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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

    SciTech Connect

    Pechan, M.J.

    1991-01-01

    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 dependant FMR (9 GHz) and room temperature magnetization indicate that strain between Ni and the non-magnetic layers if 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 transition temperature. During the next project the P.I. proposes to (1) extend the variable frequency FMR measurements to low temperature, where extremely large interface anisotropies are known to obtain in Ni/Mo and Ni/V and are proposed to exist in Ni/W; (2) obtain accurate dc anisotropies via a novel, variable temperature torque magnetometer currently under construction; (3) expand upon his initial findings in Fe/Cu multilayer investigations; (4) begin anisotropy investigations on Co/Ag and CoCr/Ag multilayers where the easy magnetization direction depends upon the Cr concentration; (4) make and characterize Bi based superconductors according to resistivity, thermal conductivity and thermoelectric power and construct YBaCuO based superconducting loop-gap'' resonators for use in his magnetic resonance work. 2 figs.

  3. Magnetic multilayer interface anisotropy

    SciTech Connect

    Pechan, M.J.

    1990-01-01

    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 transition temperature. During the next project period the P.I. proposes to (1) extend the variable frequency FMR measurements to low temperature, where extremely large interface anisotropies are known to obtain in Ni/Mo and Ni/V and are proposed to exist in Ni/W; (2) obtain accurate dc anisotropies via a novel, variable temperature torque magnetometer currently under construction; (3) expand upon his initial findings in Fe/Cu multilayer investigations; (4) begin anisotropy investigations on Co/Ag and CoCr/Ag multilayers where the easy magnetization direction depends upon the Cr concentration; (4) make and characterize Bi based superconductors according to resistivity, thermal conductivity and thermoelectric power and construct YBaCuO based superconducting loop-gap'' resonators for use in his magnetic resonance work.

  4. Isolating the Interface Magnetocrystalline Anisotropy Contributions in Magnetic Multilayers

    NASA Astrophysics Data System (ADS)

    Dhesi, S. S.; Dürr, H. A.; Münzenberg, M.; Felsch, W.

    2003-03-01

    The interface magnetocrystalline anisotropy energy (MAE) in Fe/CeH2 multilayers has been site and element-specifically isolated by combining soft x-ray resonant magnetic scattering (SXRMS) with soft x-ray standing waves. Using the different temperature evolutions of the Fe and Ce SXRMS contributions, following an in-plane to out-of-plane spin reorientation, the interface Fe 3d MAE and Ce 4f single-ion anisotropy have been separated. The results demonstrate that the transition metal interface MAE dominates the spