, Robert K; Tucker, Ian M; Petkov, Jordan T; Jones, Craig

    2016-01-01

    Enhanced surface delivery and retention of perfumes at interfaces are the keys to their more effective and efficient deployment in a wide range of home and personal care related formulations. It has been previously demonstrated that the addition of multivalent counterions, notably Ca(2+), induces multilayer adsorption at the air-water interface for the anionic surfactant, sodium dodecyl-6-benzenesulfonate, LAS-6. Neutron reflectivity, NR, measurements are reported here which demonstrate that such surfactant surface multilayer structures are a potentially promising vehicle for enhanced delivery of perfumes to interfaces. The data show that the incorporation of the model perfumes, phenylethanol, PE, and linalool, LL, into the surface multilayer structure formed by LAS-6/Ca(2+) results in the surface structures being retained up to relatively high perfume mole fractions. Furthermore the amount of perfume at the surface is enhanced by at least an order of magnitude, compared to that co-adsorbed with a surfactant monolayer. PMID:26409782

  2. Effect of the Acceleration Energy of Hydrogen Ion Irradiation on Perpendicular Magnetic Anisotropy in CoOx/Pd Multilayer Films

    NASA Astrophysics Data System (ADS)

    Shin, Sang Chul; Kim, Sanghoon; Han, Jungjin; Hong, Jongill; Kang, Shinill

    2011-11-01

    Magnetic stripes were achieved from hydrogen-ion-irradiated areas separated by the nonirradiated areas masked by UV-imprinted polymeric patterns. A perpendicular magnetic anistropy with a squareness of 0.96 and a coercivity of 2 kOe in (CoOx/Pd)10 multilayer films was induced via deoxidization, which heavily depended on the acceleration energy of hydrogen ion irradiation in the range of 400 eV. These phenomena were demonstrated via deoxidization of cobalt oxide to pure cobalt as observed by X-ray diffraction, accompanying the formation of a CoPd(111) phase indicating perpendicular magnetic anisotropy due to the preferential removal or reduction of oxygen atoms in multilayer films.

  3. Exploring interface morphology of a deeply buried layer in periodic multilayer

    NASA Astrophysics Data System (ADS)

    Das, Gangadhar; Khooha, Ajay; Singh, A. K.; Srivastava, A. K.; Tiwari, M. K.

    2016-06-01

    Long-term durability of a thin film device is strongly correlated with the nature of interface structure associated between different constituent layers. Synthetic periodic multilayer structures are primarily employed as artificial X-ray Bragg reflectors in many applications, and their reflection efficiency is predominantly dictated by the nature of the buried interfaces between the different layers. Herein, we demonstrate the applicability of the combined analysis approach of the X-ray reflectivity and grazing incidence X-ray fluorescence measurements for the reliable and precise determination of a buried interface structure inside periodic X-ray multilayer structures. X-ray standing wave field (XSW) generated under Bragg reflection condition is used to probe the different constituent layers of the W- B4C multilayer structure at 10 keV and 12 keV incident X-ray energies. Our results show that the XSW assisted fluorescence measurements are markedly sensitive to the location and interface morphology of a buried layer structure inside a periodic multilayer structure. The cross sectional transmission electron microscopy results obtained on the W-B4C multilayer structure provide a deeper look on the overall reliability and accuracy of the XSW method. The method described here would also be applicable for nondestructive characterization of a wide range of thin film based semiconductor and optical devices.

  4. Annealing effects on the properties of amorphous CoSiB/Pt multilayer films with perpendicular magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Jung, Sol; Park, Jisun; Yim, Haein; Kim, Taewan

    2014-01-01

    The perpendicular magnetic anisotropy (PMA) of amorphous CoSiB/Pt multilayer systems was studied as a function of the thickness of the CoSiB/Pt bilayer and the number of repeated CoSiB/Pt bilayers. In this letter, we investigate the thermal property of a CoSiB single layer film annealed at 150 ˜ 350 °C for 3 hours and the perpendicular magnetic anisotropic property of amorphous ferromagnetic Ta(50 °A)/Pt(30 °A)/[CoSiB(2, 3, 4, 5, 6 Å)/Pt(14 Å)]5/Ta(50 Å) multilayer films annealed at 200 ˜ 400 °C for 3 hours. The thermal properties were measured by using a differential scanning calorimeter and an X-ray diffractometer, and the magnetic properties were measured by using a vibrating sample magnetometer. The PMA of the CoSiB/Pt multilayer film disappeared and the multilayer film show isotropy after annealing at a temperature of 350 °C or above.

  5. Magnetic and magneto-optical properties of Ni/Pt multilayers with perpendicular magnetic anisotropy at room temperature

    NASA Astrophysics Data System (ADS)

    Srinivas, G.; Shin, Sung-Chul

    1999-06-01

    The magnetic and magneto-optical properties of Ni/Pt multilayers exhibiting square Kerr hysterisis loops at room temperature were studied. Squared polar Kerr hysterisis loops at room temperature in Ni/Pt multilayer thin films were obtained for the samples prepared by sequential DC magnetron sputter deposition of nickel and platinum with tNi=13-21 Å and tPt=3.5-7.5 Å. The coercivity of these multilayers was in the range of 400-1100 Oe. The saturation magnetization was found to show an inverse dependence on the nickel sublayer thickness. About a monolayer of Ni at interface was observed to behave less magnetically than the interior Ni atoms. The polar Kerr rotation exhibited an increasing trend with decreasing wavelength in the spectral range of 7000-4000 Å. The maximum of the polar Kerr rotation was found to shift to a higher wavelength with increasing nickel sublayer thickness.

  6. First principles investigation of magnetocrystalline anisotropy at Full Heusler / MgO interfaces

    NASA Astrophysics Data System (ADS)

    Vadapoo, Rajasekarakumar; Hallal, Ali; Chshiev, Mairbek

    2014-03-01

    Magnetic tunnel junctions with perpendicular magnetic anisotropy (PMA) have the potential for realizing next generation high density nonvolatile memories and logic devices. The origin of high PMA in these interfaces has been explained by orbital hybridizations at interface along with spin-orbit interactions. Here we present a systematic study of PMA in Heusler alloy [X2YZ]/ MgO interfaces using first principle methods with X =Co, YZ =FeAl, MnGe and MnSi. Among the interfaces studied, we found that Co terminated interface of Co2FeAl/MgO gives rise to PMA value of 1.2erg/cm2 in agreement with recent experimental observations. On the contrary, FeAl terminated interfaces of the same structure shows in-plane magnetic anisotropy (IMA). We also found that the most of PMA contribution originates from dyz and dz2 orbitals of Co atoms at the interface. Finally, Co2MnGe and Co2MnSi structures tend to favor IMA for any termination.

  7. Interface effect on the magnetic anisotropy of CoPt clusters

    NASA Astrophysics Data System (ADS)

    Rohart, S.; Raufast, C.; Favre, L.; Bernstein, E.; Bonet, E.; Wernsdorfer, W.; Dupuis, V.

    2007-09-01

    We study the magnetic anisotropy of CoPt clusters produced by condensation of a stoichiometric vapor with an inert gas (helium) and co-deposited with various matrices. From electron transmission microscopy we show that the clusters have a mean diameter of about 2 nm with a narrow size distribution and present the FCC A1 disordered phase. At high temperature, the clusters display a superparamagnetic behavior. The transition to the blocked state enables us to determine the clusters magnetic anisotropy energy (MAE). From a careful analysis, we show in the one hand that CoPt clusters present a higher volume and intrinsic surface MAE than pure Co ones. In the other hand, the presence of platinum at the interface in CoPt clusters decreases the strong interfacial exchange anisotropy observed for Co clusters embedded in MgO.

  8. 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.

  9. Interface stress development in the Cu/Ag nanostructured multilayered film during the tensile deformation

    SciTech Connect

    Su, R.; Nie, Z. H.; Zhang, Q. H.; Li, X. J.; Li, L. E-mail: ydwang@mail.neu.edu.cn; Zhou, X. T.; Wang, Y. D. E-mail: ydwang@mail.neu.edu.cn; Wu, Y. D.; Hui, X. D.; Wang, M. G.

    2014-12-01

    Cu/Ag nanostructured multilayered films (NMFs) with different stacking sequences were investigated by synchrotron X-ray diffraction during the tensile deformations for interface stress study. The lattice strains were carefully traced and the stress partition, which usually occurs in the multiphase bulk metallic materials during plastic deformations, was first quantitatively analyzed in the NMFs here. The interface stress of the Cu/Ag NMFs was carefully analyzed during the tensile deformation and the results revealed that the interface stress was along the loading direction and exhibited three-stage evolution. This tensile interface stress has a detrimental effect on the deformation, leading to the early fracture of the NMFs.

  10. Designing a stronger interface through graded structures in amorphous/nanocrystalline ZrCu/Cu multilayered films.

    PubMed

    Chang, C H; Hsieh, C H; Huang, J C; Wang, C; Liao, Y C; Hsueh, C H; Du, X H; Wang, Z K; Wang, X

    2016-06-01

    Many multilayered nano-structures appear to fail due to brittle matter along the interfaces. In order to toughen them, in this study, the microstructure and interface strength of multilayered thin films consisting of amorphous ZrCu and nanocrystalline Cu (with sharp or graded interfaces) are examined and analyzed. The interface possesses a gradient nature in terms of composition, nanocrystalline phase size and volume fraction. The bending results extracted from the nano-scaled cantilever bending samples demonstrate that multilayered films with graded interfaces would have a much higher interface bending strength/strain/modulus, and an overall improvement upgrade of more than 50%. The simple graded interface design of multilayered thin films with improved mechanical properties can offer much more promising performance in structural and functional applications for MEMS or optical coating. PMID:27103429

  11. Designing a stronger interface through graded structures in amorphous/nanocrystalline ZrCu/Cu multilayered films

    NASA Astrophysics Data System (ADS)

    Chang, C. H.; Hsieh, C. H.; Huang, J. C.; Wang, C.; Liao, Y. C.; Hsueh, C. H.; Du, X. H.; Wang, Z. K.; Wang, X.

    2016-06-01

    Many multilayered nano-structures appear to fail due to brittle matter along the interfaces. In order to toughen them, in this study, the microstructure and interface strength of multilayered thin films consisting of amorphous ZrCu and nanocrystalline Cu (with sharp or graded interfaces) are examined and analyzed. The interface possesses a gradient nature in terms of composition, nanocrystalline phase size and volume fraction. The bending results extracted from the nano-scaled cantilever bending samples demonstrate that multilayered films with graded interfaces would have a much higher interface bending strength/strain/modulus, and an overall improvement upgrade of more than 50%. The simple graded interface design of multilayered thin films with improved mechanical properties can offer much more promising performance in structural and functional applications for MEMS or optical coating.

  12. Cr/B4C multilayer mirrors: Study of interfaces and X-ray reflectance

    DOE PAGESBeta

    Burcklen, C.; Soufli, R.; Gullikson, E.; Meltchakov, E.; Dennetiere, D.; Polack, F.; Capitanio, B.; Thomasset, M.; Jerome, A.; de Rossi, S.; et al

    2016-03-24

    Here, we present an experimental study of the effect of layer interfaces on the x-ray reflectance in Cr/B4C multilayer interference coatings with layer thicknesses ranging from 0.7 nm to 5.4 nm. The multilayers were deposited by magnetron sputtering and by ion beam sputtering. Grazing incidence x-ray reflectometry, soft x-ray reflectometry, and transmission electron microscopy reveal asymmetric multilayer structures with a larger B4C-on-Cr interface, which we modeled with a 1–1.5 nm thick interfacial layer. Reflectance measurements in the vicinity of the Cr L2,3 absorption edge demonstrate fine structure that is not predicted by simulations using the currently tabulated refractive index (opticalmore » constants) values for Cr.« less

  13. Cr/B4C multilayer mirrors: Study of interfaces and X-ray reflectance

    NASA Astrophysics Data System (ADS)

    Burcklen, C.; Soufli, R.; Dennetiere, D.; Polack, F.; Capitanio, B.; Gullikson, E.; Meltchakov, E.; Thomasset, M.; Jérome, A.; de Rossi, S.; Delmotte, F.

    2016-03-01

    We present an experimental study of the effect of layer interfaces on the x-ray reflectance in Cr/B4C multilayer interference coatings with layer thicknesses ranging from 0.7 nm to 5.4 nm. The multilayers were deposited by magnetron sputtering and by ion beam sputtering. Grazing incidence x-ray reflectometry, soft x-ray reflectometry, and transmission electron microscopy reveal asymmetric multilayer structures with a larger B4C-on-Cr interface, which we modeled with a 1-1.5 nm thick interfacial layer. Reflectance measurements in the vicinity of the Cr L2,3 absorption edge demonstrate fine structure that is not predicted by simulations using the currently tabulated refractive index (optical constants) values for Cr.

  14. Electronic structure and magnetocrystalline anisotropy of the Bi2Se3 topological insulator/ferromagnet interface

    NASA Astrophysics Data System (ADS)

    Zhang, Jia; Velev, Julian P.; Tsymbal, Evgeny Y.

    Interesting spin-dependent phenomena are expected to emerge when a topological insulator is interfaced with a magnetic material. In this work the magnetic properties of the interface between a topological insulator Bi2Se3 and ferromagnetic metals (FM) fcc (111) Ni and Co are investigated by first-principles calculations. Different interface terminations are considered, and the most stable interface termination is identified to be an interface Ni (Co) atom located atop the hollow site of the interfacial Se monolayer. We find that the proximity effect induces a small magnetic moment on the interface Se atom (0.028 μB for Ni and 0.023 μB for Co). The surface state in Bi2Se3 disappears due to the strong interface hybridization between FM and Bi2Se3 and metal induced gap states appear in the bandgap region of Bi2Se3. We find that both the Bi2Se3/Ni(111) and Bi2Se3/Co(111) interfaces exhibit an in-plane easy axis with the magnetic anisotropy energy of around 2 erg/cm2 per interface. An interesting feature resulting from our calculations is a non-collinear k-dependent spin texture at the interface which may have important consequences for the spin-dependent transport properties, such as the spin transfer torque.

  15. Effect of MgO/Fe Interface Oxidation State on Electric-Field Modulation of Interfacial Magnetic Anisotropy

    NASA Astrophysics Data System (ADS)

    Guan, X. W.; Cheng, X. M.; Wang, S.; Huang, T.; Xue, K. H.; Miao, X. S.

    2016-06-01

    The impact of the MgO/Fe interface oxidation state on the electric-field-modified magnetic anisotropy in MgO/Fe has been revealed by density functional calculations. It is shown that the influence of the interface oxidation is strong enough to dominate the effect of the electric field on the magnetic anisotropy of MgO/Fe-based films. The magnetoelectric coefficients are calculated to be positive for the ideal and overoxidized MgO/Fe interface, but an abnormal negative value emerges in the underoxidized case. By analyzing the interface states based on density of states and band structures, we demonstrate that the considerably different electronic structures of the three oxidized MgO/Fe interfaces lead to the strong discrepancy in the electric-field modulation of the interfacial magnetic anisotropy. These results are of considerable interest in the area of electric-field-controlled magnetic anisotropy and switching.

  16. Effect of MgO/Fe Interface Oxidation State on Electric-Field Modulation of Interfacial Magnetic Anisotropy

    NASA Astrophysics Data System (ADS)

    Guan, X. W.; Cheng, X. M.; Wang, S.; Huang, T.; Xue, K. H.; Miao, X. S.

    2016-03-01

    The impact of the MgO/Fe interface oxidation state on the electric-field-modified magnetic anisotropy in MgO/Fe has been revealed by density functional calculations. It is shown that the influence of the interface oxidation is strong enough to dominate the effect of the electric field on the magnetic anisotropy of MgO/Fe-based films. The magnetoelectric coefficients are calculated to be positive for the ideal and overoxidized MgO/Fe interface, but an abnormal negative value emerges in the underoxidized case. By analyzing the interface states based on density of states and band structures, we demonstrate that the considerably different electronic structures of the three oxidized MgO/Fe interfaces lead to the strong discrepancy in the electric-field modulation of the interfacial magnetic anisotropy. These results are of considerable interest in the area of electric-field-controlled magnetic anisotropy and switching.

  17. Formation of Magnetic Anisotropy by Lithography.

    PubMed

    Kim, Si Nyeon; Nam, Yoon Jae; Kim, Yang Doo; Choi, Jun Woo; Lee, Heon; Lim, Sang Ho

    2016-01-01

    Artificial interface anisotropy is demonstrated in alternating Co/Pt and Co/Pd stripe patterns, providing a means of forming magnetic anisotropy using lithography. In-plane hysteresis loops measured along two principal directions are explained in depth by two competing shape and interface anisotropies, thus confirming the formation of interface anisotropy at the Co/Pt and Co/Pd interfaces of the stripe patterns. The measured interface anisotropy energies, which are in the range of 0.2-0.3 erg/cm(2) for both stripes, are smaller than those observed in conventional multilayers, indicating a decrease in smoothness of the interfaces when formed by lithography. The demonstration of interface anisotropy in the Co/Pt and Co/Pd stripe patterns is of significant practical importance, because this setup makes it possible to form anisotropy using lithography and to modulate its strength by controlling the pattern width. Furthermore, this makes it possible to form more complex interface anisotropy by fabricating two-dimensional patterns. These artificial anisotropies are expected to open up new device applications such as multilevel bits using in-plane magnetoresistive thin-film structures. PMID:27216420

  18. Formation of Magnetic Anisotropy by Lithography

    PubMed Central

    Kim, Si Nyeon; Nam, Yoon Jae; Kim, Yang Doo; Choi, Jun Woo; Lee, Heon; Lim, Sang Ho

    2016-01-01

    Artificial interface anisotropy is demonstrated in alternating Co/Pt and Co/Pd stripe patterns, providing a means of forming magnetic anisotropy using lithography. In-plane hysteresis loops measured along two principal directions are explained in depth by two competing shape and interface anisotropies, thus confirming the formation of interface anisotropy at the Co/Pt and Co/Pd interfaces of the stripe patterns. The measured interface anisotropy energies, which are in the range of 0.2–0.3 erg/cm2 for both stripes, are smaller than those observed in conventional multilayers, indicating a decrease in smoothness of the interfaces when formed by lithography. The demonstration of interface anisotropy in the Co/Pt and Co/Pd stripe patterns is of significant practical importance, because this setup makes it possible to form anisotropy using lithography and to modulate its strength by controlling the pattern width. Furthermore, this makes it possible to form more complex interface anisotropy by fabricating two-dimensional patterns. These artificial anisotropies are expected to open up new device applications such as multilevel bits using in-plane magnetoresistive thin-film structures. PMID:27216420

  19. Microstructure-interface-property relationships in nanometer-period x-ray multilayers

    SciTech Connect

    Nguyen, Tai Dung

    1996-12-01

    The microstructure - interface - property relationships in nanometer-period x-ray multilayer mirrors (W/C, WC/C, Cr/C, CrC/C, Cu/C, Ru/C, and Ru/B{sub 4}C) were studied using cross-sectional high resolution TEM and x-ray scattering. Microstructural and morphological evolution of as-prepared multilayers, and their behavior under thermal activation were discussed in terms of the materials thermodynamic and kinetic properties. Effects of the microstructural and the morphological evolution in reactive- component (W-C, Cr-C, and Ru-B{sub 4}C) and conjugate-component (Ru-C and Cu-C) multilayers on the normal incidence reflectance and long term stability of the mirrors are presented.

  20. Two-mode Ginzburg-Landau theory of crystalline anisotropy for fcc-liquid interfaces

    NASA Astrophysics Data System (ADS)

    Wu, Kuo-An; Lin, Shang-Chun; Karma, Alain

    2016-02-01

    We develop a Ginzburg-Landau (GL) theory for fcc crystal-melt systems at equilibrium by employing two sets of order parameters that correspond to amplitudes of density waves of principal reciprocal lattice vectors and amplitudes of density waves of a second set of reciprocal lattice vectors. The choice of the second set of reciprocal lattice vectors is constrained by the condition that this set must form closed triangles with the principal reciprocal lattice vectors in reciprocal space to make the fcc-liquid transition first order. The capillary anisotropy of fcc-liquid interfaces is investigated by GL theory with amplitudes of <111 > and <200 > density waves. Furthermore, we explore the dependence of the anisotropy of the excess free energy of the solid-liquid interface on density waves of higher-order reciprocal lattice vectors such as <311 > by extending the two-mode GL theory with an additional mode. The anisotropy calculated using GL theory with input parameters from molecular dynamics (MD) simulations for fcc Ni is compared to that measured in MD simulations.

  1. Exchange coupling in hybrid anisotropy magnetic multilayers quantified by vector magnetometry

    SciTech Connect

    Morrison, C. Miles, J. J.; Thomson, T.; Anh Nguyen, T. N.; Fang, Y.; Dumas, R. K.; Åkerman, J.

    2015-05-07

    Hybrid anisotropy thin film heterostructures, where layers with perpendicular and in-plane anisotropy are separated by a thin spacer, are novel materials for zero/low field spin torque oscillators and bit patterned media. Here, we report on magnetization reversal and exchange coupling in a archetypal Co/Pd (perpendicular)-NiFe (in-plane) hybrid anisotropy system studied using vector vibrating sample magnetometry. This technique allows us to quantify the magnetization reversal in each individual magnetic layer, and measure of the interlayer exchange as a function of non-magnetic spacer thickness. At large (>1 nm) spacer thicknesses Ruderman-Kittel-Kasuya-Yosida-like exchange dominates, with orange-peel coupling providing a significant contribution only for sub-nm spacer thickness.

  2. Exchange coupling in hybrid anisotropy magnetic multilayers quantified by vector magnetometry

    NASA Astrophysics Data System (ADS)

    Morrison, C.; Miles, J. J.; Anh Nguyen, T. N.; Fang, Y.; Dumas, R. K.; Åkerman, J.; Thomson, T.

    2015-05-01

    Hybrid anisotropy thin film heterostructures, where layers with perpendicular and in-plane anisotropy are separated by a thin spacer, are novel materials for zero/low field spin torque oscillators and bit patterned media. Here, we report on magnetization reversal and exchange coupling in a archetypal Co/Pd (perpendicular)-NiFe (in-plane) hybrid anisotropy system studied using vector vibrating sample magnetometry. This technique allows us to quantify the magnetization reversal in each individual magnetic layer, and measure of the interlayer exchange as a function of non-magnetic spacer thickness. At large (>1 nm) spacer thicknesses Ruderman-Kittel-Kasuya-Yosida-like exchange dominates, with orange-peel coupling providing a significant contribution only for sub-nm spacer thickness.

  3. Surface roughness and interface width scaling of magnetron sputter deposited Ni/Ti multilayers

    SciTech Connect

    Maidul Haque, S.; Biswas, A.; Tokas, R. B.; Bhattacharyya, D.; Sahoo, N. K.; Bhattacharya, Debarati

    2013-09-14

    Using an indigenously built r.f. magnetron sputtering system, several single layer Ti and Ni films have been deposited at varying deposition conditions. All the samples have been characterized by Grazing Incidence X-ray Reflectivity (GIXR) and Atomic Force Microscopy to estimate their thickness, density, and roughness and a power law dependence of the surface roughness on the film thickness has been established. Subsequently, at optimized deposition condition of Ti and Ni, four Ni/Ti multilayers of 11-layer, 21-layer, 31-layer, and 51-layer having different bilayer thickness have been deposited. The multilayer samples have been characterized by GIXR and neutron reflectivity measurements and the experimental data have been fitted assuming an appropriate sample structure. A power law correlation between the interface width and bilayer thickness has been observed for the multilayer samples, which was explained in the light of alternate roughening/smoothening of multilayers and assuming that at the interface the growth “restarts” every time.

  4. Defect Interactions at Metal/Ceramic Interfaces in Thin Film Multilayers

    SciTech Connect

    Misra, Amit

    2012-06-14

    Summary of metal-ceramic multilayer deformation: (1) In nanolayered Al/TiN, Al layers grow in a twin orientation with the underlying TiN/Al layers favored by N-terminated TiN layers; (2) The shear strength of Al/TiN interface varies significantly depending on whether the interface is Ti or N terminated; (3) 2 nm Al - 2 TiN multilayers exhibit unusual mechanical properties as revealed by compression testing - (a) High maximum flow strength of 4.5 GPa, which is significantly higher than hardness (6 GPa) divided by a factor of 3, (b) Extraordinarily high strain hardening rates in Al nanolayers (16-35 GPa, {approx} E/2 to E/4), (c) Co-deformability of the TiN nanolayers with Al (confirmed by TEM on nanoindents) to plastic strains in excess of 5%.

  5. Enhanced orbital magnetic moments in magnetic heterostructures with interface perpendicular magnetic anisotropy

    PubMed Central

    Ueno, Tetsuro; Sinha, Jaivardhan; Inami, Nobuhito; Takeichi, Yasuo; Mitani, Seiji; Ono, Kanta; Hayashi, Masamitsu

    2015-01-01

    We have studied the magnetic layer thickness dependence of the orbital magnetic moment in magnetic heterostructures to identify contributions from interfaces. Three different heterostructures, Ta/CoFeB/MgO, Pt/Co/AlOx and Pt/Co/Pt, which possess significant interface contribution to the perpendicular magnetic anisotropy, are studied as model systems. X-ray magnetic circular dichroism spectroscopy is used to evaluate the relative orbital moment, i.e. the ratio of the orbital to spin moments, of the magnetic elements constituting the heterostructures. We find that the relative orbital moment of Co in Pt/Co/Pt remains constant against its thickness whereas the moment increases with decreasing Co layer thickness for Pt/Co/AlOx, suggesting that a non-zero interface orbital moment exists for the latter system. For Ta/CoFeB/MgO, a non-zero interface orbital moment is found only for Fe. X-ray absorption spectra shows that a particular oxidized Co state in Pt/Co/AlOx, absent in other heterosturctures, may give rise to the interface orbital moment in this system. These results show element specific contributions to the interface orbital magnetic moments in ultrathin magnetic heterostructures. PMID:26456454

  6. Voltage controlled magnetocrystalline anisotropy at the Fe/MgO (001) interface

    NASA Astrophysics Data System (ADS)

    Lukashev, Pavel; Tsymbal, Evgeny

    2015-03-01

    The effect of electric fields on magnetocrystalline anisotropy energy (MAE) is a promising way to control the magnetization orientation purely by voltage (rather than by current required for a spin transfer torque), which can potentially alleviate the energy dissipation bottleneck of the existing magnetic memory technology. Here we perform density-functional calculations to explore the voltage controlled magnetic anisotropy (VCMA) of a thin film Fe stacked along the [001] direction when an external electric field is applied across an adjacent epitaxial MgO layer. The results are analyzed by evaluating layer and orbital resolved contributions to MAE. We find that MAE is confined to a depth of few atomic layers near the interface, as determined by the metal screening length, indicating that the VCMA is an interface effect. The applied electric field leads to a nearly linear change in the interface MAE due to a change in the 3d-orbital occupancy of the interfacial Fe atoms and is enhanced, as compared to the clean Fe (001) surface, due a relatively large dielectric constant of MgO. In addition to the electric field screening, there is a notable effect of atomic displacements driven by an applied electric field, when atomic relaxations are taken into account.

  7. Formation of intermetallics at the interface of explosively welded Ni-Al multilayered composites during annealing

    NASA Astrophysics Data System (ADS)

    Ogneva, T. S.; Lazurenko, D. V.; Bataev, I. A.; Mali, V. I.; Esikov, M. A.; Bataev, A. A.

    2016-04-01

    The Ni-Al multilayer composite was fabricated using explosive welding. The zones of mixing of Ni and Al are observed at the composite interfaces after the welding. The composition of these zones is inhomogeneous. Continuous homogeneous intermetallic layers are formed at the interface after heat treatment at 620 °C during 5 h These intermetallic layers consist of NiAl3 and Ni2Al3 phases. The presence of mixed zones significantly accelerates the growth rate of intermetallic phases at the initial stages of heating.

  8. Multi-layer and multi-component intercalation at the graphene/Ir(111) interface

    NASA Astrophysics Data System (ADS)

    Bazarnik, Maciej; Decker, Régis; Brede, Jens; Wiesendanger, Roland

    2015-09-01

    We present a scanning tunneling microscopy study of Fe and Co intercalated at the graphene-Ir(111) interface. In the case of Fe, we investigate the morphology of the surface with respect to the annealing temperature, which activates the intercalation, and as a function of coverage. By increasing the coverage we show that it is possible to intercalate multilayers at the interface. Finally, we demonstrate that the successive intercalation of Co and Fe for the same sample leads to distinct adjacent intercalation areas.

  9. NiO/Fe(001): Magnetic anisotropy, exchange bias, and interface structure

    SciTech Connect

    Mlynczak, E.; Luches, P.

    2013-06-21

    The magnetic and structural properties of NiO/Fe epitaxial bilayers grown on MgO(001) were studied using magnetooptic Kerr effect (MOKE) and conversion electron Moessbauer spectroscopy (CEMS). The bilayers were prepared under ultra high vacuum conditions using molecular beam epitaxy with oblique deposition. Two systems were compared: one showing the exchange bias (100ML-NiO/24ML-Fe), ML stands for a monolayer, and another where the exchange bias was not observed (50ML-NiO/50ML-Fe). For both, the magnetic anisotropy was found to be complex, yet dominated by the growth-induced uniaxial anisotropy. The training effect was observed for the 100ML-NiO/24ML-Fe system and quantitatively described using the spin glass model. The composition and magnetic state of the interfacial Fe layers were studied using {sup 57}Fe-CEMS. An iron oxide phase (Fe{sup 3+}{sub 4}Fe{sup 2+}{sub 1}O{sub 7}), as thick as 31 A, was identified at the NiO/Fe interface in the as-deposited samples. The ferrimagnetic nature of the interfacial iron oxide film explains the complex magnetic anisotropy observed in the samples.

  10. Enhanced magneto-ionic switching of interface anisotropy in Pt/Co/GdOx films

    NASA Astrophysics Data System (ADS)

    Tan, Aik Jun; Mann, Max; Bauer, Uwe; Beach, Geoffrey

    Voltage control of magnetic anisotropy is of great interest for reducing the switching energy barrier in spintronic devices. It has recently been shown that electric field-driven oxygen ion migration near the interface of ferromagnet/oxide bilayers can lead to very large changes in magnetic anisotropy at elevated temperature. Here, we examine magneto-ionic switching in ultrathin Pt(3nm)/Co(0.9nm)/GdOx(tox) /Au(tAu) films with perpendicular anisotropy, in which the GdOx layer and gate structure are optimized for efficient room-temperature oxygen conduction. We study voltage-induced switching dynamics as a function of the GdOx stoichiometry and the thickness of the Au gate layer. We find that for optimally oxidized GdOx, a positive bias voltage applied to the Au electrode results in a transition from PMA to in-plane magnetization, and at zero bias, the PMA spontaneously returns. The rate of this transition depends on the thickness of the Au gate which suggests that the rate-limiting step is removal and reintroduction of oxygen by gate voltage. This toggling of PMA under positive bias does not require oxidation of the Co layer, in contrast to earlier work by Uwe et al . We demonstrate that by optimizing the electrode materials, extremely fast room-temperature switching can be achieved in these devices.

  11. Microscopic thin film optical anisotropy imaging at the solid-liquid interface

    NASA Astrophysics Data System (ADS)

    Miranda, Adelaide; De Beule, Pieter A. A.

    2016-04-01

    Optical anisotropy of thin films has been widely investigated through ellipsometry, whereby typically an optical signal is averaged over a ˜1 cm2 elliptical area that extends with increasing angle-of-incidence (AOI). Here, we report on spectroscopic imaging ellipsometry at the solid-liquid interface applied to a supported lipid bilayer (SLB). We detail how a differential spectrally resolved ellipsometry measurement, between samples with and without optically anisotropic thin film on an absorbing substrate, can be applied to recover in and out of plane refractive indices of the thin film with known film thickness, hence determining the thin film optical anisotropy. We also present how optimal wavelength and AOI settings can be determined ensuring low parameter cross correlation between the refractive indices to be determined from a differential measurement in Δ ellipsometry angle. Furthermore, we detail a Monte Carlo type analysis that allows one to determine the minimal required optical ellipsometry resolution to recover a given thin film anisotropy. We conclude by presenting a new setup for a spectroscopic imaging ellipsometry based on fiber supercontinuum laser technology, multi-wavelength diode system, and an improved liquid cell design, delivering a 5 ×-10 × ellipsometric noise reduction over state-of-the-art. We attribute this improvement to increased ellipsometer illumination power and a reduced light path in liquid through the use of a water dipping objective.

  12. Microscopic thin film optical anisotropy imaging at the solid-liquid interface.

    PubMed

    Miranda, Adelaide; De Beule, Pieter A A

    2016-04-01

    Optical anisotropy of thin films has been widely investigated through ellipsometry, whereby typically an optical signal is averaged over a ∼1 cm(2) elliptical area that extends with increasing angle-of-incidence (AOI). Here, we report on spectroscopic imaging ellipsometry at the solid-liquid interface applied to a supported lipid bilayer (SLB). We detail how a differential spectrally resolved ellipsometry measurement, between samples with and without optically anisotropic thin film on an absorbing substrate, can be applied to recover in and out of plane refractive indices of the thin film with known film thickness, hence determining the thin film optical anisotropy. We also present how optimal wavelength and AOI settings can be determined ensuring low parameter cross correlation between the refractive indices to be determined from a differential measurement in Δ ellipsometry angle. Furthermore, we detail a Monte Carlo type analysis that allows one to determine the minimal required optical ellipsometry resolution to recover a given thin film anisotropy. We conclude by presenting a new setup for a spectroscopic imaging ellipsometry based on fiber supercontinuum laser technology, multi-wavelength diode system, and an improved liquid cell design, delivering a 5 ×-10 × ellipsometric noise reduction over state-of-the-art. We attribute this improvement to increased ellipsometer illumination power and a reduced light path in liquid through the use of a water dipping objective. PMID:27131681

  13. Anatomy of electric field control of perpendicular magnetic anisotropy at Fe/MgO interfaces

    NASA Astrophysics Data System (ADS)

    Ibrahim, F.; Yang, H. X.; Hallal, A.; Dieny, B.; Chshiev, M.

    2016-01-01

    The charge-mediated effect of electric field on the perpendicular magnetic anisotropy (PMA) of Fe/MgO interfaces is investigated using first-principles calculations. We present an approach by discussing this effect in relation to the intrinsic dipole field existing at the Fe/MgO interface. A firm correlation between the PMA and the interfacial dipole is established and further verified in the absence of an applied electric field. The on-site projected PMA analysis not only elucidates that the effect of electric field on the PMA extends beyond the interfacial Fe layer, but also shows that the second Fe layer carries the largest contribution to the effect. This observation is interpreted in relation to the orbital hybridization changes induced by applying an electric field.

  14. First-principles study of the Fe | MgO(0 0 1) interface: magnetic anisotropy.

    PubMed

    Bose, Thomas; Cuadrado, Ramon; Evans, Richard F L; Chepulskii, Roman V; Apalkov, Dmytro; Chantrell, Roy W

    2016-04-20

    We present a systematic first-principles study of Fe | MgO bilayer systems emphasizing the influence of the iron layer thickness on the geometry, the electronic structure and the magnetic properties. Our calculations ensure the unconstrained structural relaxation at scalar relativistic level for various numbers of iron layers placed on the magnesium oxide substrate. Our results show that due to the formation of the interface the electronic structure of the interface iron atoms is significantly modified involving charge transfer within the iron subsystem. In addition, we find that the magnetic anisotropy energy increases from 1.9 mJ m(-2) for 3 Fe layers up to 3.0 mJ m(-2) for 11 Fe layers. PMID:26987845

  15. Ru Catalyst-Induced Perpendicular Magnetic Anisotropy in MgO/CoFeB/Ta/MgO Multilayered Films.

    PubMed

    Liu, Yiwei; Zhang, Jingyan; Wang, Shouguo; Jiang, Shaolong; Liu, Qianqian; Li, Xujing; Wu, Zhenglong; Yu, Guanghua

    2015-12-01

    The high oxygen storage/release capability of the catalyst Ru is used to manipulate the interfacial electronic structure in spintronic materials to obtain perpendicular magnetic anisotropy (PMA). Insertion of an ultrathin Ru layer between the CoFeB and Ta layers in MgO/CoFeB/Ta/MgO films effectively induces PMA without annealing. Ru plays a catalytic role in Fe-O-Ta bonding and isolation at the metal-oxide interface to achieve moderate interface oxidation. In contrast, PMA cannot be obtained in the sample with a Mg insertion layer or without an insertion layer because of the lack of a catalyst. Our work would provide a new approach toward catalyst-induced PMA for future CoFeB-based spintronic device applications. PMID:26565747

  16. Contribution of individual interfaces in the MgO/Co/Pd trilayer to perpendicular magnetic anisotropy upon annealing

    SciTech Connect

    Kim, Minseok; Kim, Sanghoon; Ko, Jungho; Hong, Jongill

    2015-03-09

    The contribution of each interface of the MgO/Co/Pd trilayer to the perpendicular magnetic anisotropy (PMA) was studied by changing chemical and crystalline structures through annealing. We found that volumetric anisotropy in the MgO/Co/Pd trilayer was significantly increased due to enhanced magnetoelastic anisotropy caused by stress built up most likely at the MgO/Co interface during annealing. When the trilayer was annealed at 400 °C, the alloy formation at the Co/Pd interface additionally increased the volumetric anisotropy. Our x-ray magnetic circular dichroism study supported that those structural modifications led to an increase in the orbital moment through spin-orbit coupling (SOC) along the film normal two times larger than that of the as-deposited trilayer, thereby enhancing PMA greatly. Our experimental results prove that the Co/Pd interface, rather than the MgO/Co interface, plays an essential role in inducing strong PMA in the trilayer. The precise investigation of annealing effect on both volumetric and interfacial anisotropies can provide a methodological solution to improve the SOC of the trilayer that can serve as the core unit of spintronic devices.

  17. Controlled lateral anisotropy in correlated manganite heterostructures by interface-engineered oxygen octahedral coupling

    NASA Astrophysics Data System (ADS)

    Huijben, Mark

    Ultimate miniaturization of magnetic random access memory (MRAM) devices is expected by the utilization of spin-transfer torques, because they present an efficient means to switch elements with a very high magnetic anisotropy. To overcome the low switching speed in current collinearly magnetized devices, new routes are being explored to realize magnetic tunnel junction stacks with non-collinear magnetization between two magnetic electrodes. Controlled in-plane rotation of the magnetic easy axis in manganite heterostructures by tailoring the interface oxygen network would provide a promising direction for non-collinear magnetization in correlated oxide magnetic tunneling junctions. Here, we demonstrate how to manipulate magnetic and electronic anisotropic properties in manganite heterostructures by engineering the oxygen network on the unit-cell level. The strong oxygen octahedral coupling is found to transfer the octahedral rotation, present in the NdGaO3 (NGO) substrate, to the La2/3Sr1/3MnO3 (LSMO) film in the interface region. This causes an unexpected realignment of the magnetic easy axis along the short axis of the LSMO unit cell as well as the presence of a giant anisotropic transport in these ultrathin LSMO films. As a result we possess control of the lateral magnetic and electronic anisotropies by atomic scale design of the oxygen octahedral rotation. Membership Pending.

  18. Enhanced mobility electrons at the monolayer / multilayer MoS2 homo-interface

    NASA Astrophysics Data System (ADS)

    Jia, Y.; Lenferink, E. J.; Stanev, T.; Stern, N. P.

    2015-03-01

    Energy band alignment at interface of heterostructures can give rise to non-trivial local electronic structure and charge states with low dimensionality. In transition metal dichalcogenides (TMDCs), the optical band gap depends on the number of 2D crystal layers, transitioning from 1.29 eV in bulk to 1.88 eV for a monolayer of MoS2, for example, and providing the possibility to create unusual charge state at the monolayer/multilayer homo-interface. Here, we examine the boundaries between MoS2 monolayers and multilayers using scanning photocurrent microscopy and gate-dependent transport. Enhanced photocurrent and conductance were observed at the 1D homo-interface, which can be explained as accumulated carriers in the bent-band region of the junction. Our heterojunction modeling suggests a high local carrier density and enhanced mobility at the homo-interface. Our work presents an opportunity to achieve a 1D electron state in a homojunction and a pathway to break the mobility limit of TMDC monolayer transistors. This work was supported by the Institute for Sustainability and Energy at Northwestern and the U.S. Department of Energy (DE-SC0012130). N.P.S. acknowledges support as an Alfred P. Sloan Research Fellow.

  19. Graphene-multilayer graphene nanocomposites as highly efficient thermal interface materials.

    PubMed

    Shahil, Khan M F; Balandin, Alexander A

    2012-02-01

    We found that the optimized mixture of graphene and multilayer graphene, produced by the high-yield inexpensive liquid-phase-exfoliation technique, can lead to an extremely strong enhancement of the cross-plane thermal conductivity K of the composite. The "laser flash" measurements revealed a record-high enhancement of K by 2300% in the graphene-based polymer at the filler loading fraction f = 10 vol %. It was determined that the relatively high concentration of the single-layer and bilayer graphene flakes (~10-15%) present simultaneously with the thicker multilayers of large lateral size (~1 μm) were essential for the observed unusual K enhancement. The thermal conductivity of the commercial thermal grease was increased from an initial value of ~5.8 W/mK to K = 14 W/mK at the small loading f = 2%, which preserved all mechanical properties of the hybrid. Our modeling results suggest that graphene-multilayer graphene nanocomposite used as the thermal interface material outperforms those with carbon nanotubes or metal nanoparticles owing to graphene's aspect ratio and lower Kapitza resistance at the graphene-matrix interface. PMID:22214526

  20. Characteristics of laser ultrasound interaction with multi-layered dissimilar metals adhesive interface by numerical simulation

    NASA Astrophysics Data System (ADS)

    Zhang, Kuanshuang; Zhou, Zhenggan; Zhou, Jianghua; Sun, Guangkai

    2015-10-01

    The characteristics of laser-generated ultrasonic wave interaction with multi-layered dissimilar metals adhesive interface are investigated by finite element method (FEM). The physical model of laser-generated ultrasonic wave in the multi-layered dissimilar metals adhesive structure is built. The surface temperature evolution with different laser power densities is analyzed to obtain the parameters of pulsed laser with thermoelastic regime. The differences of laser ultrasonic waves with different center frequencies measured at the center of laser irradiation would verify the interfacial features of adhesive structures. The optimum frequency range and probe point would be beneficial for the detection of the small void defect. The numerical results indicate that the different frequency range and probe points would evidently influence the identification and quantitative characterization of the small void defect. The research findings would lay a foundation for testing interfacial integrity.

  1. Developing multi-layer mirror technology near 45 nm using Sc/Si interfaces

    SciTech Connect

    Nilsen, J; Jankowski, A; Friedman, L; Walton, C C

    2004-02-12

    Given the existing X-ray laser sources near 45 nm it would be useful to produce efficient X-ray optics in the 35 to 50 nm wavelength range that could be utilized in new applications. In this work we are developing the process to stabilize the interfaces of nanolaminate structures using materials such as Sc and Si. These materials will enable us to develop new multi-layer mirror technology that can be used in the wavelength range near 45 nm. To obtain this objective, the interfacial structure and reaction kinetics must first be well understood and then controlled for design applications. In this work we fabricate several Sc/Si multi-layer mirrors with and without a B{sub 4}C barrier layer. The structure and reflectivity of the mirrors are analyzed.

  2. Ultrafast optical nonlinearity of multi-layered graphene synthesized by the interface growth process

    NASA Astrophysics Data System (ADS)

    Kim, Won-Jun; Chang, You Min; Lee, Junsu; Kang, Dongseok; Lee, Ju Han; Song, Yong-Won

    2012-06-01

    We propose a novel photonic application as well as an optical tool to verify the crystallinity of interface-grown graphene demonstrating passive mode-locked lasers. The interface growth process enables the formation of multi-layered graphene at an interface of substrate and catalyst, therefore directly onto the targeted substrate without a transfer process. The synthesized graphene is characterized using Raman spectroscopy and x-ray photoelectron spectroscopy before ultrashort pulse formation to confirm the validity of the process for high-speed photonic applications of graphene. The resultant pulses have a repetition rate, pulse duration, RF extinction ratio of 14.01 MHz, 1.0 ps, and ˜35 dB, respectively.

  3. Elastic strains at interfaces in InAs/AlSb multilayer structures for quantum cascade lasers

    SciTech Connect

    Nicolai, J.; Gatel, Ch.; Warot-Fonrose, B.; Ponchet, A.; Teissier, R.; Baranov, A. N.; Magen, C.

    2014-01-20

    InAs/AlSb multilayers similar to those used in quantum cascade lasers have been grown by molecular beam epitaxy on (001) InAs substrates. Elastic strain is investigated by high resolution transmission electron microscopy. Thin interfacial regions with lattice distortions significantly different from the strain of the AlSb layers themselves are revealed from the geometrical phase analysis. Strain profiles are qualitatively compared to the chemical contrast of high angle annular dark field images obtained by scanning transmission electron microscopy. The strain and chemical profiles are correlated with the growth sequences used to form the interfaces. Tensile strained AlAs-like interfaces tend to form predominantly due to the high thermal stability of AlAs. Strongly asymmetric interfaces, AlAs-rich and (Al, In)Sb, respectively, can also be achieved by using appropriate growth sequences.

  4. Magnetic anisotropy and high frequency permeability of multilayered nanocomposite FeAlO thin films

    SciTech Connect

    Ma, Y. G.; Liu, Y.; Tan, C. Y.; Liu, Z. W.; Ong, C. K.

    2006-09-01

    A cool-down step deposition process (multistep deposition with cool-down interval) was used to grow nanocomposite FeAlO thin films of various thicknesses up to 440 nm by magnetron sputtering at a substrate temperature of 15 deg. C. The effect of the number of cool-down steps on the soft magnetic properties and high frequency characteristics of the nanocomposite FeAlO films were investigated. The deposition process was proved very effective in improving the soft magnetic properties and high frequency characteristics of the films. The eight-layered samples, fabricated by eight cool-down step deposition process, of thicknesses of 220 and 440 nm had obvious in-plane uniaxial anisotropies while the single-layered films were nearly isotropic. The resulting real permeability value of the eight-layered films was larger than 300 for the 220 nm film and between 200 and 300 for the 440 nm film.

  5. Fiber/matrix interfaces for SiC/SiC composites: Multilayer SiC coatings

    SciTech Connect

    Halverson, H.; Curtin, W.A.

    1996-08-01

    Tensile tests have been performed on composites of CVI SiC matrix reinforced with 2-d Nicalon fiber cloth, with either pyrolitic carbon or multilayer CVD SiC coatings [Hypertherm High-Temperature Composites Inc., Huntington Beach, CA.] on the fibers. To investigate the role played by the different interfaces, several types of measurements are made on each sample: (i) unload-reload hysteresis loops, and (ii) acoustic emission. The pyrolitic carbon and multilayer SiC coated materials are remarkably similar in overall mechanical responses. These results demonstrate that low-modulus, or compliant, interface coatings are not necessary for good composite performance, and that complex, hierarchical coating structures may possibly yield enhanced high-temperature performance. Analysis of the unload/reload hysteresis loops also indicates that the usual {open_quotes}proportional limit{close_quotes} stress is actually slightly below the stress at which the 0{degrees} load-bearing fibers/matrix interfaces slide and are exposed to atmosphere.

  6. Phase constitution and interface structure of nano-sized Ag-Cu/AlN multilayers: Experiment and ab initio modeling

    SciTech Connect

    Pigozzi, Giancarlo; Janczak-Rusch, Jolanta; Passerone, Daniele; Antonio Pignedoli, Carlo; Patscheider, Joerg; Jeurgens, Lars P. H.; Antusek, Andrej; Parlinska-Wojtan, Magdalena; Bissig, Vinzenz

    2012-10-29

    Nano-sized Ag-Cu{sub 8nm}/AlN{sub 10nm} multilayers were deposited by reactive DC sputtering on {alpha}-Al{sub 2}O{sub 3}(0001) substrates. Investigation of the phase constitution and interface structure of the multilayers evidences a phase separation of the alloy sublayers into nanosized grains of Ag and Cu. The interfaces between the Ag grains and the quasi-single-crystalline AlN sublayers are semi-coherent, whereas the corresponding Cu/AlN interfaces are incoherent. The orientation relationship between Ag and AlN is constant throughout the entire multilayer stack. These observations are consistent with atomistic models of the interfaces as obtained by ab initio calculations.

  7. Analytic Element Modeling of Steady Interface Flow in Multilayer Aquifers Using AnAqSim.

    PubMed

    Fitts, Charles R; Godwin, Joshua; Feiner, Kathleen; McLane, Charles; Mullendore, Seth

    2015-01-01

    This paper presents the analytic element modeling approach implemented in the software AnAqSim for simulating steady groundwater flow with a sharp fresh-salt interface in multilayer (three-dimensional) aquifer systems. Compared with numerical methods for variable-density interface modeling, this approach allows quick model construction and can yield useful guidance about the three-dimensional configuration of an interface even at a large scale. The approach employs subdomains and multiple layers as outlined by Fitts (2010) with the addition of discharge potentials for shallow interface flow (Strack 1989). The following simplifying assumptions are made: steady flow, a sharp interface between fresh- and salt water, static salt water, and no resistance to vertical flow and hydrostatic heads within each fresh water layer. A key component of this approach is a transition to a thin fixed minimum fresh water thickness mode when the fresh water thickness approaches zero. This allows the solution to converge and determine the steady interface position without a long transient simulation. The approach is checked against the widely used numerical codes SEAWAT and SWI/MODFLOW and a hypothetical application of the method to a coastal wellfield is presented. PMID:24942663

  8. Magnetic Pinning in Nb and YBCO Thin Films by Co/Pt Multilayers with Perpendicular Magnetic Anisotropy

    NASA Astrophysics Data System (ADS)

    Cheng, X. M.; Zhu, L. Y.; Chien, C. L.; Cieplak, Marta Z.; Adamus, Z.; Abal'Oshev, A.; Berkowski, M.

    2006-03-01

    Magnetic pinning of vortices has the advantage over intrinsic pinning in that the superconducting critical current can be reversibly tuned by the magnetic field (H). Magnetic pinning by Co/Pt multilayers with perpendicular magnetic anisotropy has been studied in two ferromagnetic/superconducting bilayers of Nb and YBCO with different superconducting properties (e.g. penetration depth λ). Magnetic force microscopy reveals similar magnetization (M) reversal process in the two cases, both exhibiting a large density of narrow residual domains but with different domain width w at the final reversal stage. However, the magnetic pinning, revealed by the M-H loop shape in the superconducting state, is different. The Nb film exhibits an enhancement of M with the strongest effect during the final reversal stage, while the YBCO film shows a suppression of M in the vicinity of central M peak and an enhancement of M in large magnetic fields. These different behaviors are related to the different λ/w ratio in the two cases.

  9. In-plane optical anisotropy of InAs/GaSb superlattices with alternate interfaces

    PubMed Central

    2013-01-01

    The in-plane optical anisotropy (IPOA) in InAs/GaSb superlattices has been studied by reflectance difference spectroscopy (RDS) at different temperatures ranging from 80 to 300 K. We introduce alternate GaAs- and InSb-like interfaces (IFs), which cause the symmetry reduced from D2d to C2v. IPOA has been observed in the (001) plane along [110] and [11¯0] axes. RDS measurement results show strong anisotropy resonance near critical point (CP) energies of InAs and GaSb. The energy positions show red shift and RDS intensity decreases with the increasing temperature. For the superlattice sample with the thicker InSb-like IFs, energy positions show red shift, and the spectra exhibit stronger IPOA. The excitonic effect is clearly observed by RDS at low temperatures. It demonstrates that biaxial strain results in the shift of the CP energies and IPOA is enhanced by the further localization of the carriers in InSb-like IFs. PMID:23799946

  10. Perpendicular magnetic tunnel junction with enhanced anisotropy obtained by utilizing an Ir/Co interface

    NASA Astrophysics Data System (ADS)

    Yakushiji, Kay; Kubota, Hitoshi; Fukushima, Akio; Yuasa, Shinji

    2016-01-01

    A highly scalable perpendicularly magnetized storage layer of a spin-torque-switching magnetic random-access memory (STT-MRAM) was developed. This storage layer attains a perpendicular magnetic anisotropy (PMA) of above 0.9 erg/cm2 at a thickness of 2 nm. Such high PMA is suitable for pushing STT-MRAM technology beyond the 20 nm node. The key was to realize dual interfacial PMA at both the Ir/Co and FeB/MgO interfaces in the united structure of the storage layer. While a high PMA was retained, a high magnetoresistance ratio (100%) and a low resistance-area product (3.0 Ω µm2) were also achieved.

  11. Interface Coupling in Twisted Multilayer Graphene by Resonant Raman Spectroscopy of Layer Breathing Modes.

    PubMed

    Wu, Jiang-Bin; Hu, Zhi-Xin; Zhang, Xin; Han, Wen-Peng; Lu, Yan; Shi, Wei; Qiao, Xiao-Fen; Ijiäs, Mari; Milana, Silvia; Ji, Wei; Ferrari, Andrea C; Tan, Ping-Heng

    2015-07-28

    Raman spectroscopy is the prime nondestructive characterization tool for graphene and related layered materials. The shear (C) and layer breathing modes (LBMs) are due to relative motions of the planes, either perpendicular or parallel to their normal. This allows one to directly probe the interlayer interactions in multilayer samples. Graphene and other two-dimensional (2d) crystals can be combined to form various hybrids and heterostructures, creating materials on demand with properties determined by the interlayer interaction. This is the case even for a single material, where multilayer stacks with different relative orientations have different optical and electronic properties. In twisted multilayer graphene there is a significant enhancement of the C modes due to resonance with new optically allowed electronic transitions, determined by the relative orientation of the layers. Here we show that this applies also to the LBMs, which can be now directly measured at room temperature. We find that twisting has a small effect on LBMs, quite different from the case of the C modes. This implies that the periodicity mismatch between two twisted layers mostly affects shear interactions. Our work shows that ultralow-frequency Raman spectroscopy is an ideal tool to uncover the interface coupling of 2d hybrids and heterostructures. PMID:26062640

  12. Phonon-interface scattering in multilayer graphene on an amorphous support

    PubMed Central

    Sadeghi, Mir Mohammad; Jo, Insun; Shi, Li

    2013-01-01

    The recent studies of thermal transport in suspended, supported, and encased graphene just began to uncover the richness of two-dimensional phonon physics, which is relevant to the performance and reliability of graphene-based functional materials and devices. Among the outstanding questions are the exact causes of the suppressed basal-plane thermal conductivity measured in graphene in contact with an amorphous material, and the layer thickness needed for supported or embedded multilayer graphene (MLG) to recover the high thermal conductivity of graphite. Here we use sensitive in-plane thermal transport measurements of graphene samples on amorphous silicon dioxide to show that full recovery to the thermal conductivity of the natural graphite source has yet to occur even after the MLG thickness is increased to 34 layers, considerably thicker than previously thought. This seemingly surprising finding is explained by long intrinsic scattering mean free paths of phonons in graphite along both basal-plane and cross-plane directions, as well as partially diffuse scattering of MLG phonons by the MLG-amorphous support interface, which is treated by an interface scattering model developed for highly anisotropic materials. Based on the phonon transmission coefficient calculated from reported experimental thermal interface conductance results, phonons emerging from the interface consist of a large component that is scattered across the interface, making rational choice of the support materials a potential approach to increasing the thermal conductivity of supported MLG. PMID:24067656

  13. Piezothermoelastic behavior of multilayered pyroelectric cylindrical actuators with weakly conducting interfaces resting on elastic foundations

    NASA Astrophysics Data System (ADS)

    Wang, Huiming

    2014-04-01

    An exact solution is obtained for multilayered pyroelectric cylindrical (MPC) actuators with weakly conducting interfaces subjected to thermo-electro-mechanical loading. The outer surface of the composite cylindrical actuator is supported by a Winkler-type elastic foundation. At the interface, all the thermal and mechanical quantities as well as the normal electric displacement are assumed to be continuous but the electric potential is discontinuous. The temperature fields are obtained by the transfer matrix method and the piezothermoelastic fields are developed by the state space method combined with the Cayley-Hamilton theorem. Numerical results are presented graphically to show the effects of the elastic foundation, interfacial parameters and heat transfer coefficient on the piezothermoelastic behavior of MPC actuators.

  14. Controlled lateral anisotropy in correlated manganite heterostructures by interface-engineered oxygen octahedral coupling

    NASA Astrophysics Data System (ADS)

    Liao, Z.; Huijben, M.; Zhong, Z.; Gauquelin, N.; Macke, S.; Green, R. J.; van Aert, S.; Verbeeck, J.; van Tendeloo, G.; Held, K.; Sawatzky, G. A.; Koster, G.; Rijnders, G.

    2016-04-01

    Controlled in-plane rotation of the magnetic easy axis in manganite heterostructures by tailoring the interface oxygen network could allow the development of correlated oxide-based magnetic tunnelling junctions with non-collinear magnetization, with possible practical applications as miniaturized high-switching-speed magnetic random access memory (MRAM) devices. Here, we demonstrate how to manipulate magnetic and electronic anisotropic properties in manganite heterostructures by engineering the oxygen network on the unit-cell level. The strong oxygen octahedral coupling is found to transfer the octahedral rotation, present in the NdGaO3 (NGO) substrate, to the La2/3Sr1/3MnO3 (LSMO) film in the interface region. This causes an unexpected realignment of the magnetic easy axis along the short axis of the LSMO unit cell as well as the presence of a giant anisotropic transport in these ultrathin LSMO films. As a result we possess control of the lateral magnetic and electronic anisotropies by atomic-scale design of the oxygen octahedral rotation.

  15. Controlled lateral anisotropy in correlated manganite heterostructures by interface-engineered oxygen octahedral coupling.

    PubMed

    Liao, Z; Huijben, M; Zhong, Z; Gauquelin, N; Macke, S; Green, R J; Van Aert, S; Verbeeck, J; Van Tendeloo, G; Held, K; Sawatzky, G A; Koster, G; Rijnders, G

    2016-04-01

    Controlled in-plane rotation of the magnetic easy axis in manganite heterostructures by tailoring the interface oxygen network could allow the development of correlated oxide-based magnetic tunnelling junctions with non-collinear magnetization, with possible practical applications as miniaturized high-switching-speed magnetic random access memory (MRAM) devices. Here, we demonstrate how to manipulate magnetic and electronic anisotropic properties in manganite heterostructures by engineering the oxygen network on the unit-cell level. The strong oxygen octahedral coupling is found to transfer the octahedral rotation, present in the NdGaO3 (NGO) substrate, to the La2/3Sr1/3MnO3 (LSMO) film in the interface region. This causes an unexpected realignment of the magnetic easy axis along the short axis of the LSMO unit cell as well as the presence of a giant anisotropic transport in these ultrathin LSMO films. As a result we possess control of the lateral magnetic and electronic anisotropies by atomic-scale design of the oxygen octahedral rotation. PMID:26950593

  16. Directional alignment of FeCo crystallites in Si/NiFe/Ru/FeCoB multilayer with high anisotropy field above 500 Oe.

    PubMed

    Hirata, Ken-Ichiro; Gomi, Shunsuke; Nakagawa, Shigeki

    2011-03-01

    In-plane magnetic anisotropy and crystal structure of FeCoB layer on Si/NiFe/Ru underlayer were investigated by using X-Ray Diffraction (XRD) measurement. A pole-figure measurement of XRD showed directionally tilted alignment of FeCo crystallites in Si/NiFe/Ru/FeCoB multilayered film with high in-plane anisotropy field H(k) but no directional alignment was found in FeCoB single layered film. The higher H(k) appeared in the Si/NiFe/Ru/FeCoB multilayered configuration with the thicker FeCoB layer. Since Ru crystallites in a multiunderlayer configuration exhibited no directional alignment, the surface structure of underlayer should be no main reason for the directional alignment of FeCo crystallites deposited on it. The dependence of hickness of FeCoB layer in Si/NiFe/Ru/FeCoB film on H(k) indicated that the in-plane magnetic anisotropy is caused by not only the structure of Ru underlayer but also oblique incidence effect of sputtered particles, which is attained in configuration of Facing Targets Sputtering (FTS) system. From these experimental results, remarkably high H(k) of 540 Oe was obtained. PMID:21449466

  17. Formation of strained interfaces in AlSb/InAs multilayers grown by molecular beam epitaxy for quantum cascade lasers

    SciTech Connect

    Nicolaï, J.; Warot-Fonrose, B.; Gatel, C. Ponchet, A.; Teissier, R.; Baranov, A. N.; Magen, C.

    2015-07-21

    Structural and chemical properties of InAs/AlSb interfaces have been studied by transmission electron microscopy. InAs/AlSb multilayers were grown by molecular beam epitaxy with different growth sequences at interfaces. The out-of-plane strain, determined using high resolution microscopy and geometrical phase analysis, has been related to the chemical composition of the interfaces analyzed by high angle annular dark field imaging. Considering the local strain and chemistry, we estimated the interface composition and discussed the mechanisms of interface formation for the different growth sequences. In particular, we found that the formation of the tensile AlAs-type interface is spontaneously favored due to its high thermal stability compared to the InSb-type interface. We also showed that the interface composition could be tuned using an appropriate growth sequence.

  18. Self-consistent iteration procedure in analyzing reflectivity and spectroscopic ellipsometry data of multilayered materials and their interfaces

    SciTech Connect

    Asmara, T. C.; Rusydi, A.; Santoso, I.

    2014-12-15

    For multilayered materials, reflectivity depends on the complex dielectric function of all the constituent layers, and a detailed analysis is required to separate them. Furthermore, for some cases, new quantum states can occur at the interface which may change the optical properties of the material. In this paper, we discuss various aspects of such analysis, and present a self-consistent iteration procedure, a versatile method to extract and separate the complex dielectric function of each individual layer of a multilayered system. As a case study, we apply this method to LaAlO{sub 3}/SrTiO{sub 3} heterostructure in which we are able to separate the effects of the interface from the LaAlO{sub 3} film and the SrTiO{sub 3} substrate. Our method can be applied to other complex multilayered systems with various numbers of layers.

  19. Spin orbit torques and Dzyaloshinskii-Moriya interaction in dual-interfaced Co-Ni multilayers

    PubMed Central

    Yu, Jiawei; Qiu, Xuepeng; Wu, Yang; Yoon, Jungbum; Deorani, Praveen; Besbas, Jean Mourad; Manchon, Aurelien; Yang, Hyunsoo

    2016-01-01

    We study the spin orbit torque (SOT) and Dzyaloshinskii-Moriya interaction (DMI) in the dual-interfaced Co-Ni perpendicular multilayers. Through the combination of top and bottom layer materials (Pt, Ta, MgO and Cu), SOT and DMI are efficiently manipulated due to an enhancement or cancellation of the top and bottom contributions. However, SOT is found to originate mostly from the bulk of a heavy metal (HM), while DMI is more of interfacial origin. In addition, we find that the direction of the domain wall (DW) motion can be either along or against the electron flow depending on the DW tilting angle when there is a large DMI. Such an abnormal DW motion induces a large assist field required for hysteretic magnetization reversal. Our results provide insight into the role of DMI in SOT driven magnetization switching, and demonstrate the feasibility of achieving desirable SOT and DMI for spintronic devices. PMID:27601317

  20. Spin orbit torques and Dzyaloshinskii-Moriya interaction in dual-interfaced Co-Ni multilayers.

    PubMed

    Yu, Jiawei; Qiu, Xuepeng; Wu, Yang; Yoon, Jungbum; Deorani, Praveen; Besbas, Jean Mourad; Manchon, Aurelien; Yang, Hyunsoo

    2016-01-01

    We study the spin orbit torque (SOT) and Dzyaloshinskii-Moriya interaction (DMI) in the dual-interfaced Co-Ni perpendicular multilayers. Through the combination of top and bottom layer materials (Pt, Ta, MgO and Cu), SOT and DMI are efficiently manipulated due to an enhancement or cancellation of the top and bottom contributions. However, SOT is found to originate mostly from the bulk of a heavy metal (HM), while DMI is more of interfacial origin. In addition, we find that the direction of the domain wall (DW) motion can be either along or against the electron flow depending on the DW tilting angle when there is a large DMI. Such an abnormal DW motion induces a large assist field required for hysteretic magnetization reversal. Our results provide insight into the role of DMI in SOT driven magnetization switching, and demonstrate the feasibility of achieving desirable SOT and DMI for spintronic devices. PMID:27601317

  1. The Influence of Interfaces on the Formation of Bubbles in He Ion Irradiated Cu/Mo Multilayers

    SciTech Connect

    Li, N.; Carter, J. J.; Misra, A.; Shao, L.; Zhang, X.

    2010-09-30

    The role of immiscible Cu/Mo interfaces on the formation of helium (He) bubbles in ion-irradiated Cu/Mo 5 nm multilayers is examined. Interfaces significantly enhance the critical He concentration above which bubbles, approximately 1 nm in diameter, are detected via through-focus imaging in a transmission electron microscope. He-to-vacancy ratio affects the formation and distribution of He bubbles. The diameter of He bubbles in Cu appears to be slightly larger than that in Mo.

  2. Verification of antiferromagnetic exchange coupling at room temperature using polar magneto-optic Kerr effect in thin EuS/Co multilayers with perpendicular magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Goschew, A.; Scott, M.; Fumagalli, P.

    2016-08-01

    We report on magneto-optic Kerr measurements in polar geometry carried out on a series of thin Co/EuS multilayers on suitable Co/Pd-multilayer substrates. Thin Co/EuS multilayers of a few nanometers individual layer thickness usually have their magnetization in plane. Co/Pd multilayers introduce a perpendicular magnetic anisotropy in the Co/EuS layers deposited on top, thus making it possible to measure magneto-optic signals in the polar geometry in remanence in order to study exchange coupling. Magneto-optic Kerr-effect spectra and hysteresis loops were recorded in the visible and ultraviolet photon-energy range at room temperature. The EuS contribution to the magneto-optic signal is extracted at 4.1 eV by combining hysteresis loops measured at different photon energies with polar magneto-optic Kerr-effect spectra recorded in remanence and in an applied magnetic field of 2.2 T. The extracted EuS signal shows clear signs of antiferromagnetic coupling of the Eu magnetic moments to the Co layers. This implies that the ordering temperature of at least a fraction of the EuS layers is above room temperature proving that magneto-optic Kerr-effect spectroscopy can be used here as a quasi-element-specific method.

  3. Evolution of the interfacial magnetic anisotropy in MgO/CoFeB/Ta/Ru based multilayers as a function of annealing temperature

    NASA Astrophysics Data System (ADS)

    Aleksandrov, Yuriy; Fowley, Ciarán; Kowalska, Ewa; Sluka, Volker; Yıldırım, Oǧuz; Lindner, Jürgen; Ocker, Berthold; Fassbender, Jürgen; Deac, Alina M.

    2016-06-01

    We report the effect of annealing temperature on the dynamic and static magnetic properties of MgO/CoFeB/Ta/Ru multilayers. Angular resolved ferromagnetic resonance measurement results show that the as-deposited film exhibits in-plane magnetic anisotropy, whereas in the annealed films the magnetic easy-axis is almost along the direction perpendicular to the plane of the layers. The extracted interfacial anisotropy energy, Ki, is maximized at an annealing temperature 225∘C, in agreement with the vibrating sample magnetometry results. Although the magnetization is not fully out-of-plane, controlling the degree of the magnetization obliqueness may be advantageous for specific applications such as spin-transfer oscillators.

  4. Influence of the deposition-induced stress on the magnetic properties of magnetostrictive amorphous (Fe80Co20)80B20 multilayers with orthogonal anisotropy

    NASA Astrophysics Data System (ADS)

    González-Guerrero, Miguel; Prieto, José Luis; Sánchez, Pedro; Aroca, Claudio

    2007-12-01

    In this work, we experimentally justify that the control of the mechanical stress induced during the deposition of sputtered amorphous magnetostrictive (Fe80Co20)80B20 allows a custom design of its magnetic properties. FeCoB multilayers have been sputtered on thermal oxide Si substrates with different buffer materials. The crystalline quality and the thermomechanical properties of the buffer layer influence both the coercive and the anisotropy field. Those buffer layers with both high rigidity and poor thermal conductivity do not allow the dissipation of energy of the incoming sputtered material. Therefore, the mechanical stresses related to the deposition process cannot be released, leading to magnetic layers with high easy-axis coercive field and low anisotropy field. This shows that the mechanical stresses accumulated during deposition are a key parameter for the control of coercivity.

  5. Correlation between Pd metal thickness and thermally stable perpendicular magnetic anisotropy features in [Co/Pd]n multilayers at annealing temperatures up to 500 °C

    NASA Astrophysics Data System (ADS)

    An, Gwang Guk; Lee, Ja Bin; Yang, Seung Mo; Kim, Jae Hong; Chung, Woo Seong; Yoon, Kap Soo; Hong, Jin Pyo

    2015-02-01

    We examine highly stable perpendicular magnetic anisotropy (PMA) features of [Co/Pd]10 multilayers (MLs) versus Pd thickness at various ex-situ annealing temperatures. Thermally stable PMA characteristics were observed up to 500 °C, confirming the suitability of these systems for industrial applications at this temperature. Experimental observations suggest that the choice of equivalent Co and Pd layer thicknesses in a ML configuration ensures thermally stable PMA features, even at higher annealing temperatures. X-ray diffraction patterns and cross-sectional transmission electron microscopy images were obtained to determine thickness, post-annealing PMA behavior, and to explore the structural features that govern these findings.

  6. Magneto-Optical Kerr Rotation Spectra and Perpendicular Anisotropy in Compositionally Modulated Multilayer Films of Co/Pt and Fe/Pt

    NASA Astrophysics Data System (ADS)

    Sugimoto, Toshio; Katayama, Toshikazu; Suzuki, Yoshishige; Nishihara, Yoshikazu

    1989-12-01

    Magneto-optical Kerr rotation (θK) spectra and magnetic properties such as saturation magnetization (Ms) and perpendicular magnetic anisotropy of Co/Pt and Fe/Pt compositionally modulated multilayer films (CMF’s) are investigated. An enhancement of θK is observed at the wavelengths of about 290 and 250 nm in Co/Pt and Fe/Pt CMF’s, respectively. It is found that Fe/Pt CMF’s turn into perpendicularly magnetized films in the same manner as Co/Pt CMF’s when the Fe layer becomes thinner than about 5 Å.

  7. Interaction of optical and interface phonons and their anisotropy in GaAs/AlAs superlattices: Experiment and calculations

    SciTech Connect

    Volodin, V. A.; Sachkov, V. A.; Sinyukov, M. P.

    2015-05-15

    The angular anisotropy of interface phonons and their interaction with optical phonons in (001) GaAs/AlAs superlattices are calculated and experimentally studied. Experiments were performed by Raman light scattering in different scattering geometries for phonons with the wave vector directed normally to the superlattice and along its layers. Phonon frequencies were calculated by the extended Born method taking the Coulomb interaction into account in the rigid-ion approximation. Raman scattering spectra were calculated in the Volkenshtein bond-polarizability approximation. Calculations confirmed that the angular anisotropy of phonons observed in experiments appears due to interaction (mixing) of optical phonons, in which atoms are mainly displaced normally to superlattices, with interface phonons (TO-IF modes). In the scattering geometry, when the wave vector lies in the plane of superlattice layers, the mixed TO-IF modes are observed under nonresonance conditions. The Raman spectra for TO-IF modes depend on the mixing of atoms at heteroboundaries.

  8. Fast contact of solid-liquid interface created high strength multi-layered cellulose hydrogels with controllable size.

    PubMed

    He, Meng; Zhao, Yanteng; Duan, Jiangjiang; Wang, Zhenggang; Chen, Yun; Zhang, Lina

    2014-02-12

    Novel onion-like and multi-layered tubular cellulose hydrogels were constructed, for the first time, from the cellulose solution in a 7% NaOH/12% urea aqueous solvent by changing the shape of the gel cores. In our findings, the contacting of the cellulose solution with the surface of the agarose gel rod or sphere loaded with acetic acid led to the close chain packing to form immediately a gel layer, as a result of the destruction of the cellulose inclusion complex by acid through inducing the cellulose self-aggregation. Subsequently, multi-layered cellulose hydrogels were fabricated via a multi-step interrupted gelation process. The size, layer thickness and inter-layer space of the multi-layered hydrogels could be controlled by adjusting the cellulose concentrations, the gel core diameter and the contacting time of the solid-liquid interface. The multi-layered cellulose hydrogels displayed good architectural stability and solvent resistance. Moreover, the hydrogels exhibited high compressive strength and excellent biocompatibility. L929 cells could adhere and proliferate on the surface of the layers and in interior space, showing great potential as tissue engineering scaffolds and cell culture carrier. This work opens up a new avenue for the construction of the high strength multi-layered cellulose hydrogels formed from inner to outside via a fast contact of solid-liquid interface. PMID:24405277

  9. Anisotropy of the solid–liquid interface properties of the Ni–Zr B33 phase from molecular dynamics simulation

    SciTech Connect

    Wilson, S. R.; Mendelev, M. I.

    2015-01-08

    Solid–liquid interface (SLI) properties of the Ni–Zr B33 phase were determined from molecular dynamics simulations. In order to perform these measurements, a new semi-empirical potential for Ni–Zr alloy was developed that well reproduces the material properties required to model SLIs in the Ni50.0Zr50.0 alloy. In particular, the developed potential is shown to provide that the solid phase emerging from the liquid Ni50.0Zr50.0alloy is B33 (apart from a small fraction of point defects), in agreement with the experimental phase diagram. The SLI properties obtained using the developed potential exhibit an extraordinary degree of anisotropy. It is observed that anisotropies in both the interfacial free energy and mobility are an order of magnitude larger than those measured to date in any other metallic compound. Moreover, the [0 1 0] interface is shown to play a significant role in the observed anisotropy. Our data suggest that the [0 1 0] interface simultaneously corresponds to the lowest mobility, the lowest free energy and the highest stiffness of all inclinations in B33 Ni–Zr. This finding can be understood by taking into account a rather complicated crystal structure in this crystallographic direction.

  10. Anisotropy of the solid–liquid interface properties of the Ni–Zr B33 phase from molecular dynamics simulation

    DOE PAGESBeta

    Wilson, S. R.; Mendelev, M. I.

    2015-01-08

    Solid–liquid interface (SLI) properties of the Ni–Zr B33 phase were determined from molecular dynamics simulations. In order to perform these measurements, a new semi-empirical potential for Ni–Zr alloy was developed that well reproduces the material properties required to model SLIs in the Ni50.0Zr50.0 alloy. In particular, the developed potential is shown to provide that the solid phase emerging from the liquid Ni50.0Zr50.0alloy is B33 (apart from a small fraction of point defects), in agreement with the experimental phase diagram. The SLI properties obtained using the developed potential exhibit an extraordinary degree of anisotropy. It is observed that anisotropies in bothmore » the interfacial free energy and mobility are an order of magnitude larger than those measured to date in any other metallic compound. Moreover, the [0 1 0] interface is shown to play a significant role in the observed anisotropy. Our data suggest that the [0 1 0] interface simultaneously corresponds to the lowest mobility, the lowest free energy and the highest stiffness of all inclinations in B33 Ni–Zr. This finding can be understood by taking into account a rather complicated crystal structure in this crystallographic direction.« less

  11. Deterioration of the coercivity due to the diffusion induced interface layer in hard/soft multilayers

    PubMed Central

    Si, Wenjing; Zhao, G. P.; Ran, N.; Peng, Y.; Morvan, F. J.; Wan, X. L.

    2015-01-01

    Hard/soft permanent magnets have aroused many interests in the past two decades because of their potential in achieving giant energy products as well as their rich variety of magnetic behaviors. Nevertheless, the experimental energy products are much smaller than the theoretical ones due to the much smaller coercivity measured in the experiments. In this paper, the deterioration of the coercivity due to the interface atomic diffusion is demonstrated based on a three dimensional (3D) micromagnetic software (OOMMF) and a formula derived for the pinning field in a hard/soft multilayer, which can be applied to both permanent magnets and exchange-coupled-composite (ECC) media. It is found that the formation of the interface layer can decrease the coercivity by roughly 50%, which is responsible for the observed smaller coercivity in both composite and single-phased permanent magnets. A method to enhance the coercivity in these systems is proposed based on the discussions, consistent with recent experiments where excellent magnetic properties are achieved. PMID:26586226

  12. Deterioration of the coercivity due to the diffusion induced interface layer in hard/soft multilayers.

    PubMed

    Si, Wenjing; Zhao, G P; Ran, N; Peng, Y; Morvan, F J; Wan, X L

    2015-01-01

    Hard/soft permanent magnets have aroused many interests in the past two decades because of their potential in achieving giant energy products as well as their rich variety of magnetic behaviors. Nevertheless, the experimental energy products are much smaller than the theoretical ones due to the much smaller coercivity measured in the experiments. In this paper, the deterioration of the coercivity due to the interface atomic diffusion is demonstrated based on a three dimensional (3D) micromagnetic software (OOMMF) and a formula derived for the pinning field in a hard/soft multilayer, which can be applied to both permanent magnets and exchange-coupled-composite (ECC) media. It is found that the formation of the interface layer can decrease the coercivity by roughly 50%, which is responsible for the observed smaller coercivity in both composite and single-phased permanent magnets. A method to enhance the coercivity in these systems is proposed based on the discussions, consistent with recent experiments where excellent magnetic properties are achieved. PMID:26586226

  13. Deterioration of the coercivity due to the diffusion induced interface layer in hard/soft multilayers

    NASA Astrophysics Data System (ADS)

    Si, Wenjing; Zhao, G. P.; Ran, N.; Peng, Y.; Morvan, F. J.; Wan, X. L.

    2015-11-01

    Hard/soft permanent magnets have aroused many interests in the past two decades because of their potential in achieving giant energy products as well as their rich variety of magnetic behaviors. Nevertheless, the experimental energy products are much smaller than the theoretical ones due to the much smaller coercivity measured in the experiments. In this paper, the deterioration of the coercivity due to the interface atomic diffusion is demonstrated based on a three dimensional (3D) micromagnetic software (OOMMF) and a formula derived for the pinning field in a hard/soft multilayer, which can be applied to both permanent magnets and exchange-coupled-composite (ECC) media. It is found that the formation of the interface layer can decrease the coercivity by roughly 50%, which is responsible for the observed smaller coercivity in both composite and single-phased permanent magnets. A method to enhance the coercivity in these systems is proposed based on the discussions, consistent with recent experiments where excellent magnetic properties are achieved.

  14. Enhancement of soft X-ray reflectivity and interface stability in nitridated Pd/Y multilayer mirrors.

    PubMed

    Xu, Dechao; Huang, Qiushi; Wang, Yiwen; Li, Pin; Wen, Mingwu; Jonnard, Philippe; Giglia, Angelo; Kozhevnikov, Igor V; Wang, Kun; Zhang, Zhong; Wang, Zhanshan

    2015-12-28

    Pd/Y multilayer mirrors operating in the soft X-ray region are characterized by a high theoretical reflectance, reaching 65% at normal incidence in the 8-12 nm wavelength range. However, a severe intermixing of neighboring Pd and Y layers results in an almost total disappearance of the interfaces inside the multilayer structures fabricated by direct current magnetron sputtering and thus a dramatic reflectivity decrease. Based on grazing incidence X-ray reflectometry and X-ray photoelectron spectroscopy, we demonstrate that the stability of the interfaces in Pd/Y multilayer structures can be essentially improved by adding a small amount of nitrogen (4-8%) to the working gas (Ar). High resolution transmission electron microscopy shows that the interlayer width is only 0.9 nm and 0.6 nm for Y(N)-on-Pd(N) and Pd(N)-on-Y(N) interfaces, respectively. A well-defined crystalline texture of YN (200) is observed on the electron diffraction pattern. As a result, the measured reflectance of the Pd(N)/Y(N) multilayer achieves 30% at λ = 9.3 nm. The peak reflectivity value is limited by the remaining interlayers and the formation of the YN compound inside the yttrium layers, resulting in an increased absorption. PMID:26831970

  15. Interfacial Dzyaloshinskii-Moriya interaction, surface anisotropy energy, and spin pumping at spin orbit coupled Ir/Co interface

    NASA Astrophysics Data System (ADS)

    Kim, Nam-Hui; Jung, Jinyong; Cho, Jaehun; Han, Dong-Soo; Yin, Yuxiang; Kim, June-Seo; Swagten, Henk J. M.; You, Chun-Yeol

    2016-04-01

    The interfacial Dzyaloshinskii-Moriya interaction (iDMI), surface anisotropy energy, and spin pumping at the Ir/Co interface are experimentally investigated by performing Brillouin light scattering. Contrary to previous reports, we suggest that the sign of the iDMI at the Ir/Co interface is the same as in the case of the Pt/Co interface. We also find that the magnitude of the iDMI energy density is relatively smaller than in the case of the Pt/Co interface, despite the large strong spin-orbit coupling (SOC) of Ir. The saturation magnetization and the perpendicular magnetic anisotropy (PMA) energy are significantly improved due to a strong SOC. Our findings suggest that an SOC in an Ir/Co system behaves in different ways for iDMI and PMA. Finally, we determine the spin pumping effect at the Ir/Co interface, and it increases the Gilbert damping constant from 0.012 to 0.024 for 1.5 nm-thick Co.

  16. Effect of MgO/Co interface and Co/MgO interface on the spin dependent transport in perpendicular Co/Pt multilayers

    SciTech Connect

    Zhang, J. Y.; Liu, Y. W.; Zhao, Z. D.; Chen, X.; Feng, C.; Yu, G. H. E-mail: ghyu@mater.ustb.edu.cn; Yang, G.; Wang, S. G. E-mail: ghyu@mater.ustb.edu.cn; Wu, Z. L.; Zhang, S. L.

    2014-10-28

    Effect of the metal/oxide interface on spin-dependent transport properties in perpendicular [Co/Pt]{sub 3} multilayers was investigated. The saturation Hall resistivity (ρ{sub xy}) is significantly increased by 45% with 1.4 nm thick CoO layer inserted at the top Co/MgO interface; whereas it is increased only 25% with 1 nm thick CoO layer at the bottom MgO/Co interface. The interfacial structures characterized by X-ray photoelectron spectroscopy show that the MgO/Co interface and Co/MgO interface including chemical states play a dominant role on spin-dependent transport, leading to different anomalous Hall behavior.

  17. Polyelectrolyte multilayer-assisted fabrication of non-periodic silicon nanocolumn substrates for cellular interface applications

    NASA Astrophysics Data System (ADS)

    Lee, Seyeong; Kim, Dongyoon; Kim, Seong-Min; Kim, Jeong-Ah; Kim, Taesoo; Kim, Dong-Yu; Yoon, Myung-Han

    2015-08-01

    Recent advances in nanostructure-based biotechnology have resulted in a growing demand for vertical nanostructure substrates with elaborate control over the nanoscale geometry and a high-throughput preparation. In this work, we report the fabrication of non-periodic vertical silicon nanocolumn substrates via polyelectrolyte multilayer-enabled randomized nanosphere lithography. Owing to layer-by-layer deposited polyelectrolyte adhesives, uniformly-separated polystyrene nanospheres were securely attached on large silicon substrates and utilized as masks for the subsequent metal-assisted silicon etching in solution. Consequently, non-periodic vertical silicon nanocolumn arrays were successfully fabricated on a wafer scale, while each nanocolumn geometric factor, such as the diameter, height, density, and spatial patterning, could be fully controlled in an independent manner. Finally, we demonstrate that our vertical silicon nanocolumn substrates support viable cell culture with minimal cell penetration and unhindered cell motility due to the blunt nanocolumn morphology. These results suggest that vertical silicon nanocolumn substrates may serve as a useful cellular interface platform for performing a statistically meaningful number of cellular experiments in the fields of biomolecular delivery, stem cell research, etc.Recent advances in nanostructure-based biotechnology have resulted in a growing demand for vertical nanostructure substrates with elaborate control over the nanoscale geometry and a high-throughput preparation. In this work, we report the fabrication of non-periodic vertical silicon nanocolumn substrates via polyelectrolyte multilayer-enabled randomized nanosphere lithography. Owing to layer-by-layer deposited polyelectrolyte adhesives, uniformly-separated polystyrene nanospheres were securely attached on large silicon substrates and utilized as masks for the subsequent metal-assisted silicon etching in solution. Consequently, non-periodic vertical

  18. Interface structure in nanoscale multilayers near continuous-to-discontinuous regime

    NASA Astrophysics Data System (ADS)

    Pradhan, P. C.; Majhi, A.; Nayak, M.; Mangla Nand, Rajput, P.; Shukla, D. K.; Biswas, A.; Rai, S. K.; Jha, S. N.; Bhattacharyya, D.; Phase, D. M.; Sahoo, N. K.

    2016-07-01

    Interfacial atomic diffusion, reaction, and formation of microstructure in nanoscale level are investigated in W/B4C multilayer (ML) system as functions of thickness in ultrathin limit. Hard x-ray reflectivity (XRR) and x-ray diffuse scattering in conjunction with x-ray absorption near edge spectroscopy (XANES) in soft x-ray and hard x-ray regimes and depth profiling x-ray photoelectron spectroscopy (XPS) have been used to precisely evaluate detailed interfacial structure by systematically varying the individual layer thickness from continuous-to-discontinuous regime. It is observed that the interfacial morphology undergoes an unexpected significant modification as the layer thickness varies from continuous-to-discontinuous regime. The interfacial atomic diffusion increases, the physical density of W layer decreases and that of B4C layer increases, and further more interestingly the in-plane correlation length decreases substantially as the layer thickness varies from continuous-to-discontinuous regime. This is corroborated using combined XRR and x-ray diffused scattering analysis. XANES and XPS results show formation of more and more tungsten compounds at the interfaces as the layer thickness decreases below the percolation threshold due to increase in the contact area between the elements. The formation of compound enhances to minimize certain degree of disorder at the interfaces in the discontinuous region that enables to maintain the periodic structure in ML. The degree of interfacial atomic diffusion, interlayer interaction, and microstructure is correlated as a function of layer thickness during early stage of film growth.

  19. Effects of tilt interface boundary on mechanical properties of Cu/Ni nanoscale metallic multilayer composites

    NASA Astrophysics Data System (ADS)

    Yang, Meng; Xu, Jian-Gang; Song, Hai-Yang; Zhang, Yun-Guang

    2015-09-01

    The effect of tilt interfaces and layer thickness of Cu/Ni multilayer nanowires on the deformation mechanism are investigated by molecular dynamics simulations. The results indicate that the plasticity of the sample with a 45° tilt angle is much better than the others. The yield stress is found to decrease with increasing the tilt angle and it reaches its lowest value at 33°. Then as the tilt angle continues to increase, the yield strength increases. Furthermore, the studies show that with the decrease of layer thickness, the yield strength gradually decreases. The study also reveals that these different deformation behaviors are associated with the glide of dislocation. Project supported by the National Natural Science Foundation of China (Grant No. 10902083), the Program for New Century Excellent Talent in University of Ministry of Education of China (Grant No. NCET-12-1046), the Program for New Scientific and Technological Star of Shaanxi Province, China (Grant No. 2012KJXX-39), and the Natural Science Basic Research Plan in Shaanxi Province, China (Grant No. 2014JQ1036).

  20. Multilayer films with sharp, stable interfaces for use in EUV and soft X-ray application

    DOEpatents

    Barbee, Jr., Troy W.; Bajt, Sasa

    2002-01-01

    The reflectivity and thermal stability of Mo/Si (molybdenum/silicon) multilayer films, used in soft x-ray and extreme ultraviolet region, is enhanced by deposition of a thin layer of boron carbide (e.g., B.sub.4 C) between alternating layers of Mo and Si. The invention is useful for reflective coatings for soft X-ray and extreme ultraviolet optics, multilayer for masks, coatings for other wavelengths and multilayers for masks that are more thermally stable than pure Mo/Si multilayers

  1. Mechanical performance of Hi-Nicalon/CVI-SiC composites with multilayer SiC/C interfaces

    SciTech Connect

    Halverson, H.G.; Carter, R.H.; Curtin, W.A.

    1997-12-01

    The mechanical properties and interfacial characteristics of new SiC/SiC ceramic composites, composed of Hi-Nicalon fibers in a CVI-SiC matrix and having a variety of multilayer SiC/C coatings between the fibers and the matrix, are studied in detail to elucidate the roles of the coatings and fibers. Axial tension tests and unload/reload hysteresis loop measurements are performed to determine mechanical performance. All materials exhibit the strong and tough behavior characteristic of good ceramic composites, with all multilayer variants performing quite similarly. SEM microscopy demonstrates that matrix cracks penetrate through the multilayers and debond at the fiber/inner-coating interface. Analysis of the hysteretic behavior leads to values for interfacial sliding resistance {tau} {approx} 11 ksi and interfacial toughness {Gamma}{sub i} {approx} 2 J/m{sup 2} that are nearly independent of multilayer structure, and are similar to values obtained for standard pyrolitic carbon interfaces. These results all indicate debonding at the fiber surface for all coating structures, which provides a common roughness, {tau}, and {Gamma}{sub i}. Analysis of fiber fracture mirrors provides an estimate of the in-situ strength of the fibers and demonstrates the high strength retention of the Hi-Nicalon fibers. The in-situ fiber strengths are combined with the measured pullout lengths to obtain an independent determination of {tau} = 8.5 ksi that agrees well with the value found from the hysteretic behavior. Predictions of composite strength using the derived fiber strengths agree well with the measured value although the predicted failure strain is too large. This study demonstrates that Hi-Nicalon fiber/CVI-SiC composites perform well for a wide range of multilayer interface structures and that the interfaces present relatively high values of {tau} and {Gamma}{sub i}, both of which are beneficial to strength and toughness. The small carbon layer thicknesses in these multilayer

  2. Formation of multilayered magnetic nanotracks with perpendicular anisotropy via deoxidization using ion irradiation on ultraviolet-imprinted intaglio nanostructures

    SciTech Connect

    Cho, Eikhyun; Shin, Sang Chul; Han, Jungjin; Shim, Jongmyeong; Shin, Ryung; Kang, Shinill; Kim, Sanghoon; Hong, Jongill

    2015-01-26

    We proposed a method to fabricate perpendicular magnetic nanotracks in the cobalt oxide/palladium multilayer films using UV-nanoimprinting lithography and low-energy hydrogen-ion irradiation. This is a method to magnetize UV-imprinted intaglio nanotracks via low-energy hydrogen ion irradiation, resulting the irradiated region are magnetically separated from the non-irradiated region. Multilayered magnetic nanotracks with a line width of 140 nm, which were fabricated by this parallel process without additional dry etching process, exhibited a saturation magnetization of 290 emu cm{sup −3} and a coercivity of 2 kOe. This study demonstrates a cost-effective mass production of multilayered perpendicular magnetic nanotracks and offers the possibility to achieve high density storage and memory devices.

  3. Substrate- and interface-mediated photocrystallization in a-Se films and multi-layers

    NASA Astrophysics Data System (ADS)

    Lindberg, G. P.; Tallman, R. E.; Weinstein, B. A.; Abbaszadeh, S.; Karim, K. S.; Reznik, A.

    2012-02-01

    Photocrystallization in a-Se films and layered a-Se structures is studied by Raman scattering as a function of temperature for photon energies near or slightly below the band gap. The samples are ˜16.5 μm thick films of a-Se grown i) directly on glass, ii) on indium tin oxide (ITO) coated glass, iii) on glass that is spin coated with 800nm polymide, and iv) on a Capton sheet. A low As-concentration (< 0.2 %) is present in several of the a-Se films. We compare the results on these samples to prior findings on a-Se HARP targets, and on a polymer-encapsulated a-Se film [1]. We observe strong evidence that the interface between the a-Se film and the underlying substrate and/or multi-layers plays an important role in the onset time and growth rate of photocrystallized Se domains. In some samples a discontinuous increase in the onset time with increasing temperature occurs near the glass transition (˜310K), and there is a surprising ``dead zone'' of no crystallization in this region. Other samples merely show a minimum in the onset time at similar temperatures, but no discontinuity and no region where crystallization is absent. Soft intermediate layers appear to increase stability against crystallization in an overlying a-Se film. The competing effects of substrate shear strain and thermal driving forces on the photocrystallization process are considered to account for these findings. [4pt] [1] R.E. Tallman et. al. J. Non-crystalline Sols. 354, 4577-81 (2008)

  4. Highly (001) oriented L1{sub 0}-CoPt/TiN multilayer films on glass substrates with perpendicular magnetic anisotropy

    SciTech Connect

    An, Hongyu; Sannomiya, Takumi; Muraishi, Shinji; Nakamura, Yoshio; Shi, Ji; Xie, Qian; Zhang, Zhengjun; Wang, Jian

    2015-03-15

    To obtain strong perpendicular magnetic anisotropy (PMA) based on L1{sub 0} structure for magnetic storage devices, costly single crystalline substrates are generally required to achieve (001) texture. Recently, various studies also have focused on depositing different kinds of seed layers on glass or other amorphous substrates to promote (001) preferred orientation of L1{sub 0} CoPt and FePt. TiN is a very promising seed layer material because of its cubic crystalline structure (similar to MgO) and excellent diffusion barring property even at high temperatures. In the present work, highly (001) oriented L1{sub 0}-CoPt/TiN multilayer films have been successfully deposited on glass substrates. After annealing at 700 °C, the film exhibits PMA, and a strong (001) peak is detected from the x-ray diffraction profiles, indicating the ordering transformation of CoPt layers from fcc (A1) to L1{sub 0} structure. It also is found that alternate deposition of cubic TiN and CoPt effectively improves the crystallinity and (001) preferred orientation of CoPt layers. This effect is verified by the substantial enhancement of (001) reflection and PMA with increasing the period number of the multilayer films.

  5. Anisotropy of Multilayered (cu, C)BA2CA3CU4OY Superconductors Studied by Torque Magnetometry

    NASA Astrophysics Data System (ADS)

    Tokiwa, K.; Koganezawa, T.; Mikusu, S.; Watanabe, T.; Iyo, A.; Tanaka, Y.

    The magnetic torque of (Cu,C)Ba2Ca3Cu4Oy ( (Cu,C)-1234) aligned samples with various carrier concentrations has been measured under a magnetic field of 9 T at 80 K and 90 K. The carrier concentration was determined by Hall effect measurements. From angular dependent torque measurements, the anisotropy ratio γ was estimated using the 3D anisotropic London model. The γvalues decreased from 23 to 10 with an increase in the average Hall number per CuO2 plane (nH); however, these samples showed a nearly constant Tc of about 117 K. These results indicate that the anisotropy of (Cu,C)-1234 strongly reflects the doping levels of the outer planes.

  6. Investigation of extrinsic damping caused by magnetic dead layer in Ta-CoFeB-MgO multilayers with perpendicular anisotropy

    NASA Astrophysics Data System (ADS)

    Sato, Noriyuki; O'Brien, Kevin P.; Millard, Kent; Doyle, Brian; Oguz, Kaan

    2016-03-01

    We systematically investigated the influence of the dead layer, the oxidation degree of naturally oxidized MgO, the structure of adjacent nonmagnetic metal layers on the damping parameter, and the perpendicular anisotropy of Ta(Ru)/Co20Fe60B20/MgO and MgO/Co20Fe60B20/Ta films using the vector network analyzer ferromagnetic resonance measurement technique. MgO/Co20Fe60B20/Ta film shows almost twice larger extrinsic damping than that for Ta/Co20Fe60B20/MgO film, whereas the perpendicular anisotropy is much smaller. This two-fold enhancement of damping parameter is successfully explained by the extrinsic damping arises from the dead layer at the CoFeB-Ta interface through the Elliott-Yafet mechanism in addition to the conventional spin-pumping model. Furthermore, we found that the oxidation degree of naturally oxidized MgO has no significant impact on the damping parameter, while the perpendicular anisotropy for MgO/Co20Fe60B20/Ta film is enhanced by longer oxidation time.

  7. Interfacial Rheology of Hydrogen-Bonded Polymer Multilayers Assembled at Liquid Interfaces: Influence of Anchoring Energy and Hydrophobic Interactions.

    PubMed

    Le Tirilly, Sandrine; Tregouët, Corentin; Reyssat, Mathilde; Bône, Stéphane; Geffroy, Cédric; Fuller, Gerald; Pantoustier, Nadège; Perrin, Patrick; Monteux, Cécile

    2016-06-21

    We study the 2D rheological properties of hydrogen-bonded polymer multilayers assembled directly at dodecane-water and air-water interfaces using pendant drop/bubble dilation and the double-wall ring method for interfacial shear. We use poly(vinylpyrrolidone) (PVP) as a proton acceptor and a series of polyacrylic acids as proton donors. The PAA series of chains with varying hydrophobicity was fashioned from poly(acrylic acid), (PAA), polymethacrylic acid (PMAA), and a homemade hydrophobically modified polymer. The latter consisted of a PAA backbone covalently grafted with C12 moieties at 1% mol (referred to as PAA-1C12). Replacing PAA with the more hydrophobic PMAA provides a route for combining hydrogen bonding and hydrophobic interactions to increase the strength and/or the number of links connecting the polyacid chains to PVP. This systematic replacement allows for control of the ability of the monomer units inside the absorbed polymer layer to reorganize as the interface is sheared or compressed. Consequently, the interplay of hydrogen bonding and hydrophobic interactions leads to control of the resistance of the polymer multilayers to both shear and dilation. Using PAA-1C12 as the first layer improves the anchoring energy of a few monomers of the chain without changing the strength of the monomer-monomer contact in the complex layer. In this way, the layer does not resist shear but resists compression. This strategy provides the means for using hydrophobicity to control the interfacial dynamics of the complexes adsorbed at the interface of the bubbles and droplets that either elongate or buckle upon compression. Moreover, we demonstrate the pH responsiveness of these interfacial multilayers by adding aliquots of NaOH to the acidic water subphase surrounding the bubbles and droplets. Subsequent pH changes can eventually break the polymer complex, providing opportunities for encapsulation/release applications. PMID:27176147

  8. Synchrotron FTIR microscopy of Langmuir-Blodgett monolayers and polyelectrolyte multilayers at the solid-solid interface.

    PubMed

    Beattie, David A; Beaussart, Audrey; Mierczynska-Vasilev, Agnieszka; Harmer, Sarah L; Thierry, Benjamin; Puskar, Ljiljana; Tobin, Mark

    2012-01-24

    Synchrotron FTIR microscopy has been used to probe the structure of model boundary lubricant layers confined at the solid-solid interface. The combination of high brightness of the IR source and a novel contact geometry that uses a hemispherical internal reflection element as the means for light delivery has enabled the detection of <2.5 nm thin monolayer lubricant layers in the solid-solid contact, in addition to allowing for spectral acquisition from specific regions of the contact. Spectra of hydration water from within a confined polyelectrolyte multilayer film have also been acquired, highlighting the altered hydrogen bonding environment within the polymer layer. PMID:22225512

  9. Layering, interface and edge effects in multi-layered composite medium

    NASA Technical Reports Server (NTRS)

    Datta, S. K.; Shah, A. H.; Karunesena, W.

    1990-01-01

    Guided waves in a cross-ply laminated plate are studied. Because of the complexity of the exact dispersion equation that governs the wave propagation in a multi-layered fiber-reinforced plate, a stiffness method that can be applied to any number of layers is presented. It is shown that, for a sufficiently large number of layers, the plate can be modeled as a homogeneous anisotropic plate. Also studied is the reflection of guided waves from the edge of a multilayered plate. These results are quite different than in the case of a single homogeneous plate.

  10. Origin of Colossal Ionic Conductivity in Oxide Multilayers: Interface Induced Sublattice Disorder

    SciTech Connect

    Pennycook, Timothy J; Beck, Matthew; Varga, Kalman; Varela del Arco, Maria; Pennycook, Stephen J; Pantelides, Sokrates T

    2010-01-01

    Oxide ionic conductors typically operate at high temperatures, which limits their usefulness. Colossal room-temperature ionic conductivity was recently discovered in multilayers of yttria-stabilized zirconia (YSZ) and SrTiO3. Here we report density-functional calculations that trace the origin of the effect to a combination of lattice-mismatch strain and O-sublattice incompatibility. Strain alone in bulk YSZ enhances O mobility at high temperatures by inducing extreme O disorder. In multilayer structures, O-sublattice incompatibility causes the same extreme disorder at room temperature.

  11. Study of interface correlation in W/C multilayer structure by specular and non-specular grazing incidence X-ray reflectivity measurements

    SciTech Connect

    Biswas, A. Bhattacharyya, D.; Sahoo, N. K.; Maidul Haque, S.; Tripathi, S.; De, Rajnarayan; Rai, S.

    2015-10-28

    W/C/W tri-layer thin film samples have been deposited on c-Si substrates in a home-built Ion Beam Sputtering system at 1.5 × 10{sup −3} Torr Ar working pressure and 10 mA grid current. The tri-layer samples have been deposited at different Ar{sup +} ion energies between 0.6 and 1.2 keV for W layer deposition and the samples have been characterized by specular and non-specular grazing incidence X-ray reflectivity (GIXR) measurements. By analyzing the GIXR spectra, various interface parameters have been obtained for both W-on-C and C-on-W interfaces and optimum Ar{sup +} ion energy for obtaining interfaces with low imperfections has been found. Subsequently, multilayer W/C samples with 5-layer, 7-layer, 9-layer, and 13-layer have been deposited at this optimum Ar{sup +} ion energy. By fitting the specular and diffused GIXR data of the multilayer samples with the parameters of each interface as fitting variables, different interface parameters, viz., interface width, in-plane correlation length, interface roughness, and interface diffusion have been estimated for each interface and their variation across the depth of the multilayers have been obtained. The information would be useful in realizing W/C multilayers for soft X-ray mirror application in the <100 Å wavelength regime. The applicability of the “restart of the growth at the interface” model in the case of these ion beam sputter deposited W/C multilayers has also been investigated in the course of this study.

  12. Capping layer-tailored interface magnetic anisotropy in ultrathin Co2FeAl films

    NASA Astrophysics Data System (ADS)

    Belmeguenai, M.; Gabor, M. S.; Petrisor, T.; Zighem, F.; Chérif, S. M.; Tiusan, C.

    2015-01-01

    Co2FeAl (CFA) thin films of various thicknesses (2 nm ≤ d ≤ 50 nm) have been grown on (001) MgO single crystal substrates and then capped with Cr, V, and Ta. Their magnetic and structural properties have been studied by x-ray diffraction (XRD), vibrating sample magnetometry, and broadband microstrip ferromagnetic resonance (MS-FMR). The XRD revealed that the films are epitaxial with the cubic [001] CFA axis normal to the substrate plane and that the chemical order varies from the B2 phase to the A2 phase when decreasing the thickness. The deduced lattice parameters showed that the Cr-capped films exhibit a larger tetragonal distortion, as compared with the films capped with V or Ta. The presence of magnetic dead layers has been observed in CFA samples capped with V and Ta but not in the case of the Cr-capped ones. The effective magnetization, deduced from the fit of MS-FMR measurements, increases (decreases) linearly with the CFA inverse thickness (1/d) for the Cr-capped (Ta-capped) films while it is constant for the V-capped ones. This allows quantifying the perpendicular surface anisotropy coefficients of -0.46 erg/cm2 and 0.74 erg/cm2 for Cr and Ta-capped films, respectively. Moreover, the fourfold and the uniaxial anisotropy fields, measured in these films, showed different trends with a respect to the CFA inverse thickness. This allows inferring that a non-negligible part of the fourfold magnetocrystalline term is of interfacial origin.

  13. Consequences of an interface-concentrated perpendicular magnetic anisotropy in ultrathin CoFeB films used in magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Sun, J. Z.

    2015-05-01

    We examine the consequences of a strongly interface-concentrated perpendicular magnetic anisotropy (PMA) energy in CoFeB thin films currently in wide use in magnetic tunnel junctions (MTJs) for spin-torque-related memory applications. The direct consequence of such an anisotropy energy distribution, in combination with a moderate exchange coupling of the interface moment to the rest of the film, is a phenomenological appearance of a fourth-order anisotropy term as the film is viewed by ferromagnetic resonance. The presence of a fourth-order anisotropy also affects the apparent thermal activation energy of a patterned nanomagnet with such thin films, and it could lead to an apparent increase in the spin-torque switching efficiency as represented by the ratio of the thermal activation energy and the threshold switching current. However, for interface-sensitive quantities such as tunnel magnetoresistance's hard-axis behavior, as well as for spin-torque excitation processes, the specifics of such separation of interface versus film-interior moment rotation could become important.

  14. Perpendicularly magnetized spin filtering Cu/Ni multilayers

    SciTech Connect

    Shirahata, Yasuhiro; Wada, Eiji; Itoh, Mitsuru; Taniyama, Tomoyasu

    2014-01-20

    Spin filtering at perpendicular magnetized Cu/Ni multilayer/GaAs(001) interfaces is demonstrated at remanence using optical spin orientation method. [Cu(9 nm)/Ni(t{sub Ni} nm)]{sub n} multilayers are found to show a crossover from the in-plane to out-of-plane magnetic anisotropy at the Cu/Ni bilayer repetition n = 4 and the Ni layer thickness t{sub Ni} = 3. For a perpendicularly magnetized Cu/Ni multilayer/n-GaAs(001) interface, circular polarization dependent photocurrent shows a clear hysteretic behavior under optical spin orientation conditions as a function of magnetic field out-of-plane while the bias dependence exhibits a substantial peak at a forward bias, verifying that Cu/Ni multilayers work as an efficient spin filter in the remanent state.

  15. Large anomalous Hall effect in Pt interfaced with perpendicular anisotropy ferrimagnetic insulator

    NASA Astrophysics Data System (ADS)

    Tang, Chi; Sellappan, Pathikumar; Liu, Yawen; Garay, Javier; Shi, Jing; Shines Team

    We demonstrate the strain induced perpendicular magnetic anisotropy (PMA) in a ferrimagnetic insulator (FMI), Tm3Fe5O12 (TIG) and the first observation of large anomalous Hall effect (AHE) in TIG/Pt bilayers. Atomically flat TIG films were deposited by a laser molecular beam epitaxy system on (111)-orientated substituted gadolinium gallium garnet substrates. The strength of PMA could be effectively tuned by controlling the oxygen pressure during deposition. Sharp squared anomalous Hall hysteresis loops were observed in bilayers of TIG/Pt over a range of thicknesses of Pt, with the maximum AHE conductivity reaching 1 S/cm at room temperature. The AHE vanishes when a 5 nm Cu layer was inserted between Pt and TIG, strongly indicating the proximity-induced ferromagnetism in Pt. The large AHE in the bilayer structures demonstrates a potential use of PMA-FMI related heterostructures in spintronics. This work was supported as part of the SHINES, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award # SC0012670.

  16. Quartz Crystal Microbalance Studies of Multilayer Glucagon Fibrillation at the Solid-Liquid Interface

    PubMed Central

    Hovgaard, Mads Bruun; Dong, Mingdong; Otzen, Daniel Erik; Besenbacher, Flemming

    2007-01-01

    We have used a quartz crystal microbalance with dissipation (QCM-D) to monitor the changes in layer thickness and viscoelastic properties accompanying multilayer amyloid deposition in situ for the first time. By means of atomic force microscope imaging, an unequivocal correlation is established between the interfacial nucleation and growth of glucagon fibrils and the QCM-D response. The combination of the two techniques allows us to study the temporal evolution of the interfacial fibrillation process. We have modeled the QCM-D data using an extension to the Kelvin-Voigt viscoelastic model. Three phases were observed in the fibrillation process: 1), a rigid multilayer of glucagon monomers forms and slowly rearranges; 2), this multilayer subsequently evolves into a dramatically more viscoelastic layer, containing a polymorphic network of micrometer-long fibrils growing from multiple nucleation sites; and 3), the fibrillar formation effectively stops as a result of the depletion of bulk-phase monomers, although the process can be continued without a lag phase by subsequent addition of fresh monomers. The robustness of the QCM-D technique, consolidated by complementary atomic force microscope studies, should make it possible to combine different components thought to be involved in the plaque formation process and thus build up realistic models of amyloid plaque formation in vitro. PMID:17513349

  17. Quantitative first-principles theory of interface absorption in multilayer heterostructures

    SciTech Connect

    Hachtel, Jordan A.; Sachan, Ritesh; Mishra, Rohan; Pantelides, Sokrates T.

    2015-08-31

    The unique chemical bonds and electronic states of interfaces result in optical properties that are different from those of the constituting bulk materials. In the nanoscale regime, the interface effects can be dominant and impact the optical response of devices. Using density functional theory (DFT), the interface effects can be calculated, but DFT is computationally limited to small systems. We describe a method to combine DFT with macroscopic methodologies to extract the interface effect on absorption in a consistent and quantifiable manner. The extracted interface effects are an independent parameter and can be applied to more complicated systems. We demonstrate, using NiSi{sub 2}/Si heterostructures, that by varying the relative volume fractions of interface and bulk, we can tune the spectral range of the heterostructure absorption.

  18. Growth of multilayers of Bi{sub 2}Se{sub 3}/ZnSe: Heteroepitaxial interface formation and strain

    SciTech Connect

    Li, H. D.; Wang, Z. Y.; Guo, X.; Xie, M. H.; Wong, Tai Lun; Wang, Ning

    2011-01-24

    Multilayers of Bi{sub 2}Se{sub 3}/ZnSe with the periodicity of a few nanometers were grown by molecular-beam epitaxy on Si(111). While epitaxial growth of Bi{sub 2}Se{sub 3} on ZnSe proceeded by two-dimensional nucleation, ZnSe growth on Bi{sub 2}Se{sub 3} showed the three-dimensional growth front. Therefore, the two complementary interfaces of Bi{sub 2}Se{sub 3}/ZnSe were asymmetric in morphological properties. Strain-relaxation rates were found to differ between epitaxial ZnSe and Bi{sub 2}Se{sub 3}, which could be attributed to the specific growth modes and the properties of Bi{sub 2}Se{sub 3} and ZnSe surfaces.

  19. Rheology at the Interface and the Role of the Interphase in Reactive Functionalized Multilayer Polymers in Coextrusion Process

    NASA Astrophysics Data System (ADS)

    Lamnawar, Khalid; Maazouz, Abderrahim

    2008-07-01

    Coextrusion technologies are commonly used to produce multilayered composite sheets or films for a large range of applications from food packaging to optics. The contrast of rheological properties between layers can lead to interfacial instabilities during flow. Important theoretical and experimental advances regarding the stability of compatible and incompatible polymers have, during the last decades, been made using a mechanical approach. However, few research efforts have been dedicated to the physicochemical affinity between the neighboring layers. The present study deals with the influence of this affinity on interfacial instabilities for functionalized incompatible polymers. Polyamide (PA6)/polyethylene grafted with glycidyl methacrylate (PE-GMA) was used as a reactive system and PE/PA6 as a non reactive one. Two grades of polyamide (PA6) were used in order to change the viscosity and elasticity ratios between PE (or PE-GMA) and PA6. It was experimentally confirmed, in this case, that weak disturbance can be predicted by considering an interphase of non-zero thickness (corresponding to an interdiffusion/reaction zone) instead of a purely geometrical interface between the two reactive layers. According to the rheological investigations from previous work which the interphase effect can be probed, an experimental strategy was here formulated to optimize the process by listing the parameters that controlled the stability of the reactive multilayer flows. Hence, based on this analysis, guidelines for a stable coextrusion of reactive functionalized polymers can be provided coupling the classical parameters (viscosity, elasticity and layer ratios) and the physicochemical affinity at the polymer/polymer interface.

  20. In-plane anisotropy in two-dimensional electron gas at LaAlO3/SrTiO3(110) interface

    NASA Astrophysics Data System (ADS)

    Sheng-Chun, Shen; Yan-Peng, Hong; Cheng-Jian, Li; Hong-Xia, Xue; Xin-Xin, Wang; Jia-Cai, Nie

    2016-07-01

    A systematic study of the two-dimensional electron gas at LaAlO3/SrTiO3(110) interface reveals an anisotropy along two specific directions, [001] and . The anisotropy becomes distinct for the interface prepared under high oxygen pressure with low carrier density. Angular dependence of magnetoresistance shows that the electron confinement is stronger along the direction. Gate-tunable magnetoresistance reveals a clear in-plane anisotropy of the spin–orbit coupling, and the spin relaxation mechanism along both directions belongs to D’yakonov–Perel’ (DP) scenario. Moreover, in-plane anisotropic superconductivity is observed for the sample with high carrier density, the superconducting transition temperature is lower but the upper critical field is higher along the direction. This in-plane anisotropy could be ascribed to the anisotropic band structure along the two crystallographic directions. Project supported by the Ministry of Science and Technology of China (Grant Nos. 2013CB921701, 2013CBA01603, and 2014CB920903), the National Natural Science Foundation of China (Grant Nos. 10974019, 51172029, 91121012, 11422430, 11374035, 11474022, and 11474024), the Program for New Century Excellent Talents in the University of the Ministry of Education of China (Grant No. NCET-13-0054), and the Beijing Higher Education Young Elite Teacher Project, China (Grant No. YETP0238).

  1. In vitro generation of a multilayered osteochondral construct with an osteochondral interface using rabbit bone marrow stromal cells and a silk peptide-based scaffold.

    PubMed

    Chen, Kelei; Shi, Pujiang; Teh, Thomas Kok Hiong; Toh, Siew Lok; Goh, James Ch

    2016-04-01

    Tissue engineering of a biological osteochondral multilayered construct with a cartilage-interface subchondral bone layer is a key challenge. This study presented a rabbit bone marrow stromal cell (BMSC)/silk fibroin scaffold-based co-culture approach to generate tissue-engineered osteochondral grafts with an interface. BMSC-seeded scaffolds were first cultured separately in osteogenic and chondrogenic stimulation media. The two differentiated pieces were then combined using an RADA self-assembling peptide and subsequently co-cultured. Gene expression, histological and biochemical analyses were used to evaluate the multilayered structure of the osteochondral graft. A complete osteochondral construct with a cartilage-subchondral bone interface was regenerated and BMSCs were used as the only cell source for the osteochondral construct and interface regeneration. Furthermore, in the intermediate region of co-cultured samples, hypertrophic chondrogenic gene markers type X collagen and MMP-13 were found on both chondrogenic and osteogenic section edges after co-culture. However, significant differences gene expression profile were found in distinct zones of the construct during co-culture and the section in the intermediate region had significantly higher hypertrophic chondrocyte gene expression. Biochemical analyses and histology results further supported this observation. This study showed that specific stimulation from osteogenic and chondrogenic BMSCs affected each other in this co-culture system and induced the formation of an osteochondral interface. Moreover, this system provided a possible approach for generating multilayered osteochondral constructs. Copyright © 2013 John Wiley & Sons, Ltd. PMID:23413023

  2. Plasmonic excitations in ZnO/Ag/ZnO multilayer systems: Insight into interface and bulk electronic properties

    SciTech Connect

    Philipp, Martin; Knupfer, Martin; Buechner, Bernd; Gerardin, Hadia

    2011-03-15

    Electron energy-loss spectroscopy experiments in transmission were carried out on silver-based multi-layer systems, consisting of a silver layer of various thicknesses (8, 10 and 50 nm) sandwiched between two Al-doped ZnO layers. The films were produced by magnetron sputtering using potassium bromide single crystals as substrates. The electronic structure of these systems was probed and analyzed with respect to their plasmonic excitations, which can be basically split up into excitations of the electrons in the bulk silver and excitations at the ZnO:Al/Ag interface. A detailed examination of the momentum dependence of the plasmon peaks revealed a positive dispersion for both, the volume and the interface plasmon, where only for the first one a quadratic behavior (as expected for a free electron gas) could be observed. Furthermore, the peak width was analyzed and set into relation to electrical conductivity measurements by calculating the plasmon lifetime and the electron scattering rate. Here, a good agreement between these different methods was obtained.

  3. Energy level alignment at the interfaces in a multilayer organic light-emitting diode structure

    NASA Astrophysics Data System (ADS)

    Olthof, S.; Meerheim, R.; Schober, M.; Leo, K.

    2009-06-01

    We use photoelectron spectroscopy to study the electronic structure and energy level alignment throughout an organic light-emitting diode. The structure under investigation is a state-of-the-art long-living red phosphorescent device composed of doped charge-injection layers, charge-blocking layers, and an emission layer. By consecutively building up the whole device, the key parameters of every interface are measured. Our results show that the doped layers have a significant influence on the device energetics, especially in controlling the built-in potential, and that there are mostly only small dipoles present at the interfaces of the intrinsic organic layers.

  4. Influence of the deposition-induced stress on the magnetic properties of magnetostrictive amorphous (Fe{sub 80}Co{sub 20}){sub 80}B{sub 20} multilayers with orthogonal anisotropy

    SciTech Connect

    Gonzalez-Guerrero, Miguel; Prieto, Jose Luis; Sanchez, Pedro; Aroca, Claudio

    2007-12-15

    In this work, we experimentally justify that the control of the mechanical stress induced during the deposition of sputtered amorphous magnetostrictive (Fe{sub 80}Co{sub 20}){sub 80}B{sub 20} allows a custom design of its magnetic properties. FeCoB multilayers have been sputtered on thermal oxide Si substrates with different buffer materials. The crystalline quality and the thermomechanical properties of the buffer layer influence both the coercive and the anisotropy field. Those buffer layers with both high rigidity and poor thermal conductivity do not allow the dissipation of energy of the incoming sputtered material. Therefore, the mechanical stresses related to the deposition process cannot be released, leading to magnetic layers with high easy-axis coercive field and low anisotropy field. This shows that the mechanical stresses accumulated during deposition are a key parameter for the control of coercivity.

  5. Effect of interface roughness on superconducting transition temperatures of Nb/Co multilayers

    NASA Astrophysics Data System (ADS)

    Liu, L. Y.; Chacón Hernandez, U. D.; Xing, Y. T.; Suguihiro, N. M.; Haeussler, D.; Baggio-Saitovitch, E.; Jäger, W.; Solórzano, I. G.

    2016-03-01

    Superconductor (SC)/ferromagnet (FM) Nb/Co multilayers have been produced by magnetron-sputtering with a 100 nm thickness of Nb and 5, 10, and 20 nm of Co. The superconducting properties have been investigated by electric transport measurements. It was found that the thicker Co layers decrease the superconducting transition temperature (Tc) less than the thinner ones. In order to understand this unexpected behavior, the microstructure of the layers has been investigated by means of Atomic Force Microscopy (AFM), Transmission Electron Microscopy (TEM) and by energy-dispersive X-ray spectroscopy line scan analyses in scanning TEM (STEM) mode. It was found that the decisive parameter which determines the effect of magnetic layers on Tc of the superconducting layers is not only the roughness (R), but the ratio of the roughness to thickness (dCo) of the magnetic Co layer, δ = R /dCo. For δ > 1 the magnetic stray field of the magnetic layers is the main reason for the Tc reduction.

  6. Human Coronary Artery Smooth Muscle Cell Responses to Bioactive Polyelectrolyte Multilayer Interfaces

    PubMed Central

    Newcomer, Robert G.; Moussallem, Maroun D.; Keller, Thomas C. S.; Schlenoff, Joseph B.; Sang, Qing-Xiang Amy

    2011-01-01

    Under normal physiological conditions, mature human coronary artery smooth muscle cells (hCASMCs) exhibit a “contractile” phenotype marked by low rates of proliferation and protein synthesis, but these cells possess the remarkable ability to dedifferentiate into a “synthetic” phenotype when stimulated by conditions of pathologic stress. A variety of polyelectrolyte multilayer (PEMU) films are shown here to exhibit bioactive properties that induce distinct responses from cultured hCASMCs. Surfaces terminated with Nafion or poly(styrenesulfonic acid) (PSS) induce changes in the expression and organization of intracellular proteins, while a hydrophilic, zwitterionic copolymer of acrylic acid and 3-[2-(acrylamido)-ethyl dimethylammonio] propane sulfonate (PAA-co-PAEDAPS) is resistant to cell attachment and suppresses the formation of key cytoskeletal components. Differential expression of heat shock protein 90 and actin is observed, in terms of both their magnitude and cellular localization, and distinct cytoplasmic patterns of vimentin are seen. The ionophore A23187 induces contraction in confluent hCASMC cultures on Nafion-terminated surfaces. These results demonstrate that PEMU coatings exert direct effects on the cytoskeletal organization of attaching hCASMCs, impeding growth in some cases, inducing changes consistent with phenotypic modulation in others, and suggesting potential utility for PEMU surfaces as a coating for coronary artery stents and other implantable medical devices. PMID:21350669

  7. Multilayer Fiber Interfaces for Improved Environmental Resistance and Slip in Carbon Fiber Reinforced Composites

    NASA Technical Reports Server (NTRS)

    Babcock, Jason R.; Ramachandran, Gautham; Williams, Brian E.; Effinger, Michael R.

    2004-01-01

    Ultraviolet-enhanced chemical vapor deposition (UVCVD) has been developed to lower the required substrate temperature thereby allowing for the application of metal oxide-based coatings to carbon and ceramic fibers without causing significant fiber damage. An effort to expand this capability to other ceramic phases chosen to maximize oxidation protection in the likely event of matrix cracking and minimize possible reaction between the coating and fiber during long-term high temperature use will be presented along with studies aimed at the demonstration of these and other benefits for the next-generation interface coating systems being developed herein.

  8. Artificial anisotropy and polarizing filters

    NASA Astrophysics Data System (ADS)

    Flory, Francois; Escoubas, Ludovic; Lazarides, Basile

    2002-06-01

    The calculated spectral transmittance of a multilayer laser mirror is used to determine the effective index of the single layer equivalent to the multilayer stack. We measure the artificial anisotropy of photoresist thin films whose structure is a one-dimensional, subwavelength grating obtained from interference fringes. The limitation of the theory of the first-order effective index homogenization is discussed. We designed normal-incidence, polarizing coating and a polarization rotator by embedding anisotropic films in simple multilayer structures.

  9. Effect of Microstructure on Magnetic Properties and Anisotropy Distributions in Co/Pd Thin Films and Nanostructures

    SciTech Connect

    Shaw, J.; Nembach, H; Silva, T; Russek, S; Geiss, R; Jones, C; Clark, N; Leo, T; Smith, D

    2009-01-01

    The structure of Co/Pd multilayers has a strong effect on the localized anisotropy distribution within a film and on the resulting switching properties of nanostructures fabricated from identical material. By varying the underlying seed layer in sputtered films, the microstructure can be controlled from being highly (111) textured to having a random grain orientation. We find a strong correlation between the lateral homogeneity of grain orientations and the localized anisotropy distribution in the material. X-ray diffraction and reflectivity indicate that the interface is better defined and more uniform in the textured case, consistent with the presence of a strong interfacelike anisotropy.

  10. The effects of neutron irradiation on shear properties of monolayered PyC and multilayered PyC/SiC interfaces of SiC/SiC composites

    NASA Astrophysics Data System (ADS)

    Nozawa, T.; Katoh, Y.; Snead, L. L.

    2007-08-01

    The effect of neutron irradiation on mechanical properties at the fiber/matrix interface of SiC/SiC composites was evaluated. The materials investigated were Hi-Nicalon™ Type-S fiber reinforced chemically vapor infiltrated SiC matrix composites with varied interphases: monolayered pyrolytic carbon (PyC) or multilayered PyC/SiC. The neutron fluence was 7.7 × 10 25 n/m 2 ( E > 0.1 MeV), and the irradiation temperature was 800 °C. Interfacial shear properties were evaluated by the fiber push-out test method. A modified shear-lag model was applied to analyze the interfacial shear parameters. Test results indicate that the interfacial debond shear strength and the interfacial friction stress for the multilayer composites were significantly degraded by irradiation. Nevertheless, the multilayer composites retained sufficient interfacial shear properties so that overall composite strength after neutron irradiation was unaffected. The actual mechanism of interphase property decrease for the multilayer composites is unknown. The interfacial shear properties of the irradiated monolayer composites appear unaffected.

  11. Electric-field control and effect of Pd capping on interface magnetocrystaline anisotropy of FePd-based thin films

    NASA Astrophysics Data System (ADS)

    Ong, Phuong-Vu; Kioussis, Nicholas; Khalili Amiri, P.; Wang, K. L.; Carman, Gregory P.; Wu, Ruqian

    2014-03-01

    Using ab initio electronic structure calculations, we investigate effects of electric field and heavy metal cap of Pd on magnetocrystalline anisotropy (MCA) of FePd ultrathin film. It is revealed that while Pd ions favor in-plan MCA, perpendicular MCA of the thin film is mainly due to the spin-orbit coupling between unoccupied Fe dxy and occupied Fe dx2 -y2 states. The sensitivity of the surface anisotropy energy to applied electric field is 18 fJ.V-1.m-1. By mapping distributions of d-orbital characters over electronic states, mechanism of the field control of anisotropy is elucidated. Furthermore, MCA of the thin film is shown to be strongly affected by Pd capping and a switching from perpendicular to in-plane anisotropy can be obtained by tuning the capping thickness. The effect is explained by spin-orbit couplings of the spin-polarized quantum well states induced by the Pd cap. These results are of practical importance since in magnetic junctions the ferromagnetic layer is mostly capped by a heavy metal electrode.

  12. A transmission electron microscopy study of the effect of interfaces on bubble formation in He-implanted Cu-Nb multilayers.

    PubMed

    Bhattacharyya, D; Demkowicz, M J; Wang, Y-Q; Baumer, R E; Nastasi, M; Misra, A

    2012-02-01

    Magnetron sputtered thin films of Cu, Nb, and Cu-Nb multilayers with 2.5 and 5 nm nominal layer thickness were deposited on Si and implanted with 4He+ and 3He+ ions. Secondary ion mass spectroscopy and nuclear reaction analysis, respectively, were used to measure the 4He+ and 3He+ concentration profile with depth inside the films. Cross-sectional transmission electron microscopy was used to characterize the helium bubbles. Analysis of the contrast from helium bubbles in defocused transmission electron microscope images showed a minimum bubble diameter of 1.25 nm. While pure Cu and Nb films showed bubble contrast over the entire range of helium implantation, the multilayers exhibited bubbles only above a critical He concentration that increased almost linearly with decreasing layer thickness. The work shows that large amounts of helium can be trapped at incoherent interfaces in the form of stable, nanometer-size bubbles. PMID:22258724

  13. Reduction of thermal conductivity in MnSi1.7 multi-layered thin films with artificially inserted Si interfaces

    NASA Astrophysics Data System (ADS)

    Kurosaki, Y.; Yabuuchi, S.; Nishide, A.; Fukatani, N.; Hayakawa, J.

    2016-08-01

    We report a lowered lattice thermal conductivity in nm-scale MnSi1.7/Si multilayers which were fabricated by controlling thermal diffusions of Mn and Si atoms. The thickness of the constituent layers is 1.5-5.0 nm, which is comparable to the phonon mean free path of both MnSi1.7 and Si. By applying the above nanostructures, we reduced the lattice thermal conductivity down to half that of bulk MnSi1.7/Si composite materials. The obtained value of 1.0 W/K m is the experimentally observed minimum in MnSi1.7-based materials without any heavy element doping and close to the minimum thermal conductivity. We attribute the reduced lattice thermal conductivity to phonon scattering at the MnSi1.7/Si interfaces in the multilayers.

  14. High post-annealing stability for perpendicular [Co/Ni] n multilayers by preventing interfacial diffusion

    NASA Astrophysics Data System (ADS)

    Li, Xu-Jing; Jiang, Shao-Long; Zhang, Jing-Yan; Han, Gang; Liu, Qian-Qian; Liu, Yi-Wei; Wang, Dong-Wei; Feng, Chun; Li, Ming-Hua; Yu, Guang-Hua

    2016-05-01

    This paper reports that by introducing an appropriate thickness of Cu spacer at a Co/Ni interface, the perpendicular magnetic anisotropy of [Co/Cu/Ni] n multilayers can be maintained at the annealing temperature as high as 400 °C, implying high post-annealing stability. X-ray reflectivity results demonstrate that the multilayers with Cu spacer exhibit good multilayer structure, indicating the weak intermixing of Co and Ni, which is one important reason for the enhanced post-annealing stability of perpendicular magnetic anisotropy. The result is of great importance for out-of-plane magnetized spintronic devices which need to be combined with complementary metal-oxide semiconductors.

  15. Calculating the role of composition in the anisotropy of solid-liquid interface energy using phase-field-crystal theory

    NASA Astrophysics Data System (ADS)

    Jugdutt, Bernadine A.; Ofori-Opoku, Nana; Provatas, Nikolas

    2015-10-01

    This work uses Ginzburg-Landau theory derived from a recent structural phase-field-crystal model of binary alloys developed by the authors to study the roles of concentration, temperature, and pressure on the interfacial energy anisotropy of a solid-liquid front. It is found that the main contribution to the change in anisotropy with concentration arises from a change in preferred crystallographic orientation controlled by solute-dependent changes in the two-point density correlation function of a binary alloy, a mechanism that leads to such phenomena as solute-induced elastic strain and dislocation-assisted solute clustering. Our results are consistent with experimental observations in recent studies by Rappaz et al. [J. Fife, P. Di Napoli, and M. Rappaz, Metall. Mater. Trans. A 44, 5522 (2013), 10.1007/s11661-013-1912-7]. This is the first PFC work, to our knowledge, to incorporate temperature, pressure, and density into the thermodynamic description of alloys.

  16. Calculating the role of composition in the anisotropy of solid-liquid interface energy using phase-field-crystal theory.

    PubMed

    Jugdutt, Bernadine A; Ofori-Opoku, Nana; Provatas, Nikolas

    2015-10-01

    This work uses Ginzburg-Landau theory derived from a recent structural phase-field-crystal model of binary alloys developed by the authors to study the roles of concentration, temperature, and pressure on the interfacial energy anisotropy of a solid-liquid front. It is found that the main contribution to the change in anisotropy with concentration arises from a change in preferred crystallographic orientation controlled by solute-dependent changes in the two-point density correlation function of a binary alloy, a mechanism that leads to such phenomena as solute-induced elastic strain and dislocation-assisted solute clustering. Our results are consistent with experimental observations in recent studies by Rappaz et al. [J. Fife, P. Di Napoli, and M. Rappaz, Metall. Mater. Trans. A 44, 5522 (2013)]. This is the first PFC work, to our knowledge, to incorporate temperature, pressure, and density into the thermodynamic description of alloys. PMID:26565255

  17. Laser spot detection-based computer interface system using autoassociative multilayer perceptron with input-to-output mapping-sensitive error back propagation learning algorithm

    NASA Astrophysics Data System (ADS)

    Jeong, Sungmoon; Jung, Chanwoong; Kim, Cheol-Su; Shim, Jae Hoon; Lee, Minho

    2011-08-01

    This paper presents a new computer interface system based on laser spot detection and moving pattern analysis of the detected laser spots in real-time processing. We propose a systematic method that uses either the frame difference of successive input images or an autoassociative multilayer perceptron (AAMLP) to detect laser spots. The AAMLP is applied only to areas of the input images where the frame difference of the successive images is not effective for detecting laser spots. In order to enhance the detection performance, the AAMLP is trained by a new training algorithm that increases the sensitivity of the input-to-output mapping of the AAMLP allowing a small variation in the input feature of the laser spot image to be successfully indicated. The proposed interface system is also able to keep track of the laser spot and recognize gesture commands. The moving pattern of the laser spot is recognized by using a multilayer perception. It is experimentally shown that the proposed computer interface system is fast enough for real-time operation with reliable accuracy.

  18. Structural and electronic properties of multilayer graphene on monolayer hexagonal boron nitride/nickel (111) interface system: A van der Waals density functional study

    NASA Astrophysics Data System (ADS)

    Yelgel, Celal

    2016-02-01

    The structural and electronic properties of multilayer graphene adsorbed on monolayer hexagonal boron nitride (h-BN)/Ni(111) interface system are investigated using the density functional theory with a recently developed non-local van der Waals density functional (rvv10). The most energetically favourable configuration for a monolayer h-BN/Ni(111) interface is found to be N atom atop the Ni atoms and B atom in fcc site with the interlayer distance of 2.04 Å and adsorption energy of 302 meV/BN. Our results show that increasing graphene layers on a monolayer h-BN/Ni(111) interface leads to a weakening of the interfacial interaction between the monolayer h-BN and Ni(111) surface. The adsorption energy of graphene layers on the h-BN/Ni(111) interface is found to be in the range of the 50-120 meV/C atom as the vertical distance from h-BN to the bottommost graphene layers decreases. With the adsorption of a multilayer graphene on the monolayer h-BN/Ni(111) interface system, the band gap of 0.12 eV and 0.25 eV opening in monolayer graphene and bilayer graphene near the K point is found with an upward shifting of the Fermi level. However, a stacking-sensitive band gap is opened in trilayer graphene. We obtain the band gap of 0.35 eV close to the K point with forming a Mexican hat band structure for ABC-stacked trilayer graphene.

  19. Interface behavior of a multi-layer fluid configuration subject to acceleration in a microgravity environment, supplement 1. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Lyell, M. J.; Roh, Michael

    1991-01-01

    With the increasing opportunities for research in a microgravity environment, there arises a need for understanding fluid mechanics under such conditions. In particular, a number of material processing configurations involve fluid-fluid interfaces which may experience instabilities in the presence of external forcing. In a microgravity environment, these accelerations may be periodic or impulse-type in nature. This research investigates the behavior of a multi-layer idealized fluid configuration which is infinite in extent. The analysis is linear, and each fluid region is considered inviscid, incompressible, and immiscible. An initial parametric study of confiquration stability in the presence of a constant acceleration field is performed. The zero mean gravity limit case serves as the base state for the subsequent time-dependent forcing cases. A stability analysis of the multi-layer fluid system in the presence of periodic forcing is investigated. Floquet theory is utilized. A parameter study is performed, and regions of stability are identified. For the impulse-type forcing case, asymptotic stability is established for the configuration. Using numerical integration, the time response of the interfaces is determined.

  20. Capping layer-tailored interface magnetic anisotropy in ultrathin Co{sub 2}FeAl films

    SciTech Connect

    Belmeguenai, M. Zighem, F.; Chérif, S. M.; Gabor, M. S. Petrisor, T.; Tiusan, C.

    2015-01-14

    Co{sub 2}FeAl (CFA) thin films of various thicknesses (2 nm ≤ d ≤ 50 nm) have been grown on (001) MgO single crystal substrates and then capped with Cr, V, and Ta. Their magnetic and structural properties have been studied by x-ray diffraction (XRD), vibrating sample magnetometry, and broadband microstrip ferromagnetic resonance (MS-FMR). The XRD revealed that the films are epitaxial with the cubic [001] CFA axis normal to the substrate plane and that the chemical order varies from the B2 phase to the A2 phase when decreasing the thickness. The deduced lattice parameters showed that the Cr-capped films exhibit a larger tetragonal distortion, as compared with the films capped with V or Ta. The presence of magnetic dead layers has been observed in CFA samples capped with V and Ta but not in the case of the Cr-capped ones. The effective magnetization, deduced from the fit of MS-FMR measurements, increases (decreases) linearly with the CFA inverse thickness (1/d) for the Cr-capped (Ta-capped) films while it is constant for the V-capped ones. This allows quantifying the perpendicular surface anisotropy coefficients of −0.46 erg/cm{sup 2} and 0.74 erg/cm{sup 2} for Cr and Ta-capped films, respectively. Moreover, the fourfold and the uniaxial anisotropy fields, measured in these films, showed different trends with a respect to the CFA inverse thickness. This allows inferring that a non-negligible part of the fourfold magnetocrystalline term is of interfacial origin.

  1. Interatomic interactions at interfaces of multilayered nanostructures (Co45Fe45Zr10/ a-Si)40 and (Co45Fe45Zr10/SiO2)32

    NASA Astrophysics Data System (ADS)

    Domashevskaya, E. P.; Terekhov, V. A.; Turishchev, S. Yu.; Spirin, D. E.; Chernyshev, A. V.; Kalinin, Yu. E.; Sitnikov, A. V.

    2016-05-01

    The interatomic interaction and phase formation at interfaces between the metallic layers Co45Fe45Zr10 and nonmetallic interlayers of amorphous silicon or silicon dioxide in multilayered nanostructures (Co45Fe45Zr10/ a-Si)40 and (Co45Fe45Zr10/SiO2)32 have been investigated using ultrasoft X-ray emission spectroscopy (USXES) and X-ray diffractometry. The multilayered nanostructures have been fabricated by ion-beam sputtering of two targets onto the surface of a rotating glass-ceramic substrate. The investigations have demonstrated that, regardless of the expected composition of the interlayer (amorphous silicon or silicon dioxide), d-metal silicides, predominantly lower cobalt silicides, are formed at the metallic layer/interlayer interface. However, in this case, the thickness of silicide interfaces in the multilayered nanostructures with oxide interlayers (series O) has a significantly lower value of ˜0.1 nm, and, therefore, the central layer of the interlayers remains oxide. In the multilayered nanostructures with amorphous silicon interlayers almost all silicon is consumed in the formation of nonmagnetic silicide phases. When the thickness of this interlayer exceeds the thickness of the metallic layer, the multilayered nanostructures become nonmagnetic.

  2. Self-ordering of quasi-quantum wire in InAlAs/AlGaAs multilayer nanostructure and its optical anisotropy

    NASA Astrophysics Data System (ADS)

    Chen, Y.; Li, G. H.; Zhang, W.; Zhu, Z. M.; Han, H. X.; Wang, Z. P.; Zhou, W.; Wang, Z. G.

    2000-02-01

    Self-ordering of quasi-quantum wires in multilayer InAlAs/AlGaAs nanostructures grown by molecular beam epitaxy is identified. The chain-like structures along the [ 1 1¯ 0 ] direction formed by coalescence of quantum dots were observed. The photoluminescence of the nanostructures is partially polarized along the [1 1¯ 0] direction. The polarization ratio depends on the wavelength and the maximum polarization is on the lower energy side. The maximum polarization increases from 0.32 at 10 K to 0.53 at 100 K, and the energy position of maximum polarization moves near to PL peak with increasing temperature. They are all related to the existence of isolated islands and quasi-quantum wires in our sample. This result provides a novel approach to produce narrow quantum wires.

  3. Interface Properties of Atomic-Layer-Deposited Al2O3 Thin Films on Ultraviolet/Ozone-Treated Multilayer MoS2 Crystals.

    PubMed

    Park, Seonyoung; Kim, Seong Yeoul; Choi, Yura; Kim, Myungjun; Shin, Hyunjung; Kim, Jiyoung; Choi, Woong

    2016-05-11

    We report the interface properties of atomic-layer-deposited Al2O3 thin films on ultraviolet/ozone (UV/O3)-treated multilayer MoS2 crystals. The formation of S-O bonds on MoS2 after low-power UV/O3 treatment increased the surface energy, allowing the subsequent deposition of uniform Al2O3 thin films. The capacitance-voltage measurement of Au-Al2O3-MoS2 metal oxide semiconductor capacitors indicated n-type MoS2 with an electron density of ∼10(17) cm(-3) and a minimum interface trap density of ∼10(11) cm(-2) eV(-1). These results demonstrate the possibility of forming a high-quality Al2O3-MoS2 interface by proper UV/O3 treatment, providing important implications for their integration into field-effect transistors. PMID:27117229

  4. Bulk and Interface effects on voltage linearity of ZrO2-SiO2 multilayered metal-insulator-metal capacitors for analog mixed-signal applications

    NASA Astrophysics Data System (ADS)

    Park, S. D.; Park, C.; Gilmer, D. C.; Park, H. K.; Kang, C. Y.; Lim, K. Y.; Burham, C.; Barnett, J.; Kirsch, P. D.; Tseng, H. H.; Jammy, R.; Yeom, G. Y.

    2009-07-01

    Quadratic voltage coefficient of capacitance (VCC) for ZrO2-SiO2 multilayered dielectric metal-insulator-metal capacitors depends strongly on the stacking sequence of the layered dielectrics. The quadratic VCC of an optimized SiO2/ZrO2/SiO2 stack and ZrO2/SiO2/ZrO2 stack were +42 and -1094 ppm/V2, respectively, despite the same total SiO2 and ZrO2 dielectric thickness in the stack. The observed difference in quadratic VCC depending on dielectric stacking sequence is explained by taking into account both the interface and bulk dielectric responses to the applied voltage.

  5. A multilayered sharp interface model of coupled freshwater and saltwater flow in coastal systems: model development and application

    USGS Publications Warehouse

    Essaid, H.I.

    1990-01-01

    The model allows for regional simulation of coastal groundwater conditions, including the effects of saltwater dynamics on the freshwater system. Vertically integrated freshwater and saltwater flow equations incorporating the interface boundary condition are solved within each aquifer. Leakage through confining layers is calculated by Darcy's law, accounting for density differences across the layer. The locations of the interface tip and toe, within grid blocks, are tracked by linearly extrapolating the position of the interface. The model has been verified using available analytical solutions and experimental results and applied to the Soquel-Aptos basin, Santa Cruz County, California. -from Author

  6. Interfacial magnetic anisotropy of Co90Zr10 on Pt layer.

    PubMed

    Kil, Joon Pyo; Bae, Gi Yeol; Suh, Dong Ik; Choi, Won Joon; Noh, Jae Sung; Park, Wanjun

    2014-11-01

    Spin Transfer Torque (STT) is of great interest in data writing scheme for the Magneto-resistive Random Access Memory (MRAM) using Magnetic Tunnel Junction (MTJ). Scalability for high density memory requires ferromagnetic electrodes having the perpendicular magnetic easy axis. We investigated CoZr as the ferromagnetic electrode. It is observed that interfacial magnetic anisotropy is preferred perpendicular to the plane with thickness dependence on the interfaces with Pt layer. The anisotropy energy (K(u)) with thickness dependence shows a change of magnetic-easy-axis direction from perpendicular to in-plane around 1.2 nm of CoZr. The interfacial anisotropy (K(i)) as the directly related parameters to switching and thermal stability, are estimated as 1.64 erg/cm2 from CoZr/Pt multilayered system. PMID:25958513

  7. Two different coercivity lattices in Co/Pd multilayers generated by single-pulse direct laser interference lithography

    SciTech Connect

    Leufke, Philipp M.; Riedel, Stephen; Leiderer, Paul; Boneberg, Johannes; Schatz, Guenter; Albrecht, Manfred; Lee, M.-S.; Li Jie; Eimueller, Thomas; Rohrmann, Hartmut

    2009-06-01

    We report on magnetic structuring of Co/Pd multilayer films with strong perpendicular magnetic anisotropy by single-pulse direct laser interference lithography technique. Multibeam laser interference generates patterns of various types. The intense laser irradiation at interference maxima causes chemical intermixing at Co/Pd interfaces, leading to local changes in magnetic properties such as the creation of pinning centers and the reduction in the strength of magnetic anisotropy. We use magnetic force microscopy and Kerr microscopy to study the magnetization reversal processes in the patterned samples and find that the structures show three distinctly different behaviors depending on the intensity of the laser used for irradiation.

  8. Investigation of frame mode unification and virtual channel multiplexing based on the multilayered satellite network OISLs interface

    NASA Astrophysics Data System (ADS)

    Deng, Boyu; Zhao, Shanghong; Li, Yongjun; Zhang, Xiwen; Cheng, Zhen

    2015-12-01

    In a multi-layered optical satellite network, a standardized data transmission is a reliable guarantee to efficiently process and transfer multi-service data for the space link. The transmission frame reframing unit (TFRU) is proposed to solve the problem of different service data having low transmission efficiency in the laser link. The TFRU uses a virtual channel (VC) technology to unify the format and rate of transmitted data using second encapsulation and VC scheduling for the service data. The Priority VC schedule algorithm is proposed to further improve multiplex efficiency. According to the principle of TFRU encapsulation and arrival rate of service data, the frame dynamic priority is defined by the VC priority and frame criticality. Furthermore, the Priority VC schedule specific method is provided. The simulation results show that the throughput increases to 3.0546 M, and the scheduling time delay reduces to 0.9183 s. Thus, the system performance has been greatly enhanced. The cache demands are satisfied because the laser terminal data transmission rate is larger than the sum of all service data rates. Using the dynamic schedule generated TFRU frames, the priority algorithm based on the TFRU ensures frame scheduling fairness in each VC.

  9. Interface study and performance of large layer pair ultra-short period W/B{sub 4}C X-ray multilayer

    SciTech Connect

    Pradhan, P. C. Nayak, M.; Mondal, P.; Lodha, G. S.

    2015-06-24

    The nature of interfaces in ultra short period W/B{sub 4}C multilayers (MLs) is studied using hard x-ray reflectivity and cross sectional transmission electron microscope. W/B{sub 4}C MLs are fabricated using magnetron sputtering system with systematic varying thickness of both W and B{sub 4}C layers from ∼5 to 30 Å keeping number of layer pairs fixed at 10. It is observed that in low period W/B{sub 4}C ML, as the layer thickness decreases, the interdiffusion plays a significant role because of the discontinuous nature of film. This gives variation of density and roughness of the layer as well as generates thickness errors in the ML structure due to volume changes which is originated by interdifusion process. Finally, W/B{sub 4}C MLs with large number of layer pairs (300) are fabricated with periodicity d= 20 Å which gives ∼54 % of reflectivity at energy 8.047 keV.

  10. Size dependent gold nanoparticle interaction at nano-micro interface using both monolayer and multilayer (tissue-like) cell models

    NASA Astrophysics Data System (ADS)

    Yohan, Darren; Yang, Celina; Lu, Xiaofeng; Chithrani, Devika B.

    2016-03-01

    Gold nanoparticles (GNPs) can be used as a model NP system to improve the interface between nanotechnology and medicine since their size and surface properties can be tailored easily. GNPs are being used as radiation dose enhancers and as drug carriers in cancer research. Hence, it is important to know the optimum NP size for uptake not only at monolayer level but also at tissue level. Once GNPs leave tumor vasculature, they enter the tumor tissue. Success of any therapeutic technique using NPs depends on how well NPs penetrate the tumor tissue and reach individual tumor cells. In this work, multicellular layers (MCLs) were grown to model the post-vascular tumor environment. GNPs of 20 nm and 50 nm diameters were used to elucidate the effects of size on the GNP penetration and distribution dynamics. Larger NPs (50 nm) were better at monolayer level, but smaller NPs (20 nm) were at tissue level. The MCLs exhibited a much more extensive extracellular matrix (ECM) than monolayer cell cultures. This increased ECM created a barrier for NP transport and ECM was also dependent on the tumor cell lines. Smaller NPs penetrated better compared to larger NPs. Transport of NPs was better in MDA-MB231 vs MCF-7. This MCL model tissue structures are better tools to optimize NP transport through tissue before using them in animal models. Based on our study, we believe that smaller NPs are better for improved outcome in future cancer therapeutics.

  11. Ion induced magnetization reorientation in Co/Pt multilayers for patterned media

    SciTech Connect

    Weller, D.; Baglin, J.E.E.; Kellock, A.J.; Hannibal, K.A.; Toney, M.F.; Kusinski, G.; Lang, S.; Best, M.E.; Terris, B.D.

    2000-01-01

    Co/Pt multilayer films with perpendicular magnetic anisotropy and large out-of-plane coercivities of 3.9 - 8.5 kOe have been found to undergo a spin reorientation transition from out-of-plane to in-plane upon irradiation with 700 keV nitrogen ions. X-ray reflectivity experiments show that the multilayer structure gets progressively disrupted with increasing ion dose, providing direct evidence for local atomic displacements at the Co/Pt interfaces. This effectively destroys the magnetic interface anisotropy, which was varied by about a factor of two, between KS@ 0.4 erg/cm2 and KS@ 0.85 erg/cm2 for two particular films. The dose required to initiate spin-reorientation, 6x1014 N+/cm2 and 1.5x1015 N+/cm2, respectively, scales with KS. It is roughly equal to the number of Co interface atoms per unit interface area contributing to KS.

  12. 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.

  13. 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.

  14. Spin configuration of magnetic multi-layers: effect of exchange, dipolar and Dzyalozhinski-Moriya interactions.

    PubMed

    Franco, A F; Kachkachi, H

    2013-08-01

    We investigate the effect of coupling (intensity and nature), applied field, and anisotropy on the spin dynamics of a multi-layer system composed of a hard magnetic layer coupled to a soft magnetic layer through a nonmagnetic spacer. The soft layer is modeled as a stack of several atomic planes while the hard layer, of a different material, is either considered as a pinned macroscopic magnetic moment or again as a stack of atomic planes. We compute the magnetization profile and hysteresis loop of the whole multi-layer system by solving the Landau-Lifshitz equations for the net magnetic moment of each (atomic) plane. We study the competition between the intra-layer anisotropy and exchange interaction, applied magnetic field, and the interface exchange, dipolar or Dzyalozhinski-Moriya interaction. Compared with the exchange coupling, the latter two couplings present peculiar features in the magnetization profile and hysteresis loop that may help identify the nature of the interface coupling in multi-layer magnetic systems. PMID:23838366

  15. The formation of surface multilayers at the air-water interface from sodium polyethylene glycol monoalkyl ether sulfate/AlCl(3) solutions: the role of the size of the polyethylene oxide group.

    PubMed

    Xu, Hui; Penfold, Jeff; Thomas, Robert K; Petkov, Jordan T; Tucker, Ian; Webster, John P R

    2013-09-17

    Neutron reflectivity, NR, and surface tension, ST, have been used to study the surface adsorption properties at the air-water interface of the anionic surfactant sodium polyethylene glycol monododecyl ether sulfate (sodium lauryl ether sulfate, SLES) in the presence of Al(3+) multivalent counterions, by the addition of AlCl3. In the absence of AlCl3 and at low AlCl3 concentrations monolayer adsorption is observed. With increasing AlCl3 concentration, surface multilayer formation is observed, driven by SLES/Al(3+) complex formation. The onset of multilayer formation occurs initially as a single bilayer or a multilayer structure with a limited number of bilayers, N, ≤3, and ultimately at higher AlCl3 concentrations N is large, >20. The evolution in the surface structure is determined by the surfactant and AlCl3 concentrations, and the size of the polyethylene oxide group in the different SLES surfactants studied. From the NR data, approximate surface phase diagrams are constructed, and the evolution of the surface structure with surfactant and electrolyte concentration is shown to be dependent on the size of the polyethylene oxide group. As the polyethylene oxide group increases in size the multilayer formation requires increasingly higher surfactant and AlCl3 concentrations to promote the formation. This is attributed to the increased steric hindrance of the polyethylene oxide group disrupting SLES/Al(3+) complex formation. PMID:23968161

  16. Influence of layer thickness on the structure and the magnetic properties of Co/Pd epitaxial multilayer films

    NASA Astrophysics Data System (ADS)

    Tobari, Kousuke; Ohtake, Mitsuru; Nagano, Katsumasa; Futamoto, Masaaki

    2012-03-01

    Co/Pd epitaxial multilayer films were prepared on Pd(111)fcc underlayers hetero-epitaxially grown on MgO(111)B1 single-crystal substrates at room temperature by ultra-high vacuum RF magnetron sputtering. In-situ reflection high energy electron diffraction shows that the in-plane lattice spacing of Co on Pd layer gradually decreases with increasing the Co layer thickness, whereas that of Pd on Co layer remains unchanged during the Pd layer formation. The CoPd alloy phase formation is observed around the Co/Pd interface. The atomic mixing is enhanced for thinner Co and Pd layers in multilayer structure. With decreasing the Co and the Pd layer thicknesses and increasing the repetition number of Co/Pd multilayer film, stronger perpendicular magnetic anisotropy is observed. The relationships between the film structure and the magnetic properties are discussed.

  17. Vibroacoustical behaviour of multilayered heterogeneous plates with elastic support and interface condition: Application to the case of the double-deck French high- speed train

    NASA Astrophysics Data System (ADS)

    Chabaud, Thierry Rene

    1998-10-01

    Mass Transit has to meet specifications of increasing difficulty which put in the forefront areas which were before considered as secondary. In particular, passengers acoustic comfort has become a major criterion, reflecting the requirements for quality transportation. The present work has its origin in this specific context and more specially in the intention of FAIVELEY TRANSPORT, a Railway equipment supplier, to improve the acoustic behaviour of its products. The aim of this study is the comprehension of the physical phenomena of the noise transmission through the doors of the transport vehicles, from outside to inside. The Railway access doors are the main application of this work. The considered frequency range is low frequencies below 500 Hz. The final objective is to notably reduce the transmitted noise in order to improve the passengers' acoustic comfort inside the transport vehicles. To do this, we developed a model based on an analytical integro-modal approach, associated with a Rayleigh-Ritz approximation. The original aspect of this work is to develop a model of a vibrating structure which take into account its multilayered and heterogeneous aspects and its complex boundary and interface conditions (linear and punctual elastic stiffness). This model is the basis of a specific software for preliminary design studies (VANTAIL) which is able to indicate, with a parametric study, the contribution of each different part of the doors to the global vibroacoustic behaviour. An experimental study on an industrial structure (the access door of the double deck French high speed train) permits us to validate the developed software, to define its limits and to validate the proposed vibroacoustic treatments.

  18. Giant magnetoresistance of copper/permalloy multilayers

    NASA Astrophysics Data System (ADS)

    Holody, P.; Chiang, W. C.; Loloee, R.; Bass, J.; Pratt, W. P., Jr.; Schroeder, P. A.

    1998-11-01

    Current perpendicular (CPP) and current in-plane (CIP) magnetoresistances (MR) have been measured on sputtered Cu/Py (Py=Permalloy) multilayers at 4.2 K. The CPP-MR is several times larger than the CIP-MR. For fixed Py layer thickness, tPy=1.5 nm, both the CPP and CIP MR's show oscillations with increasing tCu with a period similar to that previously reported for the CIP-MR. The CPP data for Cu thicknesses large enough that exchange interactions between Py layers are small are analyzed using the two spin-current model for both infinite and finite spin-diffusion length in Py. The very low coercive field of Py leads to a larger than usual uncertainty in the derived parameters, because of the uncertainty in the degree of antiparallel alignment required for the analysis. Three alternative analyses give bulk and interface spin-dependent anisotropy parameters, β, and γ, of comparable size, so that both must be considered in determining the CPP-MR. Our preferred values, based upon an assumed IPysf=5.5+/-1 nm, are β=0.65+/-0.1 and γ=0.76+/-0.1. These values produce good fits to the CPP-MR's of Co/Cu/Py/Cu multilayers.

  19. Magnetic metallic multilayers

    SciTech Connect

    Hood, R.Q.

    1994-04-01

    Utilizing self-consistent Hartree-Fock calculations, several aspects of multilayers and interfaces are explored: enhancement and reduction of the local magnetic moments, magnetic coupling at the interfaces, magnetic arrangements within each film and among non-neighboring films, global symmetry of the systems, frustration, orientation of the various moments with respect to an outside applied field, and magnetic-field induced transitions. Magnetoresistance of ferromagnetic-normal-metal multilayers is found by solving the Boltzmann equation. Results explain the giant negative magnetoresistance encountered in these systems when an initial antiparallel arrangement is changed into a parallel configuration by an external magnetic field. The calculation depends on (1) geometric parameters (thicknesses of layers), (2) intrinsic metal parameters (number of conduction electrons, magnetization, and effective masses in layers), (3) bulk sample properties (conductivity relaxation times), (4) interface scattering properties (diffuse scattering versus potential scattering at the interfaces, and (5) outer surface scattering properties (specular versus diffuse surface scattering). It is found that a large negative magnetoresistance requires considerable asymmetry in interface scattering for the two spin orientations. Features of the interfaces that may produce an asymmetrical spin-dependent scattering are studied: varying interfacial geometric random roughness with no lateral coherence, correlated (quasi-periodic) roughness, and varying chemical composition of the interfaces. The interplay between these aspects of the interfaces may enhance or suppress the magnetoresistance, depending on whether it increases or decreases the asymmetry in the spin-dependent scattering of the conduction electrons.

  20. Multi-Layer, Sharp-Interface Models of Pore Pressure Buildup within the Illinois Basin due to Basin-Wide CO2 Injection

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Person, M. A.; Gable, C. W.; Celia, M. A.; Nordbotten, J. M.; Bandilla, K.; Elliot, T. R.; Rupp, J.; Ellett, K. M.; Bowen, B.; Pickett, W.; Woolsey, E. E.

    2011-12-01

    We recently developed and applied a new parallel, multi-layer, finite-element model to the Illinois Basin in order to assess the spatial extent and magnitude of pore pressure increases resulting from the annual projected injection of 100 million metric tons of CO2. One focus of this work is to assess the potential for inducing a seismic event associated with low effective stress conditions around CO2 injection wells in the southern Illinois Basin where Mt Simon permeability is relatively low (< 50 mD). We used a sharp-interface formulation to represent a CO2, freshwater, and brine transport within each layer. A simple parallelization scheme was used in which fluid transport in each layer is solved on a separate processor. The layers are linked at the after each time step through vertical fluxes of fresh and saline water across their respective confining units. This model was validated, in part, by comparison to computed pore pressure distributions from a published 8-layer test case. Our Illinois Basin model represents spatial variations in porosity using a modified form of Athy's law. Permeability is logarithmically related to porosity so that permeability. Principal reservoirs represented in our model include the Mt. Simon Formation, the Knox Dolomite, Ordovician carbonates, Silurian-Devonian and Mississippian-Pennsylvanian sandstone/carbonates units. Key confining unit represented include the Eau Claire, Maquoketa, and New Albany Shales. A limited number of low-permeability faults were also included in the model. The permeability of fault elements were set to between 10-100 times lower than surrounding sediments. We calibrated our model using historical freshwater pumping data from the Chicago area (128 million gallons per day of H2O) as well as the salinity distribution across the Illinois Basin. We found that incorporating a stream network which included the Rock River near Chicago was important in reproducing pre-development head patterns in the Cambro

  1. Square-loop cobalt/gold multilayers

    NASA Astrophysics Data System (ADS)

    Gambino, R. J.; Ruf, R. R.

    1990-05-01

    Multilayers of Co and Au with perpendicular hysteresis loop squareness ratios of ˜1 have been prepared by e-beam evaporation. These films have perpendicular anisotropy in the as-deposited condition in contrast to other work in which Co/Au multilayers, prepared by ion beam sputtering, showed perpendicular anisotropy only after annealing at 300 °C. The Faraday rotation of these square-loop multilayers is about 9×105 deg/cm of Co or 1×105 deg/cm of total thickness at a wavelength of 633 nm. These values indicate an enhancement of the Faraday rotation of Co at this wavelength by about a factor of 2. This may be a plasma-edge enhancement effect similar to that reported by Katayama et al. [Phys. Rev. Lett. 60, 1426 (1988)] in the Kerr effect of Fe/Au multilayers.

  2. Tuning of in-plane optical anisotropy by inserting ultra-thin InAs layer at interfaces in (001)-grown GaAs/AlGaAs quantum wells

    SciTech Connect

    Yu, J. L.; Cheng, S. Y.; Lai, Y. F.; Zheng, Q.

    2015-01-07

    The in-plane optical anisotropy (IPOA) in (001)-grown GaAs/AlGaAs quantum wells (QWs) with different well widths varying from 2 nm to 8 nm has been studied by reflectance difference spectroscopy. Ultra-thin InAs layers with thickness ranging from 0.5 monolayer (ML) to 1.5 ML have been inserted at GaAs/AlGaAs interfaces to tune the asymmetry in the QWs. It is demonstrated that the IPOA can be accurately tailored by the thickness of the inserted ultra-thin InAs layer at the interfaces. Strain-induced IPOA has also been extracted by using a stress apparatus. We find that the intensity of the strain-induced IPOA decreases with the thickness of the inserted InAs layer, while that of the interface-induced IPOA increases with the thickness of the InAs layer. Theoretical calculations based on 6 band k ⋅ p theory have been carried out, and good agreements with experimental results are obtained. Our results demonstrate that, the IPOA of the QWs can be greatly and effectively tuned by inserting an ultra-thin InAs layer with different thicknesses at the interfaces of QWs, which does not significantly influence the transition energies and the transition probability of QWs.

  3. Magnetic and magneto-optical properties of Pd/Cr/Co multilayers

    SciTech Connect

    Tang, Y. J.; Wong, C. Y.; Zhou, X.

    2001-06-01

    Recent studies found that the (Pt/Co/Pt) trilayers can be used as a unit in combination with nonmagnetic or magnetic layer, X (X=Pd, Ag, Cu, and Ni), to enhance the perpendicular magnetic anisotropy of the films, reduce the Curie temperature, and alter the magneto-optical properties. The effects of intercalating Cr into Pd/Co multilayers on the magnetic and magneto-optical properties are studied in this article. The perpendicular magnetic anisotropy K{sub u} and the coercivity H{sub c} of the system decrease rapidly with increasing the Cr thickness (X{sub Cr}) up to 0.4 nm, and change slightly when Cr thickness further increases. The dependence of the coercivity H{sub c} on the Cr thickness, which obeys the law: H{sub c} (X{sub Cr})=X{sub Cr}{sup {minus}2.66}, indicates that the magnetization reversal is controlled by domain wall moving, mainly due to the interface roughness. Large decrease of the Kerr rotation {theta}{sub k} of the Pd/Cr/Co multilayers compared with pure Pd/Co multilayers is also found in the wavelength ranging from 200 to 800 nm. As it is well known, the large anisotropy and Kerr rotation in Pd/Co system are mainly caused by the polarization of Pd atoms due to nearby Co atoms. As the intercalating of Cr layer between Pd and Co layer, the average polarization of Pd atoms will be reduced largely. As a matter of fact, the Cr atoms can also be polarized by nearby Co atoms, which, however, seems to take a minor effect on the anisotropy and Kerr rotation of the system. {copyright} 2001 American Institute of Physics.

  4. Magnetic and magneto-optical properties of Pd/Cr/Co multilayers

    NASA Astrophysics Data System (ADS)

    Tang, Y. J.; Wong, C. Y.; Zhou, X.

    2001-06-01

    Recent studies found that the (Pt/Co/Pt) trilayers can be used as a unit in combination with nonmagnetic or magnetic layer, X (X=Pd, Ag, Cu, and Ni), to enhance the perpendicular magnetic anisotropy of the films, reduce the Curie temperature, and alter the magneto-optical properties. The effects of intercalating Cr into Pd/Co multilayers on the magnetic and magneto-optical properties are studied in this article. The perpendicular magnetic anisotropy Ku and the coercivity Hc of the system decrease rapidly with increasing the Cr thickness (XCr) up to 0.4 nm, and change slightly when Cr thickness further increases. The dependence of the coercivity Hc on the Cr thickness, which obeys the law: Hc (XCr)=XCr-2.66, indicates that the magnetization reversal is controlled by domain wall moving, mainly due to the interface roughness. Large decrease of the Kerr rotation θk of the Pd/Cr/Co multilayers compared with pure Pd/Co multilayers is also found in the wavelength ranging from 200 to 800 nm. As it is well known, the large anisotropy and Kerr rotation in Pd/Co system are mainly caused by the polarization of Pd atoms due to nearby Co atoms. As the intercalating of Cr layer between Pd and Co layer, the average polarization of Pd atoms will be reduced largely. As a matter of fact, the Cr atoms can also be polarized by nearby Co atoms, which, however, seems to take a minor effect on the anisotropy and Kerr rotation of the system.

  5. Ultrasonic NDE of Multilayered Structures

    SciTech Connect

    Quarry, M J; Fisher, K A; Lehman, S K

    2005-02-14

    This project developed ultrasonic nondestructive evaluation techniques based on guided and bulk waves in multilayered structures using arrays. First, a guided wave technique was developed by preferentially exciting dominant modes with energy in the layer of interest via an ultrasonic array. Second, a bulk wave technique uses Fermat's principle of least time as well as wave-based properties to reconstruct array data and image the multilayered structure. The guided wave technique enables the inspection of inaccessible areas of a multilayered structure without disassembling it. Guided waves propagate using the multilayer as a waveguide into the inaccessible areas from an accessible position. Inspecting multi-layered structures with a guided wave relies on exciting modes with sufficient energy in the layer of interest. Multilayered structures are modeled to determine the possible modes and their distribution of energy across the thickness. Suitable modes were determined and excited by designing arrays with the proper element spacing and frequency. Bulk wave imaging algorithms were developed to overcome the difficulties of multiple reflections and refractions at interfaces. Reconstruction algorithms were developed to detect and localize flaws. A bent-ray algorithm incorporates Fermat's principle to correct time delays in the ultrasonic data that result from the difference in wave speeds in each layer and refractions at the interfaces. A planar wave-based algorithm was developed using the Green function for the multilayer structure to enhance focusing on reception for improved imaging.

  6. Seed influence on the ferromagnetic resonance response of Co/Ni multilayers

    NASA Astrophysics Data System (ADS)

    Sabino, Maria Patricia Rouelli; Tran, Michael; Hin Sim, Cheow; Ji Feng, Ying; Eason, Kwaku

    2014-05-01

    The effect of Pd and Ru seed layers on the magnetic properties of [Co/Ni]N multilayers with varying number of bilayer repeats N is investigated using vector network analyzer ferromagnetic resonance. The effective anisotropy field HKeff is found to increase with N for Ru seed, but decreases for Pd until N = 15. As N is increased beyond 15, HKeff decreases for both seeds. In contrast, the damping parameter α decreases with N regardless of the seed, showing a 1/N dependence. Taking spin pumping into account, the intrinsic damping α0 for both Pd and Ru seeds reduce to α0 ≈ 0.01. These results demonstrate that there can be a strong influence of the seed/Co interface on anisotropy, especially for sufficiently low N, but not necessarily on α0.

  7. Seed influence on the ferromagnetic resonance response of Co/Ni multilayers

    SciTech Connect

    Sabino, Maria Patricia Rouelli Tran, Michael; Hin Sim, Cheow; Ji Feng, Ying; Eason, Kwaku

    2014-05-07

    The effect of Pd and Ru seed layers on the magnetic properties of [Co/Ni]{sub N} multilayers with varying number of bilayer repeats N is investigated using vector network analyzer ferromagnetic resonance. The effective anisotropy field H{sub Keff} is found to increase with N for Ru seed, but decreases for Pd until N = 15. As N is increased beyond 15, H{sub Keff} decreases for both seeds. In contrast, the damping parameter α decreases with N regardless of the seed, showing a 1/N dependence. Taking spin pumping into account, the intrinsic damping α{sub 0} for both Pd and Ru seeds reduce to α{sub 0} ≈ 0.01. These results demonstrate that there can be a strong influence of the seed/Co interface on anisotropy, especially for sufficiently low N, but not necessarily on α{sub 0}.

  8. Effects of local field and inherent strain in reflectance anisotropy spectra of AIIIBV semiconductors with naturally oxidized surfaces

    NASA Astrophysics Data System (ADS)

    Berkovits, V. L.; Kosobukin, V. A.; Gordeeva, A. B.

    2015-12-01

    Reflectance anisotropy (RA) spectra of naturally oxidized (001) surfaces of GaAs and InAs crystals are measured for photon energies from 1.5 up to 5.5 eV. The differential high-accuracy RA spectra reveal features substantially different from those caused by either a reconstruction of clean surface or a built-in near-surface electric field. Models of atomic structure with anisotropic transition layers of excess arsenic atoms specific for GaAs(001)/oxide and InAs(001)/oxide interfaces are proposed. In conformity with these models, a general theory of reflectance anisotropy is developed for semiconductor/oxide interfaces within the Green's function technique. The theory takes into account the combined effect of local field due to interface dipoles and of intrinsic near-surface strain of the crystal. Measured RA spectra are analyzed in the model of valence-bond dipoles occupying a rectangular lattice in a multilayer medium. Comparing the measured and calculated spectra, we conclude that RA spectra of oxidized GaAs(001) and InAs(001) surfaces are simultaneously influenced by interface and near-surface anisotropies. The former is responsible for the broad-band spectral features which are associated with polarizability of the valence bonds attached to As atoms at the crystal/oxide interface. The near-surface anisotropy is due to inherent uniaxial straining the near-surface region of crystal. The effect of strain on RA spectra is experimentally and theoretically substantiated for GaAs crystal wafers undergone a uniaxial applied stress. Basically, this work results in the following. It establishes the physical nature of different levels of RA spectra observed in a majority of papers, but never analyzed. It demonstrates how the studied features of RA spectra could be applied for optical characterization of strained interfaces and atomic layers.

  9. Magnetic properties of a Pt/Co2FeAl/MgO structure with perpendicular magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Li, Xiao-Qi; Xu, Xiao-Guang; Wang, Sheng; Wu, Yong; Zhang, De-Lin; Miao, Jun; Jiang, Yong

    2012-10-01

    Microstructures and magnetic properties of Ta/Pt/Co2FeAl (CFA)/MgO multilayers are studied to understand perpendicular magnetic anisotropy (PMA) of half-metallic full-Heusler alloy films. PMA is realized in a 2.5-nm CFA film with B2-ordered structure observed by a high resolution transmission electron microscope. It is demonstrated that a high quality interface between the ferromagnetic layer and oxide layer is not essential for PMA. The conversions between in-plane anisotropy and PMA are investigated to study the dependence of magnetic moment on temperature. At the intersection points, the decreasing slope of the saturation magnetization (Ms) changes because of the conversions. The dependence of Ms on the annealing temperature and MgO thickness is also studied.

  10. Fabrication of liquid-infused surfaces using reactive polymer multilayers: principles for manipulating the behaviors and mobilities of aqueous fluids on slippery liquid interfaces.

    PubMed

    Manna, Uttam; Lynn, David M

    2015-05-20

    The design of slippery liquid-infused porous surfaces (SLIPS) using nanoporous and chemically reactive polymer multilayers is reported. This approach permits fabrication of slippery anti-fouling coatings on complex surfaces and provides new means to manipulate the mobilities of contacting aqueous fluids. The results expand the range of tools that can be used to manipulate the behaviors of SLIPS and open the door to new applications of this emerging class of soft materials. PMID:25854608

  11. Cobalt-Based Hard Magnets, Thin Films and Multilayers

    NASA Astrophysics Data System (ADS)

    Gao, Chuan

    1991-02-01

    Co-based magnetic materials including bulk, thin film and magnetic multilayers have been studied. The purpose of the first part of this work is to study a Co -based transition metal alloy to be processed to result in significant enhancement of its magnetic properties (coercivity, magnetization, and energy product) in the absence rare earths. CoZr(Hf)BSi alloys have been studied. Rapidly quenched Co_ {78}Zr_{16}B_3Si_3 and Co_{76}Hf_ {76}B_3Si_3 showed the highest coercivity (6.7 kOe and 6.5 kOe respectively). This is the highest room temperature coercivity reported in a non -rare-earth containing magnet up to now. This system has excellent thermal stability. Co-based thin film alloys were also studied and we obtain coercivities as high as 700 Oe for sputtered thin films. This lies in between the maximum value obtained for as-cast bulk alloys (50 Oe) and rapidly quenched alloys (6.7 kOe). Multilayers were studied with the objective of determining the effect of interfaces on the magnetic properties of Co alloys. Multilayers of the form Co/Cu, Co_{95}B _5/Cu and Co/Al were studied and the interface anisotropy was found to favor a magnetization perpendicular to the film. Very thin magnetic layers led to very small coercivities since the size of magnetic domains was restricted. We also noted some interesting layer-layer magnetic interactions. Finally some unusual magnetization reversal behavior was noted in which the magnetic moment goes to zero and reverses before the applied field goes to zero.

  12. Growth induced magnetic anisotropy in amorphous thin films. Annual progress report year 1, November 4, 1994--October 31, 1995

    SciTech Connect

    Hellman, F.

    1995-07-01

    The work in the past year has primarily involved three areas of magnetic thin films: amorphous rare earth-transition metal alloys, epitaxial COPt3 thin films, and exchange coupled antiferromagnetic insulators. In the amorphous alloys, the authors have focused on understanding the cause and the effect of the growth-surface-induced perpendicular magnetic anisotropy. Using the results of previous work, they are able to control this anisotropy quite precisely. This anisotropy is predicted to have dramatic and as-yet unobserved effects on the underlying nature of the magnetism. The work on the epitaxial Co-Pt alloys was originally undertaken as a comparison study to the amorphous alloys. The authors have discovered that these alloys exhibit a remarkable new phenomena; a surface-induced miscibility gap in a material which is believed to be completely miscible in the bulk. This miscibility gap is 100% correlated with the perpendicular anisotropy, although the connection is not yet clear, and is presumably linked to a magnetic energy of mixing which tends to drive a material towards clustering. The problem of exchange coupling in multilayers impacts many of the current research areas in magnetism. NiO/CoO multilayers can be prepared with coherent interfaces. The specific heat shows unambiguously the ordering of the spins in the layers. The results show clearly the transition from a single transition temperature to two distinct transitions with increasing thickness of the individual layers. From this data, the authors are able to determine the interface magnetic exchange coupling constant and the effect on the transition temperature of finite layer thickness.

  13. MoRu/Be multilayers for extreme ultraviolet applications

    DOEpatents

    Bajt, Sasa C.; Wall, Mark A.

    2001-01-01

    High reflectance, low intrinsic roughness and low stress multilayer systems for extreme ultraviolet (EUV) lithography comprise amorphous layers MoRu and crystalline Be layers. Reflectance greater than 70% has been demonstrated for MoRu/Be multilayers with 50 bilayer pairs. Optical throughput of MoRu/Be multilayers can be 30-40% higher than that of Mo/Be multilayer coatings. The throughput can be improved using a diffusion barrier to make sharper interfaces. A capping layer on the top surface of the multilayer improves the long-term reflectance and EUV radiation stability of the multilayer by forming a very thin native oxide that is water resistant.

  14. Band alignment of HfO{sub 2}/multilayer MoS{sub 2} interface determined by x-ray photoelectron spectroscopy: Effect of CHF{sub 3} treatment

    SciTech Connect

    Liu, Xinke; He, Jiazhu; Tang, Dan; Jia, Fang; Lu, Youming Zhu, Deliang; Liu, Wenjun; Cao, Peijiang; Han, Sun; Liu, Qiang; Wen, Jiao; Yu, Wenjie; Pan, Jisheng; He, Zhubing; Ang, Kah-Wee

    2015-09-07

    The energy band alignment between HfO{sub 2}/multilayer (ML)-MoS{sub 2} was characterized using high-resolution x-ray photoelectron spectroscopy. The HfO{sub 2} was deposited using an atomic layer deposition tool, and ML-MoS{sub 2} was grown by chemical vapor deposition. A valence band offset (VBO) of 1.98 eV and a conduction band offset (CBO) of 2.72 eV were obtained for the HfO{sub 2}/ML-MoS{sub 2} interface without any treatment. With CHF{sub 3} plasma treatment, a VBO and a CBO across the HfO{sub 2}/ML-MoS{sub 2} interface were found to be 2.47 eV and 2.23 eV, respectively. The band alignment difference is believed to be dominated by the down-shift in the core level of Hf 4d and up-shift in the core level of Mo 3d, or the interface dipoles, which caused by the interfacial layer in rich of F.

  15. Effects of local field and inherent strain in reflectance anisotropy spectra of A{sup III}B{sup V} semiconductors with naturally oxidized surfaces

    SciTech Connect

    Berkovits, V. L.; Kosobukin, V. A.; Gordeeva, A. B.

    2015-12-28

    Reflectance anisotropy (RA) spectra of naturally oxidized (001) surfaces of GaAs and InAs crystals are measured for photon energies from 1.5 up to 5.5 eV. The differential high-accuracy RA spectra reveal features substantially different from those caused by either a reconstruction of clean surface or a built-in near-surface electric field. Models of atomic structure with anisotropic transition layers of excess arsenic atoms specific for GaAs(001)/oxide and InAs(001)/oxide interfaces are proposed. In conformity with these models, a general theory of reflectance anisotropy is developed for semiconductor/oxide interfaces within the Green's function technique. The theory takes into account the combined effect of local field due to interface dipoles and of intrinsic near-surface strain of the crystal. Measured RA spectra are analyzed in the model of valence-bond dipoles occupying a rectangular lattice in a multilayer medium. Comparing the measured and calculated spectra, we conclude that RA spectra of oxidized GaAs(001) and InAs(001) surfaces are simultaneously influenced by interface and near-surface anisotropies. The former is responsible for the broad-band spectral features which are associated with polarizability of the valence bonds attached to As atoms at the crystal/oxide interface. The near-surface anisotropy is due to inherent uniaxial straining the near-surface region of crystal. The effect of strain on RA spectra is experimentally and theoretically substantiated for GaAs crystal wafers undergone a uniaxial applied stress. Basically, this work results in the following. It establishes the physical nature of different levels of RA spectra observed in a majority of papers, but never analyzed. It demonstrates how the studied features of RA spectra could be applied for optical characterization of strained interfaces and atomic layers.

  16. Bi-phase transition diagrams of metallic thin multilayers

    SciTech Connect

    Li, J.C.; Liu, W.; Jiang, Q. . E-mail: jiangq@jlu.edu.cn

    2005-02-01

    Phase transitions of metallic multilayers induced by differences in interface energy are considered thermodynamically, based on a thermodynamic model for interface energy and the Goldschmidt premise for lattice contraction. Bi-phase transition diagrams of Co/Cr, Zr/Nb, Ti/Nb and Ti/Al multilayers are constructed, which are in agreement with experimental results.

  17. Magneto-optic multilayers

    NASA Astrophysics Data System (ADS)

    Bader, Samuel D.

    1992-08-01

    Magneto-optical multilayers are of interest to the optical data storage community as a possible second-generation medium of the future. The important Co/Pt-superlattice system is introduced in this respect, and an extensive reference listing is provided to previous research. Magneto-optical modeling studies of Co/Pt are presented, and it is concluded that the interfacial Pt is magnetized and is magneto-optically active at the short wavelengths of interest (approximately 4 eV) for applications. Magneto-optics in the ultrathin limit are discussed, and an additivity law is presented and verified experimentally utilizing data for epitaxial Fe/Ag(111) superlattices. Finally, the surface magnetic anisotropy that provides the vertical easy axes of magnetization in candidate superlattice systems is discussed and illustrated experimentally using ultrathin epitaxial films of Fe grown on a variety of substrates. It is concluded that magneto-optic multilayers will provide many stimulating basic and applied challenges in the years ahead.

  18. Artificial multilayers and nanomagnetic materials

    PubMed Central

    SHINJO, Teruya

    2013-01-01

    The author has been actively engaged in research on nanomagnetic materials for about 50 years. Nanomagnetic materials are comprised of ferromagnetic systems for which the size and shape are controlled on a nanometer scale. Typical examples are ultrafine particles, ultrathin films, multilayered films and nano-patterned films. In this article, the following four areas of the author’s studies are described. (1) Mössbauer spectroscopic studies of nanomagnetic materials and interface magnetism. (2) Preparation and characterization of metallic multilayers with artificial superstructures. (3) Giant magnetoresistance (GMR) effect in magnetic multilayers. (4) Novel properties of nanostructured ferromagnetic thin films (dots and wires). A subject of particular interest in the author’s research was the artificially prepared multilayers consisting of metallic elements. The motivation to initiate the multilayer investigation is described and the physical properties observed in the artificial multilayers are introduced. The author’s research was initially in the field of pure physical science and gradually extended into applied science. His achievements are highly regarded not only from the fundamental point of view but also from the technological viewpoint. PMID:23391605

  19. Dimensional effects in Ni-Cr multilayered thin films

    NASA Astrophysics Data System (ADS)

    Stearns, M. B.; Lee, C. H.

    1987-04-01

    The dimensionality of Ni-Cr multilayered structures (MLS) was studied from the variation of the temperature dependence of the saturation magnetization Ms with the Ni layer thickness. Since NiCr alloys containing more than 12% Cr are nonmagnetic the thickness of the interfaces and pure Ni regions can be obtained from the measured value of Ms by modeling the MLS and determining the thickness of the pure Ni regions. Assuming that the pure Ni regions are isolated sufficiently to behave independently, comparison was made with several theories. It was found that the observed behavior is similar to that described by the theory of Davis and Keffer with a surface anisotropy energy of about 0.1 that of the exchange energy. This theory uses nonperiodic boundary conditions and assumes a surface anisotropy field which causes the partial pinning of the surface spins. The magnetization decrease calculated with this theory falls off less rapidly with film thickness than other theories. At high fields the magnetization and Curie temperatures of the MLS having 20 Å or less of Ni is found to be field dependent. This is indicative that a considerable amount of the magnetic moments arise from itinerant d electrons.

  20. Amorphous FeCoSiB for exchange bias coupled and decoupled magnetoelectric multilayer systems: Real-structure and magnetic properties

    SciTech Connect

    Hrkac, V.; Strobel, J.; Kienle, L.; Lage, E.; Köppel, G.; McCord, J.; Quandt, E.; Meyners, D.

    2014-10-07

    The effect of field annealing for exchanged biased multilayer films is studied with respect to the resultant structural and magnetic film properties. The presented multilayer stacks comprise repeating sequences of Ta/Cu/(1 1 1) textured antiferromagnetic Mn₇₀Ir₃₀ /amorphous ferromagnetic Fe₇₀.₂Co₇.₈Si₂B₁₀. Within the ferromagnetic layers crystalline filaments are observed. An additional Ta layer between the antiferromagnet and ferromagnet is used in order to investigate and separate the influence of the common Mn₇₀Ir₃₀/Fe₇₀.₂Co₇.₈Si₁₂B₁₀ interface on the occurring filaments and structural changes. In situ and ex situ transmission electron microscopy is used for a comprehensive structure characterization of multilayer stacks for selected temperature stages. Up to 250 °C, the multilayers are structurally unaltered and preserve the as-deposited condition. A deliberate increase to 350 °C exhibits different crystallization processes for the films, depending on the presence of crystal nuclei within the amorphous ferromagnetic layer. The influence of volume-to-surface ratio of the multilayer stacks to the crystallization process is emphasized by the comparison of in situ and ex situ investigations as the respective specimen thickness is changed. Complementary magnetic studies reveal a defined exchange bias obtained at the first annealing step and a decrease of total anisotropy field with partial crystallization after the subsequent annealing at 350 °C.

  1. Broken lattice-symmetry influence on electronic anisotropy and interface exchange-coupling-induced ferromagnetic state in TI thin films and heterostructures

    NASA Astrophysics Data System (ADS)

    Moodera, Jagadeesh

    2014-03-01

    Inducing an exchange gap locally on the Dirac surface states of a topological insulator (TI) is ideal for observing the predicted unique features such as the quantized topological magnetoelectric effect, half-integer quantized Hall effect, as well as to con?ne Majorana fermions. Our work experimentally demonstrated the proximity-induced interface ferromagnetism in a heterostructure combining a ferromagnetic insulator EuS layer with Bi2Se3, without introducing defects. An exchange gap was observed to be induced on the surface of the TI. Extensive magnetic and magneto-transport (magnetoresistance and anomalous Hall effect) investigation of the heterostructures, including synchrotron interfacial (XAS and XMCD measurements) studies have shown the emergence of a ferromagnetic phase in TI, which is a step forward to unveiling the above exotic properties. Also, to understand the intrinsic properties of TI it is necessary to correlate structure with the exotic electronic properties as well as interaction with other materials. Molecular beam epitaxy (MBE) ideally allows us to engineer the system whereas using synchrotron and electron diffraction based experimental techniques helps us to investigate with atomic resolution. We will elucidate our studies on well-defined TI films and heterostructure, and the role of imperfections on the symmetry of the material that leads to internal atomic ordering by the decoration of the defects. Charge transport and mobility are seen to relate with film growth strain and relaxation as well as display strong directional dependence on the defect geometry. Work done in collaboration with Peng Wei, Ferhat Katmis and others. NSF and ONR grants supported this work.

  2. Resolving the controversy of a possible relationship between perpendicular magnetic anisotropy and the magnetic damping parameter

    SciTech Connect

    Shaw, Justin M.; Nembach, Hans T.; Silva, T. J.

    2014-08-11

    We use broadband ferromagnetic resonance spectroscopy to systematically measure the Landau-Lifshitz damping parameter, perpendicular anisotropy, and the orbital moment asymmetry in Co{sub 90}Fe{sub 10}/Ni multilayers. No relationship is found between perpendicular magnetic anisotropy and the damping parameter in this material. However, inadequate accounting for inhomogeneous linewidth broadening, spin-pumping, and two-magnon scattering could give rise to an apparent relationship between anisotropy and damping. In contrast, the orbital-moment asymmetry and the perpendicular anisotropy are linearly proportional to each other. These results demonstrate a fundamental mechanism by which perpendicular anisotropy can be varied independently of the damping parameter.

  3. Magnetic and magneto-optic properties of sputtered Co/Ni multilayers

    NASA Astrophysics Data System (ADS)

    Zhang, Y. B.; He, P.; Woollam, J. A.; Shen, J. X.; Kirby, R. D.; Sellmyer, D. J.

    1994-05-01

    We have investigated the magnetic and magneto-optic properties of Co/Ni multilayers deposited on Ag and Au buffer layers. The samples with Au buffer layers show perpendicular magnetic anisotropy, but those with Ag buffer layers do not. The structure and degree of crystalline alignment of the buffer layer are evidently crucial to development of perpendicular magnetic anisotropy. We also present the results of polar Kerr rotation measurements as a function of wavelength and layer thickness of the multilayers.

  4. Perpendicular magnetic anisotropy and magneto-optical Kerr effect of vapor-deposited Co/Pt-layered structures

    NASA Astrophysics Data System (ADS)

    Zeper, W. B.; Greidanus, F. J. A. M.; Carcia, P. F.; Fincher, C. R.

    1989-06-01

    We prepared by vapor deposition at room temperature thin (500 Å) Co/Pt multilayers or layered structures directly onto glass or Si substrates. They show a preferential magnetization perpendicular to the film plane for Co thicknesses below 12 Å and a 100% perpendicular remanence for Co thicknesses below 4.5 Å. The magnetic anisotropy can be explained by an interface contribution to the anisotropy. We also investigated the magneto-optical (MO) polar Kerr effect of these multilayers. Because of their excellent magnetic properties and their potentially high oxidation and corrosion resistance, these Co/Pt-layered structures are very promising candidates for MO recording. The Kerr rotation θk at λ=820 nm for a 35×(4.0 Å Co+12.7 Å Pt)-layered structure, which has 100% magnetic remanence, is modest (-0.12°), but the reflectivity R is high (70%), which results in a respectable figure of merit Rθ2k. Furthermore, the Kerr effect increases towards shorter wavelengths and thus favors future higher-density recording.

  5. Improved Reflectance and Stability of Mo/Si Multilayers

    SciTech Connect

    Bajt, S.; Almeda, J.; Naree, T.; Clift, M.; Folta, A.; Kauffman, B.; Spiller, E.

    2001-10-22

    Commercial EUV lithographic systems require multilayers with higher reflectance and better stability then that published to date. Interface-engineered Mo/Si multilayers with 70% reflectance at 13.5 nm wavelength (peak width of 0.545 nm) and 71% at 12.7 nm wavelength (peak width of 0.49 nm) were developed. These results were achieved with 50 bilayers. These new multilayers consist of Mo and Si layers separated by thin boron carbide layers. Depositing boron carbide on interfaces leads to reduction in silicide formation on the Mo-on-Si interfaces. Bilayer contraction is reduced by 30% implying that there is less intermixing of Mo and Si to form silicide. As a result the Mo-on-Si interfaces are sharper in interface-engineered multilayers than in standard Mo/Si multilayers. The optimum boron carbide thicknesses have been determined and appear to be different for Mo-on-Si and Si-on-Mo interfaces. The best results were obtained with 0.4 nm thick boron carbide layer on the Mo-on-Si interface and 0.25 nm thick boron carbide layer on the Si-on-Mo interface. Increase in reflectance is consistent with multilayers with sharper and smoother interfaces. A significant improvement in oxidation resistance of EUV multilayers has been achieved with ruthenium terminated Mo/Si multilayers. The best capping layer design consists of a Ru layer separated from the last Si layer by a boron carbide layer. This design achieves high reflectance and the best oxidation resistance in a water vapor (i.e. oxidation) environment. Electron beam exposures of 4.5 hours in the presence of 5x10{sup -7} torr water vapor partial pressure show no measurable reflectance loss and no increase in the oxide thickness of Ru terminated multilayers. Longer exposures in different environments are necessary to test lifetime stability of many years.

  6. Magnetoelectric coupling at the interface of BiFeO3/La0.7Sr0.3MnO3 multilayers

    SciTech Connect

    Calderon, M. J.; Liang, Shuhua; Yu, Rong; Salafranca, Juan; Scalapino, D. J.; Dong, Shuai; Yunoki, Seiji; Brey, L.; Moreo, Adriana; Dagotto, Elbio R

    2011-01-01

    Electric-field controlled exchange bias in a heterostructure composed of the ferromagnetic manganite La0.7Sr0.3MO3 and the ferroelectric antiferromagnetic BiFeO3 has recently been demonstrated experimentally. By means of a model Hamiltonian, we provide a possible explanation for the origin of this magnetoelectric coupling. We find, in agreement with experimental results, a net ferromagnetic moment at the BiFeO3 interface. The induced ferromagnetic moment is the result of the competition between the eg-electron double exchange and the t2g-spin antiferromagnetic superexchange that dominates in bulk BiFeO3. The balance of these simultaneous ferromagnetic and antiferromagnetic tendencies is strongly affected by the interfacial electronic charge density, which, in turn, can be controlled by the BiFeO3 ferroelectric polarization.

  7. Growth-surface-driven anisotropy and spontaneous layering in vapor-deposited alloy films

    NASA Astrophysics Data System (ADS)

    Shapiro, Alexander Leon

    Perpendicular magnetic anisotropy (PMA) developed on the growth surface has been studied in a number of vapor-deposited alloy film systems. Epitaxial (100), (110), (100) and polycrystalline CoXPt1-X ,CoX Pt1-X 1-YSiY, and NiXPt1-X alloy films have been deposited by co-evaporation over a range of growth temperatures from -50°C to 800°C. Growth induced PMA is reported in samples deposited at temperatures between 200--400°C. This PMA is closely correlated with evidence for clustering of the magnetic species. A model of the magnetic species clustered into thin platelets, with the interfaces between the platelets and the Pt matrix providing the source of PMA, is presented. Magnetic moment and Magneto-Optic Kerr Effect (MOKE) results support an interpretation of interfaces, like spontaneous incoherent multilayer fragments, perpendicular to the growth direction. Deposition rate experiments show that surface atomic mobility plays an important role in the development of platelets and PMA. Results from annealing experiments indicate that anisotropy and clustering are not bulk equilibrium phenomena, but are trapped into the growing surface. The presence of surface atomic mobility then at intermediate deposition temperatures along with a lack of bulk atomic mobility allow platelets on the surface to be trapped into the bulk by succeeding deposition layers. Studies of ternary Co-Pt-Si alloys, in which Si acts to slow surface atomic mobility, confirm that the mobility of adatoms on the surface is critical to the formation of platelet structures and PMA. The clustering and PMA found in Ni-Pt alloys remove magnetic interaction as a source of platelet formation, leading to surface segregation and reconstruction as likely to be critical to the development of PMA. The lack of clustering and anisotropy seen in (100) oriented NiPt films is correlated with a non-flat surface reconstruction which disrupts the formation of platelets.

  8. Magnetic multilayer structure

    DOEpatents

    Herget, Philipp; O'Sullivan, Eugene J.; Romankiw, Lubomyr T.; Wang, Naigang; Webb, Bucknell C.

    2016-07-05

    A mechanism is provided for an integrated laminated magnetic device. A substrate and a multilayer stack structure form the device. The multilayer stack structure includes alternating magnetic layers and diode structures formed on the substrate. Each magnetic layer in the multilayer stack structure is separated from another magnetic layer in the multilayer stack structure by a diode structure.

  9. Optimization of the random multilayer structure to break the random-alloy limit of thermal conductivity

    SciTech Connect

    Wang, Yan; Gu, Chongjie; Ruan, Xiulin

    2015-02-16

    A low lattice thermal conductivity (κ) is desired for thermoelectrics, and a highly anisotropic κ is essential for applications such as magnetic layers for heat-assisted magnetic recording, where a high cross-plane (perpendicular to layer) κ is needed to ensure fast writing while a low in-plane κ is required to avoid interaction between adjacent bits of data. In this work, we conduct molecular dynamics simulations to investigate the κ of superlattice (SL), random multilayer (RML) and alloy, and reveal that RML can have 1–2 orders of magnitude higher anisotropy in κ than SL and alloy. We systematically explore how the κ of SL, RML, and alloy changes relative to each other for different bond strength, interface roughness, atomic mass, and structure size, which provides guidance for choosing materials and structural parameters to build RMLs with optimal performance for specific applications.

  10. A multilayer sonic film

    NASA Astrophysics Data System (ADS)

    Munteanu, L.; Chiroiu, V.; Sireteanu, T.; Dumitriu, D.

    2015-10-01

    A non-periodic multilayer film was analyzed to show that, despite its non-periodicity, the film exhibits full band-gaps and localized modes at its interfaces, as well as in the sonic composites. The film consists of alternating layers of two different materials that follow a triadic Cantor sequence. The Cantor structure shows extremely low thresholds for subharmonic generation of ultrasonic waves, compared with homogeneous and periodic structures. The coupling between the extended-mode (phonon) and the localized-mode (fracton) vibration regimes explains the generation of full band-gaps, for which there are no propagating Lamb waves. The large enhancement of the nonlinear interaction results from a more favorable frequency and spatial matching of coupled modes. A full band-gap that excludes Love waves is also analyzed.

  11. Multilayer optical dielectric coating

    DOEpatents

    Emmett, John L.

    1990-01-01

    A highly damage resistant, multilayer, optical reflective coating includes alternating layers of doped and undoped dielectric material. The doping levels are low enough that there are no distinct interfaces between the doped and undoped layers so that the coating has properties nearly identical to the undoped material. The coating is fabricated at high temperature with plasma-assisted chemical vapor deposition techniques to eliminate defects, reduce energy-absorption sites, and maintain proper chemical stoichiometry. A number of differently-doped layer pairs, each layer having a thickness equal to one-quarter of a predetermined wavelength in the material are combined to form a narrowband reflective coating for a predetermined wavelength. Broadband reflectors are made by using a number of narrowband reflectors, each covering a portion of the broadband.

  12. Anomalous enhancement in interfacial perpendicular magnetic anisotropy through uphill diffusion

    NASA Astrophysics Data System (ADS)

    Das, Tanmay; Kulkarni, Prabhanjan D.; Purandare, S. C.; Barshilia, Harish C.; Bhattacharyya, Somnath; Chowdhury, Prasanta

    2014-06-01

    We observed interfacial chemical sharpening due to uphill diffusion in post annealed ultrathin multilayer stack of Co and Pt, which leads to enhanced interfacial perpendicular magnetic anisotropy (PMA). This is surprising as these elements are considered as perfectly miscible. This chemical sharpening was confirmed through quantitative energy dispersive x-ray (EDX) spectroscopy and intensity distribution of images taken on high angle annular dark field (HAADF) detector in Scanning Transmission Electron Microscopic (STEM) mode. This observation demonstrates an evidence of miscibility gap in ultrathin coherent Co/Pt multilayer stacks.

  13. Residual strain and texture in free-standing nanoscale Cu-Nb multilayers

    SciTech Connect

    Aydiner, C. C.; Brown, D. W.; Misra, A.; Mara, N. A.; Wang, Y.-C.; Wall, J. J.; Almer, J.

    2007-10-15

    We investigate the residual strains in a free-standing Cu/Nb multilayer of 30 nm nominal layer thickness with synchrotron x-rays. This material system is characterized by columnar grains of Cu and Nb with incoherent interfaces and a sharp physical-vapor-deposition texture. High energy x-rays were used with an area detector along with multiple sample rotations to yield diffraction strain components in a very large number of directions. Due to the texture and the elastic anisotropy of constituents, observed diffraction strains cannot be derived from a single strain tensor (also known as linear sin{sup 2} {psi}). Orientation-dependent diffraction strain modeling is utilized with a Vook-Witt micromechanical model. Obtained phase-resolved in-plane stress magnitudes are -515 MPa in Nb and +513 MPa in Cu, satisfying force equilibrium within experimental errors. The stresses of this magnitude will certainly influence the mechanical behavior of the multilayer upon further loading. The Vook-Witt model describes the Nb diffraction strains very well, and thereby provides information on the stress distribution in crystallites as a function of their orientation. On the other hand, the same level of agreement with the Vook-Witt model has not been achieved for Cu diffraction strains.

  14. Residual strain and texture in free-standing nanoscal Cu-Nb multilayers.

    SciTech Connect

    Aydiner, C. C.; Brown, D. W.; Misra, A.; Wang, Y. -C.; Wall, J.; Mara, N.; Almer, J.; LANL; National Cheng Kung Univ.

    2007-10-15

    We investigate the residual strains in a free-standing Cu/Nb multilayer of 30 nm nominal layer thickness with synchrotron x-rays. This material system is characterized by columnar grains of Cu and Nb with incoherent interfaces and a sharp physical-vapor-deposition texture. High energy x-rays were used with an area detector along with multiple sample rotations to yield diffraction strain components in a very large number of directions. Due to the texture and the elastic anisotropy of constituents, observed diffraction strains cannot be derived from a single strain tensor (also known as linear sin{sup 2} {psi}). Orientation-dependent diffraction strain modeling is utilized with a Vook-Witt micromechanical model. Obtained phase-resolved in-plane stress magnitudes are -515 MPa in Nb and +513 MPa in Cu, satisfying force equilibrium within experimental errors. The stresses of this magnitude will certainly influence the mechanical behavior of the multilayer upon further loading. The Vook-Witt model describes the Nb diffraction strains very well, and thereby provides information on the stress distribution in crystallites as a function of their orientation. On the other hand, the same level of agreement with the Vook-Witt model has not been achieved for Cu diffraction strains.

  15. Strain-induced magneto-optical anisotropy in epitaxial hcp Co films

    NASA Astrophysics Data System (ADS)

    Arregi, J. A.; González-Díaz, J. B.; Idigoras, O.; Berger, A.

    2015-11-01

    We investigate the existence and origin of magneto-optical anisotropy in epitaxial hcp Co films. Our results show that a significant magneto-optical anisotropy exists in our samples and, more importantly, they reveal that its amplitude is directly correlated with epitaxial strain. We find a linear coefficient of 16.8 % magneto-optical anisotropy per every 1% epitaxial strain, which is in stark contrast to an isotropic magneto-optical coupling factor Q , a very frequent and common assumption in magneto-optics of metallic thin films and multilayers. In addition, the Co films exhibit a similar strain-induced increase of the magnetocrystalline anisotropy energy, evidencing the fact that both magneto-optical anisotropy and magnetocrystalline anisotropy are dependent on the modification of the spin-orbit coupling introduced by anisotropic lattice distortions.

  16. Characterization of Mo/Si multilayer growth on stepped topographies

    SciTech Connect

    Boogaard, A. J. R. vcan den; Louis, E.; Zoethout, E.; Goldberg, K. A.; Bijkerk, F.

    2011-08-31

    Mo/Si multilayer mirrors with nanoscale bilayer thicknesses have been deposited on stepped substrate topographies, using various deposition angles. The multilayer morphology at the stepedge region was studied by cross section transmission electron microscopy. A transition from a continuous- to columnar layer morphology is observed near the step-edge, as a function of the local angle of incidence of the deposition flux. Taking into account the corresponding kinetics and anisotropy in layer growth, a continuum model has been developed to give a detailed description of the height profiles of the individual continuous layers. Complementary optical characterization of the multilayer system using a microscope operating in the extreme ultraviolet wavelength range, revealed that the influence of the step-edge on the planar multilayer structure is restricted to a region within 300 nm from the step-edge.

  17. US-Japan seminar on magnetic multilayered structures held in Kauai, Hawaii on 15-17 May 1992

    SciTech Connect

    Not Available

    1992-05-17

    This seminar included the following topics: Advancement in soft magnetic materials by means of multilayering, Elastic moduli of metallic multilayered films measured by Brillouin Scattering method, Structural aspects of the superlattices under high pressure, Structural influence on the magnetic anisotropy of Co/Pd superlattices, Low dimensional magnetic and structural effects in single crystals grown by molecular beam epitaxy, Polarized neutron reflection and diffraction from magnetic superlattices, and Nuclear magnetic resonance studies of magnetic multilayers.

  18. Ultra-thin multilayer capacitors.

    SciTech Connect

    Renk, Timothy Jerome; Monson, Todd C.

    2009-06-01

    The fabrication of ultra-thin lanthanum-doped lead zirconium titanate (PLZT) multilayer ceramic capacitors (MLCCs) using a high-power pulsed ion beam was studied. The deposition experiments were conducted on the RHEPP-1 facility at Sandia National Laboratories. The goal of this work was to increase the energy density of ceramic capacitors through the formation of a multilayer device with excellent materials properties, dielectric constant, and standoff voltage. For successful device construction, there are a number of challenging requirements including achieving correct stoichiometric and crystallographic composition of the deposited PLZT, as well as the creation of a defect free homogenous film. This report details some success in satisfying these requirements, although 900 C temperatures were necessary for PLZT perovskite phase formation. These temperatures were applied to a previously deposited multi-layer film which was then post-annealed to this temperature. The film exhibited mechanical distress attributable to differences in the coefficient of thermal expansion (CTE) of the various layers. This caused significant defects in the deposited films that led to shorts across devices. A follow-on single layer deposition without post-anneal produced smooth layers with good interface behavior, but without the perovskite phase formation. These issues will need to be addressed in order for ion beam deposited MLCCs to become a viable technology. It is possible that future in-situ heating during deposition may address both the CTE issue, and result in lowered processing temperatures, which in turn could raise the probability of successful MLCC formation.

  19. Néel coupling in Co/Cu/Co stripes with unidirectional interface roughness

    NASA Astrophysics Data System (ADS)

    Davydenko, A. V.; Pustovalov, E. V.; Ognev, A. V.; Kozlov, A. G.; Chebotkevich, L. A.; Han, X. F.

    2015-03-01

    We investigate the influence of interlayer Néel coupling on the magnetization reversal processes in epitaxial Co(5 nm)/Cu(5 nm)/Co(5 nm) stripes by experimental methods and computer modeling. The stripes with a width of 900 and 1800 nm were formed on a step-bunched Si(111) substrate by molecular beam epitaxy and focused ion beam etching. Uniaxial magnetic anisotropy with the easy axis of the magnetization along the steps is induced in the stripes by the steps of the Si(111) substrate. The stepped structure of the layers in the multilayered stripes reproduces the morphology of the Si(111) substrate. Néel coupling between the Co layers is realized due to the unidirectional roughness at the Co/Cu interfaces caused by the steps of the substrate. Interlayer Néel coupling at the interfaces overcomes antiparallel magnetostatic interaction realized through the sides of the Co layers in the trilayered stripes. We used a modified Néel model in the simulation of the magnetization reversal in the multilayered system with unidirectional interface roughness. The surface energy of Néel coupling was spatially varied against the direction of the magnetization relative to the step edge. The results of micromagnetic simulations of the Co/Cu/Co stripes with spatially non-uniform and averaged surface energies of interlayer Néel coupling are compared and discussed.

  20. Magnetic pinning in superconductor-ferromagnet multilayers

    SciTech Connect

    Bulaevskii, L. N.; Chudnovsky, E. M.; Maley, M. P.

    2000-05-01

    We argue that superconductor/ferromagnet multilayers of nanoscale period should exhibit strong pinning of vortices by the magnetic domain structure in magnetic fields below the coercive field when ferromagnetic layers exhibit strong perpendicular magnetic anisotropy. The estimated maximum magnetic pinning energy for single vortex in such a system is about 100 times larger than the pinning energy by columnar defects. This pinning energy may provide critical currents as high as 10{sup 6}-10{sup 7} A/cm{sup 2} at high temperatures (but not very close to T{sub c}) at least in magnetic fields below 0.1 T. (c) 2000 American Institute of Physics.

  1. Growth and characterisation of uranium multilayers

    NASA Astrophysics Data System (ADS)

    Springell, Ross

    plane of the film to samples displaying perpendicular magnetic anisotropy (PMA), at a gadolinium layer thickness of 5A. This transition could be achieved for thicker Gd layers if the thickness of the U layers were increased. A finite-size scaling effect was observed in a gadolinium layer thickness dependent study of the Curie temperature, indicating a transition from three to two dimensional behaviour for very thin Gd layers. Polarised neutron reflectivity spectra were taken in the specular geometry at magnetic saturation, and were simulated with separate, reduced moment and bulk moment ferromagnetic layers for U/Fe and U/Co samples and a simple bilayer structure for U/Gd samples. This simultaneous measurement of both the physical composition and bulk magnetisation measurements supported results obtained by X-ray reflectivity and magnetometry. The hybridisation of the electronic states in U/Fe and U/Gd resulted in an induced polarisation, detected using element selective techniques. X-ray magnetic circular dichroism measurements at the U Mrv and My edges were used to investigate the spin and orbital components of the uranium magnetic moment and a total magnetic moment on the U site of 0.1/b for the case of U/Fe multilayers, 0.01/zb in U/Gd samples and a signal only barely detectable above the statistical noise in the U/Co system were revealed. A uranium layer thickness dependent study of the magnetic moment values was used to indirectly deduce the profile of uranium magnetisation within the layers. X-ray resonant magnetic reflectivity measurements provided a depth dependent measure of the induced U 5f moment for selected U/Fe samples, which indicated a more complicated interfacial structure than that deduced by X- ray and neutron reflectivity techniques and showed that the majority of the U 5f moment was located at the interface region.

  2. Film bonded fuel cell interface configuration

    DOEpatents

    Kaufman, Arthur; Terry, Peter L.

    1985-01-01

    An improved interface configuration for use between adjacent elements of a fuel cell stack. The interface is impervious to gas and liquid and provides resistance to corrosion by the electrolyte of the fuel cell. A multi-layer arrangement for the interface provides bridging electrical contact with a hot-pressed resin filling the void space.

  3. Interfacial magnetic anisotropy from a 3-dimensional Rashba substrate

    NASA Astrophysics Data System (ADS)

    Li, Junwen; Haney, Paul M.

    2016-07-01

    We study the magnetic anisotropy which arises at the interface between a thin film ferromagnet and a 3-d Rashba material. We use a tight-binding model to describe the bilayer, and the 3-d Rashba material characterized by the spin-orbit strength α and the direction of broken bulk inversion symmetry n ̂ . We find an in-plane uniaxial anisotropy in the z ̂ × n ̂ direction, where z ̂ is the interface normal. For realistic values of α, the uniaxial anisotropy is of a similar order of magnitude as the bulk magnetocrystalline anisotropy. Evaluating the uniaxial anisotropy for a simplified model in 1-d shows that for small band filling, the in-plane easy axis anisotropy scales as α4 and results from a twisted exchange interaction between the spins in the 3-d Rashba material and the ferromagnet. For a ferroelectric 3-d Rashba material, n ̂ can be controlled with an electric field, and we propose that the interfacial magnetic anisotropy could provide a mechanism for electrical control of the magnetic orientation.

  4. Multilayer Insulation Material Guidelines

    NASA Technical Reports Server (NTRS)

    Finckenor, M. M.; Dooling, D.

    1999-01-01

    Multilayer Insulation Material Guidelines provides data on multilayer insulation materials used by previous spacecraft such as Spacelab and the Long-Duration Exposure Facility and outlines other concerns. The data presented in the document are presented for information only. They can be used as guidelines for multilayer insulation design for future spacecraft provided the thermal requirements of each new design and the environmental effects on these materials are taken into account.

  5. Fabrication of multilayer nanowires

    NASA Astrophysics Data System (ADS)

    Kaur, Jasveer; Singh, Avtar; Kumar, Davinder; Thakur, Anup; Kaur, Raminder

    2016-05-01

    Multilayer nanowires were fabricated by potentiostate ectrodeposition template synthesis method into the pores of polycarbonate membrane. In present work layer by layer deposition of two different metals Ni and Cu in polycarbonate membrane having pore size of 600 nm were carried out. It is found that the growth of nanowires is not constant, it varies with deposition time. Scanning electron microscopy (SEM) is used to study the morphology of fabricated multilayer nanowires. An energy dispersive X-ray spectroscopy (EDS) results confirm the composition of multilayer nanowires. The result shows that multilayer nanowires formed is dense.

  6. Mobility anisotropy in monolayer black phosphorus due to scattering by charged impurities

    NASA Astrophysics Data System (ADS)

    Liu, Yue; Low, Tony; Ruden, P. Paul

    2016-04-01

    We explore the charged-impurity-scattering-limited mobility of electrons and holes in monolayer black phosphorus (BP), a highly anisotropic material. Taking full account of the anisotropic electronic structure in effective mass approximation, the zero-temperature momentum relaxation time and the charge carrier mobility are calculated based on the Boltzmann transport equation. For carrier densities accessible in experiments, we obtain anisotropy ratios of 3-4. These results are somewhat larger than mobility anisotropy ratios determined experimentally for multilayer BP samples, but due to the complex dependence of the scattering rates on the anisotropy, they are strikingly smaller than the effective mass ratios.

  7. Structural and magnetic properties of granular CoPd multilayers

    NASA Astrophysics Data System (ADS)

    Vivas, L. G.; Figueroa, A. I.; Bartolomé, F.; Rubín, J.; García, L. M.; Deranlot, C.; Petroff, F.; Ruiz, L.; González-Calbet, J. M.; Brookes, N. B.; Wilhelm, F.; Rogalev, A.; Bartolomé, J.

    2016-02-01

    Multilayers of bimetallic CoPd alloyed and assembled nanoparticles, prepared by room temperature sequential sputtering deposition on amorphous alumina, were studied by means of high-resolution transmission electron microscopy, x-ray diffraction, SQUID-based magnetometry and x-ray magnetic circular dichroism. Alloying between Co and Pd in these nanoparticles gives rise to a high perpendicular magnetic anisotropy. Their magnetic properties are temperature dependent: at low temperature, the multilayers are ferromagnetic with a high coercive field; at intermediate temperature the behavior is of a soft-ferromagnet, and at higher temperature, the perpendicular magnetic anisotropy in the nanoparticles disappears. The magnetic orbital moment to spin moment ratio is enhanced compared with Co bare nanoparticles and Co fcc bulk.

  8. Magnetic properties of sputtered Permalloy/molybdenum multilayers

    SciTech Connect

    Romera, M.; Ciudad, D.; Maicas, M.; Aroca, C.

    2011-10-15

    In this work, we report the magnetic properties of sputtered Permalloy (Py: Ni{sub 80}Fe{sub 20})/molybdenum (Mo) multilayer thin films. We show that it is possible to maintain a low coercivity and a high permeability in thick sputtered Py films when reducing the out-of-plane component of the anisotropy by inserting thin film spacers of a non-magnetic material like Mo. For these kind of multilayers, we have found coercivities which are close to those for single layer films with no out-of-plane anisotropy. The coercivity is also dependent on the number of layers exhibiting a minimum value when each single Py layer has a thickness close to the transition thickness between Neel and Bloch domain walls.

  9. Anisotropy in Magnetism

    NASA Astrophysics Data System (ADS)

    Baberschke, Klaus

    The enormous research on magnetic properties of ultrathin films and nanostructures produces also new activities in the fundamental understanding of the magnetic anisotropy energy (MAE) and the anisotropy of the orbital magnetic momentapprox 0.05\\ Å. This small change in structure and symmetry increa ses the MAE by several orders of magnitude and lifts the quenching of the orbital moment. Increases of 20-30 % of the orbital moment mu _{L} are observed. This experimental finding is confirmed by full relativistic ab initio calculations. Various experiments deliver the full temperature dependence of all MAE contributions. The temperature dependence remains a challenge for the theory in itine rant magnetism.

  10. Killing vectors and anisotropy

    SciTech Connect

    Krisch, J. P.; Glass, E. N.

    2009-08-15

    We consider an action that can generate fluids with three unequal stresses for metrics with a spacelike Killing vector. The parameters in the action are directly related to the stress anisotropies. The field equations following from the action are applied to an anisotropic cosmological expansion and an extension of the Gott-Hiscock cosmic string.

  11. A refined model for characterizing x-ray multilayers

    SciTech Connect

    Oren, A.L.; Henke, B.L.

    1987-12-01

    The ability to quickly and accurately characterize arbitrary multilayers is very valuable for not only can we use the characterizations to predict the reflectivity of a multilayer for any soft x-ray wavelength, we also can generalize the results to apply to other multilayers of the same type. In addition, we can use the characterizations as a means of evaluating various sputtering environments and refining sputtering techniques to obtain better multilayers. In this report we have obtained improved characterizations for sample molybdenum-silicon and vanadium-silicon multilayers. However, we only examined five crystals overall, so the conclusions that we could draw about the structure of general multilayers is limited. Research involving many multilayers manufactured under the same sputtering conditions is clearly in order. In order to best understand multilayer structures it may be necessary to further refine our model, e.g., adopting a Gaussian form for the interface regions. With such improvements we can expect even better agreement with experimental values and continued concurrence with other characterization techniques. 18 refs., 30 figs., 7 tabs.

  12. Reflection of spin waves from a ferromagnetic multilayer with interfacial coupling of finite strength (reflection of spin waves from multilayer)

    NASA Astrophysics Data System (ADS)

    Gorobets, Yuri; Reshetnyak, Sergey

    2008-03-01

    The reflection coefficient of bulk spin waves from a ferromagnetic multilayer with periodically modulated parameters of the exchange interaction, the uniaxial magnetic anisotropy and the saturation magnetization (a magnonic crystal) is calculated. The dependence of the reflection coefficient upon the spin wave frequency and the values of the bias magnetic field, the parameter of interfacial coupling, and the internal structure of the unit cell are investigated.

  13. Resonant Raman spectroscopy of twisted multilayer graphene.

    PubMed

    Wu, Jiang-Bin; Zhang, Xin; Ijäs, Mari; Han, Wen-Peng; Qiao, Xiao-Fen; Li, Xiao-Li; Jiang, De-Sheng; Ferrari, Andrea C; Tan, Ping-Heng

    2014-01-01

    Graphene and other two-dimensional crystals can be combined to form various hybrids and heterostructures, creating materials on demand with properties determined by the interlayer interaction. This is the case even for a single material, where multilayer stacks with different relative orientation have different optical and electronic properties. Probing and understanding the interface coupling is thus of primary importance for fundamental science and applications. Here we study twisted multilayer graphene flakes with multi-wavelength Raman spectroscopy. We find a significant intensity enhancement of the interlayer coupling modes (C peaks) due to resonance with new optically allowed electronic transitions, determined by the relative orientation of the layers. The interlayer coupling results in a Davydov splitting of the C peak in systems consisting of two equivalent graphene multilayers. This allows us to directly quantify the interlayer interaction, which is much smaller compared with Bernal-stacked interfaces. This paves the way to the use of Raman spectroscopy to uncover the interface coupling of two-dimensional hybrids and heterostructures. PMID:25382099

  14. Technique for etching monolayer and multilayer materials

    DOEpatents

    Bouet, Nathalie C. D.; Conley, Raymond P.; Divan, Ralu; Macrander, Albert

    2015-10-06

    A process is disclosed for sectioning by etching of monolayers and multilayers using an RIE technique with fluorine-based chemistry. In one embodiment, the process uses Reactive Ion Etching (RIE) alone or in combination with Inductively Coupled Plasma (ICP) using fluorine-based chemistry alone and using sufficient power to provide high ion energy to increase the etching rate and to obtain deeper anisotropic etching. In a second embodiment, a process is provided for sectioning of WSi.sub.2/Si multilayers using RIE in combination with ICP using a combination of fluorine-based and chlorine-based chemistries and using RF power and ICP power. According to the second embodiment, a high level of vertical anisotropy is achieved by a ratio of three gases; namely, CHF.sub.3, Cl.sub.2, and O.sub.2 with RF and ICP. Additionally, in conjunction with the second embodiment, a passivation layer can be formed on the surface of the multilayer which aids in anisotropic profile generation.

  15. Tuning of the nucleation field in nanowires with perpendicular magnetic anisotropy

    SciTech Connect

    Kimling, Judith; Gerhardt, Theo; Kobs, Andre; Vogel, Andreas; Peter Oepen, Hans; Merkt, Ulrich; Meier, Guido; Wintz, Sebastian; Im, Mi-Young; Fischer, Peter

    2013-04-28

    We report on domain nucleation in nanowires consisting of Co/Pt multilayers with perpendicular magnetic anisotropy that are patterned by electron-beam lithography, sputter deposition, and lift-off processing. It is found that the nucleation field can be tuned by changing the geometry of the wire ends. A reduction of the nucleation field by up to 60% is achieved when the wire ends are designed as tips. This contrasts with the behavior of wires with in-plane anisotropy where the nucleation field increases when triangular-pointed ends are used. In order to clarify the origin of the reduction of the nucleation field, micromagnetic simulations are employed. The effect cannot be explained by the lateral geometrical variation but is attributable to a local reduction of the perpendicular anisotropy caused by shadowing effects due to the resist mask during sputter deposition of the multilayer.

  16. Tunnel magnetoresistance and spin torque switching in MgO-based magnetic tunnel junctions with a Co/Ni multilayer electrode

    NASA Astrophysics Data System (ADS)

    Moriyama, Takahiro; Gudmundsen, Theodore J.; Huang, Pinshane Y.; Liu, Luqiao; Muller, David A.; Ralph, Daniel C.; Buhrman, Robert A.

    2010-08-01

    We have fabricated MgO-barrier magnetic tunnel junctions with a Co/Ni switching layer to reduce the demagnetizing field via interface anisotropy. With a fcc-(111) oriented Co/Ni multilayer combined with an FeCoB insertion layer, the demagnetizing field is 2 kOe and the tunnel magnetoresistance can be as high as 106%. Room-temperature measurements of spin-torque switching are in good agreement with predictions for a reduced critical current associated with the small demagnetization for antiparallel-to-parallel switching. For parallel-to-antiparallel switching the small demagnetization field causes spatially nonuniform reversal nucleated at the sample ends, with a low energy barrier but a higher switching current.

  17. Multilayer dielectric diffraction gratings

    DOEpatents

    Perry, Michael D.; Britten, Jerald A.; Nguyen, Hoang T.; Boyd, Robert; Shore, Bruce W.

    1999-01-01

    The design and fabrication of dielectric grating structures with high diffraction efficiency used in reflection or transmission is described. By forming a multilayer structure of alternating index dielectric materials and placing a grating structure on top of the multilayer, a diffraction grating of adjustable efficiency, and variable optical bandwidth can be obtained. Diffraction efficiency into the first order in reflection varying between 1 and 98 percent has been achieved by controlling the design of the multilayer and the depth, shape, and material comprising the grooves of the grating structure. Methods for fabricating these gratings without the use of ion etching techniques are described.

  18. Multilayer dielectric diffraction gratings

    DOEpatents

    Perry, M.D.; Britten, J.A.; Nguyen, H.T.; Boyd, R.; Shore, B.W.

    1999-05-25

    The design and fabrication of dielectric grating structures with high diffraction efficiency used in reflection or transmission is described. By forming a multilayer structure of alternating index dielectric materials and placing a grating structure on top of the multilayer, a diffraction grating of adjustable efficiency, and variable optical bandwidth can be obtained. Diffraction efficiency into the first order in reflection varying between 1 and 98 percent has been achieved by controlling the design of the multilayer and the depth, shape, and material comprising the grooves of the grating structure. Methods for fabricating these gratings without the use of ion etching techniques are described. 7 figs.

  19. Emergence of noncollinear anisotropies from interfacial magnetic frustration in exchange-bias systems.

    SciTech Connect

    Jimenez, E.; Camarero, J.; Sort, J.; Nogues, J.; Mikuszeit, N.; Garcia-Martin, J. M.; Hoffmann, A.; Dieny, B.; Miranda, R.; Univ. Autonoma de Madrid; Univ. Autonoma de Barcelona; Inst. de Microelectronica de Madrid; SPINTEC

    2009-01-01

    Exchange bias, referred to the interaction between a ferromagnet (FM) and an antiferromagnet (AFM), is a fundamental interfacial magnetic phenomenon, which is key to current and future applications. The effect was discovered half a century ago, and it is well established that the spin structures at the FM/AFM interface play an essential role. However, currently, ad hoc phenomenological anisotropies are often postulated without microscopic justification or sufficient experimental evidence to address magnetization-reversal behavior in exchange-bias systems. We advance toward a detailed microscopic understanding of the magnetic anisotropies in exchange-bias FM/AFM systems by showing that symmetry-breaking anisotropies leave a distinct fingerprint in the asymmetry of the magnetization reversal and we demonstrate how these emerging anisotropies are correlated with the intrinsic anisotropy. Angular and vectorial resolved Kerr hysteresis loops from FM/AFM bilayers with varying degree of ferromagnetic anisotropy reveal a noncollinear anisotropy, which becomes important for ferromagnets with vanishing intrinsic anisotropy. Numerical simulations show that this anisotropy naturally arises from the inevitable spin frustration at an atomically rough FM/AFM interface. As a consequence, we show in detail how the differences observed for different materials during magnetization reversal can be understood in general terms as originating from the interplay between interfacial frustration and intrinsic anisotropies. This understanding will certainly open additional avenues to tailor future advanced magnetic materials.

  20. Atomic simulations of Fe/Ni multilayer nanocomposites on the radiation damage resistance

    NASA Astrophysics Data System (ADS)

    Chen, Feida; Tang, Xiaobin; Yang, Yahui; Huang, Hai; Liu, Jian; Li, Huan; Chen, Da

    2016-01-01

    We investigated the radiation damage resistance of the Fe/Ni multilayer nanocomposites by molecular dynamics. In the paper, two types of interface configuration with different orientation relationship were constructed. Their morphology evolution and number of final surviving defects induced by cascade collisions were discussed respectively. The interfaces of the two types of Fe/Ni multilayers kept distinct during the long-time relaxation before cascade. The comparison of surviving defects number produced by PKA with 5 keV at 100 K showed that the Fe/Ni multilayers have greater radiation tolerance than that of the bulk materials. However, the orientation relationship of the interface influences the defects self-healing capability greatly when the multilayers are irradiated by higher energy PKA or at high temperature. The radiation damage resistance of the Nishiyama - Wassermann type Fe/Ni multilayers which have larger lattice misfit is more stable than that of the Kurdjumov - Sachs type.

  1. Pinned orbital moments – A new contribution to magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Audehm, P.; Schmidt, M.; Brück, S.; Tietze, T.; Gräfe, J.; Macke, S.; Schütz, G.; Goering, E.

    2016-05-01

    Reduced dimensionality and symmetry breaking at interfaces lead to unusual local magnetic configurations, such as glassy behavior, frustration or increased anisotropy. The interface between a ferromagnet and an antiferromagnet is such an example for enhanced symmetry breaking. Here we present detailed X-ray magnetic circular dichroism and X-ray resonant magnetic reflectometry investigations on the spectroscopic nature of uncompensated pinned magnetic moments in the antiferromagnetic layer of a typical exchange bias system. Unexpectedly, the pinned moments exhibit nearly pure orbital moment character. This strong orbital pinning mechanism has not been observed so far and is not discussed in literature regarding any theory for local magnetocrystalline anisotropy energies in magnetic systems. To verify this new phenomenon we investigated the effect at different temperatures. We provide a simple model discussing the observed pure orbital moments, based on rotatable spin magnetic moments and pinned orbital moments on the same atom. This unexpected observation leads to a concept for a new type of anisotropy energy.

  2. Achieving perpendicular anisotropy in half-metallic Heusler alloys for spin device applications

    SciTech Connect

    Munira, Kamaram; Romero, Jonathon; Butler, William H.

    2014-05-07

    Various full Heusler alloys are interfaced with MgO and the magnetic properties of the Heusler-MgO junctions are studied. Next to MgO, the cubic Heusler system distorts to a tetragonal one, thereby inducing an anisotropy. The half-metallicity and nature of anisotropy (in-plane or perpendicular) in the Heusler-MgO system is governed mostly by the interface Heusler layers. There is a trend that Mn-O bonding near the MgO-Heusler junction results in perpendicular anisotropy. The ability to remain half-metallic and have perpendicular anisotropy makes some of these alloys potential candidates as free-layers in Spin Transfer Torque Random Access Memory (STT-RAM) devices, particularly, Cr{sub 2}MnAs-MgO system with MnAs interface layers and Co{sub 2}MnSi-MgO system with Mn{sub 2} interface layers.

  3. Microstructures and perpendicular magnetic properties of Co/Pd multilayers on various metal/MgO seed-layers

    NASA Astrophysics Data System (ADS)

    Kim, Sanghoon; Lee, Sangho; Kim, Joonyong; Kang, Jaeyong; Hong, Jongill

    2011-04-01

    We studied the effects of metal/MgO seeds (metal = Ta, Ru, or Pd) on the crystalline structure and perpendicular magnetic properties of Co/Pd multilayers to investigate the possibility of developing a (100) texture with sufficiently high perpendicular anisotropy and small switching field distributions for applications such as patterned media and perpendicular magnetic random access memories. The Pd/MgO or the MgO seed successfully promoted a (100) texture of Co/Pd multilayers. In particular, the Pd/MgO seed developed a strong (100) texture in the Co/Pd multilayer and resulted in perpendicular magnetic anisotropies ˜2 × 106 erg/cm3. On the other hand, the Co/Pd multilayer with the Ta/MgO or the Ru/MgO seed showed a strong (111) texture, inducing a perpendicular magnetic anisotropy higher than that of the (100) textured films. The coercive fields of Co/Pd multilayers with the (111) texture were over 4 kOe and higher than those with the (100) texture, which were ˜2 kOe when they were patterned into 2 × 2 μm2 islands. The switching field distributions of the Co/Pd multilayers with the (100) texture were smaller than those of the Co/Pd multilayers with the (111) texture. Our findings suggest that the Pd/MgO or the MgO seed can be a template suitable for device applications.

  4. Anisotropy in OLEDs

    NASA Astrophysics Data System (ADS)

    Callens, M. K.; Yokoyama, D.; Neyts, K.

    2015-09-01

    Small-molecule OLEDs, deposited by thermal evaporation, allow for precise control over layer thicknesses. This enables optimisation of the optical behaviour of the stack which ultimately determines the outcoupling efficiency. In terms of optical outcoupling there are limits to the efficiency by which the generated electromagnetic radiation can be extracted from the stack. These limitations are linked to the refractive indices of the individual layers. Values for maximum outcoupling efficiency are sometimes calculated under the implicit assumptions that the OLED stack is planar, that all layers are isotropic with a certain refractive index and that the emitters are not preferentially oriented. In reality it is known that these assumptions are not always valid, be it intentional or unintentional. In our work we transcend these limiting assumptions and look at different forms of anisotropy in OLEDs. Anisotropy in OLEDs comes in three distinct flavours; 1. Geometrical anisotropy, as for example in gratings, lenses or other internal or external scattering centres, 2. Anisotropic emitters, where the orientation significantly influences the direction in which radiation is emitted and 3. Anisotropic optical materials, where their anisotropic nature breaks the customary assumption of isotropic OLED materials. We investigate the effect of these anisotropic features on the outcoupling efficiency and ultimately, on the external quantum efficiency (EQE).

  5. Three-layer model for exchange anisotropy

    NASA Astrophysics Data System (ADS)

    Rezende, S. M.; Azevedo, A.; de Aguiar, F. M.; Fermin, J. R.; Egelhoff, W. F.; Parkin, S. S.

    2002-08-01

    Recent x-ray absorption measurements have indicated that the interface between the antiferromagnetic (AF) and the ferromagnetic (FM) layers in AF/FM bilayers instead of being abrupt, consists of a thin layer with uncompensated spins. Here the effect of an interfacial layer between the AF and FM layers on the ferromagnetic resonance response is investigated using a three-layer model for the exchange anisotropy. The calculated dependence of the resonance field with the azimuthal angle of the in-plane external field agrees quite well with experimental data in several samples, lending support to the existence of the uncompensated interfacial layer.

  6. Perpendicular magnetic anisotropy in Ta|Co40Fe40B20|MgAl2O4 structures and perpendicular CoFeB|MgAl2O4|CoFeB magnetic tunnel junction

    NASA Astrophysics Data System (ADS)

    Tao, B. S.; Li, D. L.; Yuan, Z. H.; Liu, H. F.; Ali, S. S.; Feng, J. F.; Wei, H. X.; Han, X. F.; Liu, Y.; Zhao, Y. G.; Zhang, Q.; Guo, Z. B.; Zhang, X. X.

    2014-09-01

    Magnetic properties of Co40Fe40B20 (CoFeB) thin films sandwiched between Ta and MgAl2O4 layers have been systematically studied. For as-grown state, Ta/CoFeB/MgAl2O4 structures exhibit good perpendicular magnetic anisotropy (PMA) with interface anisotropy Ki = 1.22 erg/cm2, which further increases to 1.30 erg/cm2 after annealing, while MgAl2O4/CoFeB/Ta multilayer shows in-plane magnetic anisotropy and must be annealed in order to achieve PMA. For bottom CoFeB layer, the thickness window for PMA is from 0.6 to 1.0 nm, while that for top CoFeB layer is between 0.8 and 1.4 nm. Perpendicular magnetic tunnel junctions (p-MTJs) with a core structure of CoFeB/MgAl2O4/CoFeB have also been fabricated and tunneling magnetoresistance ratio of about 36% at room temperature and 63% at low temperature have been obtained. The intrinsic excitations in the p-MTJs have been identified by inelastic electron-tunneling spectroscopy.

  7. Perpendicular magnetic anisotropy of amorphous [CoSiB/Pt]N thin films

    NASA Astrophysics Data System (ADS)

    Kim, T. W.; Choi, Y. H.; Lee, K. J.; Yoon, J. B.; Cho, J. H.; You, C.-Y.; Jung, M. H.

    2015-05-01

    Materials with perpendicular magnetic anisotropy (PMA) have been intensively studied for high-density nonvolatile memory such as spin-transfer-torque magnetic random access memory with low switching current density and high thermal stability. Compared with crystalline PMA multilayers, considerable works have been done on amorphous PMA multilayers because the amorphous materials are expected to have lower pinning site density as well as smaller domain wall width. This study is an overview of the PMA properties of amorphous [CoSiB/Pt]N multilayers with varying N, where the energy contribution is changed from domain wall energy to magnetostatic energy around N = 6. By measuring the field-induced domain wall motion, we obtain the creep exponent of μ = 1/4. These results in the amorphous PMA multilayers of [CoSiB/Pt]N demonstrate possible potential as a free layer for PMA-based memory devices.

  8. Perpendicular magnetic anisotropy of amorphous [CoSiB/Pt]{sub N} thin films

    SciTech Connect

    Kim, T. W.; Choi, Y. H.; Lee, K. J.; Jung, M. H.; Yoon, J. B.; Cho, J. H.; You, C.-Y.

    2015-05-07

    Materials with perpendicular magnetic anisotropy (PMA) have been intensively studied for high-density nonvolatile memory such as spin-transfer-torque magnetic random access memory with low switching current density and high thermal stability. Compared with crystalline PMA multilayers, considerable works have been done on amorphous PMA multilayers because the amorphous materials are expected to have lower pinning site density as well as smaller domain wall width. This study is an overview of the PMA properties of amorphous [CoSiB/Pt]{sub N} multilayers with varying N, where the energy contribution is changed from domain wall energy to magnetostatic energy around N = 6. By measuring the field-induced domain wall motion, we obtain the creep exponent of μ = 1/4. These results in the amorphous PMA multilayers of [CoSiB/Pt]{sub N} demonstrate possible potential as a free layer for PMA-based memory devices.

  9. Impact of orthogonal exchange coupling on magnetic anisotropy in antiferromagnetic oxides/ferromagnetic systems.

    PubMed

    Kuświk, Piotr; Gastelois, Pedro Lana; Głowiński, Hubert; Przybylski, Marek; Kirschner, Jürgen

    2016-10-26

    The influence of interface exchange coupling on magnetic anisotropy in the antiferromagnetic oxide/Ni system is investigated. We show how interfacial exchange coupling can be employed not only to pin the magnetization of the ferromagnetic layer but also to support magnetic anisotropy to orient the easy magnetization axis perpendicular to the film plane. The fact that this effect is only observed below the Néel temperature of all investigated antiferromagnetic oxides with significantly different magnetocrystalline anisotropies gives evidence that antiferromagnetic ordering is a source of the additional contribution to the perpendicular effective magnetic anisotropy. PMID:27589202

  10. Multilayer injection moulding of thick-walled optical plastics parts

    NASA Astrophysics Data System (ADS)

    Hopmann, Ch.; Neuss, A.; Weber, M.; Walach, P.

    2014-05-01

    Optical components are often thick-walled. The cycle time of precise polymer optics with a wall thickness of more than 20 mm exceeds several minutes. The multilayer injection moulding or compression moulding lowers the cycle time and increases the quality of the moulded parts. For the production of multilayer moulded lenses the mould design plays an important role. An innovative mould concept is presented with the possiblity to produce double or triple layer lenses. To ensure the quality and the endurance of multilayer moulded optical components in their applications, the cohesion in the interface is important. Tensile shear tests show the ability of multilayer moulded parts with high cohesion values for optical applications.

  11. Automation Enhancement of Multilayer Laue Lenses

    SciTech Connect

    Lauer K. R.; Conley R.

    2010-12-01

    X-ray optics fabrication at Brookhaven National Laboratory has been facilitated by a new, state of the art magnetron sputtering physical deposition system. With its nine magnetron sputtering cathodes and substrate carrier that moves on a linear rail via a UHV brushless linear servo motor, the system is capable of accurately depositing the many thousands of layers necessary for multilayer Laue lenses. I have engineered a versatile and automated control program from scratch for the base system and many subsystems. Its main features include a custom scripting language, a fully customizable graphical user interface, wireless and remote control, and a terminal-based interface. This control system has already been successfully used in the creation of many types of x-ray optics, including several thousand layer multilayer Laue lenses.Before reaching the point at which a deposition can be run, stencil-like masks for the sputtering cathodes must be created to ensure the proper distribution of sputtered atoms. Quality of multilayer Laue lenses can also be difficult to measure, given the size of the thin film layers. I employ my knowledge of software and algorithms to further ease these previously painstaking processes with custom programs. Additionally, I will give an overview of an x-ray optic simulator package I helped develop during the summer of 2010. In the interest of keeping my software free and open, I have worked mostly with the multiplatform Python and the PyQt application framework, utilizing C and C++ where necessary.

  12. Giant Perpendicular Magnetic Anisotropy of Graphene-Co Heterostructures

    NASA Astrophysics Data System (ADS)

    Yang, Hongxin; Hallal, Ali; Chshiev, Mairbek; Spintec theory Team

    We report strongly enhanced perpendicular anisotropy (PMA) of Co films by graphene coating via ab-initio calculations. The results show that graphene coating can improve the surface anisotropy of Co film up to twice large of the bare Co case and keep the film effective anisotropy being out-of-plane till 25 Å of Co, in agreement with experiments. Our layer resolved analysis reveals that PMA of Co (Co/Gr) films mainly originates from the adjacent 3 Co layers close to surface (interface) and can be strongly influenced by graphene. Furthermore, orbital hybridization analysis uncovers the origin of the PMA enhancement which is due to graphene-Co bonding causing an inversion of Co 3dz 2 and 3dx 2 - y 2 Bloch states close to Fermi level. Finally, we propose to design Co-graphene heterostructures which possess a linearly increasing surface anisotropy and a constant effective anisotropy. These findings point towards a possible engineering graphene-Co junctions with giant anisotropy, which stands as a hallmark for future spintronic information processing. This work was supported by European Graphene Flagship, European Union-funded STREP project CONCEPT-GRAPHENE, French ANR Projects NANOSIM-GRAPHENE and NMGEM

  13. Resonant evanescent complex fields on dielectric multilayers.

    PubMed

    Angelini, Angelo

    2015-12-15

    Complex light fields, including evanescent Bessel beams, can be generated at dielectric interfaces by means of oil-immersion optics operating in total internal reflection conditions. Here we report on the observation of evanescent complex fields produced on a dielectric multilayer through the interference of surface modes resonantly sustained by the multilayer itself. The coupling to surface modes is attained by modifying the wavefront of an incident laser beam in such a way that the resulting intensity distribution in k-space matches the dispersion of the surface mode. The phase of surface modes can be further controlled, and two-dimensional vortex beams can also be produced according to the same working principle. PMID:26670502

  14. Formation of silicides in annealed periodic multilayers

    NASA Astrophysics Data System (ADS)

    Maury, H.; Jonnard, P.; Le Guen, K.; André, J.-M.

    2009-05-01

    Periodic multilayers of nanometric period are widely used as optical components for the X-ray and extreme UV (EUV) ranges, in X-ray space telescopes, X-ray microscopes, EUV photolithography or synchrotron beamlines for example. Their optical performances depend on the quality of the interfaces between the various layers: chemical interdiffusion or mechanical roughness shifts the application wavelength and can drastically decrease the reflectance. Since under high thermal charge interdiffusion is known to get enhanced, the study of the thermal stability of such structures is essential to understand how interfacial compounds develop. We have characterized X-ray and EUV siliconcontaining multilayers (Mo/Si, Sc/Si and Mg/SiC) as a function of the annealing temperature (up to 600°C) using two non-destructive methods. X-ray emission from the silicon atoms, describing the Si valence states, is used to determine the chemical nature of the compounds present in the interphases while X-ray reflectivity in the hard and soft X-ray ranges can be related to the optical properties. In the three cases, interfacial metallic (Mo, Sc, Mg) silicides are evidenced and the thickness of the interphase increases with the annealing temperature. For Mo/Si and Sc/Si multilayers, silicides are even present in the as-prepared multilayers. Characteristic parameters of the stacks are determined: composition of the interphases, thickness and roughness of the layers and interphases if any. Finally, we have evidenced the maximum temperature of application of these multilayers to minimize interdiffusion.

  15. Control of Multilayer Networks

    PubMed Central

    Menichetti, Giulia; Dall’Asta, Luca; Bianconi, Ginestra

    2016-01-01

    The controllability of a network is a theoretical problem of relevance in a variety of contexts ranging from financial markets to the brain. Until now, network controllability has been characterized only on isolated networks, while the vast majority of complex systems are formed by multilayer networks. Here we build a theoretical framework for the linear controllability of multilayer networks by mapping the problem into a combinatorial matching problem. We found that correlating the external signals in the different layers can significantly reduce the multiplex network robustness to node removal, as it can be seen in conjunction with a hybrid phase transition occurring in interacting Poisson networks. Moreover we observe that multilayer networks can stabilize the fully controllable multiplex network configuration that can be stable also when the full controllability of the single network is not stable. PMID:26869210

  16. Multilayered Graphene in Microwaves

    NASA Astrophysics Data System (ADS)

    Kuzhir, P.; Volynets, N.; Maksimenko, S.; Kaplas, T.; Svirko, Yu.

    2013-05-01

    We report on the experimental study of electromagnetic (EM) properties of multilayered graphene in Ka-band synthesized by catalytic chemical vapor deposition (CVD) process in between nanometrically thin Cu catalyst film and dielectric (SiO2) substrate. The quality of the produced multilayered graphene samples were monitored by Raman spectroscopy. The thickness of graphene films was controlled by atomic force microscopy (AFM) and was found to be a few nanometers (up to 5 nm). We discovered, that the fabricated graphene provided remarkably high EM shielding efficiency caused by absorption losses at the level of 35-43% of incident power. Being highly conductive at room temperature, multi-layer graphene emerges as a promising material for manufacturing ultrathin microwave coatings to be used in aerospace applications.

  17. High temperature interface superconductivity

    DOE PAGESBeta

    Gozar, A.; Bozovic, I.

    2016-01-20

    High-Tc superconductivity at interfaces has a history of more than a couple of decades. In this review we focus our attention on copper-oxide based heterostructures and multi-layers. We first discuss the technique, atomic layer-by-layer molecular beam epitaxy (ALL-MBE) engineering, that enabled High-Tc Interface Superconductivity (HT-IS), and the challenges associated with the realization of high quality interfaces. Then we turn our attention to the experiments which shed light on the structure and properties of interfacial layers, allowing comparison to those of single-phase films and bulk crystals. Both ‘passive’ hetero-structures as well as surface-induced effects by external gating are discussed. Here, wemore » conclude by comparing HT-IS in cuprates and in other classes of materials, especially Fe-based superconductors, and by examining the grand challenges currently laying ahead for the field.« less

  18. High temperature interface superconductivity

    NASA Astrophysics Data System (ADS)

    Gozar, A.; Bozovic, I.

    2016-02-01

    High-Tc superconductivity at interfaces has a history of more than a couple of decades. In this review we focus our attention on copper-oxide based heterostructures and multi-layers. We first discuss the technique, atomic layer-by-layer molecular beam epitaxy (ALL-MBE) engineering, that enabled High-Tc Interface Superconductivity (HT-IS), and the challenges associated with the realization of high quality interfaces. Then we turn our attention to the experiments which shed light on the structure and properties of interfacial layers, allowing comparison to those of single-phase films and bulk crystals. Both 'passive' hetero-structures as well as surface-induced effects by external gating are discussed. We conclude by comparing HT-IS in cuprates and in other classes of materials, especially Fe-based superconductors, and by examining the grand challenges currently laying ahead for the field.

  19. Evaporated CoPt alloy films with strong perpendicular magnetic anisotropy (abstract)

    NASA Astrophysics Data System (ADS)

    Lin, C.-J.; Gorman, G. L.

    1993-05-01

    Co/Pt multilayers with large Kerr rotations at short wavelengths and the magnetic and material properties desired for magneto-optical (MO) recording have been studied extensively as potential future MO materials. Very good recording performance has been demonstrated.1 However, the typical constituent layers in Co/Pt multilayers are very thin, 0.2-0.4 nm Co layers and about 1 nm/Pt layers. To manufacture Co/Pt multilayers consisting of 10-30 periods of such thin Co and Pt layers is certainly quite a challenge. One would prefer to deal with CoPt alloys if the alloys can be made to have large perpendicular magnetic anisotropy and coercivity. Previously no one was able to directly deposit CoPt alloy films with large perpendicular magnetic anisotropy and saturated remanence. Here we will demonstrate for the first time that CoPt alloy films with large perpendicular magnetic anisotropy and coercivity, and saturated remanence can be directly deposited by e-beam evaporation onto heated substrates, at 200 °C or above. Furthermore, we will demonstrate that the perpendicular magnetic anisotropy of CoPt alloy films can be dramatically enhanced by well (111)-textured Pt underlayers. The key to this success appears to be in controlling the crystallographic orientation of these alloy films such that the CoPt(111) lattice plane is parallel to the film surface. CoPt alloys with wide composition range, e.g., 25-57 at. % Co, have been obtained with saturated perpendicular magnetic remanence, indicating that the perpendicular magnetic anisotropy obtained in these alloy films is not related to the ordered tetragonal Co50Pt50 phase. Further work, however, is needed to clarify the anisotropy mechanism in these CoPt alloy films.

  20. Hybrid magnetoresistance in Pt-based multilayers: Effect originated from strong interfacial spin-orbit coupling

    PubMed Central

    Meng, Kangkang; Xiao, Jiaxing; Wu, Yong; Miao, Jun; Xu, Xiaoguang; Zhao, Jianhua; Jiang, Yong

    2016-01-01

    The hybrid magnetoresistance (MR) behaviors in Pt/Co90Fe10/Pt, Mn1.5Ga/Pt and Mn1.5Ga/Pt/Co90Fe10/Pt multilayers have been investigated. Both planer Hall effect (PHE) and angle-dependent MR in Pt/Co90Fe10/Pt revealed the combination of spin Hall MR (SMR) and normal anisotropic MR (AMR), indicating the large contribution of strong spin-orbit coupling (SOC) at the interfaces. When Pt contacted with perpendicular magnetic anisotropy (PMA) metal Mn1.5Ga, the strong interfacial SOC modified the effective anomalous Hall effect. The MR in Mn1.5Ga/Pt/Co90Fe10/Pt is not a simple combination of SMR and AMR, but ascribed to the complicated domain wall scattering and strong interfacial SOC when Pt is sandwiched by the in-plane magnetized Co90Fe10 and the PMA Mn1.5Ga. PMID:26843035

  1. Naturally Produced Co/CoO Nanocrystalline Magnetic Multilayers: Structure and Inverted Hysteresis.

    PubMed

    Santarossa, Francesca; Pappas, Spiridon D; Delimitis, Andreas; Sousanis, Andreas; Poulopoulos, Panagiotis

    2016-05-01

    Cobalt-based multilayers with excellent sequencing are grown via radiofrequency magnetron sputtering with the use of one Co target and natural oxidation. The Co layers are continuous, fully textured {111} and have the face centered cubic structure. At the end of deposition of each Co layer air is let to flow into the vacuum chamber via a fine (leak) valve. The top of Co is oxidized. The oxidized layers consist of cubic CoO crystallites. Near the film surface hexagonal Co(OH)2 is also detected. Magneto-optical Kerr effect hysteresis loops show in-plane magnetized films. The magnetic saturation field in the out-of-plane measurements is large exceeding 12 kOe. This observation supports indirectly the fact that Co is face centered cubic; if it was c-axis textured hexagonal the magnetocrystalline anisotropy would be large resulting in smaller values of the saturation field. As the Co-layer thickness decreases the in-plane loops show reduced remanence, slow approach to magnetic saturation and the out-of-plane loops show inverted hysteresis and/or crossing loop features with sizeable remanence. The effects are discussed with respect to the enhanced orbital magnetic moment of Co and the antiferromagnetic coupling between Co spins at the Co/CoO interface. PMID:27483852

  2. Hybrid magnetoresistance in Pt-based multilayers: Effect originated from strong interfacial spin-orbit coupling

    NASA Astrophysics Data System (ADS)

    Meng, Kangkang; Xiao, Jiaxing; Wu, Yong; Miao, Jun; Xu, Xiaoguang; Zhao, Jianhua; Jiang, Yong

    2016-02-01

    The hybrid magnetoresistance (MR) behaviors in Pt/Co90Fe10/Pt, Mn1.5Ga/Pt and Mn1.5Ga/Pt/Co90Fe10/Pt multilayers have been investigated. Both planer Hall effect (PHE) and angle-dependent MR in Pt/Co90Fe10/Pt revealed the combination of spin Hall MR (SMR) and normal anisotropic MR (AMR), indicating the large contribution of strong spin-orbit coupling (SOC) at the interfaces. When Pt contacted with perpendicular magnetic anisotropy (PMA) metal Mn1.5Ga, the strong interfacial SOC modified the effective anomalous Hall effect. The MR in Mn1.5Ga/Pt/Co90Fe10/Pt is not a simple combination of SMR and AMR, but ascribed to the complicated domain wall scattering and strong interfacial SOC when Pt is sandwiched by the in-plane magnetized Co90Fe10 and the PMA Mn1.5Ga.

  3. Light dosimetry for focused and defocused beam irradiation in multi-layered tissue models

    NASA Astrophysics Data System (ADS)

    Petrova, Kremena S.; Stoykova, Elena V.

    2006-09-01

    Treatment of acupuncture points, trigger points, joint inflammations in low level laser therapy as well as various applications of lasers for treatment of soft tissues in dental medicine, require irradiation by a narrow converging laser beam. The aim of this study is to compare light delivery produced by focused or defocused narrow beam irradiation in a multi-layered skin tissue model at increasing depth of the target. The task is solved by 3-D Monte-Carlo simulation for matched and mismatched refractive indices at the tissue/ambient medium interface. The modeled light beams have a circular cross-section at the tissue entrance with uniform or Gaussian intensity distribution. Three are the tissue models used in simulation : i) a bloodless skin layer; ii) a bloodless skin layer with embedded scattering object; iii) a skin layer with small blood vessels of varying size, which are modeled as infinite cylinders parallel to the tissue surface located at different depths. Optical properties (absorption coefficient, scattering coefficient, anisotropy factor, g, and index of refraction) of different tissue constituents are chosen from the literature.

  4. MBE growth and magneto-optic properties of magnetic multilayers

    NASA Astrophysics Data System (ADS)

    Falco, Charles M.; Engel, Brad N.

    Recent interest in the magnetic and magneto-optic properties of transition metal/transition metal multilayers has been stimulated by the discovery of perpendicular magnetism in particular systems such as Co/Pd and Co/Pt. Due to their favorable magneto-optic wavelength dependence and enhanced corrosion resistance, these materials show promise as future data storage media. However, partially due to the large variety of thin-film deposition methods and growth conditions, it has been difficult to obtain a clear understanding of the mechanisms of magnetic anisotropy in these systems. In order to create controlled and well characterized model systems, we have grown a series of epitaxial Co/Pd superlattices oriented along the three high-symmetry crystal directions [001], [110], and [111] on single-crystal GaAs substrates by molecular beam epitaxy [MBE]. Simultaneously, we have deposited polycrystalline Co/Pd multilayers on Si substrates mounted alongside the GaAs for direct comparisons of epitaxial and non-epitaxial films produced under identical conditions. The structural properties of these multilayers were determined by low-and reflection high-energy electron diffraction (LEED and RHEED), low- and high-angle X-ray diffraction, and scanning tunneling microscopy (STM). The dependence of the uniaxial magnetic anisotropy energy on the Co thickness in these superlattices showed significant systematic differences for each of the three crystal orientations. A review of our work on the structural influences responsible for these differences is presented.

  5. Multilayered Si/Ni nanosprings and their magnetic properties.

    PubMed

    He, Yuping; Fu, Junxue; Zhang, Yang; Zhao, Yiping; Zhang, Lijiao; Xia, Ailin; Cai, Jianwang

    2007-01-01

    A two-turn, eight-armed, rectangular Si/Ni heterogeneous nanospring structure on Si(100) has been fabricated using a multilayer glancing-angle deposition technique. The multilayered nanosprings with a height of approximately 1.98 mum were composed of alternating layers of amorphous Si nanorods approximately 580 nm in length and face-centered cubic Ni nanorods approximately 420 nm in length, both with a diameter of approximately 35 nm. The magnetic anisotropy of the nanosprings showed that the in-plane easy and hard axes were parallel and perpendicular to the Ni nanorod plane, respectively. The out-of-plane magnetic hysteresis loop was very sensitive to the applied magnetic field direction when rotating the nanosprings about their in-plane hard axis, and the magnetization measurement revealed that the nanosprings tilted at approximately 7.5 degrees toward the plane of the Si nanorods. The magnetic anisotropy of the nanosprings is determined by their structure, and the experimental results can be interpreted by the shape anisotropy energy. PMID:17294487

  6. Process for making film-bonded fuel cell interfaces

    DOEpatents

    Kaufman, Arthur; Terry, Peter L.

    1990-07-03

    An improved interface configuration for use between adjacent elements of a fuel cell stack. The interface is impervious to gas and liquid and provides resistance to corrosion by the electrolyte of the fuel cell. A multi-layer arrangement for the interface provides bridging electrical contact with a hot-pressed resin filling the void space.

  7. Anisotropy of weakly vibrated granular flows.

    PubMed

    Wortel, Geert H; van Hecke, Martin

    2015-10-01

    We experimentally probe the anisotropy of weakly vibrated flowing granular media. Depending on the driving parameters-flow rate and vibration strength-this anisotropy varies significantly. We show how the anisotropy collapses when plotted as a function of the driving stresses, uncovering a direct link between stresses and anisotropy. Moreover, our data suggest that for small anisotropies, the shear stresses vanish. Anisotropy of the fabric of granular media thus plays a crucial role in determining the rheology of granular flows. PMID:26565148

  8. Anisotropy of weakly vibrated granular flows

    NASA Astrophysics Data System (ADS)

    Wortel, Geert H.; van Hecke, Martin

    2015-10-01

    We experimentally probe the anisotropy of weakly vibrated flowing granular media. Depending on the driving parameters—flow rate and vibration strength—this anisotropy varies significantly. We show how the anisotropy collapses when plotted as a function of the driving stresses, uncovering a direct link between stresses and anisotropy. Moreover, our data suggest that for small anisotropies, the shear stresses vanish. Anisotropy of the fabric of granular media thus plays a crucial role in determining the rheology of granular flows.

  9. Ultrathin Co/Pt and Co/Pd multilayered films as magneto-optical recording materials

    NASA Astrophysics Data System (ADS)

    Hashimoto, S.; Ochiai, Y.; Aso, K.

    1990-02-01

    Co/Pt and Co/Pd multilayered films were prepared by two-source dc magnetron sputtering. The multilayers with thin Co layers, one to three atoms thick, exhibited a perfect squareness of Kerr loop and an enhancement of Kerr rotation when the total film thickness became below several hundred angstroms. These ultrathin films have a high Kerr rotation of 0.2°-0.45° and strong perpendicular magnetic anisotropy even in the very thin-film thickness. The figure of merit of the ultrathin Co/Pt films is superior to that of TbFeCo system at 780 nm and becomes larger at shorter wavelength. The ultrathin multilayers possess very high corrosion resistance, and the layered structure is thermally stable up to 400 °C. Consequently, the ultrathin Co/Pt and Co/Pd multilayered films can be new magneto-optical recording materials, especially for higher density recording using a shorter wavelength laser.

  10. Antimicrobial polypeptide multilayer nanocoatings.

    PubMed

    Rudra, Jai S; Dave, Komal; Haynie, Donald T

    2006-01-01

    A multilayer coating (or film) of nanometer-thick layers can be made by sequential adsorption of oppositely charged polyelectrolytes on a solid support. The method is known as layer-by-layer assembly (LBL). No special apparatus is required for LBL and nanofilms can be prepared under mild, physiological conditions. A multilayer nanofilm in which at least one of the constituent species is a polypeptide is a polypeptide multilayer nanofilm. The present work was aimed at assessing whether polypeptide multilayer nanofilms with specific antimicrobial properties could be prepared by incorporation of a known antimicrobial agent in the film structure, in this case the edible protein hen egg white lysozyme (HEWL). The chicken enzyme is widely employed as a human food preservative. An advantage of LBL in this context is that the nanofilm is fabricated directly on the surface of interest, eliminating the need to incorporate the antimicrobial in other packaging materials. Here, nanofilms were made of poly(L-glutamic acid) (PLGA), which is highly negatively charged in the mildly acidic pH range, and HEWL, which has a high net positive charge at acidic pH. We show that PLGA/HEWL nanofilms inhibit growth of the model microbe Microccocus luteus in the surrounding liquid medium. The amount of HEWL released from PLGA/HEWL films depends on the number of HEWL layers and therefore on the total quantity of HEWL in the films. This initial study provides a sketch of the scope for further development of LBL in the area of antimicrobial polypeptide multilayer films. Potential applications of such films include strategies for food preservation and coatings for implant devices. PMID:17176751

  11. Characterization Of Multilayer X-Ray Analyzers: Models And Measurements

    NASA Astrophysics Data System (ADS)

    Henke, B. L.; Uejio, J. Y.; Yamada, H. T.; Tackaberry, R. E.

    1986-08-01

    A procedure is described for a detailed characterization of multilayer analyzers that can be effectively applied to their design, optimization, and application for absolute x-ray spectrometry in the 100 to 10,000 eV photon energy region. An accurate analytical model has been developed that is based upon a simple modification of the dynamical Darwin-Prins theory to extend its application to finite multilayer systems and to the low energy x-ray region. Its equivalence to the optical E&M solution of the Fresnel equations at each interface is demonstrated by detailed comparisons for the reflectivity of a multilayer throughout the angular range of incidence of 0° to 90°. A special spectrograph and an experimental method are described for the measurement of the absolute reflectivity characteristics of the multilayer. The experimental measurements at three photon energies in the 100 to 2000 eV region are fit by the analytical modified Darwin-Prins equation (MDP) for 1(0), generating a detailed characterization of two state-of-the-art multilayers: sputtered tungsten-carbon with 2d 70 A and a molecular lead stearate with 2d 100 A. The fitting parameters that are determined by this procedure are applied to help establish the structural characteristics of these multilayers.

  12. Multilayer reflective coatings for extreme-ultraviolet lithography

    SciTech Connect

    Montcalm, C., LLNL

    1998-03-10

    Multilayer mirror coatings which reflect extreme ultraviolet (EUV) radiation are a key enabling technology for EUV lithography. Mo/Si multilayers with reflectances of 67.5% at 13.4 nm are now routinely achieved and reflectances of 70 2% at 11.4 nm were obtained with MO/Be multilayers. High reflectance is achieved with careful control of substrate quality, layer thicknesses, multilayer materials, interface quality, and surface termination. Reflectance and film stress were found to be stable relative to the requirements for application to EUV lithography. The run-to-run reproducibility of the reflectance peak position was characterized to be better than 0.2%, providing the required wavelength matching among the seven multilayer-coated mirrors used in the present lithography system design. Uniformity of coating was improved to better than 0.5% across 150 mm diameter substrates. These improvements in EUV multilayer mirror technology will enable us to meet the stringent specifications for coating the large optical substrates for our next-generation EUV lithography system.

  13. Vertical vibration of a pile in transversely isotropic multilayered soils

    NASA Astrophysics Data System (ADS)

    Ai, Zhi Yong; Liu, Chun Lin

    2015-11-01

    A new method for the dynamic response of a vertically loaded single pile embedded in transversely isotropic multilayered soils is proposed in this paper. The dynamic response of the pile is governed by the one-dimensional (1D) vibration theory, and that of transversely isotropic multilayered soils is achieved by using an analytical layer-element method. Then, with the aid of the displacement compatibility and the contact forces equilibrium along the pile-soil contact surface, the dynamic pile-soil interaction problem is solved efficiently. The presented solution method is proved to be correct and efficient by comparing the obtained results with other existing solutions. Selected numerical results are presented to study the influence of mass density ratio, length-radius ratio, frequency of excitation, soil anisotropy and hard soil stratum on the pile vertical impedance.

  14. Magnetic properties of epitaxial and polycrystalline Fe/Si multilayers

    SciTech Connect

    Chaiken, A.; Michel, R.P.; Wang, C.T.

    1995-08-01

    Fe/Si multilayers with antiferromagnetic interlayer coupling have been grown via ion-beam sputtering on both glass and single-crystal substrates. X-ray diffraction measurements show that both sets of films have crystalline iron silicide spacer layers and a periodic composition modulation. Films grown on glass have smaller crystallite sizes than those grown on single-crystal substrates and have a significant remanent magnetization. Films grown on single-crystal substrates have a smaller remanence. The observation of magnetocrystalline anisotropy in hysteresis loops and (hkl) peaks in x-ray diffraction demonstrates that the films grown on MgO and Ge are epitaxial. The smaller remanent magnetization in Fe/Si multilayers with better crystallinity suggests that the remanence is not intrinsic.

  15. Effective electromagnetic shielding in multilayer printed circuit boards

    NASA Astrophysics Data System (ADS)

    Wiles, K. G.; Moe, J. L.

    Multilayer printed circuit boards have proven to be recurrent abettors of electromagnetic coupling problems created by the incessantly faster response times in integrated circuit technologies. Coupling within multilayer boards has not only inhibited meeting certain EMI requirements but has also precipitated 'self-inflicted' malfunctions commonly experienced during development of avionic systems. A recent avionic system, interfacing two asynchronous processors through a fourteen-layer motherboard, permitted coupling through ground plane connector apertures of sufficient amplitude and duration as to cause unintentional intercommunication and system malfunctions. The coupling mechanism and ground plane modifications which reduced this coupling by 40 dB and eliminated the incompatibility are discussed in this paper

  16. Can we understand rocks without anisotropy?

    NASA Astrophysics Data System (ADS)

    Dabrowski, Marcin

    2014-05-01

    An effectively isotropic heterogeneous medium subject to deformation should develop compositional layering parallel to stretching direction. A layered anisotropic rock subject to layer-parallel extension may undergo mechanical instability leading to internal boudinage development. The question that arises is as to whether the formation of layering could be hampered by boudinage formation before the compositional layering is well developed. With regard to the issue, the three critical questions are: (1) How does the rock fabric evolution depend on the mechanical properties of rock constituents and the initial microstructure? (2) How does the mechanical (viscous) anisotropy relate to the shape anisotropy of a composite rock? (3) How does the internal boudinage development manifest in a rock consisting of elongated elements rather than well-developed layers? I will numerically investigate the development of shape preferred orientation and mechanical anisotropy in a composite two-phase rock undergoing stretching. A two-dimensional inclusion-host type of composite, in which an interconnected host embeds non-overlapping inclusions, is considered. Different inclusion fractions, shapes and size distributions are studied. The initial spatial distribution of the inclusions is intended to be random, statistically homogeneous (no clustering) and isotropic. In a series of complementary simulation runs, periodic inclusion arrays are analyzed. Both the inclusion and host materials are considered as viscous fluids and the intrinsic viscosities of the inclusion and the host phases are isotropic. A coherent inclusion-host interface is assumed and interfacial processes such as surface tension or diffusional mass transfer are neglected. The deformation is studied in the Stokes limit and under no gravity. A self-developed FEM code (www.milamin.org, Dabrowski et al., 2008) is used to find the velocity vectors at the inclusion interfaces. Unstructured triangular computational meshes

  17. High reflectance and low stress Mo2C/Be multilayers

    DOEpatents

    Bajt, Sasa; Barbee, Jr., Troy W.

    2001-01-01

    A material for extreme ultraviolet (EUV) multilayers that will reflect at about 11.3 nm, have a high reflectance, low stress, and high thermal and radiation stability. The material consists of alternating layers of Mo.sub.2 C and Be deposited by DC magnetron sputtering on a substrate, such as silicon. In one example a Mo.sub.2 C/Be multilayer gave 65.2% reflectance at 11.25 nm measured at 5 degrees off normal incidence angle, and consisted of 70 bilayers with a deposition period of 5.78 nm, and was deposited at 0.83 mTorr argon (Ar) sputtering pressure, with the first and last layers being Be. The stress of the multilayer is tensile and only +88 MPa, compared to +330 MPa of a Mo/Be multilayers of the same thickness. The Mo.sub.2 C/Be multilayer was capped with carbon which produced an increase in reflectivity of about 7% over a similar multilayer with no carbon capping material, thus raising the reflectivity from 58.3% to over 65%. The multilayers were formed using either Mo.sub.2 C or Be as the first and last layers, and initial testing has shown the formation of beryllium carbide at the interfaces between the layers which both stabilizes and has a smoothing effect, and appear to be smoother than the interfaces in Mo/Be multilayers.

  18. Origins of Asymmetric Magnetization Reversal in Exchange Biased Multilayers

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Wang, Shuoguo; Li, Yang; Chen, Ning; Liu, Shuai; Li, Minghua; Yu, Guanghua; Department of Materials Physics; Chemistry, University of Science; Technology Beijing Team; State Key Laboratory Of Magnetism, Beijing National LaboratoryCondensed Matter Physics, Institu Team; University of Puerto Rico At Mayaguez Team

    2011-03-01

    Novel asymmetric magnetization reversal behaviors (ARBs) as well as positive exchange bias (EB) are observed by using the alternating gradient force magnetometer (AGM) in both Co/FeMn bilayer with an oblique out-of-plane exchange anisotropy and the Co/FeMn bilayer in which Co layer has a quite heavy thickness. There are two different ARBs, arised from the ferromagnetic and the antiferromagnetic layer respectively under the perpendicular magnetization. Our results show that two intrinsic origins of the ARBs (i.e. the competing anisotropy and the inhomogeneity of the magnetic structure) coexist. Both of them are indispensable for the development of the ARBs in our Co/FeMn multilayers. This work was supported by the National Science Foundation under Grant no. DMR-0821284, NASA under Grant Nos. NNX10AM80H and NNX07AO30A.

  19. Design and development of multilayer vascular graft

    NASA Astrophysics Data System (ADS)

    Madhavan, Krishna

    2011-07-01

    Vascular graft is a widely-used medical device for the treatment of vascular diseases such as atherosclerosis and aneurysm as well as for the use of vascular access and pediatric shunt, which are major causes of mortality and morbidity in this world. Dysfunction of vascular grafts often occurs, particularly for grafts with diameter less than 6mm, and is associated with the design of graft materials. Mechanical strength, compliance, permeability, endothelialization and availability are issues of most concern for vascular graft materials. To address these issues, we have designed a biodegradable, compliant graft made of hybrid multilayer by combining an intimal equivalent, electrospun heparin-impregnated poly-epsilon-caprolactone nanofibers, with a medial equivalent, a crosslinked collagen-chitosan-based gel scaffold. The intimal equivalent is designed to build mechanical strength and stability suitable for in vivo grafting and to prevent thrombosis. The medial equivalent is designed to serve as a scaffold for the activity of the smooth muscle cells important for vascular healing and regeneration. Our results have shown that genipin is a biocompatible crosslinker to enhance the mechanical properties of collagen-chitosan based scaffolds, and the degradation time and the activity of smooth muscle cells in the scaffold can be modulated by the crosslinking degree. For vascular grafting and regeneration in vivo, an important design parameter of the hybrid multilayer is the interface adhesion between the intimal and medial equivalents. With diametrically opposite affinities to water, delamination of the two layers occurs. Physical or chemical modification techniques were thus used to enhance the adhesion. Microscopic examination and graft-relevant functional characterizations have been performed to evaluate these techniques. Results from characterization of microstructure and functional properties, including burst strength, compliance, water permeability and suture

  20. Multilayer permalloy films grown by molecular-beam epitaxy

    NASA Astrophysics Data System (ADS)

    Rook, K.; Zeltser, A. M.; Artman, J. O.; Laughlin, D. E.; Kryder, M. H.

    1991-04-01

    The magnetic properties of single-layer and multilayer 111-line textured Cu and Permalloy films, deposited by MBE on 111-plane Si substrates, have been measured by both ferromagnetic resonance and M-H loop tracer; microstructural characterizations were conducted by TEM, XRD, and reflection high-energy electron diffraction. The single-layer films had lower easy-axis coercivity H(ce) and a lower in-plane anisotropy field than sputter-deposited Permalloy films of similar thickness. The five-layer, Cu-interlayer separated Permalloy structures, having a magnetic thickness in excess of 100 nm, exhibited lower H(ce) than equivalent single-layer films.

  1. Magneto-optical properties of Pd-Ni multilayers

    NASA Astrophysics Data System (ADS)

    Flevaris, N. K.

    1991-05-01

    The magneto-optical polar Kerr effect properties of compositionally modulated Pdm-Nin multilayers have been studied, at room temperature, for modulation wavelengths containing just a few monolayers. A perpendicular anisotropy component was observed to develop for very thin Ni layers (n=2 or 1 atomic planes). The rotation values were found to depend strongly on both m and n suggesting a modulation-induced property modification. These results were supported by magnetic studies. Also, they are discussed on the basis of extensive structural and other investigations.

  2. Thermal structure, radial anisotropy, and dynamics of oceanic boundary layers

    NASA Astrophysics Data System (ADS)

    Auer, Ludwig; Becker, Thorsten W.; Boschi, Lapo; Schmerr, Nicholas

    2015-11-01

    Defining the oceanic lithosphere as a thermal boundary layer allows to explain, to first order, age-dependent bathymetry and isotropic wave speeds. In contrast, SS precursors and receiver functions suggest a subhorizontal interface within this layer, on top of a radially anisotropic zone. Comparing a suite of geodynamic scenarios against surface wave dispersion data and seismic discontinuities, we find that only weak age dependency of the radially anisotropic zone is compatible with observations. We show that this zone is confined from below by a second weaker seismic interface. While observed azimuthal anisotropy is consistent with lattice-preferred orientation of olivine due to asthenospheric flow underneath the lithosphere, radial anisotropy requires additional contributions, perhaps from petrological fabrics or melt ponding. This implies that seismic reflectors previously associated with the base of the lithosphere are instead associated with preserved structures embedded in it. They carry information about plate formation but have little control on plate deformation.

  3. Anisotropy in solid inflation

    SciTech Connect

    Bartolo, Nicola; Matarrese, Sabino; Ricciardone, Angelo; Peloso, Marco E-mail: sabino.matarrese@pd.infn.it E-mail: angelo.ricciardone@pd.infn.it

    2013-08-01

    In the model of solid / elastic inflation, inflation is driven by a source that has the field theoretical description of a solid. To allow for prolonged slow roll inflation, the solid needs to be extremely insensitive to the spatial expansion. We point out that, because of this property, the solid is also rather inefficient in erasing anisotropic deformations of the geometry. This allows for a prolonged inflationary anisotropic solution, providing the first example with standard gravity and scalar fields only which evades the conditions of the so called cosmic no-hair conjecture. We compute the curvature perturbations on the anisotropic solution, and the corresponding phenomenological bound on the anisotropy. Finally, we discuss the analogy between this model and the f(φ)F{sup 2} model, which also allows for anisotropic inflation thanks to a suitable coupling between the inflaton φ and a vector field. We remark that the bispectrum of the curvature perturbations in solid inflation is enhanced in the squeezed limit and presents a nontrivial angular dependence, as had previously been found for the f(φ)F{sup 2} model.

  4. Anisotropy in rotating drums

    NASA Astrophysics Data System (ADS)

    Povall, Timothy; McBride, Andrew; Govender, Indresan

    2015-11-01

    An anisotropic relationship between the stress and the strain rate has been observed in two-dimensional simulations of rotating drums. The objective of this work is to investigate the structure of the constitutive relation using three-dimensional discrete-element-method simulations of a rotating drum containing identical rigid spheres for a range of rotational speeds. Anisotropy is quantified from the alignment of the stress and strain rate tensors, with the strain rate computed using a least-squares fit. It is shown that in certain regions there is a strong anisotropic relationship, regardless of the speed of rotation. The effective friction coefficient is examined in order to determine the phase space in which the μ (I) rheology is valid. Lastly, a depth-averaged approach through the flowing layer is employed to determine the relationship between the velocity tangential to the equilibrium surface and the height of the flowing layer. A power-law relationship that approaches linear at high speeds is observed. Supported by NRF/DST Scarce Skills (South Africa).

  5. Calculation of magnetocrystalline anisotropy

    NASA Astrophysics Data System (ADS)

    Schneider, Gunter

    The magnetocrystalline anisotropy energy (MAE) for fcc Ni and bcc Fe is calculated as the difference of single particle energy eigenvalue sums using a tight-binding model. For nickel we predict a MAE of -0.15 eV and the wrong easy axis, for iron we find a MAE of -0.7 eV with the easy axis in agreement with experiment. Our results compare favorably with previously reported first-principles calculations based on density functional theory and the local spin density approximation. The inclusion of an orbital polarization correction improves the magnitude of the MAE for iron, but fails to bring the result for nickel closer to the experimental value. The outstanding feature of our calculations is the careful handling of the necessary Brillouin zone integrals. Linear interpolation schemes and methods based on Fermi surface smearing were used and analyzed. An alternative method of calculating the MAE based on the torque on a magnetic moment centered on an atom is found to be equivalent to the calculation of the MAE in terms of energy differences.

  6. Brownian thermal noise in multilayer coated mirrors

    NASA Astrophysics Data System (ADS)

    Hong, Ting; Yang, Huan; Gustafson, Eric K.; Adhikari, Rana X.; Chen, Yanbei

    2013-04-01

    We analyze the Brownian thermal noise of a multilayer dielectric coating used in high-precision optical measurements, including interferometric gravitational-wave detectors. We assume the coating material to be isotropic, and therefore study thermal noises arising from shear and bulk losses of the coating materials. We show that coating noise arises not only from layer thickness fluctuations, but also from fluctuations of the interface between the coating and substrate, driven by fluctuating shear stresses of the coating. Although thickness fluctuations of different layers are statistically independent, there exists a finite coherence between the layers and the substrate-coating interface. In addition, photoelastic coefficients of the thin layers (so far not accurately measured) further influence the thermal noise, although at a relatively low level. Taking into account uncertainties in material parameters, we show that significant uncertainties still exist in estimating coating Brownian noise.

  7. Braneworld cosmological models with anisotropy

    NASA Astrophysics Data System (ADS)

    Campos, Antonio; Maartens, Roy; Matravers, David; Sopuerta, Carlos F.

    2003-11-01

    For a cosmological Randall-Sundrum braneworld with anisotropy, i.e., of Bianchi type, the modified Einstein equations on the brane include components of the five-dimensional Weyl tensor for which there are no evolution equations on the brane. If the bulk field equations are not solved, this Weyl term remains unknown, and many previous studies have simply prescribed it as ad hoc. We construct a family of Bianchi braneworlds with anisotropy by solving the five-dimensional field equations in the bulk. We analyze the cosmological dynamics on the brane, including the Weyl term, and shed light on the relation between anisotropy on the brane and the Weyl curvature in the bulk. In these models, it is not possible to achieve geometric anisotropy for a perfect fluid or scalar field—the junction conditions require anisotropic stress on the brane. But the solutions can isotropize and approach a Friedmann brane in an anti de Sitter bulk.

  8. Perpendicular magnetic anisotropy in Ta|Co{sub 40}Fe{sub 40}B{sub 20}|MgAl{sub 2}O{sub 4} structures and perpendicular CoFeB|MgAl{sub 2}O{sub 4}|CoFeB magnetic tunnel junction

    SciTech Connect

    Tao, B. S.; Li, D. L.; Yuan, Z. H.; Liu, H. F.; Ali, S. S.; Feng, J. F.; Wei, H. X.; Han, X. F.; Liu, Y.; Zhao, Y. G.; Zhang, Q.; Guo, Z. B.; Zhang, X. X.

    2014-09-08

    Magnetic properties of Co{sub 40}Fe{sub 40}B{sub 20} (CoFeB) thin films sandwiched between Ta and MgAl{sub 2}O{sub 4} layers have been systematically studied. For as-grown state, Ta/CoFeB/MgAl{sub 2}O{sub 4} structures exhibit good perpendicular magnetic anisotropy (PMA) with interface anisotropy K{sub i} = 1.22 erg/cm{sup 2}, which further increases to 1.30 erg/cm{sup 2} after annealing, while MgAl{sub 2}O{sub 4}/CoFeB/Ta multilayer shows in-plane magnetic anisotropy and must be annealed in order to achieve PMA. For bottom CoFeB layer, the thickness window for PMA is from 0.6 to 1.0 nm, while that for top CoFeB layer is between 0.8 and 1.4 nm. Perpendicular magnetic tunnel junctions (p-MTJs) with a core structure of CoFeB/MgAl{sub 2}O{sub 4}/CoFeB have also been fabricated and tunneling magnetoresistance ratio of about 36% at room temperature and 63% at low temperature have been obtained. The intrinsic excitations in the p-MTJs have been identified by inelastic electron-tunneling spectroscopy.

  9. High spin-polarization in ultrathin Co2MnSi/CoPd multilayers

    NASA Astrophysics Data System (ADS)

    Galanakis, I.

    2015-03-01

    Half-metallic Co2MnSi finds a broad spectrum of applications in spintronic devices either in the form of thin films or as spacer in multilayers. Using state-of-the-art ab-initio electronic structure calculations we exploit the electronic and magnetic properties of ultrathin Co2MnSi/CoPd multilayers. We show that these heterostructures combine high values of spin-polarization at the Co2MnSi spacer with the perpendicular magnetic anisotropy of binary compounds such as CoPd. Thus they could find application in spintronic/magnetoelectronic devices.

  10. Orientational anisotropy and interfacial transport in polycrystals

    NASA Astrophysics Data System (ADS)

    Moghadam, M. M.; Rickman, J. M.; Harmer, M. P.; Chan, H. M.

    2016-04-01

    Interfacial diffusion is governed to a large degree by geometric parameters that are determined by crystallographic orientation. In this study, we assess the impact of orientational anisotropy on mass transport at internal interfaces, focusing on the role of preferred crystallographic orientation (i.e., texture) on mass diffusion in a polycrystal. More specifically, we perform both numerical and analytical studies of steady-state diffusion for polycrystals having various grain-orientation distributions. By relating grain misorientation to grain-boundary energies and, via the Borisov relation, to the diffusivity, we link microstructure variability to kinetics. Our aim is to correlate shape features of the orientation distribution, such as the location and shapes of peaks, with the calculated effective diffusivity. Finally, we discuss the role of crystallographic constraints, such as those associated with grain junctions, in determining the effective diffusivity of a polycrystal.

  11. Role of magnetic anisotropy in spin-filter junctions

    SciTech Connect

    Chopdekar, R.V.; Wong, F.; Nelson-Cheeseman, B.B.; Liberati, M.; Arenholz, E.; Suzuki, Y.

    2011-01-10

    We have fabricated oxide-based spin-filter junctions in which we demonstrate that magnetic anisotropy can be used to tune the transport behavior of spin-filter junctions. We have demonstrated spin-filtering behavior in La{sub 0.7}Sr{sub 0.3}MnO{sub 3}/CoCr{sub 2}O{sub 4}/Fe{sub 3}O{sub 4} and La{sub 0.7}Sr{sub 0.3}MnO{sub 3}/MnCr{sub 2}O{sub 4}/Fe{sub 3}O{sub 4} junctions where the interface anisotropy plays a significant role in determining transport behavior. Detailed studies of chemical and magnetic structure at the interfaces indicate that abrupt changes in magnetic anisotropy across the nonisostructural interface is the cause of the significant suppression of junction magnetoresistance in junctions with MnCr{sub 2}O{sub 4} barrier layers.

  12. Laboratory seismic anisotropy in mylonites

    NASA Astrophysics Data System (ADS)

    Almqvist, B. S. G.; Herwegh, M.; Hirt, A. M.; Ebert, A.; Linckens, J.; Precigout, J.; Leiss, B.; Walter, J. M.; Burg, J.-P.

    2012-04-01

    Tectonic strain is often accommodated along narrow zones in the Earth's crust and upper mantle, and these high-strain zones represent an important mechanical and rheological component in geodynamics. In outcrop we observe the intense deformation along and across these structures. But at depth, in the mid and lower crust, and in the mantle, we are dependent on geophysical methods for analysis of structures, such as seismic reflection and refraction surveys. A natural progression has therefore been to understand the remote geophysical signal in terms of laboratory ultrasonic pulse transmission measurements on rock cores, collected in the field or from borehole drill core. Here we first present a brief review that consider key studies in the area of laboratory seismic measurements in strongly anisotropic rocks, ranging from calcite mylonites to metapelites. In the second part we focus attention on ongoing research projects targetting laboratory seismic anisotropy in mylonitized rocks, and associated challenges. Measurements of compressional (P) and shear (S) waves were made at high confining pressure (up to 5 kbar). Mineral texture analysis was performed with electron backscatter diffraction (EBSD) and neutron texture diffraction to determine crystallographic preferred orientation (CPO). So-called "rock-recipe" models are used to calculate seismic anisotropy, which consider the elastic properties of minerals that constitutes the rock, and their respective CPO. However, the outcome of such models do not always simply correspond to the measured seismic anisotropy. Differences are attributed to several factors, such as grain boundaries, mineral microstructures including shape-preferred orientation (SPO), micro-cracks and pores, and grain-scale stress-strain conditions. We highlight the combination of these factors in case studies on calcite and peridotite mylonites. In calcite mylonites, sampled in the Morcles nappe shear zone, the measured seismic anisotropy generally

  13. Anatomy and Giant Enhancement of the Perpendicular Magnetic Anisotropy of Cobalt-Graphene Heterostructures

    NASA Astrophysics Data System (ADS)

    Yang, Hongxin; Vu, Anh Duc; Hallal, Ali; Rougemaille, Nicolas; Coraux, Johann; Chen, Gong; Schmid, Andreas K.; Chshiev, Mairbek

    2016-01-01

    We report strongly enhanced perpendicular magnetic anisotropy (PMA) of Co films by graphene coating from both first-principles and experiments. Our calculations show that graphene can dramatically boost the surface anisotropy of Co films up to twice the value of its pristine counterpart and can extend the out-of-plane effective anisotropy up to unprecedented thickness of 25~\\AA. These findings are supported by our experiments on graphene coating on Co films grown on Ir substrate. Furthermore, we report layer-resolved and orbital-hybridization-resolved anisotropy analysis which help understanding the physical mechanisms of PMA and more practically can help design structures with giant PMA. As an example, we propose super-exchange stabilized Co-graphene heterostructures with a robust out-of-plane constant effective PMA and linearly increasing interfacial anisotropy as a function of film thickness. These findings point towards possibilities to engineer graphene/ferromagnetic metal heterostructures with giant magnetic anisotropy more than 20 times larger compared to conventional multilayers, which constitutes a hallmark for future graphene and traditional spintronic technologies.

  14. Anatomy and Giant Enhancement of the Perpendicular Magnetic Anisotropy of Cobalt-Graphene Heterostructures.

    PubMed

    Yang, Hongxin; Vu, Anh Duc; Hallal, Ali; Rougemaille, Nicolas; Coraux, Johann; Chen, Gong; Schmid, Andreas K; Chshiev, Mairbek

    2016-01-13

    We report strongly enhanced perpendicular magnetic anisotropy (PMA) of Co films by graphene coating from both first-principles and experiments. Our calculations show that graphene can dramatically boost the surface anisotropy of Co films up to twice the value of its pristine counterpart and can extend the out-of-plane effective anisotropy up to unprecedented thickness of 25 Å. These findings are supported by our experiments on graphene coating on Co films grown on Ir substrate. Furthermore, we report layer-resolved and orbital-hybridization-resolved anisotropy analysis, which help understanding of the physical mechanisms of PMA and more practically can help design structures with giant PMA. As an example, we propose superexchange stabilized Co-graphene heterostructures with a robust constant effective PMA and linearly increasing interfacial anisotropy as a function of film thickness. These findings point toward possibilities to engineer graphene/ferromagnetic metal heterostructures with giant magnetic anisotropy more than 20-times larger compared to conventional multilayers, which constitutes a hallmark for future graphene and traditional spintronic technologies. PMID:26641927

  15. Mitigation of substrate defects in reticles using multilayer buffer layers

    DOEpatents

    Mirkarimi, Paul B.; Bajt, Sasa; Stearns, Daniel G.

    2001-01-01

    A multilayer film is used as a buffer layer to minimize the size of defects on a reticle substrate prior to deposition of a reflective coating on the substrate. The multilayer buffer layer deposited intermediate the reticle substrate and the reflective coating produces a smoothing of small particles and other defects on the reticle substrate. The reduction in defect size is controlled by surface relaxation during the buffer layer growth process and by the degree of intermixing and volume contraction of the materials at the multilayer interfaces. The buffer layers are deposited at near-normal incidence via a low particulate ion beam sputtering process. The growth surface of the buffer layer may also be heated by a secondary ion source to increase the degree of intermixing and improve the mitigation of defects.

  16. Boron containing multilayer coatings and method of fabrication

    DOEpatents

    Makowiecki, Daniel M.; Jankowski, Alan F.

    1997-01-01

    Hard coatings are fabricated from multilayer boron/boron carbide, boron carbide/cubic boron nitride, and boron/boron nitride/boron carbide, and the fabrication thereof involves magnetron sputtering in a selected atmosphere. These hard coatings may be applied to tools and engine and other parts, as well to reduce wear on tribological surfaces and electronic devices. These boron coatings contain no morphological growth features. For example, the boron and boron carbide used in forming the multilayers are formed in an inert (e.g. argon) atmosphere, while the cubic boron nitride is formed in a reactive (e.g. nitrogen) atmosphere. The multilayer boron/boron carbide, and boron carbide/cubic boron nitride is produced by depositing alternate layers of boron, cubic boron nitride or boron carbide, with the alternate layers having a thickness of 1 nanometer to 1 micrometer, and at least the interfaces of the layers may be of a discrete or a blended or graded composition.

  17. Roughness induced magnetic inhomogeneity in Co/Ni multilayers: Ferromagnetic resonance and switching properties in nanostructures

    NASA Astrophysics Data System (ADS)

    Shaw, Justin M.; Nembach, Hans T.; Silva, T. J.

    2010-11-01

    We report on the effect roughness has on the magnetic properties of Co/Ni multilayers with perpendicular anisotropy. We can systematically vary the surface roughness and grain size by the variation in the Cu seed layer thickness. The roughness has a significant effect on the lateral anisotropy variation across the material, which was studied through the size dependence of the switching field and switching field distribution in nanostructures. Ferromagnetic resonance measurements show a large dependence of the linewidth on the topography. However, only the inhomogeneous linewidth broadening varied significantly with roughness with little to no effect on the intrinsic damping parameter of α =0.015-0.018.

  18. Fascination and challenge of subwavelength-structured interfaces

    NASA Astrophysics Data System (ADS)

    Wyrowski, Frank; Kley, Ernst-Bernhard; Schnabel, Bernd; Turunen, Jari P.; Honkanen, Marko

    1998-04-01

    We consider an interesting domain of diffractive optics, namely the physics and technology of optical interface with subwavelength-structured features. Such interfaces act as effective media, which may, e.g., simulate the operation of multilayer film stacks and often feature anisotropic optical properties. The principles of the analysis and design of these interfaces are covered, and several prominent fields of application are described. The challenge of fabricating subwavelength-structured interface by low-voltage electron beam nanolithography is considered.

  19. Perpendicular magnetic anisotropy in FePt/AlN layered structure

    NASA Astrophysics Data System (ADS)

    Zhang, Cong; Sannomiya, Takumi; Muraishi, Shinji; Shi, Ji; Nakamura, Yoshio

    2014-09-01

    FePt/AlN layered structures were deposited onto fused quartz substrate by magnetron sputtering method and found to show in-plane anisotropy. However, annealing of the films leads to a transition of magnetic anisotropy from in-plane to perpendicular direction, and the perpendicular anisotropy gets stronger as the annealing temperature increases. Structural analysis shows that the FePt and AlN layers are textured with (111) and (002) orientations, respectively, along the film normal, and no ordering transformation is found for FePt alloy. To study the origin of the developed anisotropy, stress condition was analyzed with an equal biaxial stress model using X-ray diffraction 2 θ- ω scan method and interface quality was evaluated by X-ray reflectivity measurement and transmission electron microscopy observation. The results reveal that perpendicular magnetic anisotropy of the annealed FePt/AlN layered structure can be attributed to the enhanced interface anisotropy, which is due to flattening of the interfaces through annealing.

  20. Ion polished Cr/Sc attosecond multilayer mirrors for high water window reflectivity

    DOE PAGESBeta

    Guggenmos, Alexander; Radünz, Stefan; Rauhut, Roman; Hofstetter, Michael; Venkatesan, Sriram; Wochnik, Angela; Gullikson, Eric M.; Fischer, Stefan; Nickel, Bert; Scheu, Christina; et al

    2014-01-20

    Recent advances in the development of attosecond soft X-ray sources ranging into the water window spectral range, between the 1s states of carbon and oxygen (284 eV–543 eV), are also driving the development of suited broadband multilayer optics for steering and shaping attosecond pulses. The relatively low intensity of current High Harmonic Generation (HHG) soft X-ray sources calls for an efficient use of photons, thus the development of low-loss multilayer optics is of uttermost importance. Here, we report about the realization of broadband Cr/Sc attosecond multilayer mirrors with nearly atomically smooth interfaces by an optimized ion beam deposition and assistedmore » interface polishing process. This yields to our knowledge highest multilayer mirror reflectivity at 300 eV near normal incidence. The results are verified by transmission electron microscopy (TEM) and soft/hard X-ray reflectometry.« less

  1. Ion polished Cr/Sc attosecond multilayer mirrors for high water window reflectivity

    SciTech Connect

    Guggenmos, Alexander; Radünz, Stefan; Rauhut, Roman; Hofstetter, Michael; Venkatesan, Sriram; Wochnik, Angela; Gullikson, Eric M.; Fischer, Stefan; Nickel, Bert; Scheu, Christina; Kleineberg, Ulf

    2014-01-20

    Recent advances in the development of attosecond soft X-ray sources ranging into the water window spectral range, between the 1s states of carbon and oxygen (284 eV–543 eV), are also driving the development of suited broadband multilayer optics for steering and shaping attosecond pulses. The relatively low intensity of current High Harmonic Generation (HHG) soft X-ray sources calls for an efficient use of photons, thus the development of low-loss multilayer optics is of uttermost importance. Here, we report about the realization of broadband Cr/Sc attosecond multilayer mirrors with nearly atomically smooth interfaces by an optimized ion beam deposition and assisted interface polishing process. This yields to our knowledge highest multilayer mirror reflectivity at 300 eV near normal incidence. The results are verified by transmission electron microscopy (TEM) and soft/hard X-ray reflectometry.

  2. Process for manufacturing multilayer capacitors

    DOEpatents

    Lauf, R.J.; Holcombe, C.E.; Dykes, N.L.

    1996-01-02

    The invention is directed to a method of manufacture of multilayer electrical components, especially capacitors, and components made by such a method. High capacitance dielectric materials and low cost metallizations layered with such dielectrics may be fabricated as multilayer electrical components by sintering the metallizations and the dielectrics during the fabrication process by application of microwave radiation. 4 figs.

  3. Process for manufacturing multilayer capacitors

    DOEpatents

    Lauf, Robert J.; Holcombe, Cressie E.; Dykes, Norman L.

    1996-01-01

    The invention is directed to a method of manufacture of multilayer electrical components, especially capacitors, and components made by such a method. High capacitance dielectric materials and low cost metallizations layered with such dielectrics may be fabricated as multilayer electrical components by sintering the metallizations and the dielectrics during the fabrication process by application of microwave radiation.

  4. Constraining depth-dependent anisotropy: A new approach

    NASA Astrophysics Data System (ADS)

    Ishii, M.; Okeler, A.

    2014-12-01

    Splitting of shear waves is commonly used to infer anisotropy of the Earth's interior. However, most data, such as SKS splitting, provide depth-integrated measure of anisotropy along the ray path, and it is difficult to separate contributions from different layers within the Earth. There have been efforts to focus on specific depth range by analyzing differences in splitting between two ray paths, but these studies only report observed differences or rely upon forward modeling with limited parameter-space search. We have developed a new approach to examine the P-to-S converted phases that allows one to construct depth-dependent multi-layer anisotropy models through combination of inversion and grid search. In addition to the conventional fast splitting direction and delay time, the technique allows one to investigate the tilt of the symmetry axis and dip of the discontinuity associated with the P-to-S conversion. Furthermore, the formulation is such that it naturally extends to include and examine multiple layers with different anisotropic properties. With these flexibilities, we can address anisotropic contributions from different layers in two separate procedures. The first scheme takes advantage of data with similar ray paths (e.g., SKS and SKKS waves recorded at the same station). The rays sample different structure when their ray paths differ (e.g., near the core-mantle boundary), but they sample the same structure when the paths are similar (e.g., in the upper part of the mantle and crust). Using our new approach, we can set up the problem as a two-layer anisotropy model where the layer with ray paths sampling different regions (e.g., lowermost mantle) is allowed to vary laterally. The second type of problem that can be addressed by the new approach is layer-by-layer investigation of anisotropy from top to bottom. This procedure combines the new method with receiver function analysis to obtain anisotropic properties of each layer using P-to-S converted waves

  5. Thermally induced magnetization switching in Gd/Fe multilayers

    NASA Astrophysics Data System (ADS)

    Xu, C.; Ostler, T. A.; Chantrell, R. W.

    2016-02-01

    A theoretical model of Gd/Fe multilayers is constructed using the atomistic spin dynamics formalism. By varying the thicknesses and number of layers we have shown that a strong dependence of the energy required for thermally induced magnetization switching (TIMS) is present; with a larger number of interfaces, lower energy is required. The results of the layer resolved dynamics show that the reversal process of the multilayered structures, similar to that of a GdFeCo alloy, is driven by the antiferromagnetic interaction between the transition-metal and rare-earth components. Finally, while the presence of the interface drives the reversal process, we show here that the switching process does not initiate at the surface but from the layers furthest from it, a departure from the alloy behavior which expands the classes of material types exhibiting TIMS.

  6. Nanostructure multilayer dielectric materials for capacitors and insulators

    DOEpatents

    Barbee, T.W. Jr.; Johnson, G.W.

    1998-04-21

    A capacitor is formed of at least two metal conductors having a multilayer dielectric and opposite dielectric-conductor interface layers in between. The multilayer dielectric includes many alternating layers of amorphous zirconium oxide (ZrO{sub 2}) and alumina (Al{sub 2}O{sub 3}). The dielectric-conductor interface layers are engineered for increased voltage breakdown and extended service life. The local interfacial work function is increased to reduce charge injection and thus increase breakdown voltage. Proper material choices can prevent electrochemical reactions and diffusion between the conductor and dielectric. Physical vapor deposition is used to deposit the zirconium oxide (ZrO{sub 2}) and alumina (Al{sub 2}O{sub 3}) in alternating layers to form a nano-laminate. 1 fig.

  7. Nanostructure multilayer dielectric materials for capacitors and insulators

    DOEpatents

    Barbee, Jr., Troy W.; Johnson, Gary W.

    1998-04-21

    A capacitor is formed of at least two metal conductors having a multilayer dielectric and opposite dielectric-conductor interface layers in between. The multilayer dielectric includes many alternating layers of amorphous zirconium oxide (ZrO.sub.2) and alumina (Al.sub.2 O.sub.3). The dielectric-conductor interface layers are engineered for increased voltage breakdown and extended service life. The local interfacial work function is increased to reduce charge injection and thus increase breakdown voltage. Proper material choices can prevent electrochemical reactions and diffusion between the conductor and dielectric. Physical vapor deposition is used to deposit the zirconium oxide (ZrO.sub.2) and alumina (Al.sub.2 O.sub.3) in alternating layers to form a nano-laminate.

  8. Interfacial oxygen migration and its effect on the magnetic anisotropy in Pt/Co/MgO/Pt films

    SciTech Connect

    Chen, Xi; Feng, Chun E-mail: ghyu@mater.ustb.edu.cn; Liu, Yang; Jiang, Shaolong; Hua Li, Ming; Hua Yu, Guang E-mail: ghyu@mater.ustb.edu.cn; Long Wu, Zheng; Yang, Feng

    2014-02-03

    This paper reports the interfacial oxygen migration effect and its induced magnetic anisotropy evolution in Pt/Co/MgO/Pt films. During depositing the MgO layer, oxygen atoms from the MgO combine with the neighboring Co atoms, leading to the formation of CoO at the Co/MgO interface. Meanwhile, the films show in-plane magnetic anisotropy (IMA). After annealing, most of the oxygen atoms in CoO migrate back to the MgO layer, resulting in obvious improvement of Co/MgO interface and the enhancement of effective Co-O orbital hybridization. These favor the evolution of magnetic anisotropy from IMA to perpendicular magnetic anisotropy (PMA). The oxygen migration effect is achieved by the redox reaction at the Co/MgO interface. On the contrary, the transfer from IMA to PMA cannot be observed in Pt/Co/Pt films due to the lack of interfacial oxygen migration.

  9. Interfacial oxygen migration and its effect on the magnetic anisotropy in Pt/Co/MgO/Pt films

    NASA Astrophysics Data System (ADS)

    Chen, Xi; Feng, Chun; Long Wu, Zheng; Yang, Feng; Liu, Yang; Jiang, Shaolong; Hua Li, Ming; Hua Yu, Guang

    2014-02-01

    This paper reports the interfacial oxygen migration effect and its induced magnetic anisotropy evolution in Pt/Co/MgO/Pt films. During depositing the MgO layer, oxygen atoms from the MgO combine with the neighboring Co atoms, leading to the formation of CoO at the Co/MgO interface. Meanwhile, the films show in-plane magnetic anisotropy (IMA). After annealing, most of the oxygen atoms in CoO migrate back to the MgO layer, resulting in obvious improvement of Co/MgO interface and the enhancement of effective Co-O orbital hybridization. These favor the evolution of magnetic anisotropy from IMA to perpendicular magnetic anisotropy (PMA). The oxygen migration effect is achieved by the redox reaction at the Co/MgO interface. On the contrary, the transfer from IMA to PMA cannot be observed in Pt/Co/Pt films due to the lack of interfacial oxygen migration.

  10. Spin confinement by anisotropy modulation

    NASA Astrophysics Data System (ADS)

    Bland, J. A. C.; Lew, W. S.; Li, S. P.; Lopez-Diaz, L.; Vaz, C. A. F.; Natali, M.; Chen, Y.

    2002-10-01

    The spin configuration in a magnet is in general a `natural' consequence of both the intrinsic properties of the material and the sample dimensions. We demonstrate that this limitation can be overcome in a homogeneous ferromagnetic film by engineering an anisotropy contrast. Substrates with laterally modulated single-crystal and polycrystalline surface regions were used to induce selective epitaxial growth of a ferromagnetic Ni film. The resulting spatially varying magnetic anisotropy leads to regular perpendicular and in-plane magnetic domains, separated by a new type of magnetic domain wall-the `anisotropy constrained' magnetic wall. Micromagnetic simulations indicate that the wall is asymmetric, has a small out-of-plane component and has no mobility under external perturbation.

  11. In situ x-ray investigation of freestanding nanoscale Cu-Nb multilayers under tensile load.

    SciTech Connect

    Aydiner, C. C.; Misra, A.; Brown, D. W.; Mara, N. A.; Almer, J. D

    2009-01-01

    The yield behavior in a freestanding sputter-deposited Cu/Nb multilayer with 30 nm nominal individual layer thickness has been investigated with in situ synchrotron x-ray diffraction during tensile loading. A pronounced elastic-plastic transition is observed with the fraction of plastically yielded grains increasing gradually with strain. Near synchronous yielding is observed in the Cu and Nb grains. The gradual progression in yield behavior is interpreted in terms of residual stresses, and elastic and plastic anisotropy.

  12. Wrapped Multilayer Insulation

    NASA Technical Reports Server (NTRS)

    Dye, Scott A.

    2015-01-01

    New NASA vehicles, such as Earth Departure Stage (EDS), Orion, landers, and orbiting fuel depots, need improved cryogenic propellant transfer and storage for long-duration missions. Current cryogen feed line multilayer insulation (MLI) performance is 10 times worse per area than tank MLI insulation. During each launch, cryogenic piping loses approximately 150,000 gallons (equivalent to $300,000) in boil-off during transfer, chill down, and ground hold. Quest Product Development Corp., teaming with Ball Aerospace, developed an innovative advanced insulation system, Wrapped MLI (wMLI), to provide improved thermal insulation for cryogenic feed lines. wMLI is high-performance multilayer insulation designed for cryogenic piping. It uses Quest's innovative discrete-spacer technology to control layer spacing/ density and reduce heat leak. The Phase I project successfully designed, built, and tested a wMLI prototype with a measured heat leak 3.6X lower than spiral-wrapped conventional MLI widely used for piping insulation. A wMLI prototype had a heat leak of 7.3 W/sq m, or 27 percent of the heat leak of conventional MLI (26.7 W/sq m). The Phase II project is further developing wMLI technology with custom, molded polymer spacers and advancing the product toward commercialization via a rigorous testing program, including developing advanced vacuuminsulated pipe for ground support equipment.

  13. Wrapped Multilayer Insulation

    NASA Technical Reports Server (NTRS)

    Dye, Scott A.

    2015-01-01

    New NASA vehicles, such as Earth Departure Stage (EDS), Orion, landers, and orbiting fuel depots, need improved cryogenic propellant transfer and storage for long-duration missions. Current cryogen feed line multilayer insulation (MLI) performance is 10 times worse per area than tank MLI insulation. During each launch, cryogenic piping loses approximately 150,000 gallons (equivalent to $300,000) in boil-off during transfer, chill down, and ground hold. Quest Product Development Corp., teaming with Ball Aerospace, developed an innovative advanced insulation system, Wrapped MLI (wMLI), to provide improved thermal insulation for cryogenic feed lines. wMLI is high-performance multilayer insulation designed for cryogenic piping. It uses Quest's innovative discrete-spacer technology to control layer spacing/ density and reduce heat leak. The Phase I project successfully designed, built, and tested a wMLI prototype with a measured heat leak 3.6X lower than spiral-wrapped conventional MLI widely used for piping insulation. A wMLI prototype had a heat leak of 7.3 W/m2, or 27 percent of the heat leak of conventional MLI (26.7 W/m2). The Phase II project is further developing wMLI technology with custom, molded polymer spacers and advancing the product toward commercialization via a rigorous testing program, including developing advanced vacuuminsulated pipe for ground support equipment.

  14. Ultrahard Multilayer Coatings

    SciTech Connect

    Chrzan, D.C.; Dugger, M.; Follstaedt, D.M.; Friedman, Lawrence H.; Friedmann, T.A.; Knapp, J.A.; McCarty, K.F.; Medlin, D.L.; Mirkarimi, P.B.; Missert, N.; Newcomer, P.P.; Sullivan, J.P.; Tallant, D.R.

    1999-05-01

    We have developed a new multilayer a-tC material that is thick stress-free, adherent, low friction, and with hardness and stiffness near that of diamond. The new a-tC material is deposited by J pulsed-laser deposition (PLD) at room temperature, and fully stress-relieved by a short thermal anneal at 600°C. A thick multilayer is built up by repeated deposition and annealing steps. We measured 88 GPa hardness, 1100 GPa Young's modulus, and 0.1 friction coefficient (under high load). Significantly, these results are all well within the range reported for crystalline diamond. In fact, this material, if considered separate from crystalline diamond, is the 2nd hardest material known to man. Stress-free a-tC also has important advantages over thin film diamond; namely, it is smooth, processed at lower temperature, and can be grown on a much broader range of substrates. This breakthrough will enable a host of applications that we are actively pursuing in MEMs, sensors, LIGA, etc.

  15. Nucleation and Growth of Bubbles in He Ion Implanted V/Ag Multilayers

    SciTech Connect

    Wei, Q. M.; Wang, Y. Q.; Nastasi, Michael; Misra, A.

    2011-11-18

    Microstructures of He ion-implanted pure Ag, pure V and polycrystalline V/Ag multilayers with individual layer thickness ranging from 1 nm to 50 nm were investigated by transmission electron microscopy (TEM). The bubbles in the Ag layer were faceted and larger than the non-faceted bubbles in the V layer under the same implantation conditions for both pure metals and multilayers. The substantially higher single defects surviving the spike phase and lower mobility of trapped He in bcc than those in fcc could account for this difference. For multilayers, the bubbles nucleate at interfaces but grow preferentially in Ag layers due to high mobility of trapped He in fcc Ag. In addition, the He concentration above which bubbles can be detected in defocused TEM images increases with decreasing layer thickness, from 0 for pure Ag to 4–5 at. % for 1 nm V/1 nm Ag multilayers. In contrast, the bubble size decreases with decreasing layer thickness, from approximately 4 nm in diameter in pure Ag to 1 nm in the 1 nm V/1 nm Ag multilayers. Elongated bubbles confined in the Ag layer by the V–Ag interfaces were observed in 1 nm multilayers. These observations show that bubble nucleation and growth can be suppressed to high He concentrations in nanoscale composites with interfaces that have high He solubility.

  16. Co/Pt and Co/Pd multilayers as new magneto-optical recording media (abstract)

    NASA Astrophysics Data System (ADS)

    Zeper, W. B.; van Kesteren, H. W.; Jacobs, B. A. J.; Spruit, J. H. M.; Carcia, P. F.

    1991-04-01

    In this paper we will discuss Co/Pt and, to a lesser extent, Co/Pd multilayers optimized for magneto-optical storage applications. Perpendicular magnetic anisotropy and square hysteresis loops are achieved for multilayers with a total thickness below about 200 Å if they consist of very thin (≂4 Å) Co layers alternated with 10-20-Å Pt layers. Multilayer made by evaporation show a high coercivity (≳100 kA/m) and have proven to be suitable as magneto-optical recording medium. Recently we showed that Co/Pt layers with high coercivity can be made by sputtering as well, if not Ar but Kr is used as sputter gas.1 We will discuss the properties of Co/Pt multilayers in relation to the preparation technique and will present magneto-optical recording results for both evaporated and sputtered Co/Pt multilayer films. The written domain patterns can be very regular, as observed by scanning magnetic force microscopy, and a CNR as high as 55 dB (1 MHz carrier, 5 m/s, 30 kHz BW) is observed. The good oxidation and corrosion resistance together with increasing Kerr effect towards shorter wavelengths, where higher storage densities are possible, make that Co/Pt multilayers are attractive new magneto-optical recording media.

  17. Amiba Observation of CMB Anisotropies

    NASA Astrophysics Data System (ADS)

    Ng, Kin-Wang

    2003-03-01

    The Array for Microwave Background Anisotropies (AMiBA), a 13-element dual-channel 85-105 GHz interferometer array with full polarization capabilities, is being built to search for high redshift clusters of galaxies via the Sunyaev-Zel'dovich effect as well as to probe the polarization properties of the cosmic microwave background (CMB). We discuss several important issues in the observation of the CMB anisotropies such as observing strategy, l space resolution and mosaicing, optimal estimation of the power spectra, and ground pickup removal.

  18. Second order anisotropy contribution in perpendicular magnetic tunnel junctions

    PubMed Central

    Timopheev, A. A.; Sousa, R.; Chshiev, M.; Nguyen, H. T.; Dieny, B.

    2016-01-01

    Hard-axis magnetoresistance loops were measured on perpendicular magnetic tunnel junction pillars of diameter ranging from 50 to 150 nm. By fitting these loops to an analytical model, the effective anisotropy fields in both free and reference layers were derived and their variations in temperature range between 340 K and 5 K were determined. It is found that a second-order anisotropy term of the form −K2cos4θ must be added to the conventional uniaxial –K1cos2θ term to explain the experimental data. This higher order contribution exists both in the free and reference layers. At T = 300 K, the estimated −K2/K1 ratios are 0.1 and 0.24 for the free and reference layers, respectively. The ratio is more than doubled at low temperatures changing the ground state of the reference layer from “easy-axis” to “easy-cone” regime. The easy-cone regime has clear signatures in the shape of the hard-axis magnetoresistance loops. The existence of this higher order anisotropy was also confirmed by ferromagnetic resonance experiments on FeCoB/MgO sheet films. It is of interfacial nature and is believed to be due to spatial fluctuations at the nanoscale of the first order anisotropy parameter at the FeCoB/MgO interface. PMID:27246631

  19. Second order anisotropy contribution in perpendicular magnetic tunnel junctions.

    PubMed

    Timopheev, A A; Sousa, R; Chshiev, M; Nguyen, H T; Dieny, B

    2016-01-01

    Hard-axis magnetoresistance loops were measured on perpendicular magnetic tunnel junction pillars of diameter ranging from 50 to 150 nm. By fitting these loops to an analytical model, the effective anisotropy fields in both free and reference layers were derived and their variations in temperature range between 340 K and 5 K were determined. It is found that a second-order anisotropy term of the form -K2cos(4)θ must be added to the conventional uniaxial -K1cos(2)θ term to explain the experimental data. This higher order contribution exists both in the free and reference layers. At T = 300 K, the estimated -K2/K1 ratios are 0.1 and 0.24 for the free and reference layers, respectively. The ratio is more than doubled at low temperatures changing the ground state of the reference layer from "easy-axis" to "easy-cone" regime. The easy-cone regime has clear signatures in the shape of the hard-axis magnetoresistance loops. The existence of this higher order anisotropy was also confirmed by ferromagnetic resonance experiments on FeCoB/MgO sheet films. It is of interfacial nature and is believed to be due to spatial fluctuations at the nanoscale of the first order anisotropy parameter at the FeCoB/MgO interface. PMID:27246631

  20. Second order anisotropy contribution in perpendicular magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Timopheev, A. A.; Sousa, R.; Chshiev, M.; Nguyen, H. T.; Dieny, B.

    2016-06-01

    Hard-axis magnetoresistance loops were measured on perpendicular magnetic tunnel junction pillars of diameter ranging from 50 to 150 nm. By fitting these loops to an analytical model, the effective anisotropy fields in both free and reference layers were derived and their variations in temperature range between 340 K and 5 K were determined. It is found that a second-order anisotropy term of the form ‑K2cos4θ must be added to the conventional uniaxial –K1cos2θ term to explain the experimental data. This higher order contribution exists both in the free and reference layers. At T = 300 K, the estimated ‑K2/K1 ratios are 0.1 and 0.24 for the free and reference layers, respectively. The ratio is more than doubled at low temperatures changing the ground state of the reference layer from “easy-axis” to “easy-cone” regime. The easy-cone regime has clear signatures in the shape of the hard-axis magnetoresistance loops. The existence of this higher order anisotropy was also confirmed by ferromagnetic resonance experiments on FeCoB/MgO sheet films. It is of interfacial nature and is believed to be due to spatial fluctuations at the nanoscale of the first order anisotropy parameter at the FeCoB/MgO interface.

  1. Mechanism of tailored magnetic anisotropy in amorphous Co{sub 68}Fe{sub 24}Zr{sub 8} thin films

    SciTech Connect

    Fu, Yu E-mail: cangcangzhulin@gmail.com; Meckenstock, R.; Farle, M.; Barsukov, I.; Lindner, J.; Raanaei, H.; Hjörvarsson, B.

    2014-02-17

    The mechanism of tailored magnetic anisotropy in amorphous Co{sub 68}Fe{sub 24}Zr{sub 8} thin films was investigated by ferromagnetic resonance (FMR) on samples deposited without an applied magnetic field, with an out-of-plane field and an in-plane field. Analysis of FMR spectra profiles, high frequency susceptibility calculations, and statistical simulations using a distribution of local uniaxial magnetic anisotropy reveal the presence of atomic configurations with local uniaxial anisotropy, of which the direction can be tailored while the magnitude remains at an intrinsically constant value of 3.0(2) kJ/m{sup 3}. The in-plane growth field remarkably sharpens the anisotropy distribution and increases the sample homogeneity. The results benefit designing multilayer spintronic devices based on highly homogeneous amorphous layers with tailored magnetic anisotropy.

  2. Pinned orbital moments - A new contribution to magnetic anisotropy.

    PubMed

    Audehm, P; Schmidt, M; Brück, S; Tietze, T; Gräfe, J; Macke, S; Schütz, G; Goering, E

    2016-01-01

    Reduced dimensionality and symmetry breaking at interfaces lead to unusual local magnetic configurations, such as glassy behavior, frustration or increased anisotropy. The interface between a ferromagnet and an antiferromagnet is such an example for enhanced symmetry breaking. Here we present detailed X-ray magnetic circular dichroism and X-ray resonant magnetic reflectometry investigations on the spectroscopic nature of uncompensated pinned magnetic moments in the antiferromagnetic layer of a typical exchange bias system. Unexpectedly, the pinned moments exhibit nearly pure orbital moment character. This strong orbital pinning mechanism has not been observed so far and is not discussed in literature regarding any theory for local magnetocrystalline anisotropy energies in magnetic systems. To verify this new phenomenon we investigated the effect at different temperatures. We provide a simple model discussing the observed pure orbital moments, based on rotatable spin magnetic moments and pinned orbital moments on the same atom. This unexpected observation leads to a concept for a new type of anisotropy energy. PMID:27151436

  3. Pinned orbital moments – A new contribution to magnetic anisotropy

    PubMed Central

    Audehm, P.; Schmidt, M.; Brück, S.; Tietze, T.; Gräfe, J.; Macke, S.; Schütz, G.; Goering, E.

    2016-01-01

    Reduced dimensionality and symmetry breaking at interfaces lead to unusual local magnetic configurations, such as glassy behavior, frustration or increased anisotropy. The interface between a ferromagnet and an antiferromagnet is such an example for enhanced symmetry breaking. Here we present detailed X-ray magnetic circular dichroism and X-ray resonant magnetic reflectometry investigations on the spectroscopic nature of uncompensated pinned magnetic moments in the antiferromagnetic layer of a typical exchange bias system. Unexpectedly, the pinned moments exhibit nearly pure orbital moment character. This strong orbital pinning mechanism has not been observed so far and is not discussed in literature regarding any theory for local magnetocrystalline anisotropy energies in magnetic systems. To verify this new phenomenon we investigated the effect at different temperatures. We provide a simple model discussing the observed pure orbital moments, based on rotatable spin magnetic moments and pinned orbital moments on the same atom. This unexpected observation leads to a concept for a new type of anisotropy energy. PMID:27151436

  4. MD simulation of nanoindentation on (001) and (111) surfaces of Ag-Ni multilayers

    NASA Astrophysics Data System (ADS)

    Zhao, Yinbo; Peng, Xianghe; Fu, Tao; Sun, Rong; Feng, Chao; Wang, Zhongchang

    2015-11-01

    We perform MD simulations of the nanoindentation on (001) and (111) surfaces of Ag-Ni multilayers with different modulation periods, and find that both the hardness and maximum force increase with the increase of modulation period, in agreement with the inverse Hall-Petch relation. A prismatic partial dislocation loop is observed in the Ni(111)/Ag(111) sample when the modulation period is relatively large. We also find that misfit dislocation network shows a square shape for the Ni(111)/Ag(111) interface, while a triangle shape for the Ni(001)/Ag(001) interface. The pyramidal defect zones are also observed in Ni(001)/Ag(001) sample, while the intersecting stacking faults are observed in Ni(111)/Ag(111) sample after dislocation traversing interface. The results offer insights into the nanoindentation behaviors in metallic multilayers, which should be important for clarifying strengthening mechanism in many other multilayers.

  5. Multilayer heterostructures of magnetic Heusler and binary compounds from first principles

    NASA Astrophysics Data System (ADS)

    Garoufalis, Christos; Galanakis, Iosif

    2016-03-01

    Employing first-principles state-of-the-art electronic structure calculations, we study a series of multilayer heterostructures composed of ferro/ferrimagnetic half-metallic Heusler compounds and binary compounds presenting perpendicular magnetic anisotropy. We relax these heterostructures and study both their electronic and magnetic properties. In most studied cases the Heusler spacer keeps a large value of spin-polarization at the Fermi level even for ultrathin films which attends the maximum value of 100% in the case of the Mn2VSi/MnSi multilayer. Our results pave the way both experimentally and theoretically towards the growth of such multilayer heterostructures and their incorporation in spintronic/magnetoelectronic devices.

  6. Ellipsometric and magneto-optic properties of sputtered dysprosium-iron multilayers

    NASA Astrophysics Data System (ADS)

    Tiwald, Thomas E.; Woollam, John A.; Sellmyer, D. J.

    1988-04-01

    Ellipsometric and magneto-optical properties of Dy (3.5 Å thick) and Fe (2.5-12.5 Å thick) multilayers were investigated over the spectral range from 3000 to 8000 Å in magnetic fields to 0.21 T. In this range of layer thickness the magnetic anisotropy is vertical. Kerr rotations, were found to be weakly spectrally dependent, and as large as 0.06°. The magnetically driven change of ellipticity of reflected light was as large as 0.13, depending on sample and wavelength. Ellipsometric analysis of layer thickness was performed assuming a multilayer geometry. In addition, the optical constants were determined assuming the multilayer was a homogeneous layer with ``effective'' properties.

  7. Mirroring the dynamic magnetic behavior of magnetostrictive Co/(Ag,Cu,Ta) multilayers grown onto rigid and flexible substrates

    NASA Astrophysics Data System (ADS)

    Agra, K.; Gomes, R. R.; Della Pace, R. D.; Dorneles, L. S.; Bohn, F.; Corrêa, M. A.

    2015-11-01

    We investigate the magnetoimpedance effect in a wide frequency range in magnetostrictive Co/(Ag,Cu,Ta) multilayers grown onto rigid and flexible substrates. We observe a direct correlation between structural and quasi-static magnetic properties and the magnetoimpedance effect, since they are directly dependent on the nature of the spacer material. Moreover, we verify that all these properties are insensitive to the kind of employed substrate. We compare the magnetoimpedance results measured for multilayers in rigid and flexible substrates and discuss them in terms of different mechanisms that govern the impedances changes, magnetic anisotropy, structural character, and of numerical calculation results found in the literature. The fact that magnetostrictive multilayers can be reproduced in distinct kinds of substrates corresponds to an important advance for their applicability. The results place multilayers grown onto flexible substrates as attractive candidates for application as probe element in the development of MI-based sensor devices.

  8. Tactile display with dielectric multilayer elastomer actuatorsq

    NASA Astrophysics Data System (ADS)

    Matysek, Marc; Lotz, Peter; Schlaak, Helmut F.

    2009-03-01

    Tactile perception is the human sensation of surface textures through the vibrations generated by stroking a finger over the surface. The skin responds to several distributed physical quantities. Perhaps the most important are high-frequency vibrations, pressure distributions (static shape) and thermal properties. The integration of tactile displays in man-machine interfaces promises a more intuitive handling. For this reason many tactile displays are developed using different technologies. We present several state-of-the-art tactile displays based on different types of dielectric elastomer actuators to clarify the advantages of our matrix display based on multilayer technology. Using this technology perpendicular and hexagonal arrays of actuator elements (tactile stimulators) can be integrated into a PDMS substrate. Element diameters down to 1 mm allow stimuli at the range of the human two-point-discrimination threshold. Driving the elements by column and row addressing enables various stimulation patterns with a reduced number of feeding lines. The transient analysis determines charging times of the capacitive actuators depending on actuator geometry and material parameters. This is very important to ensure an adequate dynamic characteristic of the actuators to stimulate the human skin by vibrations. The suitability of multilayer dielectric elastomer actuators for actuation in tactile displays has been determined. Beside the realization of a static tactile display - where multilayer DEA are integrated as drives for movable contact pins - we focus on the direct use of DEA as a vibrotactile display. Finally, we present the scenario and achieved results of a recognition threshold test. Even relative low voltages in the range of 800 V generate vibrations with 100% recognition ratio within the group of participants. Furthermore, the frequency dependent characteristic of the determined recognition threshold confirms with established literature.

  9. Patterning of magnetic thin films and multilayers using nanostructured tantalum gettering templates.

    PubMed

    Qiu, Wenlan; Chang, Long; Lee, Dahye; Dannangoda, Chamath; Martirosyan, Karen; Litvinov, Dmitri

    2015-03-25

    This work demonstrates that a nonmagnetic thin film of cobalt oxide (CoO) sandwiched between Ta seed and capping layers can be effectively reduced to a magnetic cobalt thin film by annealing at 200 °C, whereas CoO does not exhibit ferromagnetic properties at room temperature and is stable at up to ∼400 °C. The CoO reduction is attributed to the thermodynamically driven gettering of oxygen by tantalum, similar to the exothermic reduction-oxidation reaction observed in thermite systems. Similarly, annealing at 200 °C of a nonmagnetic [CoO/Pd]N multilayer thin film sandwiched between Ta seed and Ta capping layers results in the conversion into a magnetic [Co/Pd]N multilayer, a material with perpendicular magnetic anisotropy that is of interest for magnetic data storage applications. A nanopatterning approach is introduced where [CoO/Pd]N multilayers is locally reduced into [Co/Pd]N multilayers to achieve perpendicular magnetic anisotropy nanostructured array. This technique can potentially be adapted to nanoscale patterning of other systems for which thermodynamically favorable combination of oxide and gettering layers can be identified. PMID:25761738

  10. A functional protein retention and release multilayer with high stability

    NASA Astrophysics Data System (ADS)

    Nie, Kun; An, Qi; Zhang, Yihe

    2016-04-01

    Effective and robust interfacial protein retention lies at the heart of the fabrication of protein-based functional interfaces, which is potentially applicable in catalysis, medical therapy, antifouling, and smart devices, but remains challenging due to the sensitive nature of proteins. This study reports a general protein retention strategy to spatial-temporally confine various types of proteins at interfacial regions. The proteins were preserved in mesoporous silica nanoparticles embedded in covalently woven multilayers. It is worth noting that the protein retention strategy effectively preserves the catalytic capabilities of the proteins, and the multilayer structure is robust enough to withstand the bubbling catalytic reactions and could be repeatedly used due to conservation of proteins. The spatiotemporal retention of proteins could be adjusted by varying the number of capping layers. Furthermore, we demonstrate that the protein-loaded interfacial layers could not only be used to construct catalytic-active interfaces, but also be integrated as the power-generating unit to propel a macroscopic floating device.Effective and robust interfacial protein retention lies at the heart of the fabrication of protein-based functional interfaces, which is potentially applicable in catalysis, medical therapy, antifouling, and smart devices, but remains challenging due to the sensitive nature of proteins. This study reports a general protein retention strategy to spatial-temporally confine various types of proteins at interfacial regions. The proteins were preserved in mesoporous silica nanoparticles embedded in covalently woven multilayers. It is worth noting that the protein retention strategy effectively preserves the catalytic capabilities of the proteins, and the multilayer structure is robust enough to withstand the bubbling catalytic reactions and could be repeatedly used due to conservation of proteins. The spatiotemporal retention of proteins could be adjusted by

  11. Anisotropy of machine building materials

    NASA Technical Reports Server (NTRS)

    Ashkenazi, Y. K.

    1981-01-01

    The results of experimental studies of the anisotropy of elastic and strength characteristics of various structural materials, including pressure worked metals and alloys, laminated fiberglass plastics, and laminated wood plastics, are correlated and classified. Strength criteria under simple and complex stresses are considered as applied to anisotropic materials. Practical application to determining the strength of machine parts and structural materials is discussed.

  12. Varying deformation patterns in central Tibet revealed by radial anisotropy tomography

    NASA Astrophysics Data System (ADS)

    Zhang, Heng; Zhao, Dapeng; Yu, Chunquan; Zhao, Junmeng

    2016-05-01

    P wave radial anisotropy tomography of the upper mantle beneath the central Tibetan plateau is derived using a large number of traveltime data of teleseismic events. Our results show a prominent high-velocity (high-V) zone which is separated by a low-velocity (low-V) anomaly beneath the Himalayan block, extending to ~33°N, and a low-V zone down to ~300 km depth beneath the northern Qiangtang block. The upper mantle beneath northern Qiangtang exhibits a significant positive radial anisotropy (i.e., horizontal Vp > vertical Vp), implying lateral material flow rather than material upwelling in the upper mantle. In the central part of the study region, a prominent high-V zone exists at depths of 150 to 300 km and exhibits a negative radial anisotropy (i.e., horizontal Vp < vertical Vp), reflecting the subducting Indian lithospheric mantle. Variations of shear wave splitting in this region revealed by previous studies may be attributed to the low-V layer above the Indian lithospheric mantle. A high-V zone with a positive radial anisotropy is located beneath the southern Lhasa block, which is interpreted to be the northward underthrusting Indian lithospheric mantle. Multilayer radial anisotropy is detected beneath southern Tibet, which may reflect a complex deformation pattern there.

  13. Exchange anisotropy, engineered coercivity and spintronics in atomically engineered L1{sub 0} heterostructures

    SciTech Connect

    Krishnan, Kannan M

    2011-08-30

    undisturbed. As a result, the method is unsuitable for epitaxial growth, since the latter often involves growth at elevated temperatures higher than the glass transition temperature of the resist. Therefore, a mask transfer NIL process was developed to grow epitaxial nanostructure arrays at elevated temperatures where organic resists are rendered unstable. In the case of the metal/oxide heterostructures, the domain structure of the metal is carefully modulated by that of the underlying oxide, opening the possibility of carrying out novel experiments to study spin-dependent domain-wall scattering and quantify domain wall resistance in mesoscopic geometries. Utilizing state-of-the-art characterization methods, using synchrotron radiation and electron holography, we addressed the critical role of all aspects of the microstructure, at relevant length scales, in determining these specific magnetic properties. Two significant highlights of this project were the use of photoemission electron microscopy (PEEM) work to elucidate their asymmetric magnetization reversal mechanism and the use of element-specific X-ray magnetic reflectivity and x-ray resonant scattering to probe buried interfaces, both of importance in understanding the fundamental physics of exchange bias. In the latter case, a complex magnetic interfacial configuration in Fe/MnPd, consisting of a 2-monolayer-thick induced ferromagnetic region, and pinned uncompensated Mn moments that reach far deeper (~13 Å), both in the antiferromagnet, were found. Such epitaxial EB samples also show in-plane reorientation transitions, determined by the competition between the interface exchange coupling and the intrinsic uniaxial energies, and is driven by the temperature, as well as the thickness of MnPd and Fe layers. Complementing these results, work on multilayers show that perpendicular EB arise from a complex interplay between unidirectional anisotropy at the terminating FM/AFM interface, the perpendicular anisotropy of the FM

  14. WSi2/Si multilayer sectioning by reactive ion etching for multilayer Laue lens fabrication

    NASA Astrophysics Data System (ADS)

    Bouet, N.; Conley, R.; Biancarosa, J.; Divan, R.; Macrander, A. T.

    2010-09-01

    for only a small number of materials, and even less recipes exist for concurrent etching of more than one element so a fully material specific process needs to be developed. In this paper, sectioning of WSi2/Si multilayers for MLL fabrication using fluorinated gases is investigated. The main goals were to demonstrate the feasibility of this technique, achievement of high anisotropy, adequate sidewall roughness control and high etching rates. We note that this development for MLL sidewalls should be distinguished from work on improving aspect ratios in traditional Fresnel zone plates. Aspect ratios for MLL sidewalls are not similarly constrained.

  15. Multilayer graphene condenser microphone

    NASA Astrophysics Data System (ADS)

    Todorović, Dejan; Matković, Aleksandar; Milićević, Marijana; Jovanović, Djordje; Gajić, Radoš; Salom, Iva; Spasenović, Marko

    2015-12-01

    Vibrating membranes are the cornerstone of acoustic technology, forming the backbone of modern loudspeakers and microphones. Acoustic performance of a condenser microphone is derived mainly from the membrane’s size, surface mass and achievable static tension. The widely studied and available nickel has been a dominant membrane material for professional microphones for several decades. In this paper we introduce multilayer graphene as a membrane material for condenser microphones. The graphene device outperforms a high end commercial nickel-based microphone over a significant part of the audio spectrum, with a larger than 10 dB enhancement of sensitivity. Our experimental results are supported with numerical simulations, which also show that a 300 layer thick graphene membrane under maximum tension would offer excellent extension of the frequency range, up to 1 MHz.

  16. Multilayer diamond coated WC tools

    SciTech Connect

    Fan, W.D.; Jagannaham, K.; Narayan, J.

    1995-12-31

    To increase adhesion of diamond coatings, a multilayer structure was developed. The multilayer diamond coating consisted of a first discontinuous diamond layer, an interposing layer, and a top continuous diamond layer. The diamond layer was grown on WC substrates by hot filament chemical vapor deposition and the interposing layer was grown by pulsed laser deposition. Machining tests were used to characterize adhesion properties of the multilayer diamond coatings on WC(Co) substrates. Results indicate that diamond coatings exhibit good adhesion on the WC tool substrates. The wear resistance of the WC tool is improved significantly by the diamond coatings.

  17. Integrated Multilayer Insulation

    NASA Technical Reports Server (NTRS)

    Dye, Scott

    2009-01-01

    Integrated multilayer insulation (IMLI) is being developed as an improved alternative to conventional multilayer insulation (MLI), which is more than 50 years old. A typical conventional MLI blanket comprises between 10 and 120 metallized polymer films separated by polyester nets. MLI is the best thermal- insulation material for use in a vacuum, and is the insulation material of choice for spacecraft and cryogenic systems. However, conventional MLI has several disadvantages: It is difficult or impossible to maintain the desired value of gap distance between the film layers (and consequently, it is difficult or impossible to ensure consistent performance), and fabrication and installation are labor-intensive and difficult. The development of IMLI is intended to overcome these disadvantages to some extent and to offer some additional advantages over conventional MLI. The main difference between IMLI and conventional MLI lies in the method of maintaining the gaps between the film layers. In IMLI, the film layers are separated by what its developers call a micro-molded discrete matrix, which can be loosely characterized as consisting of arrays of highly engineered, small, lightweight, polymer (typically, thermoplastic) frames attached to, and placed between, the film layers. The term "micro-molded" refers to both the smallness of the frames and the fact that they are fabricated in a process that forms precise small features, described below, that are essential to attainment of the desired properties. The term "discrete" refers to the nature of the matrix as consisting of separate frames, in contradistinction to a unitary frame spanning entire volume of an insulation blanket.

  18. The microwave background anisotropies: observations.

    PubMed

    Wilkinson, D

    1998-01-01

    Most cosmologists now believe that we live in an evolving universe that has been expanding and cooling since its origin about 15 billion years ago. Strong evidence for this standard cosmological model comes from studies of the cosmic microwave background radiation (CMBR), the remnant heat from the initial fireball. The CMBR spectrum is blackbody, as predicted from the hot Big Bang model before the discovery of the remnant radiation in 1964. In 1992 the cosmic background explorer (COBE) satellite finally detected the anisotropy of the radiation-fingerprints left by tiny temperature fluctuations in the initial bang. Careful design of the COBE satellite, and a bit of luck, allowed the 30 microK fluctuations in the CMBR temperature (2.73 K) to be pulled out of instrument noise and spurious foreground emissions. Further advances in detector technology and experiment design are allowing current CMBR experiments to search for predicted features in the anisotropy power spectrum at angular scales of 1 degrees and smaller. If they exist, these features were formed at an important epoch in the evolution of the universe--the decoupling of matter and radiation at a temperature of about 4,000 K and a time about 300,000 years after the bang. CMBR anisotropy measurements probe directly some detailed physics of the early universe. Also, parameters of the cosmological model can be measured because the anisotropy power spectrum depends on constituent densities and the horizon scale at a known cosmological epoch. As sophisticated experiments on the ground and on balloons pursue these measurements, two CMBR anisotropy satellite missions are being prepared for launch early in the next century. PMID:9419320

  19. Finite element analysis of multilayer coextrusion.

    SciTech Connect

    Hopkins, Matthew Morgan; Schunk, Peter Randall; Baer, Thomas A.; Mrozek, Randy A.; Lenhart, Joseph Ludlow; Rao, Rekha Ranjana; Collins, Robert; Mondy, Lisa Ann

    2011-09-01

    Multilayer coextrusion has become a popular commercial process for producing complex polymeric products from soda bottles to reflective coatings. A numerical model of a multilayer coextrusion process is developed based on a finite element discretization and two different free-surface methods, an arbitrary-Lagrangian-Eulerian (ALE) moving mesh implementation and an Eulerian level set method, to understand the moving boundary problem associated with the polymer-polymer interface. The goal of this work is to have a numerical capability suitable for optimizing and troubleshooting the coextrusion process, circumventing flow instabilities such as ribbing and barring, and reducing variability in layer thickness. Though these instabilities can be both viscous and elastic in nature, for this work a generalized Newtonian description of the fluid is used. Models of varying degrees of complexity are investigated including stability analysis and direct three-dimensional finite element free surface approaches. The results of this work show how critical modeling can be to reduce build test cycles, improve material choices, and guide mold design.

  20. Guided modes in a uniaxial multilayer.

    PubMed

    Avrutsky, Ivan

    2003-03-01

    An algorithm is presented for simulation of guided modes in a multilayer uniaxial structure with each layer characterized by its own ellipsoid of refractive indices and direction of optical axis. The proposed approach is based on presenting an electromagnetic field in each layer as a linear combination of ordinary and extraordinary waves coupled through the boundary conditions. The problem is reduced to two dimensions by considering the waves with a given projection of the wave vector on the plane of the waveguide. No a priori assumption about the guided-mode polarization is required in this method. Hybrid polarized modes appear naturally as solutions of a system of linear equations with respect to the amplitudes of the ordinary and extraordinary waves. The proposed approach covers a wide variety of important practical cases including isotropic waveguides, surface waves at the boundary between positive uniaxial crystal and isotropic medium, surface plasmons at metallic interfaces, uniaxial multilayers in a very general form, and leaky modes in such structures. PMID:12630841

  1. Simulation of EUV multilayer mirror buried defects

    NASA Astrophysics Data System (ADS)

    Brukman, Matthew J.; Deng, Yunfei; Neureuther, Andrew R.

    2000-07-01

    A new interface has been created to link existing deposition/etching and electromagnetic simulation software, allowing the user to program deposition and etching conditions and then find the reflective properties of the resultant structure. The application studied in this paper is the problem of three-dimensional defects which become buried during fabrication of multilayer mirrors for extreme ultraviolet lithography. The software link reads in surface information in the form of linked triangles, determines all nodes within the triangles, and then creates nodes lying between triangles of different layers to create a 3- dimensional inhomogeneous matrix containing the materials' indices of refraction. This allows etching and depositions to be input into SAMPLE-3D, a multi-surface topology to be generated, and then the electromagnetic properties of the structure to be assessed with TEMPEST. This capability was used to study substrate defects in multilayer mirrors by programming a defect and then sputter-depositing some forty layers on top of the defect. Specifically examined was how the topography depended on sputter conditions and determined the defects' impact on the mirrors' imaging properties. While this research was focused on application to EUV lithography, the general technique may be extended to other optical processes such as alignment and mask defects.

  2. Direct laser interference patterning of Co/Pt thin film multilayers

    NASA Astrophysics Data System (ADS)

    Aktag, Aliekber; Yue, Lanping; Michalski, Steven; Hawang Liou, Sy; Kirby, Roger D.

    2004-03-01

    Direct laser interference patterning can be used to pattern magnetic thin films. By controlling the number of interfering laser beams, and their incidence angles, polarization, wavelength and power, a wide variety of nanodot arrays can be obtained through local heating in the regions of constructive interference. We used three interfering laser beams to create magnetically- and topographically-modified nanodot arrays (500 nm length scale) in Co/Pt multilayer thin films. The topographic and magnetic modifications of the films were studied by AFM and MFM, while the magnetic properties were studied using magneto-optic effects. Hysteresis loops and MFM patterns are consistent with the formation of an "anisotropy lattice", where the nanodots have in-plane magnetic anisotropy in a perpendicular anisotropy matrix. The complex roles that the nanodots play in the magnetization reversal process will be discussed. This work is supported by NSF-MRSEC and CMRA.

  3. Isomorphic surface acoustic waves on multilayer structures

    NASA Astrophysics Data System (ADS)

    Hunt, William D.

    2001-03-01

    There has been growing interest in recent years over the investigation of bulk acoustic waves (BAWs) which propagate along certain directions in anisotropic crystals with a minimum of diffraction. One application of these BAWs is for multichannel acousto-optic devices. The fact that the beams propagate with the minimum diffraction implies that the channels in such a device can be closely packed. Since surface acoustic waves (SAWs) are constrained to be within roughly one acoustic wavelength from the surface, the possibility exists to deposit thin films of isotropic or anisotropic material on the substrate and embue the aggregate multilayer structure with properties not present in the beginning substrate material. The characteristic investigated in this article is the velocity anisotropy which, as is known, predominates SAW diffraction. Specifically, we present a method whereby self-collimating SAWs can be generated on surfaces even though the substrate material itself does not exhibit this behavior. We discuss the particular case of a ZnO layer on (001)-cut <110>-propagating GaAs for which a fair amount of slowness surface data exists. Finally, using angular spectrum of plane waves diffraction theory, we present data which substantiate the claim that self-collimating can more accurately be viewed as isomorphic because the SAW beam profile can propagate without changing its shape.

  4. Time-Dependent Thermally-Driven Interfacial Flows in Multilayered Fluid Structures

    NASA Technical Reports Server (NTRS)

    Haj-Hariri, Hossein; Borhan, A.

    1996-01-01

    A computational study of thermally-driven convection in multilayered fluid structures will be performed to examine the effect of interactions among deformable fluid-fluid interfaces on the structure of time-dependent flow in these systems. Multilayered fluid structures in two models configurations will be considered: the differentially heated rectangular cavity with a free surface, and the encapsulated cylindrical liquid bridge. An extension of a numerical method developed as part of our recent NASA Fluid Physics grant will be used to account for finite deformations of fluid-fluid interfaces.

  5. Structure of copper-hafnium multilayers

    SciTech Connect

    Clemens, B.M.; Stec, J.P.; Heald, S.M.; Tranquada, J.M.

    1986-01-01

    The structure of copper-hafnium multilayers has been studied as a function of composition modulation wavelength by x-ray diffraction and EXAFS. Sputter deposited samples were produced with composition modulation wavelengths of 1/2, 5, 7, 10, 14, and 20 close packed planes of each constituent per layer. The structure evolved anisotropically from amorphous to crystalline with increasing composition modulation wavelength, with crystalline order first appearing in the growth direction in the 7 monolayer sample. Structural coherence in the growth direction was not observed to extend beyond one elemental layer in any sample, and evidence for a disordered interfacial layer was observed by EXAFS for all samples. Small angle x-ray diffraction showed strong composition modulation for all but the 1/2 monolayer sample. The amorphous interface is the result of reaction during deposition similar to the solid state reaction observed in other systems such as nickel-zirconium.

  6. Trench-parallel anisotropy produced by serpentine deformation in the hydrated mantle wedge.

    PubMed

    Katayama, Ikuo; Hirauchi, Ken-ichi; Michibayashi, Katsuyoshi; Ando, Jun-ichi

    2009-10-22

    Seismic anisotropy is a powerful tool for detecting the geometry and style of deformation in the Earth's interior, as it primarily reflects the deformation-induced preferred orientation of anisotropic crystals. Although seismic anisotropy in the upper mantle is generally attributed to the crystal-preferred orientation of olivine, the strong trench-parallel anisotropy (delay time of one to two seconds) observed in several subduction systems is difficult to explain in terms of olivine anisotropy, even if the entire mantle wedge were to act as an anisotropic source. Here we show that the crystal-preferred orientation of serpentine, the main hydrous mineral in the upper mantle, can produce the strong trench-parallel seismic anisotropy observed in subduction systems. High-pressure deformation experiments reveal that the serpentine c-axis tends to rotate to an orientation normal to the shear plane during deformation; consequently, seismic velocity propagating normal to the shear plane (plate interface) is much slower than that in other directions. The seismic anisotropy estimated for deformed serpentine aggregates is an order of magnitude greater than that for olivine, and therefore the alignment of serpentine in the hydrated mantle wedge results in a strong trench-parallel seismic anisotropy in the case of a steeply subducting slab. This hypothesis is also consistent with the presence of a hydrous phase in the mantle wedge, as inferred from anomalously low seismic-wave velocities. PMID:19847262

  7. Systematic study of in-plane magnetic anisotropy in CoCrPtB/Cr media

    NASA Astrophysics Data System (ADS)

    Yu, Mingjun; Choe, Geon; Johnson, Kenneth E.

    2002-05-01

    Circumferential texturing in longitudinal recording media induces in-plane magnetic anisotropy. It is characterized by orientation ratio (OR), which is an important parameter affecting media performance. Our work shows that among the media with different OR values (including isotropic media with OR=1), the ones with higher OR have both better thermal stability and better recording performance. Therefore, it is important to have a better understanding of the mechanism for in-plane anisotropy so that OR can be further increased. Several mechanisms for in-plane anisotropy have been proposed through micromagnetic analysis or empirical methods. A systematic study of OR in CoCrPtB/Cr media was performed to explore the mechanism of in-plane magnetic anisotropy. Circumferential texture roughness has the most effect on OR, but OR is also strongly affected by magnetic alloy composition and sputtering process parameters such as substrate temperature, underlayer thickness, and magnetic-layer thickness. Higher substrate temperature, thinner underlayer thickness, and thinner magnetic-layer thickness all lead to higher OR. These results suggest that the in-plane magnetic anisotropy comes from stress anisotropy via the inverse magnetostriction effect. The stress is induced at the magnetic-layer/underlayer and underlayer/substrate interfaces, while the anisotropy is suggested to arise from the topology of the circumferential texture lines.

  8. Multilayered Magnetic Gelatin Membrane Scaffolds.

    PubMed

    Samal, Sangram K; Goranov, Vitaly; Dash, Mamoni; Russo, Alessandro; Shelyakova, Tatiana; Graziosi, Patrizio; Lungaro, Lisa; Riminucci, Alberto; Uhlarz, Marc; Bañobre-López, Manuel; Rivas, Jose; Herrmannsdörfer, Thomas; Rajadas, Jayakumar; De Smedt, Stefaan; Braeckmans, Kevin; Kaplan, David L; Dediu, V Alek

    2015-10-21

    A versatile approach for the design and fabrication of multilayer magnetic scaffolds with tunable magnetic gradients is described. Multilayer magnetic gelatin membrane scaffolds with intrinsic magnetic gradients were designed to encapsulate magnetized bioagents under an externally applied magnetic field for use in magnetic-field-assisted tissue engineering. The temperature of the individual membranes increased up to 43.7 °C under an applied oscillating magnetic field for 70 s by magnetic hyperthermia, enabling the possibility of inducing a thermal gradient inside the final 3D multilayer magnetic scaffolds. On the basis of finite element method simulations, magnetic gelatin membranes with different concentrations of magnetic nanoparticles were assembled into 3D multilayered scaffolds. A magnetic-gradient-controlled distribution of magnetically labeled stem cells was demonstrated in vitro. This magnetic biomaterial-magnetic cell strategy can be expanded to a number of different magnetic biomaterials for various tissue engineering applications. PMID:26451743

  9. Finite element modeling of multilayered structures of fish scales.

    PubMed

    Chandler, Mei Qiang; Allison, Paul G; Rodriguez, Rogie I; Moser, Robert D; Kennedy, Alan J

    2014-12-01

    The interlinked fish scales of Atractosteus spatula (alligator gar) and Polypterus senegalus (gray and albino bichir) are effective multilayered armor systems for protecting fish from threats such as aggressive conspecific interactions or predation. Both types of fish scales have multi-layered structures with a harder and stiffer outer layer, and softer and more compliant inner layers. However, there are differences in relative layer thickness, property mismatch between layers, the property gradations and nanostructures in each layer. The fracture paths and patterns of both scales under microindentation loads were different. In this work, finite element models of fish scales of A. spatula and P. senegalus were built to investigate the mechanics of their multi-layered structures under penetration loads. The models simulate a rigid microindenter penetrating the fish scales quasi-statically to understand the observed experimental results. Study results indicate that the different fracture patterns and crack paths observed in the experiments were related to the different stress fields caused by the differences in layer thickness, and spatial distribution of the elastic and plastic properties in the layers, and the differences in interface properties. The parametric studies and experimental results suggest that smaller fish such as P. senegalus may have adopted a thinner outer layer for light-weighting and improved mobility, and meanwhile adopted higher strength and higher modulus at the outer layer, and stronger interface properties to prevent ring cracking and interface cracking, and larger fish such as A. spatula and Arapaima gigas have lower strength and lower modulus at the outer layers and weaker interface properties, but have adopted thicker outer layers to provide adequate protection against ring cracking and interface cracking, possibly because weight is less of a concern relative to the smaller fish such as P. senegalus. PMID:25300062

  10. Multilayer thermal barrier coating systems

    DOEpatents

    Vance, Steven J.; Goedjen, John G.; Sabol, Stephen M.; Sloan, Kelly M.

    2000-01-01

    The present invention generally describes multilayer thermal barrier coating systems and methods of making the multilayer thermal barrier coating systems. The thermal barrier coating systems comprise a first ceramic layer, a second ceramic layer, a thermally grown oxide layer, a metallic bond coating layer and a substrate. The thermal barrier coating systems have improved high temperature thermal and chemical stability for use in gas turbine applications.

  11. Magnetoresistance Anisotropy in WTe2

    NASA Astrophysics Data System (ADS)

    Thoutam, Laxman Raju; Wang, Yonglei; Xiao, Zhili; Das, Saptarshi; Luican Mayer, Adina; Divan, Ralu; Crabtree, George W.; Kwok, Wai Kwong

    We report the angle dependence of the magnetoresistance in WTe2. Being a layered material, WTe2 is considered to be electronically two-dimensional (2D). Our results demonstrate that it is in fact 3D with an anisotropy of effective mass as small as 2. We measured the magnetic field dependence of the sample resistance R(H) at various angles between the applied magnetic field with respect to the c-axis of the crystal and found that they can be scaled based on the mass anisotropy, which changes from ~2 to ~5 with decreasing temperature in the Fermi liquid state. We will also discuss the origin of the turn-on temperature behavior in this material.

  12. Azimuthal anisotropy of direct photons

    SciTech Connect

    Kopeliovich, B. Z.; Pirner, H. J.; Rezaeian, A. H.; Schmidt, Ivan

    2008-02-01

    The electromagnetic bremsstrahlung produced by a quark interacting with nucleons or nuclei is azimuthally asymmetric. In the light-cone dipole approach this effect is related to the orientation dependent dipole cross section. Such a radiation anisotropy is expected to contribute to the azimuthal asymmetry of direct photons in pA and AA collisions, as well as in deep-inelastic scattering and in the production of dileptons.

  13. Reflectance, Optical Properties, and Stability of Molybdenum/Strontium and Molybdenum/Yttrium Multilayer Mirrors

    SciTech Connect

    Kjornrattanawanich, B

    2002-09-01

    yttrium layers, respectively. Based on the optical properties, multilayers with higher oxygen content should have higher absorption. However, the 25%-oxygen multilayer had less interface roughness and thus had higher reflectance than the 0%-oxygen sample. The 39%-oxygen multilayer had the highest absorption and roughness, thus had the lowest reflectance among three samples. The optical and structural properties of the multilayers are competing in the reflectance results.

  14. Accurate determination of the magnetic anisotropy in cluster-assembled nanostructures

    NASA Astrophysics Data System (ADS)

    Tamion, Alexandre; Hillenkamp, Matthias; Tournus, Florent; Bonet, Edgar; Dupuis, Véronique

    2009-08-01

    The simultaneous triple adjustment of experimental magnetization curves under different conditions is shown to allow the unambiguous and consistent determination of both the magnetic particle size distribution and anisotropy for granular nanostructures of Co clusters embedded in protective matrices. The importance of interface effects resulting in magnetically dead layers is demonstrated.

  15. [Cosmic Microwave Background (CMB) Anisotropies

    NASA Technical Reports Server (NTRS)

    Silk, Joseph

    1998-01-01

    One of the main areas of research is the theory of cosmic microwave background (CMB) anisotropies and analysis of CMB data. Using the four year COBE data we were able to improve existing constraints on global shear and vorticity. We found that, in the flat case (which allows for greatest anisotropy), (omega/H)0 less than 10(exp -7), where omega is the vorticity and H is the Hubble constant. This is two orders of magnitude lower than the tightest, previous constraint. We have defined a new set of statistics which quantify the amount of non-Gaussianity in small field cosmic microwave background maps. By looking at the distribution of power around rings in Fourier space, and at the correlations between adjacent rings, one can identify non-Gaussian features which are masked by large scale Gaussian fluctuations. This may be particularly useful for identifying unresolved localized sources and line-like discontinuities. Levin and collaborators devised a method to determine the global geometry of the universe through observations of patterns in the hot and cold spots of the CMB. We have derived properties of the peaks (maxima) of the CMB anisotropies expected in flat and open CDM models. We represent results for angular resolutions ranging from 5 arcmin to 20 arcmin (antenna FWHM), scales that are relevant for the MAP and COBRA/SAMBA space missions and the ground-based interferometer. Results related to galaxy formation and evolution are also discussed.

  16. [Cosmic Microwave Background (CMB) Anisotropies

    NASA Astrophysics Data System (ADS)

    Silk, Joseph

    1998-01-01

    One of the main areas of research is the theory of cosmic microwave background (CMB) anisotropies and analysis of CMB data. Using the four year COBE data we were able to improve existing constraints on global shear and vorticity. We found that, in the flat case (which allows for greatest anisotropy), (omega/H)0 less than 10-7, where omega is the vorticity and H is the Hubble constant. This is two orders of magnitude lower than the tightest, previous constraint. We have defined a new set of statistics which quantify the amount of non-Gaussianity in small field cosmic microwave background maps. By looking at the distribution of power around rings in Fourier space, and at the correlations between adjacent rings, one can identify non-Gaussian features which are masked by large scale Gaussian fluctuations. This may be particularly useful for identifying unresolved localized sources and line-like discontinuities. Levin and collaborators devised a method to determine the global geometry of the universe through observations of patterns in the hot and cold spots of the CMB. We have derived properties of the peaks (maxima) of the CMB anisotropies expected in flat and open CDM models. We represent results for angular resolutions ranging from 5 arcmin to 20 arcmin (antenna FWHM), scales that are relevant for the MAP and COBRA/SAMBA space missions and the ground-based interferometer. Results related to galaxy formation and evolution are also discussed.

  17. Multilayer volume microwave filters

    NASA Astrophysics Data System (ADS)

    Gvozdev, V. I.; Smirnov, S. V.; Chernushenko, A. M.

    1985-09-01

    Multilayer volume microwave filters are particularly suitable for miniaturization of radioelectronic devices by way of circuit integration, the principal advantage over planar filters being the much higher Q-factor; Q sub 0 or = 10 to the 3rd power as compared with Q sub 0 or = 10 to the 2nd power. Their metal-dielectric structure forms an array of coupled half-wavelength resonators electrically symmetric with respect to the center layer, coupling being effected by a magnetic field normal to the plane of resonators. The structure consists of an asymmetric strip line with conductor at the input end, followed by a metal layer with cut out symmetric slot line, a dielectric layer, a symmetric strip line with conductor, a metal layer with cut out symmetric slot line, a dielectric layer, and an asymmetric strip line with conductor at the output end. The size of such a filter depends directly on the number of resonator stages and, without the case, is comparable with the size of conventional filters on symmetric strip lines only but is much smaller than that of conventional filters on asymmetric strip lines only.

  18. Multilayer graphene rubber nanocomposites

    NASA Astrophysics Data System (ADS)

    Schartel, Bernhard; Frasca, Daniele; Schulze, Dietmar; Wachtendorf, Volker; Krafft, Bernd; Morys, Michael; Böhning, Martin; Rybak, Thomas

    2016-05-01

    Multilayer Graphene (MLG), a nanoparticle with a specific surface of BET = 250 m2/g and thus made of only approximately 10 graphene sheets, is proposed as a nanofiller for rubbers. When homogenously dispersed, it works at low loadings enabling the replacement of carbon black (CB), increase in efficiency, or reduction in filler concentration. Actually the appropriate preparation yielded nanocomposites in which just 3 phr are sufficient to significantly improve the rheological, curing and mechanical properties of different rubbers, as shown for Chlorine-Isobutylene-Isoprene Rubber (CIIR), Nitrile-Butadiene Rubber (NBR), Natural Rubber (NR), and Styrene-Butadiene Rubber (SBR). A mere 3 phr of MLG tripled the Young's modulus of CIIR, an effect equivalent to 20 phr of carbon black. Similar equivalents are observed for MLG/CB mixtures. MLG reduces gas permeability, increases thermal and electrical conductivities, and retards fire behavior. The later shown by the reduction in heat release rate in the cone calorimeter. The higher the nanofiller concentration is (3 phr, 5 phr, and 10 phr was investigated), the greater the improvement in the properties of the nanocomposites. Moreover, the MLG nanocomposites improve stability of mechanical properties against weathering. An increase in UV-absorption as well as a pronounced radical scavenging are proposed and were proved experimentally. To sum up, MLG is interesting as a multifunctional nanofiller and seems to be quite ready for rubber development.

  19. Theory of magnetoelectric effect in multilayer nanocomposites on a substrate: Resonant bending-mode response

    NASA Astrophysics Data System (ADS)

    Krantz, Matthias C.; Gerken, Martina

    2013-05-01

    Resonant bending-mode magnetoelectric (ME) coefficients of magnetostrictive-piezoelectric multilayer cantilevers are calculated analytically using a model developed for arbitrary multilayers on a substrate. Without quality factor effects the ME coefficient maxima in the four-dimensional parameter space of layer numbers, layer sequences, piezoelectric volume fractions, and substrate thicknesses are found to be essentially constant for nonzero substrate thickness. Global maxima occur for bilayers without substrates. Vanishing magnetoelectric response regions result from voltage cancellation in piezoelectric layers or absence of bending-mode excitation. They are determined by the neutral plane position in the multilayer stack. With Q-factor effects dominated by viscous air damping ME coefficients strongly increase with cantilever thickness primarily due to increasing resonance frequencies. The results yield a layer specific prediction of ME coefficients, resonance frequencies, and Q-factors in arbitrary multilayers and thus distinction of linear-coupling and Q-factor effects from exchange interaction, interface, or nonlinear ME effects.

  20. Enhanced radiation tolerance in nitride multilayered nanofilms with small period-thicknesses

    SciTech Connect

    Hong Mengqing; Ren Feng; Zhang Hongxiu; Xiao Xiangheng; Tian Canxin; Fu Dejun; Jiang Changzhong; Yang Bing; Wang Yongqiang

    2012-10-08

    This paper demonstrates a substantial enhancement in radiation tolerance for small period-thickness of CrN/AlTiN multilayered nanofilms. CrN/AlTiN multilayered nanofilms with period-thicknesses of 3, 5, 7, and 9 nm were irradiated by 190 keV Ar{sup +} ions to fluences ranging from 1 to 5 Multiplication-Sign 10{sup 16} ions/cm{sup 2}. Nanofilm with 3 nm period-thickness begins to be amorphized under 5 Multiplication-Sign 10{sup 16} ions/cm{sup 2}, while those with larger period-thicknesses are amorphized under 3 Multiplication-Sign 10{sup 16} ions/cm{sup 2}. Our results show that multilayered ceramic nanofilms are potential radiation tolerant materials with good properties. The interfaces in the multilayered nanofilms act as good sinks to absorb the radiation-induced defects.

  1. Carrier transport in multilayer organic photodetectors: I. Effects of layer structure on dark current and photoresponse

    NASA Astrophysics Data System (ADS)

    Xue, Jiangeng; Forrest, Stephen R.

    2004-02-01

    In this and the following article (Parts I and II, respectively), we discuss carrier transport in multilayer organic photodetectors. In Part I, we analyze carrier tunneling in multilayer organic photodetectors, both within the organic active region and at the anode/organic interface. The external quantum efficiency of an organic photodetector whose individual layers in the active region are ⩽30 Å thick shows an activation energy of ⩽0.1 eV, suggesting that the photogenerated carriers tunnel through the potential wells formed by the multilayer stack. In such photodetectors, electron tunneling injection from the anode into the organic active region dominates the dark current at T⩾200 K. Fitting of the dark current-voltage characteristics using a semiclassical tunneling model leads to barrier heights in agreement with experimental data. In Part II, the effects of anode preparation on performance of multilayer organic photodetectors are discussed.

  2. Ultra-high efficiency multilayer blazed gratings through deposition kinetic control

    SciTech Connect

    Voronov, D. L.; Anderson, Erik H.; Gullikson, Eric M.; Salmassi, Farhad; Warwick, Tony; Yashchuk, Valeriy V.; Padmore, Howard A.

    2012-05-07

    Diffraction efficiency of multilayer coated blazed gratings (MBG) strongly depends on the perfection of the saw-tooth-shaped layers in the overall composite structure. Growth of multilayers on saw-tooth substrates should be carefully optimized in order to reduce groove profile distortion and at the same time to avoid significant roughening of multilayer interfaces. In this work we report on a new way to optimize growth of sputter-deposited Mo/Si multilayers on saw-tooth substrates through variation of the sputtering gas pressure. Lastly, a new record for diffraction efficiency of 44% was achieved for a optimized MBG with groove density of 5250 lines/mm at the wavelength of 13.1 nm.

  3. Measurement of residual stress in a multi-layer semiconductor heterostructure by micro-Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Qiu, Wei; Cheng, Cui-Li; Liang, Ren-Rong; Zhao, Chun-Wang; Lei, Zhen-Kun; Zhao, Yu-Cheng; Ma, Lu-Lu; Xu, Jun; Fang, Hua-Jun; Kang, Yi-Lan

    2016-07-01

    Si-based multilayer structures are widely used in current microelectronics. During their preparation, some inhomogeneous residual stress is induced, resulting in competition between interface mismatching and surface energy and even leading to structure failure. This work presents a methodological study on the measurement of residual stress in a multi-layer semiconductor heterostructure. Scanning electron microscopy (SEM), micro-Raman spectroscopy (MRS), and transmission electron microscopy (TEM) were applied to measure the geometric parameters of the multilayer structure. The relationship between the Raman spectrum and the stress/strain on the [100] and [110] crystal orientations was determined to enable surface and cross-section residual stress analyses, respectively. Based on the Raman mapping results, the distribution of residual stress along the depth of the multi-layer heterostructure was successfully obtained.

  4. Residual stresses in sputter-deposited copper/330 stainless steel multilayers

    SciTech Connect

    Zhang, X.; Misra, A.

    2004-12-15

    The evolution of residual stresses as a function of bilayer period from 10 nm to 1 {mu}m in sputter-deposited Cu/330 stainless-steel (SS) multilayered films is evaluated by the substrate curvature technique. The multilayer stress evolution is compared with residual stresses in single layer Cu films and single layer 330 SS films, also measured by substrate curvature technique, with respective film thicknesses varying from 5 to 500 nm. Both single layer and multilayer films exhibit high tensile residual stresses that increase with decreasing layer thickness, but are found to be lower than the respective yield strengths. The intrinsic tensile residual stress evolution with film thickness is explained using the island coalescence model. The difference between the multilayer residual stress and the average residual stresses in single-layered Cu and 330 SS films is interpreted in terms of interface stress.

  5. Residual stresses in sputter-deposited copper/330 stainless steel multilayers

    NASA Astrophysics Data System (ADS)

    Zhang, X.; Misra, A.

    2004-12-01

    The evolution of residual stresses as a function of bilayer period from 10nmto1μm in sputter-deposited Cu/330 stainless-steel (SS) multilayered films is evaluated by the substrate curvature technique. The multilayer stress evolution is compared with residual stresses in single layer Cu films and single layer 330 SS films, also measured by substrate curvature technique, with respective film thicknesses varying from 5to500nm. Both single layer and multilayer films exhibit high tensile residual stresses that increase with decreasing layer thickness, but are found to be lower than the respective yield strengths. The intrinsic tensile residual stress evolution with film thickness is explained using the island coalescence model. The difference between the multilayer residual stress and the average residual stresses in single-layered Cu and 330 SS films is interpreted in terms of interface stress.

  6. MAXIMA: Observations of CMB anisotropy

    NASA Astrophysics Data System (ADS)

    Rabii, Bahman

    This document describes the Millimeter Anisotropy eXperiment IMaging Array (MAXIMA), a balloon-borne experiment measuring the temperature anisotropy of the Cosmic Microwave Background (CMB) on angular scales of 10 ' to 5°. MAXIMA data are used to discriminate between cosmological models and to determine cosmological parameters. MAXIMA maps the CMB using 16 bolometric detectors observing in spectral bands centered at 150 GHz, 230 GHz, and 410 GHz, with 10 ' resolution at all frequencies. The combined receiver sensitivity to CMB anisotropy is ˜40 μK sec , the best reported by any CMB experiment. Systematic errors are rejected by using four uncorrelated spatial modulations, multiple independent CMB observations, heavily baffled optics, and strong spectral discrimination. Observation patterns are well cross-linked and optimized for the extraction of cosmological information. Pointing is reconstructed to an accuracy of 1'. Absolute calibration uncertainty of 3 4% is the best achieved by any sub-orbital CMB experiment. Two MAXIMA flights were launched from the National Scientific Balloon Facility in Palestine Texas in 1998 and 1999. During a total of 8.5 hours of CMB observations, 300 deg2 of the sky were mapped, with ˜50 deg2 overlap between the two flights. The observed region was selected for low foreground emission and post-flight data analysis confirms that foreground contamination is negligible. Cosmological results are presented from the 1998 flight, MAXIMA-I , in which 122 deg2 of sky were mapped over 3 hours. A maximum likelihood map with 3' pixelization is obtained from the three most sensitive and best tested detectors. The angular power spectrum derived from this map shows a narrow peak near ℓ = 200, and is consistent with inflationary Big Bang models. Within these models, cosmological parameters are estimated, including total density Ωtot = 0.9+0.18-0.16 , baryon density Ωbh2 = 0.033 ± 0.013, and power spectrum normalization C

  7. Pyroelectric origin of the carrier density modulation at graphene-ferroelectric interface

    NASA Astrophysics Data System (ADS)

    Morozovska, Anna N.; Strikha, Maksym V.

    2013-07-01

    Using continuous media theory approach we study the static and high-frequency heat dissipation in multi-layer graphene on a ferroelectric. Performed calculations have proved that the pyroelectric effect can modify essentially the free carrier density at the graphene-ferroelectric interface and consequently the conductivity of multi-layer graphene channel. Pyroelectric mechanism can be critical for understanding of the complex thermal and electrical processes taking place across and along graphene-ferroelectric interfaces at terahertz frequencies.

  8. A Finite Difference Method for Modeling Migration of Impurities in Multilayer Systems

    NASA Astrophysics Data System (ADS)

    Tosa, V.; Kovacs, Katalin; Mercea, P.; Piringer, O.

    2008-09-01

    A finite difference method to solve the one-dimensional diffusion of impurities in a multilayer system was developed for the special case in which a partition coefficient K impose a ratio of the concentrations at the interface between two adiacent layers. The fictitious point method was applied to derive the algebraic equations for the mesh points at the interface, while for the non-uniform mesh points within the layers a combined method was used. The method was tested and then applied to calculate migration of impurities from multilayer systems into liquids or solids samples, in migration experiments performed for quality testing purposes. An application was developed in the field of impurities migrations from multilayer plastic packagings into food, a problem of increasing importance in food industry.

  9. Unfolding single- and multilayers

    NASA Astrophysics Data System (ADS)

    Llorens, Maria-Gema; Bons, Paul D.; Griera, Albert; Gomez-Rivas, Enrique

    2014-05-01

    When planar structures (e.g. sedimentary layers, veins, dykes, cleavages, etc.) are subjected to deformation, they have about equal chances to be shortened or stretched. The most common shortening and stretching structures are folds and boudinage, respectively. However, boudinage requires additional deformation mechanisms apart from viscous flow, like formation of fractures or strain localization. When folded layers are subjected to extension, they could potentially unfold back to straight layers. Although probably not uncommon, this would be difficult to recognize. Open questions are whether folded layers can unfold, what determines their mechanical behaviour and how we can recognize them in the field. In order to approach these questions, we present a series of numerical experiments that simulate stretching of previously folded single- and multi-layers in simple shear, using the two dimensional numerical modelling platform ELLE, including the finite element module BASIL that calculates viscous deformation. We investigate the parameters that affect a fold train once it rotates into the extensional field. The results show that the unfolding process strongly depends on the viscosity contrast between the layer and matrix (Llorens et al., 2013). Layers do not completely unfold when they experience softening before or during the stretching process or when other neighbouring competent layers prevent them from unfolding. The foliation refraction patterns are the main indicators of unfolded folds. Additionally, intrafolial folds and cusp-like folds adjacent to straight layers, as well as variations in fold amplitudes and limb lengths of irregular folds can also be used as indicators of stretching of a layer after shortening and folding. References: Llorens, M-.G., Bons, P.D., Griera, A. and Gomez-Rivas, E. 2013. When do folds unfold during progressive shear?. Geology, 41, 563-566.

  10. Ferromagnetic/Superconducting Multilayers

    NASA Astrophysics Data System (ADS)

    Bader, S. D.

    1998-03-01

    Although it is well known that magnetism influences superconductivity, the converse issue has been less well explored. Recent theoretical predictions for ferromagnetic/ superconducting/ ferromagnetic trilayers exhibiting interlayer magnetic coupling in the normal state indicate that the coupling should be suppressed below the superconducting transition temperature.(C.A. R. Sá de Melo, Phys. Rev. Lett. 79), 1933 (1997); O. Sipr, B.L. Györffy, J. Phys. Cond. Matt. 7, 5239 (1995). To realize such a situation, a requirement (when the magnetic layers are thick) is that the superconducting layer thickness must simultaneously be less than the range over which the magnetic interlayer coupling decays, but greater than the superconducting coherence length. This introduces serious materials constraints. The present work describes initial explorations of three sputtered multilayer systems in an attempt to observe coupling of the ferromagnetic layers across a superconducting spacer:((a) J.E. Mattson, R.M. Osgood III, C.D. Potter, C.H. Sowers, and S.D. Bader, J. Vac. Sci. Technol. A 15), 1774 (1997); (b) J.E. Mattson, C.D. Potter, M.J. Conover, C.H. Sowers, and S.D. Bader, Phys. Rev. B 55, 70 (1997), and (c) R.M. Osgood III, J.E. Pearson, C.H. Sowers, and S.D. Bader, submitted (1997). (a) Ni/Nb, (b) Fe_4N/NbN, and (c) GdN/NbN. In these systems we have retained thinner superconducting layers than had been achieved previously, but interlayer magnetic coupling is not observed even in the normal state. For Ni/Nb the interfacial Ni loses its moment, which also reduces the superconducting pair-breaking. GdN is an insulating ferromagnet, so itinerancy is sacrificed, and, probably as a result of this, no coupling is observed. Each system gives rise to interesting and anisotropic superconducting properties. Thus, although the goal remains elusive, our search highlights the challenges and opportunities.

  11. Depth-variant azimuthal anisotropy in Tibet revealed by surface wave tomography

    NASA Astrophysics Data System (ADS)

    Pandey, Shantanu; Yuan, Xiaohui; Debayle, Eric; Tilmann, Frederik; Priestley, Keith; Li, Xueqing

    2015-06-01

    Azimuthal anisotropy derived from multimode Rayleigh wave tomography in China exhibits depth-dependent variations in Tibet, which can be explained as induced by the Cenozoic India-Eurasian collision. In west Tibet, the E-W fast polarization direction at depths <100 km is consistent with the accumulated shear strain in the Tibetan lithosphere, whereas the N-S fast direction at greater depths is aligned with Indian Plate motion. In northeast Tibet, depth-consistent NW-SE directions imply coupled deformation throughout the whole lithosphere, possibly also involving the underlying asthenosphere. Significant anisotropy at depths of 225 km in southeast Tibet reflects sublithospheric deformation induced by northward and eastward lithospheric subduction beneath the Himalaya and Burma, respectively. The multilayer anisotropic surface wave model can explain some features of SKS splitting measurements in Tibet, with differences probably attributable to the limited back azimuthal coverage of most SKS studies in Tibet and the limited horizontal resolution of the surface wave results.

  12. Multilayer coatings for flexible high-barrier materials

    NASA Astrophysics Data System (ADS)

    Vaško, Karol; Noller, Klaus; Mikula, Milan; Amberg-Schwab, Sabine; Weber, Ulrike

    2009-06-01

    A multilayer, flexible, and transparent high-barrier system based on flexible plastic foils, polyethyleneterephthalate (PET) and ethylene-tetrafluoroethylene-copolymer (ETFE), combined with vacuum-deposited, inorganic SiOx layers and hybrid ORMOCER® varnish layers were prepared in different orders on a semiproduction level. Barrier properties of prepared systems, as water vapour transmission (WVTR) and oxygen transmission (OTR), were measured and studied in connection with surface energy, surface topography, and water vapour adsorption properties. Correlations among layers sequence, barrier properties, and other parameters are presented, including some basic principles of permeation of substances through multilayer barrier systems. A combination of several inorganic and hybrid varnish layers is necessary to achieve the technological demands from a barrier standpoint. It is easier to suppress the oxygen transport than the water transport, due to the additional active penetration of water through hydrogen bonds and silanol creations at oxide interfaces, capillary condensation, and swelling with high internal pressure, leading to new defects.

  13. Multilayer coatings for flexible high-barrier materials

    NASA Astrophysics Data System (ADS)

    Vaško, Karol; Noller, Klaus; Mikula, Milan; Amberg-Schwab, Sabine; Weber, Ulrike

    2009-06-01

    A multilayer, flexible, and transparent high-barrier system based on flexible plastic foils, polyethyleneterephthalate (PET) and ethylene-tetrafluoroethylene-copolymer (ETFE), combined with vacuum-deposited, inorganic SiOx layers and hybrid ORMOCER® varnish layers were prepared in different orders on a semiproduction level. Barrier properties of prepared systems, as water vapour transmission (WVTR) and oxygen transmission (OTR), were measured and studied in connection with surface energy, surface topography, and water vapour adsorption properties. Correlations among layers sequence, barrier properties, and other parameters are presented, including some basic principles of permeation of substances through multilayer barrier systems. A combination of several inorganic and hybrid varnish layers is necessary to achieve the technological demands from a barrier standpoint. It is easier to suppress the oxygen transport than the water transport, due to the additional active penetration of water through hydrogen bonds and silanol creations at oxide interfaces, capillary condensation, and swelling with high internal pressure, leading to new defects.

  14. He ion irradiation damage to Al/Nb multilayers

    SciTech Connect

    Misra, Amit; Li, Nan; Martin, M S; Anderoglu, Osman; Shao, L; Wang, H; Zhang, X

    2009-01-01

    We investigated the evolution of microstructure and mechanical properties of sputter-deposited Al/Nb multilayers with individual layer thickness, h, of 1-200 nm, subjected to helium ion irradiations: 100 keV He{sup +} ions with a dose of 6 x 10{sup 16}/cm{sup 2}. Helium bubbles, 1-2 nm in diameter, were observed. When h is greater than 25 nm, hardnesses of irradiated multilayers barely change, whereas radiation hardening is more significant at smaller h. Transmission electron microscopy and scanning transmission electron microscopy studies reveal the formation of a thin layer of Nb{sub 3}Al intermetallic along the Al/Nb interface as a consequence of radiation induced intermixing. The dependence of radiation hardening on h is interpreted by using a composite model considering the formation of the hard Nb{sub 3}Al intermetallic layer.

  15. Energetic ion bombarded Fe/Al multilayers

    SciTech Connect

    Al-Busaidy, M.S.; Crapper, M.D.

    2006-05-15

    The utility of ion-assisted deposition is investigated to explore the possibility of counteracting the deficiency of back-reflected current of Ar neutrals in the case of lighter elements such as Al. A range of energetically ion bombarded Fe/Al multilayers sputtered with applied surface bias of 0, -200, or -400 V were deposited onto Si(111) substrates in an argon atmosphere of 4 mTorr using a computer controlled dc magnetron sputtering system. Grazing incidence reflectivity and rocking curve scans by synchrotron x rays of wavelength of 1.38 A were used to investigate the structures of the interfaces produced. Substantial evidence has been gathered to suggest the gradual suppression of interfacial mixing and reduction in interfacial roughness with increases of applied bias. The densification of the Al microstructure was noticeable and may be a consequence of resputtering attributable to the induced ion bombardment. The average interfacial roughnesses were calculated for the 0, -200, and -400 V samples to be 7{+-}0.5, 6{+-}0.5, and 5{+-}0.5 A respectfully demonstrating a 30% improvement in interface quality. Data from rocking curve scans point to improved long-range correlated roughness in energetically deposited samples. The computational code based on the recursive algorithm developed by Parratt [Phys. Rev. 95, 359 (1954)] was successful in the simulation of the specular reflectivity curves.

  16. Tamm plasmon polaritons in multilayered cylindrical structures

    NASA Astrophysics Data System (ADS)

    Little, C. E.; Anufriev, R.; Iorsh, I.; Kaliteevski, M. A.; Abram, R. A.; Brand, S.

    2012-12-01

    It is shown that cylindrical Bragg reflector structures with either a metal core, a metal cladding, or both can support Tamm plasmon polaritons (TPPs) that can propagate axially along the interface between the metallic layer and the adjacent dielectric. A transfer matrix formalism for cylindrical multilayered structures is used in association with cavity phase matching considerations to design structures that support Tamm plasmon polaritons at specified frequencies, and to explore the field distributions and the dispersion relations of the excitations. The cylindrical TPPs can exist in both the TE and TM polarizations for the special cases of modes with either azimuthal isotropy or zero axial propagation constant and also as hybrid cylindrical modes when neither of those conditions applies. In the cases considered the TPPs have low effective masses and low group velocities. Also, when there is both metallic core and cladding, near degenerate modes localized at each metallic interface can couple to produce symmetric and antisymmetric combinations whose frequency difference is in the terahertz regime.

  17. Chiral magnetism at oxide interfaces

    NASA Astrophysics Data System (ADS)

    Randeria, Mohit

    2014-03-01

    There are tantalizing hints of magnetism at the n-type LaAlO3/SrTiO3 interface, but the experimental evidence remains controversial in view of some of the differences between different samples and probes. I will argue that if magnetism exists at interfaces, symmetry arguments imply chiral interactions that lead to a spiral ground state in zero external field and skyrmion crystals for H ≠ 0 . I will next present a microscopic model that provides a possible mechanism for the formation of local moments. I will show that the coupling of these moments to itinerant electrons leads to ferromagnetic double exchange together with Dzyaloshinskii-Moriya (DM) interactions and an easy-plane ``compass'' anisotropy, which arise from Rashba spin-orbit coupling (SOC) due to the lack of inversion symmetry at the interface. The compass term, often ignored in the literature on chiral magnetism, is shown to play a crucial role in determining the magnetic ground state. I will compare our results with existing torque magnetometry data on LAO/STO and try to reconcile it with scanning SQUID magnetometry. Finally, I will present the phase diagram in a field and show that easy-plane anisotropy stabilizes an unexpectedly large skyrmion crystal phase and describe its properties. (Work done in collaboration with Sumilan Banerjee, Onur Erten, Daniel Kestner and James Rowland). Supported by DOE-BES DE-SC0005035, NSF-DMR-1006532 and NSF MRSEC DMR-0820414.

  18. Engineering skyrmions in transition-metal multilayers for spintronics

    NASA Astrophysics Data System (ADS)

    Dupé, B.; Bihlmayer, G.; Böttcher, M.; Blügel, S.; Heinze, S.

    2016-06-01

    Magnetic skyrmions are localized, topologically protected spin structures that have been proposed for storing or processing information due to their intriguing dynamical and transport properties. Important in terms of applications is the recent discovery of interface stabilized skyrmions as evidenced in ultra-thin transition-metal films. However, so far only skyrmions at interfaces with a single atomic layer of a magnetic material were reported, which greatly limits their potential for application in devices. Here we predict the emergence of skyrmions in [4d/Fe2/5d]n multilayers, that is, structures composed of Fe biatomic layers sandwiched between 4d and 5d transition-metal layers. In these composite structures, the exchange and the Dzyaloshinskii-Moriya interactions that control skyrmion formation can be tuned separately by the two interfaces. This allows engineering skyrmions as shown based on density functional theory and spin dynamics simulations.

  19. Engineering skyrmions in transition-metal multilayers for spintronics.

    PubMed

    Dupé, B; Bihlmayer, G; Böttcher, M; Blügel, S; Heinze, S

    2016-01-01

    Magnetic skyrmions are localized, topologically protected spin structures that have been proposed for storing or processing information due to their intriguing dynamical and transport properties. Important in terms of applications is the recent discovery of interface stabilized skyrmions as evidenced in ultra-thin transition-metal films. However, so far only skyrmions at interfaces with a single atomic layer of a magnetic material were reported, which greatly limits their potential for application in devices. Here we predict the emergence of skyrmions in [4d/Fe2/5d]n multilayers, that is, structures composed of Fe biatomic layers sandwiched between 4d and 5d transition-metal layers. In these composite structures, the exchange and the Dzyaloshinskii-Moriya interactions that control skyrmion formation can be tuned separately by the two interfaces. This allows engineering skyrmions as shown based on density functional theory and spin dynamics simulations. PMID:27257020

  20. The mechanical behavior of nanoscale metallic multilayers: A survey

    NASA Astrophysics Data System (ADS)

    Zhou, Q.; Xie, J. Y.; Wang, F.; Huang, P.; Xu, K. W.; Lu, T. J.

    2015-06-01

    The mechanical behavior of nanoscale metallic multilayers (NMMs) has attracted much attention from both scientific and practical views. Compared with their monolithic counterparts, the large number of interfaces existing in the NMMs dictates the unique behavior of this special class of structural composite materials. While there have been a number of reviews on the mechanical mechanism of microlaminates, the rapid development of nanotechnology brought a pressing need for an overview focusing exclusively on a property-based definition of the NMMs, especially their size-dependent microstructure and mechanical performance. This article attempts to provide a comprehensive and up-to-date review on the microstructure, mechanical property and plastic deformation physics of NMMs. We hope this review could accomplish two purposes: (1) introducing the basic concepts of scaling and dimensional analysis to scientists and engineers working on NMM systems, and (2) providing a better understanding of interface behavior and the exceptional qualities the interfaces in NMMs display at atomic scale.

  1. Engineering skyrmions in transition-metal multilayers for spintronics

    PubMed Central

    Dupé, B.; Bihlmayer, G.; Böttcher, M.; Blügel, S.; Heinze, S.

    2016-01-01

    Magnetic skyrmions are localized, topologically protected spin structures that have been proposed for storing or processing information due to their intriguing dynamical and transport properties. Important in terms of applications is the recent discovery of interface stabilized skyrmions as evidenced in ultra-thin transition-metal films. However, so far only skyrmions at interfaces with a single atomic layer of a magnetic material were reported, which greatly limits their potential for application in devices. Here we predict the emergence of skyrmions in [4d/Fe2/5d]n multilayers, that is, structures composed of Fe biatomic layers sandwiched between 4d and 5d transition-metal layers. In these composite structures, the exchange and the Dzyaloshinskii–Moriya interactions that control skyrmion formation can be tuned separately by the two interfaces. This allows engineering skyrmions as shown based on density functional theory and spin dynamics simulations. PMID:27257020

  2. Size dependent strengthening mechanisms in sputtered Fe/W multilayers

    NASA Astrophysics Data System (ADS)

    Li, Nan; Yu, K. Y.; Lee, J.; Wang, H.; Zhang, X.

    2010-05-01

    We investigate size dependent strengthening mechanisms in sputtered Fe/W multilayers with individual layer thickness, h, varying from 1 to 200 nm. Microstructure analyses reveal that Fe/W has incoherent bcc/bcc interface when h is greater than 5 nm. When h decreases to 1-2.5 nm, the interface becomes semicoherent, and Fe and W show significant lattice distortions comparing to their bulk counterpart due to interface constraint. The layer thickness dependent drastic variations in x-ray diffraction profiles are simulated well by using an analytical model. Film hardness increases with decreasing h, and approaches a maximum value of 12.5 GPa when h is 1 nm. The layer thickness dependent film hardnesses are compared with analytical models. Koehler's image force plays a major role in determining the maximum strength of composites at smaller h.

  3. Influence of capping layers on CoFeB anisotropy and damping

    SciTech Connect

    Natarajarathinam, A.; Tadisina, Z. R.; Gupta, S.; Mewes, T.; Watts, S.; Chen, E.

    2012-09-01

    Magnetic behavior of CoFeB at various thicknesses ranging from 2 nm to 8 nm capped with different materials, such as MgO, Ta, Ru, and V have been studied. The films were sputter-deposited and subsequently characterized by magnetometry and broadband ferromagnetic resonance (FMR). There are magnetically dead layers at the interface observed with Ru and Ta capping layers, while MgO and V have almost no effect on the magnetization of the CoFeB. As the ferromagnetic layer is made thinner, the effective magnetization decreases, indicating an interfacial perpendicular anisotropy. Particularly in the case of MgO, V/Ru, and V/Ta capping layers, interfacial perpendicular anisotropy is induced in CoFeB, and the Gilbert damping parameter is also reduced. The origin of this perpendicular magnetic anisotropy (PMA) is understood to be caused by the interface anisotropy between the free layer and the capping layer. The effect of post-deposition annealing and CoFeB thickness on the anisotropy and damping of V/Ta capped samples are reported. Doping CoFeB with vanadium (V) greatly reduced the 4{pi}M{sub s} and 4{pi}M{sub eff} values, resulting in an effective increase in the PMA.

  4. Dielectric singularity in hyperbolic metamaterials: the inversion point of coexisting anisotropies

    PubMed Central

    Caligiuri, V.; Dhama, R.; Sreekanth, K. V.; Strangi, G.; De Luca, A.

    2016-01-01

    Hyperbolic Metamaterials are artificially engineered materials whose optical properties can be specifically tailored to manifest an extremely high level of anisotropy. Due to this remarkable anisotropy they represent a unique opportunity to realize effective bulk meta-structure with extraordinary optical properties in the visible range. A simultaneous dielectric singularity in the in plane permittivity, with respect to the propagation direction, has to lead to a complete sign inversion of the same permittivity for that specific visible frequency. Such a drastic phase change has been theoretically highlighted in the past as the major challenge to be overcome in order to unlock many remarkable optical properties not present artificial optical systems. In this paper we experimentally demonstrate the realization of a metal-dielectric multilayer structure showing an inversion point of coexisting anisotropies at a specified wavelength in the visible range, rising from the particular design and fabrication process. Theoretical models and numerical simulations are in very good agreement with experimental data. Ellipsometrical experiments and optical modeling demonstrate the drastic type I/type II transition. Supercollimation effect has been achieved at the inversion point of the coexisting extreme anisotropies, whereas at the epsilon near zero and pole frequency the perfect lens behavior has been observed. PMID:26833022

  5. Dielectric singularity in hyperbolic metamaterials: the inversion point of coexisting anisotropies

    NASA Astrophysics Data System (ADS)

    Caligiuri, V.; Dhama, R.; Sreekanth, K. V.; Strangi, G.; de Luca, A.

    2016-02-01

    Hyperbolic Metamaterials are artificially engineered materials whose optical properties can be specifically tailored to manifest an extremely high level of anisotropy. Due to this remarkable anisotropy they represent a unique opportunity to realize effective bulk meta-structure with extraordinary optical properties in the visible range. A simultaneous dielectric singularity in the in plane permittivity, with respect to the propagation direction, has to lead to a complete sign inversion of the same permittivity for that specific visible frequency. Such a drastic phase change has been theoretically highlighted in the past as the major challenge to be overcome in order to unlock many remarkable optical properties not present artificial optical systems. In this paper we experimentally demonstrate the realization of a metal-dielectric multilayer structure showing an inversion point of coexisting anisotropies at a specified wavelength in the visible range, rising from the particular design and fabrication process. Theoretical models and numerical simulations are in very good agreement with experimental data. Ellipsometrical experiments and optical modeling demonstrate the drastic type I/type II transition. Supercollimation effect has been achieved at the inversion point of the coexisting extreme anisotropies, whereas at the epsilon near zero and pole frequency the perfect lens behavior has been observed.

  6. Tunable magnetic anisotropy in perpendicular exchange-coupled CoFeB/(Co/Pt) films

    NASA Astrophysics Data System (ADS)

    You, Long; Lee, Oukjae; Glenn, Terrell; Abdel-Raziq, Haron; Salahuddin, Sayeef

    2015-03-01

    Spintronic materials with strong perpendicular magnetic anisotropy (PMA), such as Co/Pd, Co/Pt and Co/Ni multilayers, have been introduced to improve the functional performance of STT devices (e.g. enhanced thermal stability, scalability and switching speeds of spin memory/logic). Furthermore, by coupling magnetic layers with PMA and longitudinal magnetic anisotropy (LMA), added benefits such as a variable magnetization tilt angle and tunable damping have been shown. In our study, we discuss how to precise control the anisotropy tilt angle by coupling the PMA hard layer (Co/Pt) with an in-plane soft layer (IMA, CoFeB). Due to the competition between the PMA and IMA, the tilted angle can be tuned by varying thickness of IMA. The stack of Pt(5nm)/Co (1nm)/CoFeB(Xnm)/MgO (2nm) (x varied from 0 to 1nm) was deposited by magneto-sputtering system. The magnetic properties were investigated by vibrating sample magnetometer and anomalous Hall effect . The electric transport of microscale devices comprised of that stack were also studied by our probe station with electromagnet. The experiments show the magnetic anisotropy can be tuned well by changing thickness of in plane layer and open a promising new avenue to next generation spintronics devices.

  7. Dielectric singularity in hyperbolic metamaterials: the inversion point of coexisting anisotropies.

    PubMed

    Caligiuri, V; Dhama, R; Sreekanth, K V; Strangi, G; De Luca, A

    2016-01-01

    Hyperbolic Metamaterials are artificially engineered materials whose optical properties can be specifically tailored to manifest an extremely high level of anisotropy. Due to this remarkable anisotropy they represent a unique opportunity to realize effective bulk meta-structure with extraordinary optical properties in the visible range. A simultaneous dielectric singularity in the in plane permittivity, with respect to the propagation direction, has to lead to a complete sign inversion of the same permittivity for that specific visible frequency. Such a drastic phase change has been theoretically highlighted in the past as the major challenge to be overcome in order to unlock many remarkable optical properties not present artificial optical systems. In this paper we experimentally demonstrate the realization of a metal-dielectric multilayer structure showing an inversion point of coexisting anisotropies at a specified wavelength in the visible range, rising from the particular design and fabrication process. Theoretical models and numerical simulations are in very good agreement with experimental data. Ellipsometrical experiments and optical modeling demonstrate the drastic type I/type II transition. Supercollimation effect has been achieved at the inversion point of the coexisting extreme anisotropies, whereas at the epsilon near zero and pole frequency the perfect lens behavior has been observed. PMID:26833022

  8. Structural reducibility of multilayer networks

    NASA Astrophysics Data System (ADS)

    de Domenico, Manlio; Nicosia, Vincenzo; Arenas, Alexandre; Latora, Vito

    2015-04-01

    Many complex systems can be represented as networks consisting of distinct types of interactions, which can be categorized as links belonging to different layers. For example, a good description of the full protein-protein interactome requires, for some organisms, up to seven distinct network layers, accounting for different genetic and physical interactions, each containing thousands of protein-protein relationships. A fundamental open question is then how many layers are indeed necessary to accurately represent the structure of a multilayered complex system. Here we introduce a method based on quantum theory to reduce the number of layers to a minimum while maximizing the distinguishability between the multilayer network and the corresponding aggregated graph. We validate our approach on synthetic benchmarks and we show that the number of informative layers in some real multilayer networks of protein-genetic interactions, social, economical and transportation systems can be reduced by up to 75%.

  9. Conformal growth of Mo/Si multilayers on grating substrates using collimated ion beam sputtering

    NASA Astrophysics Data System (ADS)

    Voronov, D. L.; Gawlitza, P.; Cambie, R.; Dhuey, S.; Gullikson, E. M.; Warwick, T.; Braun, S.; Yashchuk, V. V.; Padmore, H. A.

    2012-05-01

    Deposition of multilayers on saw-tooth substrates is a key step in the fabrication of multilayer blazed gratings (MBG) for extreme ultraviolet and soft x-rays. Growth of the multilayers can be perturbed by shadowing effects caused by the highly corrugated surface of the substrates, which results in distortion of the multilayer stack structure and degradation of performance of MBGs. To minimize the shadowing effects, we used an ion-beam sputtering machine with a highly collimated atomic flux to deposit Mo/Si multilayers on saw-tooth substrates. The sputtering conditions were optimized by finding a balance between smoothening and roughening processes in order to minimize degradation of the groove profile in the course of deposition and at the same time to keep the interfaces of a multilayer stack smooth enough for high efficiency. An optimal value of energy of 200 eV for sputtering Kr+ ions was found by deposition of test multilayers on flat substrates at a range of ion energies. Two saw-tooth substrates were deposited at energies of 200 eV and 700 eV for the sputtering ions. It was found that reduction of the ion energy improved the blazing performance of the MBG and resulted in a 40% gain in the diffraction efficiency due to better replication of the groove profile by the multilayer. As a result of the optimization performed, an absolute diffraction efficiency of 28.8% was achieved for the 2nd blaze order of the MBG with a groove density of 7350 lines/mm at a wavelength of 13.5 nm. Details of the growth behavior of the multilayers on flat and saw-tooth substrates are discussed in terms of the linear continuous model of film growth.

  10. Conformal growth of Mo/Si multilayers on grating substrates using collimated ion beam sputtering

    SciTech Connect

    Gawlitza, Peter; Cambie, Rossana; Dhuey, Scott; Gullikson, Eric; Warwick, Tony; Braun, Stefan; Yashchuk, Valeriy; Padmore, Howard

    2012-01-23

    Deposition of multilayers on saw-tooth substrates is a key step in the fabrication of multilayer blazed gratings (MBG) for extreme ultraviolet and soft x-rays. Growth of the multilayers can be perturbed by shadowing effects caused by the highly corrugated surface of the substrates, which results in distortion of the multilayer stack structure and degradation of performance of MBGs. To minimize the shadowing effects we used an ionbeam sputtering machine with a highly collimated atomic flux to deposit Mo/Si multilayers on saw-tooth substrates. The sputtering conditions were optimized by finding a balance between smoothening and roughening processes in order to minimize degradation of the groove profile in the course of deposition and at the same time to keep the interfaces of a multilayer stack smooth enough for high efficiency. An optimal value of energy of 200 eV for sputtering Kr{sup +} ions was found by deposition of test multilayers on flat substrates at a range of ion energies. Two saw-tooth substrates were deposited at energies of 200 eV and 700 eV for the sputtering ions. It was found that reduction of the ion energy improved the blazing performance of the MBG and resulted in a 40% gain in the diffraction efficiency due to better replication of the groove profile by the multilayer. As a result of the optimization performed, an absolute diffraction efficiency of 28.8% was achieved for the 2nd blaze order of the MBG with a groove density of 7350 lines/mm at a wavelength of 13.5 nm. Details of the growth behavior of the multilayers on flat and saw-tooth substrates are discussed in terms of the Linear Continuous Model of film growth.

  11. Conformal growth of Mo/Si multilayers on grating substrates using collimated ion beam sputtering

    SciTech Connect

    Voronov, D. L.; Cambie, R.; Dhuey, S.; Gullikson, E. M.; Warwick, T.; Yashchuk, V. V.; Padmore, H. A.; Gawlitza, P.; Braun, S.

    2012-05-01

    Deposition of multilayers on saw-tooth substrates is a key step in the fabrication of multilayer blazed gratings (MBG) for extreme ultraviolet and soft x-rays. Growth of the multilayers can be perturbed by shadowing effects caused by the highly corrugated surface of the substrates, which results in distortion of the multilayer stack structure and degradation of performance of MBGs. To minimize the shadowing effects, we used an ion-beam sputtering machine with a highly collimated atomic flux to deposit Mo/Si multilayers on saw-tooth substrates. The sputtering conditions were optimized by finding a balance between smoothening and roughening processes in order to minimize degradation of the groove profile in the course of deposition and at the same time to keep the interfaces of a multilayer stack smooth enough for high efficiency. An optimal value of energy of 200 eV for sputtering Kr{sup +} ions was found by deposition of test multilayers on flat substrates at a range of ion energies. Two saw-tooth substrates were deposited at energies of 200 eV and 700 eV for the sputtering ions. It was found that reduction of the ion energy improved the blazing performance of the MBG and resulted in a 40% gain in the diffraction efficiency due to better replication of the groove profile by the multilayer. As a result of the optimization performed, an absolute diffraction efficiency of 28.8% was achieved for the 2nd blaze order of the MBG with a groove density of 7350 lines/mm at a wavelength of 13.5 nm. Details of the growth behavior of the multilayers on flat and saw-tooth substrates are discussed in terms of the linear continuous model of film growth.

  12. Long-term stability of a Mo/Si multilayer structure

    SciTech Connect

    Barbee, T.W. Jr. ); Rife, J.C.; Kowalski, M.P.; Cruddace, R.G.; Seely, J.F. ); Hunter, W.R. )

    1993-09-01

    The normal-incidence reflectance of a Mo/Si multilayer mirror, with peak reflectance near 130 A, was measured over a period of 20 months by using synchrotron radiation. The measured reflectances were unchanged over this period of time, and this indicates that the material layers and interfaces were stable.

  13. Effects of Co layer thickness and annealing temperature on the magnetic properties of inverted [Pt/Co] multilayers

    SciTech Connect

    Lee, Tae Young; Chan Won, Young; Su Son, Dong; Lee, Seong-Rae; Ho Lim, Sang

    2013-11-07

    The effects of Co layer thickness and annealing temperature on the perpendicular magnetic anisotropy (PMA) properties of inverted [Pt (0.2 nm)/Co (t{sub Co})]{sub 6} multilayers (where t{sub Co} indicates the thickness of the Co layer) have been investigated. The cross-sectional microstructure, as observed from the high-resolution transmission electron microscope images, shows a clear layered structure with atomically flat interfaces both in the as-deposited state as well as after annealing, indicating the interface effects for PMA. The effective PMA energy density (K{sub eff}) increases significantly with an increase in t{sub Co} from 0.2 to 0.28 nm and then becomes almost saturated with further increases in t{sub Co}, followed by a slight reduction at the highest Co thickness, t{sub Co} = 0.6 nm. In order to explain the t{sub Co} dependence on K{sub eff}, the intrinsic PMA energy density (K{sub i}) is calculated by additionally measuring a similar set of results for the saturation magnetization. The K{sub i} value increases nearly linearly with the increase in t{sub Co} from 0.2 to 0.5 nm, followed by saturation at a higher t{sub Co} value of 0.6 nm. Owing to a close relationship between K{sub i} and the quality of the interfaces, these results indicate a similar t{sub Co} dependence on the quality of the interfaces. This is further supported from the magnetic measurements of the samples annealed at the highest temperature of 500 °C, where a second phase is formed, which show a similar t{sub Co} dependence on the amount of the second phase. The K{sub i} value is nearly independent of the annealing temperature at t{sub Co} ≤ 0.4 nm, above which a substantial reduction is observed, when the annealing temperature exceeds 500 °C.

  14. Spin-orbit torque in a bulk perpendicular magnetic anisotropy Pd/FePd/MgO system

    PubMed Central

    Lee, Hwang-Rae; Lee, Kyujoon; Cho, Jaehun; Choi, Young-Ha; You, Chun-Yeol; Jung, Myung-Hwa; Bonell, Frédéric; Shiota, Yoichi; Miwa, Shinji; Suzuki, Yoshishige

    2014-01-01

    Spin-orbit torques, including the Rashba and spin Hall effects, have been widely observed and investigated in various systems. Since interesting spin-orbit torque (SOT) arises at the interface between heavy nonmagnetic metals and ferromagnetic metals, most studies have focused on the ultra-thin ferromagnetic layer with interface perpendicular magnetic anisotropy. Here, we measured the effective longitudinal and transverse fields of bulk perpendicular magnetic anisotropy Pd/FePd (1.54 to 2.43 nm)/MgO systems using harmonic methods with careful correction procedures. We found that in our range of thicknesses, the effective longitudinal and transverse fields are five to ten times larger than those reported in interface perpendicular magnetic anisotropy systems. The observed magnitude and thickness dependence of the effective fields suggest that the SOT do not have a purely interfacial origin in our samples. PMID:25293693

  15. Skyrmion dynamics under uniaxial anisotropy

    NASA Astrophysics Data System (ADS)

    Ehlers, D.; Stasinopoulos, I.; Tsurkan, V.; Krug von Nidda, H.-A.; Fehér, T.; Leonov, A.; Kézsmárki, I.; Grundler, D.; Loidl, A.

    2016-07-01

    Broadband microwave spectroscopy has been performed on single-crystalline GaV4S8 , which exhibits a complex magnetic phase diagram including cycloidal and Néel-type skyrmion lattice phases below 13 K. At small magnetic fields two collective modes with large frequency separation are found that reflect the cycloid state subject to a large uniaxial anisotropy. In the skyrmion lattice phase three modes are resolved. Analyzing the spin-precessional motion microscopically, we explain the low frequency of the breathing mode in these Néel skyrmions by the hard-axis orientation of relevant spins.

  16. Variance Anisotropy in Kinetic Plasmas

    NASA Astrophysics Data System (ADS)

    Parashar, Tulasi N.; Oughton, Sean; Matthaeus, William H.; Wan, Minping

    2016-06-01

    Solar wind fluctuations admit well-documented anisotropies of the variance matrix, or polarization, related to the mean magnetic field direction. Typically, one finds a ratio of perpendicular variance to parallel variance of the order of 9:1 for the magnetic field. Here we study the question of whether a kinetic plasma spontaneously generates and sustains parallel variances when initiated with only perpendicular variance. We find that parallel variance grows and saturates at about 5% of the perpendicular variance in a few nonlinear times irrespective of the Reynolds number. For sufficiently large systems (Reynolds numbers) the variance approaches values consistent with the solar wind observations.

  17. Cold rolling induced alloying behaviors in metallic multilayers

    NASA Astrophysics Data System (ADS)

    Wang, Zhe

    Phase transformation and atomic scale intermixing induced by deformation are important and fundamental issues in the mechanical alloying processes. Repeated cold rolling and folding experiments were performed on the metallic multilayers in order to study the deformation driven behaviors. Various binary systems such as isomorphous, eutectic and thermodynamically immiscible systems were studied. Moreover, monometallic Pd, Pt and Fe were selected in order to study the deformation driven recrystallization behavior. In Cu/Ni multilayers, the composition of the solid solution is revealed by an oscillation in the composition profile across the multilayers, which is different from the smoothly varying profile due to thermally activated diffusion. During the reaction, Cu mixed into Ni preferentially compared to Ni mixing into Cu, which is also in contrast to the thermal diffusion behavior. During the cold rolling of multilayers of Ni and V, deformation induces phase transformation and an interfacial mixing with suppression of nucleation of intermetallic phases. The results also demonstrate that between pure Ni and V layers a metastable fcc solid solution phase forms in Ni70V30, a metastable bcc solid solution phase forms in Ni30V70 and metastable fcc and bcc solid solution phases form in Ni57V43. Compared to the stored energy due to dislocation and interfaces, the excess chemical free energy from the interfacial mixing is the largest portion of total stored energy from deformation, which represents a form of mechanochemical transduction. The difference in the intermixing behaviors between Cu/Ni and Ni/V systems is due to that the systems have different heat of mixing and interface characters. Deformation of Cu/Fe multilayers yields a smooth and monotonic variation in the composition profile. From the local composition consumption it is revealed that that Fe mixes into Cu preferentially than Cu mixing into Fe. The room temperature deformation driven recrystallization was

  18. Synthesis and tribology of doped carbon films and oxide multilayers

    NASA Astrophysics Data System (ADS)

    Freyman, Christina A.

    The focus of this research is to synthesize thin films coatings by reactive magnetron sputtering with properties that will result in energy savings. Tailoring of hydrogenated carbon film properties to minimize environment effects on friction is accomplished by sulfur doping. Synthesis results in smooth surfaces and mid-range hardness. The stabilization of ultra-low friction in humid air can be attributed to the reduction of water adsorption on the surface, which is verified by results of quartz crystal microbalance and temperature-programmed desorption experiments. Even at 90% relative humidity, sulfur-doped films have less than one monolayer of water adsorbed on the surface. This reduction in water coverage is due to the decrease in residence time of water on the surface, which is related to the strength of the bonding between water molecules and the sulfur-doped surface. These results indicate that sulfur doping results in weaker bonding between water and the film surface due to a reduction in the polar nature of the surface. Metal nitrides, carbides, and borides are widely used as protective coatings due to their high hardness, but are not stable above 600°C due to coating oxidation. Hardness enhancement techniques have been applied to thermally stable oxide multilayers for use at high temperatures. Amorphous Al2 O3 and crystalline TiO2 nanoscale layers have been deposited using reactive d.c. magnetron sputtering at different partial pressures of oxygen. Hardness enhancement of twice the rule of mixtures has been observed in oxide multilayers for the first time due to clear interfaces and large difference in modulus between amorphous Al2O3 and crystalline TiO2 layers. Multilayer films with majority bilayer component of Al2O3 showed greater resistance to wear due to increased elastic recovery and H/E ratio over monolithic films and TiO2 majority phase multilayers. Multilayer films retain their high hardness up to ˜800°C in air; some hardness enhancement in the

  19. Shear-induced permeability anisotropy of simulated serpentinite gouge

    NASA Astrophysics Data System (ADS)

    Okazaki, K.; Katayama, I.; Noda, H.; Takahashi, M.

    2012-12-01

    Fluids in fault zone play an important role on mechanical weakening of fault strength due to elevated pore fluid pressures and absorbed on the crystal surface. The heterogeneous occurrence of earthquake in subduction zone are probably linked to the heterogeneous distribution of fluids that have significant influence on the fault instability. Permeability in fault zone control fluid flow in In this study, permeability in three orthogonal directions of antigorite serpentinite gouge was measured during pre-cut frictional experiments using triaxial gas apparatus in Hiroshima University. kx, ky, and kz denote permeabilities in the slip direction, normal to the slip direction in the fault, and normal to the fault. All experiments were conducted at a room temperature, a confining pressure of 150 MPa, a pore pressure of 100 MPa, and a constant slip rate of 0.575 μm/s while the initial gouge thickness is about 1.2 mm. Permeabilities in different directrions are measured for different but similar samples continuously during shear deformation by the pore pressure oscillation method [e.g., Fischer and Paterson, 1992]. The friction coefficient reached its maximum value at a slip displacement of about 0.8 mm. Permeabilities in all directions decreases by one order of magnitude until this point without showing significant anisotropy. After the shear stress reaches steady-state, anisotropy of permeability becomes remarkable. At the steady state in terms of shear stress, permeability anisotropies kx/kz and ky/kz stayed at their steady state value as high as nearly one order magnitude. Microstructures of recovered samples suggest that the permeability anisotropy is caused by developments of R- and P-shear band structures that may act as fluid conduits and encourage fluid flow parallel to the fault in serpentinite gouge. These permeability anisotropies may enhance fluid flow along subduction plate interface and active fault zones. In addition, this anisotropic permeability structure

  20. Fluctuation-driven anisotropy in effective pair interactions between nanoparticles: Thiolated gold nanoparticles in ethane

    SciTech Connect

    Jabes, B. Shadrack; Yadav, Hari O. S.; Chakravarty, Charusita; Kumar, Sanat K.

    2014-10-21

    Fluctuations within the ligand shell of a nanoparticle give rise to a significant degree of anisotropy in effective pair interactions for low grafting densities [B. Bozorgui, D. Meng, S. K. Kumar, C. Chakravarty, and A. Cacciuto, Nano Lett. 13, 2732 (2013)]. Here, we examine the corresponding fluctuation-driven anisotropy for gold nanocrystals densely passivated with short ligands. In particular, we consider gold nanocrystals capped by alkylthiols, both in vacuum and in ethane solvent at high density. As in the preceding study, we show that the anisotropy in the nanoparticle pair potential can be quantified by an angle-dependent correction term to the isotropic potential of mean force (PMF). We find that the anisotropy of the ligand shells is distance dependent, and strongly influenced by ligand interdigitation effects as well as expulsion of ligand chains from the interparticle region at short distances. Such fluctuation-driven anisotropy can be significant for alkylthiol-coated gold nanoparticles, specially for longer chain lengths, under good solvent conditions. The consequences of such anisotropy for self-assembly, specially as a function of grafting density, solvent quality and at interfaces, should provide some interesting insights in future work. Our results clearly show that an isotropic two-body PMF cannot adequately describe the thermodynamics and assembly behavior of nanoparticles in this dense grafting regime and inclusion of anisotropic effects, as well as possibly many-body interactions, is necessary. Extensions of this approach to other passivated nanoparticle systems and implications for self-assembly are considered.

  1. Cap-Induced Magnetic Anisotropy in Ultra-thin Fe/MgO(001) Films

    NASA Astrophysics Data System (ADS)

    Brown-Heft, Tobias; Pendharkar, Mihir; Lee, Elizabeth; Palmstrom, Chris

    Magnetic anisotropy plays an important role in the design of spintronic devices. Perpendicular magnetic anisotropy (PMA) is preferred for magnetic tunnel junctions because the resulting energy barrier between magnetization states can be very high and this allows enhanced device scalability suitable for magnetic random access memory applications. Interface induced anisotropy is often used to control magnetic easy axes. For example, the Fe/MgO(001) system has been predicted to exhibit PMA in the ultrathin Fe limit. We have used in-situ magneto optic Kerr effect and ex-situ SQUID to study the changes in anisotropy constants between bare Fe/MgO(001) films and those capped with MgO, Pt, and Ta. In some cases in-plane anisotropy terms reverse sign after capping. We also observe transitions from superparamagnetic to ferromagnetic behavior induced by capping layers. Perpendicular anisotropy is observed for Pt/Fe/MgO(001) films after annealing to 300°C. These effects are characterized and incorporated into a magnetic simulation that accurately reproduces the behavior of the films. This work was supported in part by the Semiconductor Research Corporation programs (1) MSR-Intel, and (2) C-SPIN.

  2. Thermally stable anomalous Hall behavior in perpendicular Co/Pt multilayers sandwiched by HfO2 layers

    NASA Astrophysics Data System (ADS)

    Jiang, Shao-Long; Li, Xu-Jing; Liu, Yi-Wei; Chen, Xi; Liu, Qian-Qian; Han, Gang; Yang, Guang; Wang, Dong-Wei; Zhang, Jing-Yan; Teng, Jiao; Yu, Guang-Hua

    2016-01-01

    The effect of annealing on the anomalous Hall effect (AHE) in perpendicular Co/Pt multilayers sandwiched by HfO2 layers has been studied. It was found that thermally stable AHE features can be obtained in perpendicular Co/Pt multilayers with the introduction of two Co/HfO2 interfaces, leading to the improvement of the skew scattering contribution to the AHE after annealing. On the contrary, thermally stable AHE behavior cannot be observed in Co/Pt multilayers sandwiched by Pt layers or MgO layers because of Co-Pt interdiffusion during annealing.

  3. Anomalous Nernst Effect with Magnetocrystalline Anisotropy (110)

    NASA Astrophysics Data System (ADS)

    Chesman, Carlos; Costa Neto, Jose; Department of Physics-UFRN Team

    2014-03-01

    When a ferromagnetic material is submitted to a temperature gradient and the magnetic field generates voltage on the edges of the samples, this is called the Anomalous Nernst Effect (ANE). The Heusler alloys that currently exhibit this effect are the most promising for spintronics and spin caloritronics. In this study we perform a theoretical investigation of voltage curves associated to the ANE, when the material displays magnetocrystalline anisotropy for experimental results in two configurations, ANE versus applied magnetic field and planar angle variations of ANE. We analyzed three types of magnetocrystalline anisotropy: cubic anisotropy (100) with C4 symmetry, uniaxial anisotropy with C2 symmetry and cubic anisotropy (110). The aim was to prove that cubic anisotropy (110) is equivalent to anisotropy (100) combined with uniaxial anisotropy. Theoretical fitting of experimental ANE data demonstrates this total equivalence and that a new interpretation with the use of cubic anisotropy (110) may be due to the atomic arrangement of the so-called full-Heusler. Comparative analyses of Co2FeAl and Co2MnGe alloys will be presented. CNPq, CAPES, FAPERN.

  4. Thermal flux limited electron Kapitza conductance in copper-niobium multilayers

    SciTech Connect

    Cheaito, Ramez; Hattar, Khalid Mikhiel; Gaskins, John T.; Yadav, Ajay K.; Duda, John C.; Beechem, III, Thomas Edwin; Ihlefeld, Jon; Piekos, Edward S.; Baldwin, Jon K.; Misra, Amit; Hopkins, Patrick E.

    2015-03-05

    The interplay between the contributions of electron thermal flux and interface scattering to the Kapitza conductance across metal-metal interfaces through measurements of thermal conductivity of copper-niobium multilayers was studied. Thermal conductivities of copper-niobium multilayer films of period thicknesses ranging from 5.4 to 96.2 nm and sample thicknesses ranging from 962 to 2677 nm are measured by time-domain thermoreflectance over a range of temperatures from 78 to 500 K. The Kapitza conductances between the Cu and Nb interfaces in multilayer films are determined from the thermal conductivities using a series resistor model and are in good agreement with the electron diffuse mismatch model. The results for the thermal boundary conductance between Cu and Nb are compared to literature values for the thermal boundary conductance across Al-Cu and Pd-Ir interfaces, and demonstrate that the interface conductance in metallic systems is dictated by the temperature derivative of the electron energy flux in the metallic layers, rather than electron mean free path or scattering processes at the interface.

  5. Thermal flux limited electron Kapitza conductance in copper-niobium multilayers

    SciTech Connect

    Cheaito, Ramez; Gaskins, John T.; Duda, John C.; Hopkins, Patrick E.; Hattar, Khalid; Beechem, Thomas E.; Ihlefeld, Jon F.; Piekos, Edward S.; Yadav, Ajay K.; Baldwin, Jon K.; Misra, Amit

    2015-03-02

    We study the interplay between the contributions of electron thermal flux and interface scattering to the Kapitza conductance across metal-metal interfaces through measurements of thermal conductivity of copper-niobium multilayers. Thermal conductivities of copper-niobium multilayer films of period thicknesses ranging from 5.4 to 96.2 nm and sample thicknesses ranging from 962 to 2677 nm are measured by time-domain thermoreflectance over a range of temperatures from 78 to 500 K. The Kapitza conductances between the Cu and Nb interfaces in multilayer films are determined from the thermal conductivities using a series resistor model and are in good agreement with the electron diffuse mismatch model. Our results for the thermal boundary conductance between Cu and Nb are compared to literature values for the thermal boundary conductance across Al-Cu and Pd-Ir interfaces, and demonstrate that the interface conductance in metallic systems is dictated by the temperature derivative of the electron energy flux in the metallic layers, rather than electron mean free path or scattering processes at the interface.

  6. Thermal flux limited electron Kapitza conductance in copper-niobium multilayers

    DOE PAGESBeta

    Cheaito, Ramez; Hattar, Khalid Mikhiel; Gaskins, John T.; Yadav, Ajay K.; Duda, John C.; Beechem, III, Thomas Edwin; Ihlefeld, Jon; Piekos, Edward S.; Baldwin, Jon K.; Misra, Amit; et al

    2015-03-05

    The interplay between the contributions of electron thermal flux and interface scattering to the Kapitza conductance across metal-metal interfaces through measurements of thermal conductivity of copper-niobium multilayers was studied. Thermal conductivities of copper-niobium multilayer films of period thicknesses ranging from 5.4 to 96.2 nm and sample thicknesses ranging from 962 to 2677 nm are measured by time-domain thermoreflectance over a range of temperatures from 78 to 500 K. The Kapitza conductances between the Cu and Nb interfaces in multilayer films are determined from the thermal conductivities using a series resistor model and are in good agreement with the electron diffusemore » mismatch model. The results for the thermal boundary conductance between Cu and Nb are compared to literature values for the thermal boundary conductance across Al-Cu and Pd-Ir interfaces, and demonstrate that the interface conductance in metallic systems is dictated by the temperature derivative of the electron energy flux in the metallic layers, rather than electron mean free path or scattering processes at the interface.« less

  7. Optical transmittance of multilayer graphene

    NASA Astrophysics Data System (ADS)

    Zhu, Shou-En; Yuan, Shengjun; Janssen, G. C. A. M.

    2014-10-01

    We study the optical transmittance of multilayer graphene films up to 65 layers thick. By combing large-scale tight-binding simulation and optical measurement on CVD multilayer graphene, the optical transmission through graphene films in the visible region is found to be solely determined by the number of graphene layers. We argue that the optical transmittance measurement is more reliable in the determination of the number of layers than the commonly used the Raman spectroscopy. Moreover, the optical transmittance measurement can be applied also to other 2D materials with weak van der Waals interlayer interaction.

  8. Large Voltage-Induced Changes in the Perpendicular Magnetic Anisotropy of an MgO-Based Tunnel Junction with an Ultrathin Fe Layer

    NASA Astrophysics Data System (ADS)

    Nozaki, Takayuki; Kozioł-Rachwał, Anna; Skowroński, Witold; Zayets, Vadym; Shiota, Yoichi; Tamaru, Shingo; Kubota, Hitoshi; Fukushima, Akio; Yuasa, Shinji; Suzuki, Yoshishige

    2016-04-01

    We study the voltage control of perpendicular magnetic anisotropy in an ultrathin Fe layer sandwiched between the Cr buffer and MgO tunneling barrier layers. A high-interface magnetic anisotropy energy of 2.1 mJ /m2 is achieved in the Cr/ultrathin Fe /MgO structure. A large voltage-induced perpendicular magnetic anisotropy change is observed under the negative-bias voltage applications for the case of the Fe layer thinner than 0.6 nm. The amplitude of the voltage-induced anisotropy energy change exhibits a strong Fe-thickness dependence and it reaches as high as 290 fJ /Vm . The observed high values of the surface anisotropy and voltage-induced anisotropy energy change demonstrate the feasibility of voltage-driven spintronic devices.

  9. Electrochromism and electrocatalysis in viologen polyelectrolyte multilayers

    SciTech Connect

    Stepp, J.; Schlenoff, J.B.

    1997-06-01

    Polyelectrolyte multilayers were constructed from a polyviologen and poly(styrene sulfonate) using an alternating polyion solution deposition technique. In situ absorption spectroscopy showed multilayers to be strongly electrochromic. Oxygen reduction at multilayer-coated conducting glass electrodes was also shown to be facilitated.

  10. Patterned submicrometer-thick optical polarizing films using stretched silver island multilayers

    NASA Astrophysics Data System (ADS)

    Baba, Kazutaka; Sato, Yoshinori; Yoshitake, Tsutomu; Miyagi, Mitsunobu

    2000-04-01

    We demonstrate a patterned submicrometer-thick optical polarizing film in which non-polarizing areas are formed where the light transmits insensitively to polarization. The polarizing film is fabricated by stretching a silver island multilayer consisting of thin glass layers and silver island layers composed of silver nanoclusters of high density. By stretching the silver island multilayer at a temperature higher than the glass annealing point, the silver islands are elongated along the stretching direction and the large optical anisotropy is induced in the silver island multilayer. In this optical polarizing film, the non- polarizing areas can be easily formed by laser irradiation with high power density as the optical anisotorpy is reduce das the elongated silver islands become spherical ones from the thermal deformation in the irradiated area. We have successfully patterned the optical polarizing films fabricated for the wavelength of 800 nm by laser writing with a 1 W-class carbon dioxide laser. In order to confirm that the optical anisotropy is reduced in the laser written are, the optical characteristics of that area have been measured. In most commercially available optical polarizers including a polarization beam splitter and various polarizing prisms, it is difficult to form the transparent non-polarizing areas. Therefore, the demonstrated patterned optical polarizing films are useful for switchable spatial modulators and filters.

  11. Magnetic anisotropy of ferrosmectic phases

    NASA Astrophysics Data System (ADS)

    Ponsinet, Virginie; Fabre, Pascale; Veyssié, Madeleine; Cabanel, Régis

    1994-10-01

    A new anisotropic magnetic fluid, called ferrosmectic, is obtained when using a colloidal suspension of submicronic magnetic particles (ferrofluid), as a component in a smectic phase of fluid membranes. These lamellar phases present specific magnetic properties. The anisotropy of their magnetic susceptilities as a function of particles concentration is studied and interpreted : a microscopic mechanism involving a steric hindrance between particles and membranes is used to understand the experimental results. Un nouveau fluide magnétique anisotrope, appelé ferrosmectique, est obtenu lorsque nous utilisons un ferrofluide, c'est-à-dire une suspension colloïdale de particules magnétiques de taille inférieure au micron, comme composant dans la fabrication d'une phase smectique de membranes fluides. Ces phases adoptent des comportements spécifiques sous champ magnétique, et nous présentons ici une étude de l'anisotropie de leur susceptibilité magnétique en fonction de la concentration en particules. Nous interprétons les résultats obtenus par un mécanisme microscopique basé sur l'existence d'une gêne stérique entre membranes et particules.

  12. Pressure anisotropy generation in a magnetized plasma configuration with a shear flow velocity

    NASA Astrophysics Data System (ADS)

    De Camillis, S.; Cerri, S. S.; Califano, F.; Pegoraro, F.

    2016-04-01

    The nonlinear evolution of the Kelvin Helmholtz instability in a magnetized plasma with a perpendicular flow close to, or in, the supermagnetosonic regime can produce a significant parallel-to-perpendicular pressure anisotropy. This anisotropy, localized inside the flow shear region, can make the configuration unstable either to the mirror or to the firehose instability and, in general, can affect the development of the KHI. The interface between the solar wind and the Earth’s magnetospheric plasma at the magnetospheric equatorial flanks provides a relevant setting for the development of this complex nonlinear dynamics.

  13. Plastic Deformation Modes of CuZr/Cu Multilayers

    NASA Astrophysics Data System (ADS)

    Cui, Yan; Abad, Oscar Torrents; Wang, Fei; Huang, Ping; Lu, Tian-Jian; Xu, Ke-Wei; Wang, Jian

    2016-03-01

    We synthesized CuZr/Cu multilayers and performed nanoindentation testing to explore the dependence of plastic deformation modes on the thickness of CuZr layers. The Cu layers were 18 nm thick and the CuZr layers varied in thickness from 4 nm to 100 nm. We observed continuous plastic co-deformation in the 4 nm and 10 nm CuZr ‑ 18 nm Cu multilayers and plastic-induced shear instability in thick CuZr layers (>20 nm). The plastic co-deformation is ascribed to the nucleation and interaction of shear transformation zones in CuZr layers at the adjacent interfaces, while the shear instability is associated with the nucleation and propagation of shear bands in CuZr layers. Shear bands are initialized in the CuZr layers due to the accumulated glide dislocations along CuZr-Cu interfaces, and propagate into adjacent Cu layers via slips on {111} plane non-parallel to the interface. Due to crystallographic constraint of the Cu layers, shear bands are approximately parallel to {111} plane in the Cu layer.

  14. Plastic Deformation Modes of CuZr/Cu Multilayers.

    PubMed

    Cui, Yan; Abad, Oscar Torrents; Wang, Fei; Huang, Ping; Lu, Tian-Jian; Xu, Ke-Wei; Wang, Jian

    2016-01-01

    We synthesized CuZr/Cu multilayers and performed nanoindentation testing to explore the dependence of plastic deformation modes on the thickness of CuZr layers. The Cu layers were 18 nm thick and the CuZr layers varied in thickness from 4 nm to 100 nm. We observed continuous plastic co-deformation in the 4 nm and 10 nm CuZr - 18 nm Cu multilayers and plastic-induced shear instability in thick CuZr layers (>20 nm). The plastic co-deformation is ascribed to the nucleation and interaction of shear transformation zones in CuZr layers at the adjacent interfaces, while the shear instability is associated with the nucleation and propagation of shear bands in CuZr layers. Shear bands are initialized in the CuZr layers due to the accumulated glide dislocations along CuZr-Cu interfaces, and propagate into adjacent Cu layers via slips on {111} plane non-parallel to the interface. Due to crystallographic constraint of the Cu layers, shear bands are approximately parallel to {111} plane in the Cu layer. PMID:26984537

  15. Design of radiation resistant metallic multilayers for advanced nuclear systems

    SciTech Connect

    Zhernenkov, Mikhail E-mail: gills@bnl.gov; Gill, Simerjeet E-mail: gills@bnl.gov; Stanic, Vesna; DiMasi, Elaine; Kisslinger, Kim; Ecker, Lynne; Baldwin, J. Kevin; Misra, Amit; Demkowicz, M. J.

    2014-06-16

    Helium implantation from transmutation reactions is a major cause of embrittlement and dimensional instability of structural components in nuclear energy systems. Development of novel materials with improved radiation resistance, which is of the utmost importance for progress in nuclear energy, requires guidelines to arrive at favorable parameters more efficiently. Here, we present a methodology that can be used for the design of radiation tolerant materials. We used synchrotron X-ray reflectivity to nondestructively study radiation effects at buried interfaces and measure swelling induced by He implantation in Cu/Nb multilayers. The results, supported by transmission electron microscopy, show a direct correlation between reduced swelling in nanoscale multilayers and increased interface area per unit volume, consistent with helium storage in Cu/Nb interfaces in forms that minimize dimensional changes. In addition, for Cu/Nb layers, a linear relationship is demonstrated between the measured depth-dependent swelling and implanted He density from simulations, making the reflectivity technique a powerful tool for heuristic material design.

  16. Plastic Deformation Modes of CuZr/Cu Multilayers

    PubMed Central

    Cui, Yan; Abad, Oscar Torrents; Wang, Fei; Huang, Ping; Lu, Tian-Jian; Xu, Ke-Wei; Wang, Jian

    2016-01-01

    We synthesized CuZr/Cu multilayers and performed nanoindentation testing to explore the dependence of plastic deformation modes on the thickness of CuZr layers. The Cu layers were 18 nm thick and the CuZr layers varied in thickness from 4 nm to 100 nm. We observed continuous plastic co-deformation in the 4 nm and 10 nm CuZr − 18 nm Cu multilayers and plastic-induced shear instability in thick CuZr layers (>20 nm). The plastic co-deformation is ascribed to the nucleation and interaction of shear transformation zones in CuZr layers at the adjacent interfaces, while the shear instability is associated with the nucleation and propagation of shear bands in CuZr layers. Shear bands are initialized in the CuZr layers due to the accumulated glide dislocations along CuZr-Cu interfaces, and propagate into adjacent Cu layers via slips on {111} plane non-parallel to the interface. Due to crystallographic constraint of the Cu layers, shear bands are approximately parallel to {111} plane in the Cu layer. PMID:26984537

  17. Multilayer analytic element modeling of radial collector wells.

    PubMed

    Bakker, Mark; Kelson, Victor A; Luther, Kenneth H

    2005-01-01

    A new multilayer approach is presented for the modeling of ground water flow to radial collector wells. The approach allows for the inclusion of all aspects of the unique boundary condition along the lateral arms of a collector well, including skin effect and internal friction losses due to flow in the arms. The hydraulic conductivity may differ between horizontal layers within the aquifer, and vertical anisotropy can be taken into account. The approach is based on the multilayer analytic element method, such that regional flow and local three-dimensional detail may be simulated simultaneously and accurately within one regional model. Horizontal flow inside a layer is computed analytically, while vertical flow is approximated with a standard finite-difference scheme. Results obtained with the proposed approach compare well to results obtained with three-dimensional analytic element solutions for flow in unconfined aquifers. The presented approach may be applied to predict the yield of a collector well in a regional setting and to compute the origin and residence time, and thus the quality, of water pumped by the collector well. As an example, the addition of three lateral arms to a collector well that already has three laterals is investigated. The new arms are added at an elevation of 2 m above the existing laterals. The yield increase of the collector well is computed as a function of the lengths of the three new arms. PMID:16324013

  18. First Principles Modeling of Metal/Ceramic Multilayer Nano-heterostructures.

    SciTech Connect

    Yadav, Satyesh K.; Wang, Jian; Misra, Amit; Liu, Xiang-Yang; Ramprasad, Ramamurthy

    2012-07-31

    Nanoscaled multilayer films composed of metals and ceramics have been explored for their potential applications as ductile, yet strong, materials. It is believed that at the nanoscale, the interfaces between the two materials constituting the multilayer assume an increasingly important role in determining the properties, as they comprise a more significant volume fraction of the multilayer with decreasing layer thickness. In this ab initio work, density functional theory was used to calculate the ideal shear strengths of pure Al, pure TiN, the Al/TiN interfacial region, and Al/TiN multilayers. The ideal shear strength of the Al/TiN interface was found to vary from very low (on the order of the ideal shear strength of Al) to very high (on the order of the ideal shear strength of TiN), depending on whether the TiN at the interface was Ti- or N-terminated, respectively. The results suggest that the shear properties of Al/TiN depend strongly on the chemistry of the interface, Al:N versus Al:Ti terminations. Nevertheless, for the Al/TiN multilayers, the ideal shear strength was limited by shear in the Al layer away from the interface, even when the individual layer thickness is less than a nanometer. Further we found an unusual structural rotation of bulk single-crystal Al under uniaxial compressive strains. It was found that under strains either along the <11-2> or the <111> directions, beyond a critical stress of about 13 GPa, the Al crystal can rotate through shear in the Shockley partial direction (i.e.,<11-2>) on the {l_brace}111{r_brace} plane, in an attempt to relieve internal stresses. This phenomenon reveals a possible mechanism leading to the onset of homogeneous dislocation nucleation in Al under high uniaxial compressions.

  19. Control of normal chirality at hexagonal interfaces

    SciTech Connect

    Haraldsen, Jason T; Fishman, Randy Scott

    2010-01-01

    We study the net chirality created by the Dzyaloshinkii-Moriya interaction (DMI) at the boundary between hexagonal layers of magnetic and non-magnetic materials. It is shown that another mechanism besides elastic torsion is required to understand the change in chirality observed in Dy/Y multilayers during field-cooling. The paper shows that due to the overlap between magnetic and non-magnetic atoms, interfacial steps may produce a DMI normal to the interface in magnetic heterostructures.

  20. Multilayer infrared beamsplitter film system

    NASA Technical Reports Server (NTRS)

    Bastien, R. C.; Heinrich, P. L.

    1969-01-01

    Multilayer infrared beamsplitter film system on a potassium bromide crystal substrate is operational over a wavelength range of 2.5 to 25 microns with nearly equal broadband reflectance and transmittance. It is useful in optical coating, vacuum deposition, radiometry, interferometry, and spectrometry.

  1. Panelized high performance multilayer insulation

    NASA Technical Reports Server (NTRS)

    Burkley, R. A.; Shriver, C. B.; Stuckey, J. M.

    1968-01-01

    Multilayer insulation coverings with low conductivity foam spacers are interleaved with quarter mil aluminized polymer film radiation shields to cover flight type liquid hydrogen tankage of space vehicles with a removable, structurally compatible, lightweight, high performance cryogenic insulation capable of surviving extended space mission environments.

  2. Multilayer printed wiring board lamination

    SciTech Connect

    Lula, J.W.

    1980-06-01

    The relationship of delamination resistance of multilayer PWBs made from GF material to manufacturing process variables was investigated. A unique quantitative test method developed during this project shows that delamination resistance is highly sensitive to material conditioning, to innerlayer surface treatment, and to post-lamination storage conditions, but is relatively insensitive to cure cycle variations.

  3. Multilayer High-Gradient Insulators

    SciTech Connect

    Harris, J R

    2006-08-16

    Multilayer High-Gradient Insulators are vacuum insulating structures composed of thin, alternating layers of dielectric and metal. They are currently being developed for application to high-current accelerators and related pulsed power systems. This paper describes some of the High-Gradient Insulator research currently being conducted at Lawrence Livermore National Laboratory.

  4. Microwave assisted magnetization switching in Co/Pt multilayer

    SciTech Connect

    Okamoto, S.; Kikuchi, N.; Kitakami, O.; Shimatsu, T.; Aoi, H.

    2011-04-01

    In this study, we have experimentally investigated the microwave assisted magnetization by switching (MAS) on the microstructured Co/Pt multilayer. The sample exhibits the typical magnetization curve peculiar to perpendicular anisotropy films, that is, a steep reversal initiated by nucleation of a reversed domain followed by its subsequent gradual expansion by the domain wall displacement. By applying microwaves with the frequency of GHz order, the nucleation field H{sub n} is significantly reduced at three frequencies. Taking into account the effective anisotropy field of our sample, the first dip of H{sub n} at the lowest frequency probably corresponds to the Kittel mode excitation, and the other two dips at higher frequencies correspond to unidentified excitation modes other than the Kittel mode. Among them, the last dip of H{sub n} at the highest frequency reaches about 1/3 of that without microwave application. These results suggest the existence of more effective excitation modes for MAS than the Kittel mode.

  5. Structure analysis of layer-by-layer multilayer films of colloidal particles

    NASA Astrophysics Data System (ADS)

    Batys, Piotr; Nosek, Magdalena; Weroński, Paweł

    2015-03-01

    We have mimicked the layer-by-layer self-assembling process of monodisperse colloidal particles at a solid-liquid interface using the extended random sequential adsorption model of hard spheres. We have studied five multilayer structures of similar thickness, each created at a different single-layer surface coverage. For each multilayer, we have determined its particle volume fraction as a function of distance from the interface. Additionally, we have characterized the film structure in terms of 2D and 3D pair-correlation functions. We have found that the coverage of about 0.3 is optimal for producing a uniform, constant-porosity multilayer in a minimum number of adsorption cycles. The single-layer coverage has also a significant effect on the primary maximum of 2D radial distribution function. In the case of multilayer with the coverage lower than 0.30 the 2D pair-correlation functions of even layers exhibit maxima decreasing with the increase in the layer number. We have verified our theoretical predictions experimentally. We have used fluorescence microscopy to determine the 2D pair-correlation functions for the second, third, and fourth layers of multilayer formed of micron-sized spherical latex particles. We have found a good agreement between our theoretical and experimental results, which confirms the validity of the extended RSA model.

  6. Quasi magnetic isotropy and microwave performance of FeCoB multilayer laminated by uniaxial anisotropic layers

    NASA Astrophysics Data System (ADS)

    Li, Shandong; Du, Honglei; Zhang, Yongcheng; Xue, Qian; Gao, Xiaoyang; Shao, Weiquan; Zhou, Ziyao; Nan, Tianxiang; Sun, Nian X.

    2014-05-01

    A Fe0.7Co0.3-B multilayer was laminated by three Fe0.7Co0.3-B ferromagnetic sublayers prepared by composition gradient sputtering. Three Fe0.7Co0.3-B ferromagnetic sublayers have their individual directions of uniaxial magnetic anisotropy, and the easy magnetic axis of neighboring sublayer successively rotates 60° in the film plane. It is exciting that a quasi magnetic isotropy was achieved in the designed multilayer with a quasi-isotropic hysteresis loop and quasi-isotorpic ferromagnetic resonance around 3.7 GHz. This omnidirectional multilayer is promising for the application in inductors since the 100% hard-axis excitation is achieved for any shaped inductors.

  7. Multilayer Composite Pressure Vessels

    NASA Technical Reports Server (NTRS)

    DeLay, Tom

    2005-01-01

    A method has been devised to enable the fabrication of lightweight pressure vessels from multilayer composite materials. This method is related to, but not the same as, the method described in gMaking a Metal- Lined Composite-Overwrapped Pressure Vessel h (MFS-31814), NASA Tech Briefs, Vol. 29, No. 3 (March 2005), page 59. The method is flexible in that it poses no major impediment to changes in tank design and is applicable to a wide range of tank sizes. The figure depicts a finished tank fabricated by this method, showing layers added at various stages of the fabrication process. In the first step of the process, a mandrel that defines the size and shape of the interior of the tank is machined from a polyurethane foam or other suitable lightweight tooling material. The mandrel is outfitted with metallic end fittings on a shaft. Each end fitting includes an outer flange that has a small step to accommodate a thin layer of graphite/epoxy or other suitable composite material. The outer surface of the mandrel (but not the fittings) is covered with a suitable release material. The composite material is filament- wound so as to cover the entire surface of the mandrel from the step on one end fitting to the step on the other end fitting. The composite material is then cured in place. The entire workpiece is cut in half in a plane perpendicular to the axis of symmetry at its mid-length point, yielding two composite-material half shells, each containing half of the foam mandrel. The halves of the mandrel are removed from within the composite shells, then the shells are reassembled and bonded together with a belly band of cured composite material. The resulting composite shell becomes a mandrel for the subsequent steps of the fabrication process and remains inside the final tank. The outer surface of the composite shell is covered with a layer of material designed to be impermeable by the pressurized fluid to be contained in the tank. A second step on the outer flange of

  8. Temperature memory of the induced magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Vetcfinski, V. S.; Tunyi, I.

    2012-04-01

    Methods of higher harmonics applied to study the effects associated with the induced magnetic anisotropy (IMA) of ferro- and ferrimagnetic materials are considered. Physical processes causing the anisotropy and small value of these effects are analyzed. It is demonstrated that the IMA can remember the pressure at which it was formed.

  9. Modelling of the Peltier effect in magnetic multilayers

    NASA Astrophysics Data System (ADS)

    Juarez-Acosta, Isaac; Olivares-Robles, Miguel A.; Bosu, Subrojati; Sakuraba, Yuya; Kubota, Takahide; Takahashi, Saburo; Takanashi, Koki; Bauer, Gerrit E. W.

    2016-02-01

    We model the charge, spin, and heat currents in ferromagnetic metal|normal metal|normal metal trilayer structures in the two current model, taking into account bulk and interface thermoelectric properties as well as Joule heating. The results include the temperature distribution as well as resistance-current curves that reproduce the observed shifted parabolic characteristics. Thin tunneling barriers can enhance the apparent Peltier cooling. The model agrees with the experimental results for wide multilayer pillars, but the giant effects observed for diameters ≲100 nm are still under discussion.

  10. Layer-Resolved Magnetic Moments in Ni/Pt Multilayers

    NASA Astrophysics Data System (ADS)

    Wilhelm, F.; Poulopoulos, P.; Ceballos, G.; Wende, H.; Baberschke, K.; Srivastava, P.; Benea, D.; Ebert, H.; Angelakeris, M.; Flevaris, N. K.; Niarchos, D.; Rogalev, A.; Brookes, N. B.

    2000-07-01

    The magnetic moments in Ni/Pt multilayers are thoroughly studied by combining experimental and ab initio theoretical techniques. SQUID magnetometry probes the samples' magnetizations. X-ray magnetic circular dichroism separates the contribution of Ni and Pt and provides a layer-resolved magnetic moment profile for the whole system. The results are compared to band-structure calculations. Induced Pt magnetic moments localized mostly at the interface are revealed. No magnetically ``dead'' Ni layers are found. The magnetization per Ni volume is slightly enhanced compared to bulk NiPt alloys.

  11. Mono- and multilayers of molecular spoked carbazole wheels on graphite

    PubMed Central

    Aggarwal, A Vikas; Kalle, Daniel; Höger, Sigurd

    2014-01-01

    Summary Self-assembled monolayers of a molecular spoked wheel (a shape-persistent macrocycle with an intraannular spoke/hub system) and its synthetic precursor are investigated by scanning tunneling microscopy (STM) at the liquid/solid interface of 1-octanoic acid and highly oriented pyrolytic graphite. The submolecularly resolved STM images reveal that the molecules indeed behave as more or less rigid objects of certain sizes and shapes – depending on their chemical structures. In addition, the images provide insight into the multilayer growth of the molecular spoked wheels (MSWs), where the first adlayer acts as a template for the commensurate adsorption of molecules in the second layer. PMID:25550744

  12. High-index-contrast multilayer hollow waveguides for mid-IR laser delivery

    NASA Astrophysics Data System (ADS)

    Melzer, Jeffrey E.; Kendall, Wesley Y.; Harrington, James A.

    2016-03-01

    Hollow glass waveguides (HGWs) have been researched extensively for the efficient transmission of radiation over a broad spectral range spanning from the visible region to the far-IR. One such HGW film structure consists of a metallic substrate with overlaying multilayer dielectric thin film stack of alternating high and low refractive index films. The optical properties of such multilayer thin film stacks are well established and provide a method for developing photonic bandgap fibers with exceptionally low attenuation losses at a desired wavelength. Transmission losses can be minimized in multilayer waveguides through two main approaches; either maximizing the number of alternating layer pairs or maximizing the index contrast between adjacent films. In practice, it has been shown that for liquid-phase deposition-based procedures, the former approach leads to compounding surface and interface roughness, negating the low-loss advantage of a multilayer waveguide. Thus, this research focuses on maximizing index contrast between adjacent dielectrics in an attempt to minimize the number of films required to achieve acceptable transmission characteristics both in theory and in practice. In this study, multilayer waveguides are fabricated using three dielectric materials: silver iodide, lead sulfide, and cyclic olefin copolymer. Through exploitation of their high index contrast, these materials are used to develop low-film-count multilayer waveguides designed for enhanced transmission at both Er:YAG and CO2 laser wavelengths.

  13. High efficiency carbon-based multilayers for LAMP at 250 eV

    NASA Astrophysics Data System (ADS)

    Wen, Mingwu; Huang, Qiushi; She, Rui; Jiang, Li; Zhang, Zhong; Wang, Zhanshan; Feng, Hua; Spiga, Daniele; Giglia, Angelo

    2015-09-01

    X-ray reflection near the Brewster's angle by multilayer mirrors can be used to detect the polarization from X-ray sources. The photon emission spectra from some isolated neutron stars and AGN/blazars etc. show that their emission is peaked at low energies near 250eV, which is just below carbon K-absorption edge. The Lightweight Asymmetry and Magnetism Probe (LAMP) is proposed as a micro-satellite mission dedicated for astronomical X-ray polarimetry working at 250 eV and is currently under early phase study. Co/C multilayers are selected and designed at the energy near 250eV with a grazing incident angle of 45°. The carbon layer thickness ratio is optimized to get the highest integral reflectivity which means larger effective signals in the astrophysics observation. The multilayer coatings were manufactured by direct current magnetron sputtering on D263 glasses and electroformed nickels and characterized using Grazing incidence X-ray reflectometry at 8keV. Reactive sputtering with 4%, 6% and 8% nitrogen were used to improve the Co/C multilayer interfaces respectively. Reflectivity for s-polarization and p-polarization light was measured at BEAR beamline in Elettra synchtron facility. Co/C multilayer deposited with 6% nitrogen exhibits the best performance comparing to other multilayers with different nitrogen content.

  14. Ratcheting fluid with geometric anisotropy

    NASA Astrophysics Data System (ADS)

    Thiria, Benjamin; Zhang, Jun

    2015-02-01

    We investigate a mechanism that effectively transports fluids using vibrational motion imposed onto fluid boundary with anisotropy. In our experiment, two asymmetric, sawtooth-like structures are placed facing each other and form a corrugated fluid channel. This channel is then forced to open and close periodically. Under reciprocal motion, fluid fills in the gap during the expansion phase of the channel and is then forced out during contraction. Since the fluid experiences different impedances when flowing in different directions, the stagnation point that separates flows of two directions changes within each driving period. As a result, fluid is transported unidirectionally. This ratcheting effect of fluid is demonstrated through our measurements and its working principle discussed in some detail.

  15. Texture induced microwave background anisotropies

    SciTech Connect

    Borrill, Julian; Copeland, Edmund J.; Liddle, Andrew R.; Stebbins, Albert; Veeraraghavan, Shoba

    1994-03-01

    We use numerical simulations to calculate the cosmic microwave background anisotropy induced by the evolution of a global texture field, with special emphasis on individual textures. Both spherically symmetric and general configurations are analyzed, and in the latter case we consider field configurations which exhibit unwinding events and also ones which do not. We compare the results given by evolving the field numerically under both the expanded core (XCORE) and non-linear sigma model (NLSM) approximations with the analytic predictions of the NLSM exact solution for a spherically symmetric self-similar (SSSS) unwinding. We find that the random unwinding configuration spots' typical peak height is 60-75\\% and angular size typically only 10% of those of the SSSS unwinding, and that random configurations without an unwinding event nonetheless may generate indistinguishable hot and cold spots. A brief comparison is made with other work.

  16. Shale seismic anisotropy vs. compaction trend

    NASA Astrophysics Data System (ADS)

    Pervukhina, M.

    2015-12-01

    Shales comprise more than 60% of sedimentary rocks and form natural seals above hydrocarbon reservoirs. Their sealing capacity is also used for storage of nuclear wastes. Shales are notorious for their strong elastic anisotropy, so-called, vertical transverse isotropy or VTI. This VTI anisotropy is of practical importance as it is required for correct surface seismic data interpretation, seismic to well tie and azimuth versus offset analysis. A number of competing factors are responsible for VTI anisotropy in shales, namely, (1) micro-scale elastic anisotropy of clay particles, (2) anisotropic orientation distribution function of clay particles, (3) anisotropic orientation of pores and organic matter. On the contrary, silt (non-clay mineralogy grains with size between 0.06 -0.002 mm) is known to reduce elastic anisotropy of shales. Methods developed for calculations of anisotropy in polycrystalline materials can be used to estimate elastic anisotropy of shales from orientation distribution function (ODF) of clay platelets if elastic properties of individual clay platelets are known. Unfortunately, elastic properties of individual clay platelets cannot be directly measured. Recently, elastic properties of properties of individual clay platelets with different mineralogy were calculated from first principles based on density functional theory. In this work we use these elastic properties of individual platelets of muscovite, illite-smectite and kaolinite to obtain correlations between elastic anisotropy and Legendre coefficients W200 and W400 of different ODFs. Comparison of the Legendre coefficients calculated for more than 800 shales from depths 0 - 6 km (www.rockphysicists.org/data) with those of compaction ODFs shows that compaction has no first order effect on elastic anisotropy. Thus, elastic anisotropy is to large extent determined by factors other than compaction processes, such as depositional environment, chemical composition of fluid, silt fraction, etc.

  17. Basic research needs and opportunities on interfaces in solar materials

    SciTech Connect

    Czanderna, A. W.; Gottschall, R. J.

    1981-04-01

    The workshop on research needs and recommended research programs on interfaces in solar energy conversion devices was held June 30-July 3, 1980. The papers deal mainly with solid-solid, solid-liquid, and solid-gas interfaces, sometimes involving multilayer solid-solid interfaces. They deal mainly with instrumental techniques of studying these interfaces so they can be optimized, so they can be fabricated with quality control and so changes with time can be forecast. The latter is required because a long lifetime (20 yrs is suggested) is necessary for economic reasons. Fifteen papers have been entered individually into EDB and ERA. (LTN)

  18. Pd/B4C/Y multilayer coatings for extreme ultraviolet applications near 10  nm wavelength.

    PubMed

    Windt, David L; Gullikson, Eric M

    2015-06-20

    A new extreme ultraviolet (EUV) multilayer coating has been developed comprising Pd and Y layers with thin B4C barrier layers at each interface, for normal incidence applications near 10 nm wavelength. Periodic, nonperiodic, and dual-stack coatings have been investigated and compared with similar structures comprising either Mo/Y or Pd/B4C bilayers. We find that Pd/B4C/Y multilayers provide higher reflectance than either Mo/Y or Pd/B4C, with much lower film stress than Pd/B4C. We have also investigated the performance of periodic multilayers comprising repetitions of Pd/Y, Ru/Y, or Ru/B4C/Y, as well as Pd/B4C multilayers deposited using reactive sputtering with an Ar:N2 gas mixture in order to reduce stress: these material combinations were all found to provide poor EUV performance. The temporal stability of a periodic Pd/B4C/Y multilayer stored in air was investigated over a period of 16 months, and a slight reduction in peak reflectance was observed. Periodic Pd/B4C/Y multilayers were also found to be thermally stable up to 100°C; at higher temperatures (200°C and 300°C) we observe a slight reduction in peak reflectance and a slight increase in multilayer period. High-resolution transmission electron microscopy and selected area diffraction of an as-deposited Pd/B4C/Y film indicates a fully amorphous structure, with interfaces that are both smoother and more abrupt than those observed in a comparable Pd/B4C multilayer in which the Pd layers are polycrystalline. The new Pd/B4C/Y multilayers are suitable for normal-incidence imaging and spectroscopy applications, including solar physics, plasma physics, high-brightness EUV light sources, and others. PMID:26193039

  19. In-plane uniaxial magnetic anisotropy induced by anisotropic strain relaxation in high lattice-mismatched Dy/Sc superlattices

    NASA Astrophysics Data System (ADS)

    Benito, L.; Ballesteros, C.; Ward, R. C. C.

    2014-04-01

    We report on the magnetic and structural characterization of high lattice-mismatched [Dy2nm/SctSc] superlattices, with variable Sc thickness tSc= 2-6 nm. We find that the characteristic in-plane effective hexagonal magnetic anisotropy K66,ef reverses sign and undergoes a dramatic reduction, attaining values of ≈13-24 kJm-3, when compared to K66=-0.76 MJm-3 in bulk Dy. As a result, the basal plane magnetic anisotropy is dominated by a uniaxial magnetic anisotropy (UMA) unfound in bulk Dy, which amounts to ≈175-142 kJm-3. We attribute the large downsizing in K66,ef to the compression epitaxial strain, which generates a competing sixfold magnetoelastic (MEL) contribution to the magnetocrystalline (strain-free) magnetic anisotropy. Our study proves that the in-plane UMA is caused by the coupling between a giant symmetry-breaking MEL constant Mγ ,22≈1 GPa and a morphic orthorhombiclike strain ɛγ ,1≈10-4, whose origin resides on the arising of an in-plane anisotropic strain relaxation process of the pseudoepitaxial registry between the nonmagnetic bottom layers in the superstructure. This investigation shows a broader perspective on the crucial role played by epitaxial strains at engineering the magnetic anisotropy in multilayers.

  20. Exchange coupling in metallic multilayers with a top FeRh layer

    NASA Astrophysics Data System (ADS)

    Yamada, S.; Tanikawa, K.; Hirayama, J.; Kanashima, T.; Taniyama, T.; Hamaya, K.

    2016-05-01

    We study magnetic properties of metallic multilayers with FeRh/ferromagnet interfaces grown by low-temperature molecular beam epitaxy. Room-temperature coercivity of the ferromagnetic layers is significantly enhanced after the growth of FeRh, proving the existence of the exchange coupling between the antiferromagnetic FeRh layer and the ferromagnetic layer. However, exchange bias is not clearly observed probably due to the presence of disordered structures, which result from the lattice strain at the FeRh/ferromagnet interfaces due to the lattice mismatch. We infer that the lattice matched interface between FeRh and ferromagnetic layers is a key parameter for controlling magnetic switching fields in such multilayer systems.

  1. Joint perpendicular anisotropy and strong interlayer exchange coupling in systems with thin vanadium spacers

    SciTech Connect

    Devolder, T. Le Goff, A.; Eimer, S.; Adam, J.-P.

    2015-04-28

    We study the influence of the insertion of a vanadium spacer layer between an FeCoB layer and a [Co/Ni] multilayer in an MgO substrate-based system mimicking the reference system of a perpendicular anisotropy magnetic tunnel junction. The anisotropy of the [Co/Ni] multilayer gradually improves with the vanadium thicknesses t, up to an optimized state for t = 8 Å, with little influence of the thermal annealing. The interlayer exchange coupling is ferromagnetic and very strong for t≤6 Å. It can be adjusted by thermal treatment at t = 8 Å from no coupling in the as-grown state to more than 2 mJ/m{sup 2} after 250 °C annealing. For this spacer thickness, the magnetic properties are consistent with the occurrence of a bcc (001) to an fcc (111) crystalline structure transition at the vanadium spacer. The remaining interlayer exchange coupling at t = 8 Å is still substantially higher than the one formerly obtained with a Tantalum spacer, which holds promise for further optimization of the reference layers of tunnel junctions meant for magnetic random access memories.

  2. Joint perpendicular anisotropy and strong interlayer exchange coupling in systems with thin vanadium spacers

    NASA Astrophysics Data System (ADS)

    Devolder, T.; Le Goff, A.; Eimer, S.; Adam, J.-P.

    2015-04-01

    We study the influence of the insertion of a vanadium spacer layer between an FeCoB layer and a [Co/Ni] multilayer in an MgO substrate-based system mimicking the reference system of a perpendicular anisotropy magnetic tunnel junction. The anisotropy of the [Co/Ni] multilayer gradually improves with the vanadium thicknesses t, up to an optimized state for t = 8 Å, with little influence of the thermal annealing. The interlayer exchange coupling is ferromagnetic and very strong for t ≤6 Å. It can be adjusted by thermal treatment at t = 8 Å from no coupling in the as-grown state to more than 2 mJ/m2 after 250 °C annealing. For this spacer thickness, the magnetic properties are consistent with the occurrence of a bcc (001) to an fcc (111) crystalline structure transition at the vanadium spacer. The remaining interlayer exchange coupling at t = 8 Å is still substantially higher than the one formerly obtained with a Tantalum spacer, which holds promise for further optimization of the reference layers of tunnel junctions meant for magnetic random access memories.

  3. Magnetic anisotropy in isotropic and nanopatterned strongly exchange-coupled nanolayers

    NASA Astrophysics Data System (ADS)

    Vergara, José; Favieres, Cristina; Madurga, Vicente

    2012-10-01

    In this study, the fabrication of magnetic multilayers with a controlled value of the in-plane uniaxial magnetic anisotropy field in the range of 12 to 72 kA/m was achieved. This fabrication was accomplished by the deposition of bilayers consisting of an obliquely deposited (54°) 8-nm-thick anisotropic Co layer and a second isotropic Co layer that was deposited at a normal incidence over the first layer. By changing the thickness value of this second Co layer ( X) by modifying the deposition time, the value of the anisotropy field of the sample could be controlled. For each sample, the thickness of each bilayer did not exceed the value of the exchange correlation length calculated for these Co bilayers. To increase the volume of the magnetic films without further modification of their magnetic properties, a Ta spacer layer was deposited between successive Co bilayers at 54° to prevent direct exchange coupling between consecutive Co bilayers. This step was accomplished through the deposition of multilayered films consisting of several (Co8 nm-54°/Co X nm-0°/Ta6 nm-54°) trilayers.

  4. Magnetic anisotropy in isotropic and nanopatterned strongly exchange-coupled nanolayers

    PubMed Central

    2012-01-01

    In this study, the fabrication of magnetic multilayers with a controlled value of the in-plane uniaxial magnetic anisotropy field in the range of 12 to 72 kA/m was achieved. This fabrication was accomplished by the deposition of bilayers consisting of an obliquely deposited (54°) 8-nm-thick anisotropic Co layer and a second isotropic Co layer that was deposited at a normal incidence over the first layer. By changing the thickness value of this second Co layer (X) by modifying the deposition time, the value of the anisotropy field of the sample could be controlled. For each sample, the thickness of each bilayer did not exceed the value of the exchange correlation length calculated for these Co bilayers. To increase the volume of the magnetic films without further modification of their magnetic properties, a Ta spacer layer was deposited between successive Co bilayers at 54° to prevent direct exchange coupling between consecutive Co bilayers. This step was accomplished through the deposition of multilayered films consisting of several (Co8 nm-54°/CoX nm-0°/Ta6 nm-54°) trilayers. PMID:23088782

  5. Irradiation-enhanced reactivity of multilayer Al/Ni nanomaterials.

    PubMed

    Manukyan, Khachatur V; Tan, Wanpeng; deBoer, Richard J; Stech, Edward J; Aprahamian, Ani; Wiescher, Michael; Rouvimov, Sergei; Overdeep, Kyle R; Shuck, Christopher E; Weihs, Timothy P; Mukasyan, Alexander S

    2015-06-01

    We have investigated the effect of accelerated ion beam irradiation on the structure and reactivity of multilayer sputter deposited Al/Ni nanomaterials. Carbon and aluminum ion beams with different charge states and intensities were used to irradiate the multilayer materials. The conditions for the irradiation-assisted self-ignition of the reactive materials and corresponding ignition thresholds for the beam intensities were determined. We discovered that relatively short (40 min or less) ion irradiations enhance the reactivity of the Al/Ni nanomaterials, that is, significantly decrease the thermal ignition temperatures (Tig) and ignition delay times (τig). We also show that irradiation leads to atomic mixing at the Al/Ni interfaces with the formation of an amorphous interlayer, in addition to the nucleation of small (2-3 nm) Al3Ni crystals within the amorphous regions. The amorphous interlayer is thought to enhance the reactivity of the multilayer energetic nanomaterial by increasing the heat of the reaction and by speeding the intermixing of the Ni and the Al. The small Al3Ni crystals may also enhance reactivity by facilitating the growth of this Al-Ni intermetallic phase. In contrast, longer irradiations decrease reactivity with higher ignition temperatures and longer ignition delay times. Such changes are also associated with growth of the Al3Ni intermetallic and decreases in the heat of reaction. Drawing on this data set, we suggest that ion irradiation can be used to fine-tune the structure and reactivity of energetic nanomaterials. PMID:25915560

  6. Electric field induced morphological transitions in polyelectrolyte multilayers.

    PubMed

    Cho, Chungyeon; Jeon, Ju-Won; Lutkenhaus, Jodie; Zacharia, Nicole S

    2013-06-12

    In this work, the morphological transitions in weak polyelectrolyte (PE) multilayers (PEMs) assembled from linear poly(ethylene imine) (LPEI) and poly(acrylic acid) (PAA) upon application of an electric field were studied. Exposure to an electric field results in the creation of a porous structure, which can be ascribed to local changes in pH from the hydrolysis of water and subsequent structural rearrangements of the weak PE constituents. Depending on the duration of application of the field, the porous transition gradually develops into a range of structures and pore sizes. It was discovered that the morphological transition of the LbL films starts at the multilayer-electrode interface and propagates through the film. First an asymmetrical structure forms, consisting of microscaled pores near the electrode and nanoscaled pores near the surface in contact with the electrolyte solution. At longer application of the field the porous structures become microscaled throughout. The results revealed in this study not only demonstrate experimental feasibility for controlling variation in pore size and porosity of multilayer films but also deepens the understanding of the mechanism of the porous transition. In addition, electrical potential is used to release small molecules from the PEMs. PMID:23683121

  7. Boron containing multilayer coatings and method of fabrication

    DOEpatents

    Makowiecki, D.M.; Jankowski, A.F.

    1997-09-23

    Hard coatings are fabricated from multilayer boron/boron carbide, boron carbide/cubic boron nitride, and boron/boron nitride/boron carbide, and the fabrication thereof involves magnetron sputtering in a selected atmosphere. These hard coatings may be applied to tools and engine and other parts, as well to reduce wear on tribological surfaces and electronic devices. These boron coatings contain no morphological growth features. For example, the boron and boron carbide used in forming the multilayers are formed in an inert (e.g. argon) atmosphere, while the cubic boron nitride is formed in a reactive (e.g. nitrogen) atmosphere. The multilayer boron/boron carbide, and boron carbide/cubic boron nitride is produced by depositing alternate layers of boron, cubic boron nitride or boron carbide, with the alternate layers having a thickness of 1 nanometer to 1 micrometer, and at least the interfaces of the layers may be of a discrete or a blended or graded composition. 6 figs.

  8. Structural transformations in Sc/Si multilayers irradiated by EUVlasers

    SciTech Connect

    Voronov, D.L.; Zubarev, E.N.; Pershyn, Y.P.; Sevryukova, V.A.; Kondratenko, V.V.; Vinogradov, A.V.; Artioukov, I.A.; Uspenskiy, Y.A.; Grisham, M.; Vaschenko, G.; Menoni, C.S.; Rocca, J.J.

    2007-08-21

    Multilayer mirrors for the extreme ultraviolet (EUV) are keyelements for numerous applications of coherent EUV sources such as newtabletop lasers and free-electron lasers. However the field ofapplications is limited by the radiation and thermal stability of themultilayers. Taking into account the growing power of EUV sources thestability of the optics becomes crucial. To overcome this problem it isnecessary to study the degradation of multilayers and try to increasetheir temporal and thermal stability. In this paper we report the resultsof detailed study of structural changes in Sc/Simultilayers when exposedto intense EUV laser pulses. Various types of surface damage such asmelting, boiling, shockwave creation and ablation were observed asirradiation fluencies increase. Cross-sectional TEM study revealed thatthe layer structure was completely destroyed in the upper part ofmultilayer, but still survived below. The layers adjacent tothe substrateremained intact even through the multilayer surface melted down, thoughthe structure of the layers beneath the molten zone was noticeablychanged. The layer structure in this thermally affected zone is similarto that of isothermally annealed samples. All stages of scandium silicideformation such as interdiffusion, solid-state amorphization, silicidecrystallization, etc., are present in the thermally affected zone. Itindicates a thermal nature of the damage mechanism. The tungstendiffusion barriers were applied to the scandium/silicon interfaces. Itwas shown that the barriers inhibited interdiffusion and increased thethermal stability of Sc/Si mirrors.

  9. Magnetic anisotropy, damping, and interfacial spin transport in Pt/LSMO bilayers

    DOE PAGESBeta

    Lee, H. K.; Barsukov, I.; Swartz, A. G.; Kim, B.; Yang, L.; Hwang, H. Y.; Krivorotov, I. N.

    2016-05-16

    In this paper, we report ferromagnetic resonance measurements of magnetic anisotropy and damping in epitaxial La0.7Sr0.3MnO3 (LSMO) and Pt capped LSMO thin films on SrTiO3 (001) substrates. The measurements reveal large negative perpendicular magnetic anisotropy and a weaker uniaxial in-plane anisotropy that are unaffected by the Pt cap. The Gilbert damping of the bare LSMO films is found to be low α = 1.9(1) × 10-3, and two-magnon scattering is determined to be significant and strongly anisotropic. The Pt cap increases the damping by 50% due to spin pumping, which is also directly detected via inverse spin Hall effect inmore » Pt. Our research demonstrates efficient spin transport across the Pt/LSMO interface.« less

  10. Anisotropy enhancement of the Casimir-Polder force between a nanoparticle and graphene

    NASA Astrophysics Data System (ADS)

    Biehs, S.-A.; Agarwal, G. S.

    2014-10-01

    We derive the analytical expressions for the thermal Casimir-Polder energy and force between a spheroidal nanoparticle above a semi-infinite material and a graphene covered interface. We analyze in detail the Casimir-Polder force between a gold nanoparticle and a single sheet of pristine graphene focusing on the impact of anisotropy. We show that the effect of anisotropy, i.e., the shape and orientation of the spheroidal nanoparticle, has a much larger influence on the force than the tunability of graphene. The effect of tuning and anisotropy both add up such that we observe a force between the particle and the sheet of graphene which is between 20% and 50% of that between the same particle and an ideal metal plate. Hence the observed force is much larger than the results found for the Casimir force between a metal half-space and a layer of graphene.

  11. Influence of controlled surface oxidation on the magnetic anisotropy of Co ultrathin films

    SciTech Connect

    Di, N.; Maroun, F. Allongue, P.; Kubal, J.; Zeng, Z.; Greeley, J.

    2015-03-23

    We studied the influence of controlled surface-limited oxidation of electrodeposited epitaxial Co(0001)/Au(111) films on their magnetic anisotropy energy using real time in situ magneto optical Kerr effect and density functional theory (DFT) calculations. We investigated the Co first electrochemical oxidation step which we demonstrate to be completely reversible and determined the structure of this oxide layer. We show that the interface magnetic anisotropy of the Co film increases by 0.36 erg/cm{sup 2} upon Co surface oxidation. We performed DFT calculations to determine the different surface structures in a wide potential range as well as the charge transfer at the Co surface. Our results suggest that the magnetic anisotropy change is correlated with a positive charge increase of 0.54 e{sup −} for the Co surface atom upon oxidation.

  12. Magnetic anisotropy, damping, and interfacial spin transport in Pt/LSMO bilayers

    NASA Astrophysics Data System (ADS)

    Lee, H. K.; Barsukov, I.; Swartz, A. G.; Kim, B.; Yang, L.; Hwang, H. Y.; Krivorotov, I. N.

    2016-05-01

    We report ferromagnetic resonance measurements of magnetic anisotropy and damping in epitaxial La0.7Sr0.3MnO3 (LSMO) and Pt capped LSMO thin films on SrTiO3 (001) substrates. The measurements reveal large negative perpendicular magnetic anisotropy and a weaker uniaxial in-plane anisotropy that are unaffected by the Pt cap. The Gilbert damping of the bare LSMO films is found to be low α = 1.9(1) × 10-3, and two-magnon scattering is determined to be significant and strongly anisotropic. The Pt cap increases the damping by 50% due to spin pumping, which is also directly detected via inverse spin Hall effect in Pt. Our work demonstrates efficient spin transport across the Pt/LSMO interface.

  13. Optical Anisotropy in Type-II ZnTe/ZnSe Submonolayer Quantum Dots

    NASA Astrophysics Data System (ADS)

    Ji, Haojie; Dhomkar, Siddharth; Tamargo, Maria; Kuskovsky, Igor

    2014-03-01

    Type-II semiconductor quantum dots (QDs) characterized by spatial separation of charge carriers are good candidates for photovoltaics and photon manipulation applications. Implementation of practical devices requires detail understandings of the QD morphology, the mechanism of strain relief and defect formation. Here we report our study of polarization dependent photoluminescence (PL) in type-II ZnTe/ZnSe submonolayer QD superlattices, grown by migration-enhanced epitaxy. We show that the PL does not depend on the polarization state of excitation and exhibits strong linear polarization, indicating strong anisotropy in this material. We spectrally analyze the degree of linear polarization in samples grown with different Te fluxes, spacer thicknesses and number of periods. Based on our observations, we propose several reasons for the optical anisotropy, focusing on the anisotropic shape of the QDs and the anisotropy at the interfaces in the superlattices.

  14. Development of Ni-based multilayers for future focusing soft gamma ray telescopes

    NASA Astrophysics Data System (ADS)

    Girou, David A.; Massahi, Sonny; Sleire, Erlend K.; Jakobsen, Anders C.; Christensen, Finn E.

    2015-09-01

    Ni-based multilayers are a possible solution to extend the upper energy range of hard X-ray focusing telescopes currently limited at ≈79:4 keV by the Pt-K absorption edge. In this study 10 bilayers multilayers with a constant bilayer thickness were coated with the DC magnetron sputtering facility at DTU Space, characterized at 8 keV using X-ray reectometry and fitted using the IMD software. Ni/C multilayers were found to have a mean interface roughness ≈ 1:5 times lower than Ni/B4C multilayers. Reactive sputtering with ≈ 76% of Ar and ≈ 24% of N2 reduced the mean interface roughness by a factor of ≈ 1:7. It also increased the coating rate of C by a factor of ≈ 3:1 and lead to a coating process going ≈ 1:6 times faster. Honeycomb collimation proved to limit the increase in mean interface roughness when the bilayer thickness increases at the price of a coating process going ≈ 1:9 times longer than with separator plates. Finally a Ni/C 150 bilayers depth-graded mutilayer was coated with reactive sputtering and honeycomb collimation and then characterized from 10 keV to 150 keV. It showed 10% reectance up to 85 keV.

  15. In situ study of heavy ion irradiation response of immiscible Cu/Fe multilayers

    NASA Astrophysics Data System (ADS)

    Chen, Y.; Li, N.; Bufford, D. C.; Li, J.; Hattar, K.; Wang, H.; Zhang, X.

    2016-07-01

    Recent studies show that immiscible metallic multilayers with incoherent interfaces can effectively reduce defect density in ion irradiated metals by providing active defect sinks that capture and annihilate radiation induced defect clusters. Although it is anticipated that defect density within the layers should vary as a function of distance to the layer interface, there is, to date, little in situ TEM evidence to validate this hypothesis. In this study monolithic Cu films and Cu/Fe multilayers with individual layer thickness, h, of 100 and 5 nm were subjected to in situ Cu ion irradiation at room temperature to nominally 1 displacement-per-atom inside a transmission electron microscope. Rapid formation and propagation of defect clusters were observed in monolithic Cu, whereas fewer defects with smaller dimensions were generated in Cu/Fe multilayers with smaller h. Furthermore in situ video shows that the cumulative defect density in Cu/Fe 100 nm multilayers indeed varies, as a function of distance to the layer interfaces, supporting a long postulated hypothesis.

  16. Structure of lipid multilayers via drop casting of aqueous liposome dispersions.

    PubMed

    Sironi, Beatrice; Snow, Tim; Redeker, Christian; Slastanova, Anna; Bikondoa, Oier; Arnold, Thomas; Klein, Jacob; Briscoe, Wuge H

    2016-05-01

    Understanding the structure of solid supported lipid multilayers is crucial to their application as a platform for novel materials. Conventionally, they are prepared from drop casting or spin coating of lipids dissolved in organic solvents, and lipid multilayers prepared from aqueous media and their structural characterisation have not been reported previously, due to their extremely low lipid solubility (i.e.∼10(-9) M) in water. Herein, using X-ray reflectivity (XRR) facilitated by a "bending mica" method, we have studied the structural characteristics of dioleoylphosphatidylcholine (DOPC) multilayers prepared via drop casting aqueous small unilamellar and multilamellar vesicle or liposome (i.e. SUV and MLV) dispersions on different surfaces, including mica, positively charged polyethylenimine (PEI) coated mica, and stearic trimethylammonium iodide (STAI) coated mica which exposes a monolayer of hydrocarbon tails. We suggest that DOPC liposomes served both as a delivery matrix where an appreciable lipid concentration in water (∼25 mg mL(-1) or 14 mM) was feasible, and as a structural precursor where the lamellar structure was readily retained on the rupture of the vesicles at the solid surface upon solvent evaporation to facilitate rapid multilayer formation. We find that multilayers on mica from MLVs exhibited polymorphism, whereas the SUV multilayers were well ordered and showed stronger stability against water. The influence of substrate chemistry (i.e. polymer coating, charge and hydrophobicity) on the multilayer structure is discussed in terms of lipid-substrate molecular interactions determining the bilayer packing proximal to the solid-liquid interface, which then had a templating effect on the structure of the bilayers distal from the interface, resulting in the overall different multilayer structural characteristics on different substrates. Such a fundamental understanding of the correlation between the physical parameters that characterise liposomes

  17. Scaling method for fast Monte Carlo simulation of diffuse reflectance spectra from multilayered turbid media

    NASA Astrophysics Data System (ADS)

    Liu, Quan; Ramanujam, Nirmala

    2007-04-01

    A scaling Monte Carlo method has been developed to calculate diffuse reflectance from multilayered media with a wide range of optical properties in the ultraviolet-visible wavelength range. This multilayered scaling method employs the photon trajectory information generated from a single baseline Monte Carlo simulation of a homogeneous medium to scale the exit distance and exit weight of photons for a new set of optical properties in the multilayered medium. The scaling method is particularly suited to simulating diffuse reflectance spectra or creating a Monte Carlo database to extract optical properties of layered media, both of which are demonstrated in this paper. Particularly, it was found that the root-mean-square error (RMSE) between scaled diffuse reflectance, for which the anisotropy factor and refractive index in the baseline simulation were, respectively, 0.9 and 1.338, and independently simulated diffuse reflectance was less than or equal to 5% for source-detector separations from 200 to 1500 μm when the anisotropy factor of the top layer in a two-layered epithelial tissue model was varied from 0.8 to 0.99; in contrast, the RMSE was always less than 5% for all separations (from 0 to 1500 μm) when the anisotropy factor of the bottom layer was varied from 0.7 to 0.99. When the refractive index of either layer in the two-layered tissue model was varied from 1.3 to 1.4, the RMSE was less than 10%. The scaling method can reduce computation time by more than 2 orders of magnitude compared with independent Monte Carlo simulations.

  18. Effect of Ply Orientation and Crack Location on SIFs in Finite Multilayers with Aligned Cracks

    NASA Astrophysics Data System (ADS)

    Chen, Linfeng; Pindera, Marek-Jerzy

    2008-02-01

    An exact elasticity solution is presented for arbitrarily laminated finite multilayers in a state of generalized plane deformation under horizontally pinned end constraints that are weakened by aligned cracks. Based on half-range Fourier series and the local/global stiffness matrix approach, the mixed boundary-value problem is reduced to Cauchy-type singular integral equations in the unknown displacement discontinuities. Solution to these equations is obtained using the approach developed by Erdogan and co-workers. Numerical results quantify the thus-far undocumented geometric and material effects on Mode I, II and III stress intensity factors in composite multilayers with interacting cracks under uniform vertical displacement. These effects include finite dimensions, crack location, material anisotropy due to a unidirectional fiber-reinforced layer/s orientation, and orientational grading.

  19. Normal and inverse magnetocaloric effect in magnetic multilayers with antiferromagnetic interlayer coupling

    NASA Astrophysics Data System (ADS)

    Szałowski, Karol; Balcerzak, Tadeusz

    2014-09-01

    The thermodynamics of a spin-1/2 magnetic multilayer system with antiferromagnetic interplanar couplings is studied using the pair approximation method. Special attention is paid to magnetocaloric properties, quantified by isothermal entropy change. The multilayer consists of two kinds of magnetic planes, one of which is diluted. The intraplanar couplings in both planes have arbitrary anisotropy ranging between Ising and isotropic Heisenberg interactions. The phase diagram related to the occurrence of magnetic compensation phenomenon is constructed and discussed. Then the isothermal entropy change is discussed as a function of interaction parameters, magnetic component concentration and external magnetic field amplitude. The ranges of normal and inverse magnetocaloric effect are found and related to the presence or absence of compensation.

  20. Normal and inverse magnetocaloric effect in magnetic multilayers with antiferromagnetic interlayer coupling.

    PubMed

    Szałowski, Karol; Balcerzak, Tadeusz

    2014-09-24

    The thermodynamics of a spin-1/2 magnetic multilayer system with antiferromagnetic interplanar couplings is studied using the pair approximation method. Special attention is paid to magnetocaloric properties, quantified by isothermal entropy change. The multilayer consists of two kinds of magnetic planes, one of which is diluted. The intraplanar couplings in both planes have arbitrary anisotropy ranging between Ising and isotropic Heisenberg interactions. The phase diagram related to the occurrence of magnetic compensation phenomenon is constructed and discussed. Then the isothermal entropy change is discussed as a function of interaction parameters, magnetic component concentration and external magnetic field amplitude. The ranges of normal and inverse magnetocaloric effect are found and related to the presence or absence of compensation. PMID:25186229

  1. Generalized scattering-matrix approach for magneto-optics in periodically patterned multilayer systems

    NASA Astrophysics Data System (ADS)

    Caballero, B.; García-Martín, A.; Cuevas, J. C.

    2012-06-01

    We present here a generalization of the scattering-matrix approach for the description of the propagation of electromagnetic waves in nanostructured magneto-optical systems. Our formalism allows us to describe all the key magneto-optical effects in any configuration in periodically patterned multilayer structures. The method can also be applied to describe periodic multilayer systems comprising materials with any type of optical anisotropy. We illustrate the method with the analysis of a recent experiment in which the transverse magneto-optical Kerr effect was measured in an Fe film with a periodic array of subwavelength circular holes. We show, in agreement with the experiments, that the excitation of surface plasmon polaritons in this system leads to a resonant enhancement of the transverse magneto-optical Kerr effect.

  2. Subwavelength imaging from a multilayered structure containing interleaved nonspherical metal-dielectric composites

    NASA Astrophysics Data System (ADS)

    Shi, Lihong; Gao, Lei

    2008-05-01

    A thin multilayered structure with interleaved nonspherical metal-dielectric composites slices and dielectric slices may be modeled as the metamaterial with anisotropic permittivity. The signs of diagonal elements of the permittivity tensor can be controlled by the particles’ shape, the volume fraction of metal particles, and the incidental wavelengths. To one’s interest, when the spheroidal nanoparticles are oblate in shape, the wavelength range in which components of the permittivity have different signs is widened, and the magnitude of optical absorption band becomes weak. Since both physical anisotropy and low absorption are helpful for improving the subwavelength image resolution, the multilayered structure containing metal-dielectric composite layer of nonspherical particles may be designed as a superlens device. In addition, the incident wavelength and the number of nanolayers are found to play crucial roles in enhancing the evanescent field performance too.

  3. Structure and property of heteroepitaxial TiO sub 2 /VO sub 2 multilayers

    SciTech Connect

    Chang, H.L.M.; Gao, Y.; Zhang, T.J.; Lam, D.J.

    1992-06-01

    Various types of TiO{sub 2}/VO{sub 2} multilayer structures have been prepared on sapphire substrates by a low-pressure metal-organic chemical vapor deposition process. X-ray diffraction and transmission electron microscopy techniques were used to study the crystallinity and epitaxial relationships of the deposited films. High resolution electron microscopy was used to examine the microstructure of the overlayers and interfaces. Electrical resistivity measurements were performed to investigate the metal-semiconductor phase transition of VO{sub 2} layers in multilayer structures.

  4. Structure and property of heteroepitaxial TiO{sub 2}/VO{sub 2} multilayers

    SciTech Connect

    Chang, H.L.M.; Gao, Y.; Zhang, T.J.; Lam, D.J.

    1992-06-01

    Various types of TiO{sub 2}/VO{sub 2} multilayer structures have been prepared on sapphire substrates by a low-pressure metal-organic chemical vapor deposition process. X-ray diffraction and transmission electron microscopy techniques were used to study the crystallinity and epitaxial relationships of the deposited films. High resolution electron microscopy was used to examine the microstructure of the overlayers and interfaces. Electrical resistivity measurements were performed to investigate the metal-semiconductor phase transition of VO{sub 2} layers in multilayer structures.

  5. Carrier recombination in tailored multilayer Si/Si1-xGex nanostructures

    NASA Astrophysics Data System (ADS)

    Mala, S. A.; Tsybeskov, L.; Lockwood, D. J.; Wu, X.; Baribeau, J.-M.

    2014-11-01

    Photoluminescence (PL) measurements were performed in Si/Si1-xGex nanostructures with a single Si0.92Ge0.08 nanometer-thick layer incorporated into Si/Si0.6Ge0.4 cluster multilayers. Under pulsed laser excitation, the PL decay associated with the Si0.92Ge0.08 nano-layer is found to be nearly a 1000 times faster compared to that in Si/Si0.6Ge0.4 cluster multilayers. A model considering Si/SiGe hetero-interface composition and explaining the fast and slow time-dependent recombination rates is proposed.

  6. Spin-orbit enhanced demagnetization rate in Co/Pt-multilayers

    SciTech Connect

    Kuiper, K. C.; Schellekens, A. J.; Koopmans, B.; Roth, T.; Schmitt, O.; Cinchetti, M.; Aeschlimann, M.

    2014-11-17

    In order to explore the role of enhanced spin-orbit interactions on the laser-induced ultrafast magnetization dynamics, we performed a comparative study on cobalt thin films and Co/Pt multilayers. We show that the presence of the Co/Pt interfaces gives rise to a three-fold faster demagnetization upon femtosecond laser heating. Experimental data for a wide range of laser fluences are analyzed using the Microscopic 3-Temperature Model. We find that the Elliott-Yafet spin-flip scattering in the multilayer structure is increased by at least a factor of four with respect to the elementary Co film.

  7. Magnetic and magneto-optical properties and domain structure of Co/Pd multilayers

    NASA Technical Reports Server (NTRS)

    Gadetsky, S.; Wu, Teho; Suzuki, T.; Mansuripur, M.

    1993-01-01

    The domain structure of Co/Pd(1.6/6.3 A)xN multilayers and its relation to the bulk magnetic properties of the samples were studied. The Co/Pd multilayers were deposited by rf and dc magnetron sputtering onto different substrates. It was found that magnetic and magnetooptical properties and domain structure of the multilayers were affected by total film thickness and substrate condition. Magnetization, coercivity, and anisotropy of the films decreased significantly as the film thickness dropped below 100 A. However, Kerr rotation angle had a maximum at the same thickness. The width of the domain structure increased with the decrease of the film thickness attaining the single domain state at N = 10. The initial curves in Co/Pd multilayers were found to depend on demagnetization process. The samples demagnetized by inplane field showed the largest difference between initial curves and the corresponding parts of the loops. Different domain structures were observed in the samples demagnetized by perpendicular and in-plane magnetic fields.

  8. Phase-field modeling and experimental observation of the irregular interface morphology during directional solidification

    NASA Astrophysics Data System (ADS)

    Guo, Taiming

    Evolution of the complex solid-liquid interface morphology during a solidification process is an important issue in solidification theory since the morphology eventually dictates the final microstructure of the solidified material and therefore the material properties. Significant progress have been made in recent years in the study of the formation and development of regular dendritic growth, while only limited understanding is achieved for the irregular interface patterns observed in many industry processes. This dissertation focuses on the physical mechanisms of the development and transition of various irregular interface patterns, including the tilted dendritic, the seaweed, and the degenerate patterns. Both experimental observations and numerical simulation using the phase field modeling are performed. A special effort is devoted on the effects of the capillary anisotropy and the kinetic anisotropy in the evolution of the interface morphology during solidification. Experimentally, a directional solidification system is constructed to observe in situ the interface morphology by using the transparent organic material succinonitrile. With such a system, both the regular interface patterns (cellular and dendritic) and the irregular interface patterns (seaweed, degenerate and tilted dendritic) are observed. The effects of the temperature gradient and the interface velocity on the development and transition of the irregular interface patterns are investigated. It is found that the interface morphology transits from the seaweed to the tilted dendritic pattern as the interface velocity increases, while the tilted dendritic pattern may transit to the degenerate seaweed pattern as the temperature gradient increases. Under certain conditions, dendrites and seaweed coexist within the same grain. The dynamic transitions among various patterns and the effect of the solidification conditions are examined in detail. Numerically, a 2-D phase field model is developed to

  9. Structural and magnetic properties of Co68Fe24Zr8/Al2O3 multilayers

    NASA Astrophysics Data System (ADS)

    Lidbaum, Hans; Raanaei, Hossein; Papaioannou, Evangelos Th.; Leifer, Klaus; Hjörvarsson, Björgvin

    2010-02-01

    The structural and magnetic properties of Co68Fe24Zr8/Al2O3 multilayers grown by using magnetron sputtering were investigated with X-ray reflectivity, transmission electron microscopy and magneto-optical Kerr effect. The Co68Fe24Zr8 form amorphous islands when the nominal thickness of the Co68Fe24Zr8 layers is 10 Å, exhibiting an isotropic superparamagnetic behavior. Continuous layers with mostly a nano-crystalline structure are instead formed when the nominal thickness of the Co68Fe24Zr8 layers is increased to 20 Å. The continuous layers exhibit random, in-plane, magnetic anisotropy resulting from the growth process. However, induced uniaxial anisotropy is obtained when growing the sample in the presence of an applied magnetic field, regardless of the combination of amorphous and nano-crystalline material.

  10. Hyperbolic interfaces.

    PubMed

    Giomi, Luca

    2012-09-28

    Fluid interfaces, such as soap films, liquid droplets, or lipid membranes, are known to give rise to several special geometries, whose complexity and beauty continue to fascinate us, as observers of the natural world, and challenge us as scientists. Here I show that a special class of surfaces of constant negative Gaussian curvature can be obtained in fluid interfaces equipped with an orientational ordered phase. These arise in various soft and biological materials, such as nematic liquid crystals, cytoskeletal assemblies, or hexatic colloidal suspensions. The purely hyperbolic morphology originates from the competition between surface tension, that reduces the area of the interface at the expense of increasing its Gaussian curvature, and the orientational elasticity of the ordered phase, that in turn suffers for the distortion induced by the underlying curvature. PMID:23030106

  11. Hyperbolic Interfaces

    NASA Astrophysics Data System (ADS)

    Giomi, Luca

    2012-09-01

    Fluid interfaces, such as soap films, liquid droplets, or lipid membranes, are known to give rise to several special geometries, whose complexity and beauty continue to fascinate us, as observers of the natural world, and challenge us as scientists. Here I show that a special class of surfaces of constant negative Gaussian curvature can be obtained in fluid interfaces equipped with an orientational ordered phase. These arise in various soft and biological materials, such as nematic liquid crystals, cytoskeletal assemblies, or hexatic colloidal suspensions. The purely hyperbolic morphology originates from the competition between surface tension, that reduces the area of the interface at the expense of increasing its Gaussian curvature, and the orientational elasticity of the ordered phase, that in turn suffers for the distortion induced by the underlying curvature.

  12. Nanorods of Co/Pd multilayers fabricated by glancing angle deposition for advanced media

    NASA Astrophysics Data System (ADS)

    Su, Hao; Natarajarathinam, Anusha; Gupta, Subhadra

    2013-05-01

    Perpendicular anisotropy magnetic nanorods composed of Co/Pd multilayers have been successfully fabricated by glancing angle deposition (GLAD) in a planetary sputtering system. Co and Pd layer thickness, ratio, and bilayer number were optimized for both normal and GLAD depositions. Scanning electron micrographs estimated the nanorods to be about 12 nm in diameter. M-H loops showed that the coercivity for the GLAD nanorods increased from 1.3 kOe for the normally deposited continuous films to 2.9 kOe for the GLAD nanorod array, a 123% increase.

  13. Microscopic investigation of the magnetic saturation process for Co/Pt multilayers

    NASA Astrophysics Data System (ADS)

    Quach, Duy-Truong; Kim, Dong-Hyun; Lee, Kyung-Min; Jeong, Jong-Ryul; Pham, Duc-Thang

    2016-07-01

    We have systematically investigated the magnetic saturation process for Co/Pt multilayers with perpendicular magnetic anisotropy by using the first-order reversal-curve (FORC) technique. We find that even for a field that apparently is higher than the major-loop saturation field, some microscopically not-yet-annihilated domains still remain. The true saturation on a microscopic scale field is found to be about 1.5 to 2.5 times greater than the macroscopicall-determined majorloop saturation field. Not-yet-annihilated domains are observed to be exponentially reduced with respect to the applied magnetic field.

  14. Spin-Wave Theory for the Dynamics Induced by Direct Currents in Magnetic Multilayers

    NASA Astrophysics Data System (ADS)

    Rezende, S. M.; de Aguiar, F. M.; Azevedo, A.

    2005-01-01

    A spin-wave theory is presented for the magnetization dynamics in a ferromagnetic film that is traversed by spin-polarized carriers at high direct-current densities. It is shown that nonlinear effects due to four-magnon interactions arising from dipolar and surface anisotropy energies limit the growth of the driven spin wave and produce shifts in the microwave frequency oscillations. The theory explains quantitatively recent experimental results in nanometric point contacts onto magnetic multilayers showing downward frequency shifts (redshifts) with increasing current, if the external field is on the film plane, and upward shifts (blueshifts), if the field is perpendicular to the film.

  15. Nanorods of Co/Pd multilayers fabricated by glancing angle deposition for advanced media

    SciTech Connect

    Su, Hao; Gupta, Subhadra; Natarajarathinam, Anusha

    2013-05-28

    Perpendicular anisotropy magnetic nanorods composed of Co/Pd multilayers have been successfully fabricated by glancing angle deposition (GLAD) in a planetary sputtering system. Co and Pd layer thickness, ratio, and bilayer number were optimized for both normal and GLAD depositions. Scanning electron micrographs estimated the nanorods to be about 12 nm in diameter. M-H loops showed that the coercivity for the GLAD nanorods increased from 1.3 kOe for the normally deposited continuous films to 2.9 kOe for the GLAD nanorod array, a 123% increase.

  16. Magnetic and Magneto-Optical Properties of Nano - Multilayer Thin Films

    NASA Astrophysics Data System (ADS)

    Shen, Jian Xiang

    Structural, magnetic and magneto-optical properties were investigated experimentally in nanostructured rare earth/Fe (rare earth=Gd, Tb, Dy), Co/Pt and Bi-doped DIG/T (T=Fe, Co, Dy and DIG=Dy-Iron-Garnet) multilayer thin films. In the rare earth/Fe system, it was found that the magnetization reversal could be correlated with the intrinsic magnetic parameters, especially the perpendicular magnetic anisotropy. It was found that higher anisotropy leads to magnetization reversal primarily by domain wall motion due to the higher domain wall energy. The coercivities of these multilayers were strongly dependent on the temperature as well as magnetic field sweep rate, and a strong magnetic after effect was observed. These results demonstrate that thermal activation plays an important role in the determination of the coercivity. The coercivity of Co/Pt multilayer thin films increases with increasing total thickness of the film and magnetization reversal behavior was largely by wall motion, independent of thickness. However the magnetic domain structure depends strongly on the total thickness, presumably due to subtle differences in the defect structures which pin domain walls. In agreement with other studies, it was found that magnetic polarization of the Pt atoms contributed significantly to the total magnetization and Kerr rotation at blue wavelength. Amorphous DIG/Fe multilayer films were prepared by magnetron sputtering, and subsequently crystallized by rapid thermal annealing. The resulting films had small grain size (down to 10 nm) so that they are appropriate materials for magneto-optical storage applications. Depending on the Bi composition, Faraday rotation of up to 15 degrees/ μm was observed. Domain wall expansion into maze-like domains dominated the reversal process. The dielectric constant tensors, including the off-diagonal component responsible for magneto-optical activity, are reported for several samples.

  17. Primordial anisotropies in gauged hybrid inflation

    NASA Astrophysics Data System (ADS)

    Akbar Abolhasani, Ali; Emami, Razieh; Firouzjahi, Hassan

    2014-05-01

    We study primordial anisotropies generated in the model of gauged hybrid inflation in which the complex waterfall field is charged under a U(1)gauge field. Primordial anisotropies are generated either actively during inflation or from inhomogeneities modulating the surface of end of inflation during waterfall transition. We present a consistent δN mechanism to calculate the anisotropic power spectrum and bispectrum. We show that the primordial anisotropies generated at the surface of end of inflation do not depend on the number of e-folds and therefore do not produce dangerously large anisotropies associated with the IR modes. Furthermore, one can find the parameter space that the anisotropies generated from the surface of end of inflation cancel the anisotropies generated during inflation, therefore relaxing the constrains on model parameters imposed from IR anisotropies. We also show that the gauge field fluctuations induce a red-tilted power spectrum so the averaged power spectrum from the gauge field can change the total power spectrum from blue to red. Therefore, hybrid inflation, once gauged under a U(1) field, can be consistent with the cosmological observations.

  18. Multilayer weighted social network model

    NASA Astrophysics Data System (ADS)

    Murase, Yohsuke; Török, János; Jo, Hang-Hyun; Kaski, Kimmo; Kertész, János

    2014-11-01

    Recent empirical studies using large-scale data sets have validated the Granovetter hypothesis on the structure of the society in that there are strongly wired communities connected by weak ties. However, as interaction between individuals takes place in diverse contexts, these communities turn out to be overlapping. This implies that the society has a multilayered structure, where the layers represent the different contexts. To model this structure we begin with a single-layer weighted social network (WSN) model showing the Granovetterian structure. We find that when merging such WSN models, a sufficient amount of interlayer correlation is needed to maintain the relationship between topology and link weights, while these correlations destroy the enhancement in the community overlap due to multiple layers. To resolve this, we devise a geographic multilayer WSN model, where the indirect interlayer correlations due to the geographic constraints of individuals enhance the overlaps between the communities and, at the same time, the Granovetterian structure is preserved.

  19. The Stereoscopic Anisotropy Develops During Childhood

    PubMed Central

    Serrano-Pedraza, Ignacio; Herbert, William; Villa-Laso, Laura; Widdall, Michael; Vancleef, Kathleen; Read, Jenny C. A.

    2016-01-01

    Purpose Human vision has a puzzling stereoscopic anisotropy: horizontal depth corrugations are easier to detect than vertical depth corrugations. To date, little is known about the function or the underlying mechanism responsible for this anisotropy. Here, we aim to find out whether this anisotropy is independent of age. To answer this, we compare detection thresholds for horizontal and vertical depth corrugations as a function of age. Methods The depth corrugations were defined solely by the horizontal disparity of random dot patterns. The disparities depicted a horizontal or vertical sinusoidal depth corrugation of spatial frequency 0.1 cyc/deg. Detection thresholds were obtained using Bayesian adaptive staircases from a total of 159 subjects aged from 3 to 73 years. For each participant we computed the anisotropy index, defined as the log10-ratio of the detection threshold for vertical corrugations divided by that for horizontal. Results Anisotropy index was highly variable between individuals but was positive in 87% of the participants. There was a significant correlation between anisotropy index and log-age (r = 0.21, P = 0.008) mainly driven by a significant difference between children and adults. In 67 children aged 3 to 13 years, the mean anisotropy index was 0.34 ± 0.38 (mean ± SD, meaning that vertical thresholds were on average 2.2 times the horizontal ones), compared with 0.59 ± 0.55 in 84 adults aged 18 to 73 years (vertical 3.9 times horizontal). This was mainly driven by a decline in the sensitivity to vertical corrugations. Children had poorer stereoacuity than adults, but had similar sensitivity to adults for horizontal corrugations and were actually more sensitive than adults to vertical corrugations. Conclusions The fact that adults show stronger stereo anisotropy than children raises the possibility that visual experience plays a critical role in developing and strengthening the stereo anisotropy. PMID:26962692

  20. Magnetic properties of ultrathin discontinuous Co/Pt multilayers: Comparison with short-range ordered and isotropic CoPt3 films

    NASA Astrophysics Data System (ADS)

    Charilaou, M.; Bordel, C.; Berche, P.-E.; Maranville, B. B.; Fischer, P.; Hellman, F.

    2016-06-01

    Magnetic properties of thin Co/Pt multilayers have been investigated in order to study the dependence of magnetization M , uniaxial anisotropy Ku, and Curie temperature TC on the multilayer thickness, composition, and structure. A comparison between epitaxial submonolayer multilayers and epitaxial fcc CoPt3 alloy films with large perpendicular magnetic anisotropy (PMA) attributed to growth-induced Co clustering reveals significant differences in the temperature dependence of magnetization M (T ) , despite the presence of thin planar Co platelets in both cases. Even the thinnest discontinuous multilayered structure shows a Langevin-like M (T ) , while the alloy films with PMA show a broadened and enhanced M (T ) indicating a distribution of environments, including monolayer Co platelets separated by only 1-2 layers of Pt. These differences have been reproduced in Monte Carlo simulations, and are shown to be due to different distributions of Co-Co and Co-Pt nearest neighbors. The relatively uniform Co-Co coordination of even a discontinuous rough multilayer produces a Langevin-like M (T ) , whereas the broader distribution associated with platelets in the PMA films results in a nearly linear T dependence of M .

  1. Multilayer material characterization using thermographic signal reconstruction

    NASA Astrophysics Data System (ADS)

    Shepard, Steven M.; Beemer, Maria Frendberg

    2016-02-01

    Active-thermography has become a well-established Nondestructive Testing (NDT) method for detection of subsurface flaws. In its simplest form, flaw detection is based on visual identification of contrast between a flaw and local intact regions in an IR image sequence of the surface temperature as the sample responds to thermal stimulation. However, additional information and insight can be obtained from the sequence, even in the absence of a flaw, through analysis of the logarithmic derivatives of individual pixel time histories using the Thermographic Signal Reconstruction (TSR) method. For example, the response of a flaw-free multilayer sample to thermal stimulation can be viewed as a simple transition between the responses of infinitely thick samples of the individual constituent layers over the lifetime of the thermal diffusion process. The transition is represented compactly and uniquely by the logarithmic derivatives, based on the ratio of thermal effusivities of the layers. A spectrum of derivative responses relative to thermal effusivity ratios allows prediction of the time scale and detectability of the interface, and measurement of the thermophysical properties of one layer if the properties of the other are known. A similar transition between steady diffusion states occurs for flat bottom holes, based on the hole aspect ratio.

  2. Interfacial effects in Fe/4d TM multilayers (abstract)

    SciTech Connect

    Tomaz, M.A.; Antel, W.J., Jr.; Harp, G.R.; OBrien, W.L.

    1997-04-01

    We have studied Fe/TM multilayers (TM=Mo, Nb, Ru, Rh, Pd) using x-ray magnetic circular dischroism, magneto-optical Kerr effect, and x-ray diffraction. A diverse set of magnetic behaviors emerges from the analysis. We focus on the behavior which can be attributed to the existence of a physical interface between different chemical species. In particular, we have measured an enhanced Fe moment in some cases (TM=Ru, Mo, Rh, Pd) yet not in others (TM=Nb). These results will be discussed, including the relative orbital and spin moments and the effects of alloying at the interface. The measured induced moments in the TM layer will be presented as well where applicable. {copyright} {ital 1997 American Institute of Physics.}

  3. Ground state and constrained domain walls in Gd /Fe multilayers

    NASA Astrophysics Data System (ADS)

    Van Aken, Bas B.; Prieto, José L.; Mathur, Neil D.

    2005-03-01

    The magnetic ground state of antiferromagnetically coupled Gd /Fe multilayers and the evolution of in-plane domain walls is modeled with micromagnetics. The twisted state is characterized by a rapid decrease of the interface angle with increasing magnetic field. We found that for certain ratios MFe:MGd, the twisted state is already present at low fields. However, the magnetic ground state is not only determined by the ratio MFe:MGd but also by the thicknesses of the layers; that is by the total moments of the layer. The dependence of the magnetic ground state is explained by the amount of overlap of the domain walls at the interface. Thicker layers suppress the Fe-aligned and the Gd-aligned state in favor of the twisted state. On the other hand, ultrathin layers exclude the twisted state, since wider domain walls cannot form in these ultrathin layers.

  4. Ferromagnetic resonance studies of nanopillars with Co/Ni multilayer free layers

    NASA Astrophysics Data System (ADS)

    Chen, Wenyu; Beaujour, J.-M. L.; de Loubens, G.; Kent, Andrew D.; Rooks, M. J.; Ruiz, N.; Sun, Jonathan Z.

    2007-03-01

    Recently it has become possible to study ferromagnetic resonance (FMR) of magnetic layers in nanopillar junctions using the spin-transfer interaction [1,2]. This enables powerful new quantitative studies of the layer magnetic anisotropy and damping in confined structures. Here we report studies of Co/Ni multilayer free layers with variable easy plane anisotropy. Experiments were conducted on ||[t nm Co 2t nm Ni] x 1.2/t| 10 nm Cu| 12 nm Co|| layer structures patterned to ˜50 nm lateral dimensions using a nanostencil process, with t=0.1, 0.2, 0.3 and 0.4. Varying the Co thickness (t) enables systematic variation of the Co/Ni easy-plane anisotropy, while the total magnetic moment and thickness of the free layer is kept constant. Field swept FMR measurements were conducted using a microwave signal generator (1 to 20 GHz) with a magnetic field applied perpendicular to the surface of the layers. The resonance field and linewidth were measured as a function of frequency and DC current bias. Magnetic anisotropy constants and damping parameters are determined and compared to those found in FMR studies of extended films of the same layer structure. [1] A. A. Tulapurkar et al., Nature, 438, 339 (2005) [2] J. C. Sankey et al., Phys. Rev. Lett., 96, 227601 (2006)

  5. Casting Of Multilayer Ceramic Tapes

    NASA Technical Reports Server (NTRS)

    Collins, Earl R., Jr.

    1991-01-01

    Procedure for casting thin, multilayer ceramic membranes, commonly called tapes, involves centrifugal casting at accelerations of 1,800 to 2,000 times normal gravitational acceleration. Layers of tape cast one at a time on top of any previous layer or layers. Each layer cast from slurry of ground ceramic suspended in mixture of solvents, binders, and other components. Used in capacitors, fuel cells, and electrolytic separation of oxygen from air.

  6. Magnetic Domain Confinement by Anisotropy Modulation

    NASA Astrophysics Data System (ADS)

    Li, S. P.; Lew, W. S.; Bland, J. A.; Lopez-Diaz, L.; Vaz, C. A.; Natali, M.; Chen, Y.

    2002-02-01

    The spin configuration in a magnet is in general a ``natural'' consequence of both the intrinsic properties of the material and the sample dimensions. We demonstrate that this limitation can be overcome in a homogeneous ferromagnetic film by engineering an anisotropy contrast. Substrates with laterally modulated single-crystal and polycrystalline surface regions were used to induce selective epitaxial growth of a ferromagnetic Ni film. The resulting spatially varying magnetic anisotropy leads to regular perpendicular and in-plane magnetic domains, separated by a new type of magnetic wall-the ``anisotropy constrained'' magnetic wall.

  7. Mechanical anisotropy of the Yucca Mountain tuffs

    SciTech Connect

    Price, R.H.; Boyd, P.J.; Martin, R.J.; Haupt, R.W.; Noel, J.S.

    1991-12-31

    Three series of measurements were performed on oriented cores of several Yucca Mountain tuffs to determine the importance of mechanical anisotropy in the intact rock. Outcrop and drillhole samples were tested for acoustic velocities, linear compressibilities, and strengths in different orientations. The present data sets are preliminary, but suggest the tuffs are transversely anisotropic for these mechanical properties. The planar fabric that produces the anisotropy is believed to be predominantly the result of the preferred orientation of shards and pumice fragments. The potential of significant anisotropy has direct relevance to the formulation of constitutive formulation and the analyses of an underground opening within the Yucca Mountain.

  8. Mathematical Formulation of Multilayer Networks

    NASA Astrophysics Data System (ADS)

    De Domenico, Manlio; Solé-Ribalta, Albert; Cozzo, Emanuele; Kivelä, Mikko; Moreno, Yamir; Porter, Mason A.; Gómez, Sergio; Arenas, Alex

    2013-10-01

    A network representation is useful for describing the structure of a large variety of complex systems. However, most real and engineered systems have multiple subsystems and layers of connectivity, and the data produced by such systems are very rich. Achieving a deep understanding of such systems necessitates generalizing “traditional” network theory, and the newfound deluge of data now makes it possible to test increasingly general frameworks for the study of networks. In particular, although adjacency matrices are useful to describe traditional single-layer networks, such a representation is insufficient for the analysis and description of multiplex and time-dependent networks. One must therefore develop a more general mathematical framework to cope with the challenges posed by multilayer complex systems. In this paper, we introduce a tensorial framework to study multilayer networks, and we discuss the generalization of several important network descriptors and dynamical processes—including degree centrality, clustering coefficients, eigenvector centrality, modularity, von Neumann entropy, and diffusion—for this framework. We examine the impact of different choices in constructing these generalizations, and we illustrate how to obtain known results for the special cases of single-layer and multiplex networks. Our tensorial approach will be helpful for tackling pressing problems in multilayer complex systems, such as inferring who is influencing whom (and by which media) in multichannel social networks and developing routing techniques for multimodal transportation systems.

  9. Leveraging intrinsic chain anisotropy to align coil-coil block copolymers with magnetic fields

    NASA Astrophysics Data System (ADS)

    Rokhlenko, Yekaterina; Zhang, Kai; Gopinadhan, Manesh; Larson, Steve; Majewski, Pawel; Yager, Kevin; Gopalan, Padma; O'Hern, Corey; Osuji, Chinedum

    Magnetic field alignment of block copolymers (BCPs) has typically relied on the presence of liquid crystalline or crystalline assemblies to provide sufficient magnetic anisotropy to drive alignment. Recent experiments however show that alignment is also possible in simple coil-coil BCPs. In particular, alignment of lamellae was observed in poly(styrene-b-4-vinylpyridine) (PS-P4VP) on cooling across the order-disorder transition at field strengths as low as 1 T, with alignment improving markedly with increasing field strength and decreasing cooling rate. Here we discuss the intrinsic chain anisotropy which drives the observed alignment, and its display as a net microdomain anisotropy due to chain tethering at the block interface. We use in-situ X-ray scattering to study the phase behavior and temperature-, time-, and field- dependent dynamics of magnetic alignment in coil-coil BCPs, highlighting the important roles of chain anisotropy and grain size in alignment. For the right combination of field strength and grain size, we can leverage intrinsic chain anisotropy to magnetically direct self-assembly in other coil-coil systems, including cylinder-forming poly(styrene-b-dimethylsiloxane). Field alignment of PS-P4VP with PEO and other blends provides a route to form functional materials such as nanoporous films and ion conducting polymers.

  10. Creation of artificial skyrmions and antiskyrmions by anisotropy engineering

    PubMed Central

    Zhang, S.; Petford-Long, A. K.; Phatak, C.

    2016-01-01

    Topologically non-trivial spin textures form a fundamental paradigm in solid-state physics and present unique opportunities to explore exciting phenomena such as the topological Hall effect. One such texture is a skyrmion, in which the spins can be mapped to point in all directions wrapping around a sphere. Understanding the formation of these spin textures, and their energetic stability, is crucial in order to control their behavior. In this work, we report on controlling the perpendicular anisotropy of continuous Co/Pt multilayer films with ion irradiation to form unique spin configurations of artificial skyrmions and antiskyrmions that are stabilized by their demagnetization energy. We elucidate their behavior using aberration-corrected Lorentz transmission electron microscopy. We also discuss the energetic stability of these structures studied through in-situ magnetizing experiments performed at room temperature, combined with micromagnetic simulations that successfully reproduce the spin textures and behavior. This research offers new opportunities towards creation of artificial skyrmion or antiskyrmion lattices that can be used to investigate not only fundamental properties of their interaction with electron currents but also technological applications such as artificial magnonic crystals. PMID:27507196

  11. Creation of artificial skyrmions and antiskyrmions by anisotropy engineering.

    PubMed

    Zhang, S; Petford-Long, A K; Phatak, C

    2016-01-01

    Topologically non-trivial spin textures form a fundamental paradigm in solid-state physics and present unique opportunities to explore exciting phenomena such as the topological Hall effect. One such texture is a skyrmion, in which the spins can be mapped to point in all directions wrapping around a sphere. Understanding the formation of these spin textures, and their energetic stability, is crucial in order to control their behavior. In this work, we report on controlling the perpendicular anisotropy of continuous Co/Pt multilayer films with ion irradiation to form unique spin configurations of artificial skyrmions and antiskyrmions that are stabilized by their demagnetization energy. We elucidate their behavior using aberration-corrected Lorentz transmission electron microscopy. We also discuss the energetic stability of these structures studied through in-situ magnetizing experiments performed at room temperature, combined with micromagnetic simulations that successfully reproduce the spin textures and behavior. This research offers new opportunities towards creation of artificial skyrmion or antiskyrmion lattices that can be used to investigate not only fundamental properties of their interaction with electron currents but also technological applications such as artificial magnonic crystals. PMID:27507196

  12. Creation of artificial skyrmions and antiskyrmions by anisotropy engineering

    NASA Astrophysics Data System (ADS)

    Zhang, S.; Petford-Long, A. K.; Phatak, C.

    2016-08-01

    Topologically non-trivial spin textures form a fundamental paradigm in solid-state physics and present unique opportunities to explore exciting phenomena such as the topological Hall effect. One such texture is a skyrmion, in which the spins can be mapped to point in all directions wrapping around a sphere. Understanding the formation of these spin textures, and their energetic stability, is crucial in order to control their behavior. In this work, we report on controlling the perpendicular anisotropy of continuous Co/Pt multilayer films with ion irradiation to form unique spin configurations of artificial skyrmions and antiskyrmions that are stabilized by their demagnetization energy. We elucidate their behavior using aberration-corrected Lorentz transmission electron microscopy. We also discuss the energetic stability of these structures studied through in-situ magnetizing experiments performed at room temperature, combined with micromagnetic simulations that successfully reproduce the spin textures and behavior. This research offers new opportunities towards creation of artificial skyrmion or antiskyrmion lattices that can be used to investigate not only fundamental properties of their interaction with electron currents but also technological applications such as artificial magnonic crystals.

  13. A functional protein retention and release multilayer with high stability.

    PubMed

    Nie, Kun; An, Qi; Zhang, Yihe

    2016-04-21

    Effective and robust interfacial protein retention lies at the heart of the fabrication of protein-based functional interfaces, which is potentially applicable in catalysis, medical therapy, antifouling, and smart devices, but remains challenging due to the sensitive nature of proteins. This study reports a general protein retention strategy to spatial-temporally confine various types of proteins at interfacial regions. The proteins were preserved in mesoporous silica nanoparticles embedded in covalently woven multilayers. It is worth noting that the protein retention strategy effectively preserves the catalytic capabilities of the proteins, and the multilayer structure is robust enough to withstand the bubbling catalytic reactions and could be repeatedly used due to conservation of proteins. The spatiotemporal retention of proteins could be adjusted by varying the number of capping layers. Furthermore, we demonstrate that the protein-loaded interfacial layers could not only be used to construct catalytic-active interfaces, but also be integrated as the power-generating unit to propel a macroscopic floating device. PMID:27064353

  14. Anisotropy of the electron g factor in quantum wells based on cubic semiconductors

    SciTech Connect

    Alekseev, P. S.

    2013-09-15

    A new mechanism for the spin splitting of electron levels in asymmetric quantum wells based on GaAs-type semiconductors relative to rotations of the magnetic field in the well plane is suggested. It is demonstrated that the anisotropy of the Zeeman splitting (linear in a magnetic field) arises in asymmetric quantum wells due to the interface spin-orbit terms in the electron Hamiltonian. In the case of symmetric quantum wells, it is shown that the anisotropy of the Zeeman splitting is a cubic function of the magnitude of the magnetic field, depends on the direction of the magnetic field in the interface plane as the fourth-order harmonic, and is governed by the spin-orbit term of the fourth order by the kinematic momentum in the electron Hamiltonian of a bulk semiconductor.

  15. Multi-layer seal for electrochemical devices

    DOEpatents

    Chou, Yeong-Shyung [Richland, WA; Meinhardt, Kerry D [Kennewick, WA; Stevenson, Jeffry W [Richland, WA

    2010-11-16

    Multi-layer seals are provided that find advantageous use for reducing leakage of gases between adjacent components of electrochemical devices. Multi-layer seals of the invention include a gasket body defining first and second opposing surfaces and a compliant interlayer positioned adjacent each of the first and second surfaces. Also provided are methods for making and using the multi-layer seals, and electrochemical devices including said seals.

  16. Multi-layer seal for electrochemical devices

    SciTech Connect

    Chou, Yeong-Shyung; Meinhardt, Kerry D; Stevenson, Jeffry W

    2010-09-14

    Multi-layer seals are provided that find advantageous use for reducing leakage of gases between adjacent components of electrochemical devices. Multi-layer seals of the invention include a gasket body defining first and second opposing surfaces and a compliant interlayer positioned adjacent each of the first and second surfaces. Also provided are methods for making and using the multi-layer seals, and electrochemical devices including said seals.

  17. Multilayer Radar Absorbing Non-Woven Material

    NASA Astrophysics Data System (ADS)

    Dedov, A. V.; Nazarov, V. G.

    2016-06-01

    We study the electrical properties of multilayer radar absorbing materials obtained by adding nonwoven sheets of dielectric fibers with an intermediate layer of electrically conductive carbon fibers. Multilayer materials that absorb electromagnetic radiation in a wide frequency range are obtained by varying the content of the carbon fibers. The carbon-fiber content dependent mechanism of absorption of electromagnetic radiation by sheets and multilayer materials is considered.

  18. Temperature-dependent perpendicular magnetic anisotropy of Co-Pt on Cr2O3 antiferromagnetic oxide

    NASA Astrophysics Data System (ADS)

    Nozaki, T.; Oida, M.; Ashida, T.; Shimomura, N.; Sahashi, M.

    2013-12-01

    We clarify the origin of the interface perpendicular magnetic anisotropy (PMA) at the Cr2O3/ferromagnet interface by investigating the temperature dependence of the magnetic properties of Cr2O3/Co-Pt. We observed positive large interface PMA both above and below the blocking temperature of Cr2O3, with the PMA being less sensitive to temperature. Our results indicate that the effect of the metal/oxide interface, as well as that of the MgO/CoFeB interface, contributes strongly to the PMA at the Cr2O3/Co-Pt interface, although the effect of perpendicular exchange coupling might also slightly contribute to the interface PMA.

  19. Pressure anisotropy in Jupiter's magnetodisc

    NASA Astrophysics Data System (ADS)

    Nichols, J. D.; Achilleos, N.; Cowley, S. W. H.

    2013-09-01

    The magnetosphere-ionosphere coupling current system at Jupiter has been studied by a number of authors over the last decade. Until recently, however, the various modelling studies treated the magnetic field as an empirically-based input derived from Voyager observations. This limitation was removed by Nichols (2011), who employed a self-consistent field model calculated using force-balance between the outward plasma pressure gradients plus the centrifugal force of the rotating iogenic plasma, and the inward JxB force arising from the azimuthal current sheet. However, the above study, which incorporated the magnetic field model of Caudal (1983), employed isotropic plasma pressure, whereas it is known that anisotropic plasma pressure plays a key role in the stress balance at Jupiter (e.g. Paranicas et al., 1991). In this paper we generalise the computation to include anisotropic pressure, and compute the magnetic field by summing over elliptical integrals. We then calculate the magnetosphere-ionosphere coupling currents assuming an equatorial parallel-to-perpendicular pressure ratio of 1.14, the value determined by Paranicas et al. (1991), and we also consider the effect on the system of solar wind-induced compression events. We find that the anisotropy current dominates the current sheet in the middle magnetosphere between 20-40RJ, and that Jupiter's magnetosphere is susceptible to the firehose instability.

  20. Fracture toughness anisotropy in shale

    NASA Astrophysics Data System (ADS)

    Chandler, Michael R.; Meredith, Philip G.; Brantut, Nicolas; Crawford, Brian R.

    2016-03-01

    The use of hydraulic fracturing to recover shale gas has focused attention on the fundamental fracture properties of gas-bearing shales, but there remains a paucity of available experimental data on their mechanical and physical properties. Such shales are strongly anisotropic, so that their fracture propagation trajectories depend on the interaction between their anisotropic mechanical properties and the anisotropic in situ stress field in the shallow crust. Here we report fracture toughness measurements on Mancos shale determined in all three principal fracture orientations: Divider, Short Transverse, and Arrester, using a modified short-rod methodology. Experimental results for a range of other sedimentary and carbonate rocks are also reported for comparison purposes. Significant anisotropy is observed in shale fracture toughness measurements at ambient conditions, with values, as high as 0.72 MPa m1/2 where the crack plane is normal to the bedding, and values as low as 0.21 MPa m1/2 where the crack plane is parallel to the bedding. For cracks propagating nonparallel to bedding, we observe a tendency for deviation toward the bedding-parallel orientation. Applying a maximum energy release rate criterion, we determined the conditions under which such deviations are more or less likely to occur under more generalized mixed-mode loading conditions. We find for Mancos shale that the fracture should deviate toward the plane with lowest toughness regardless of the loading conditions.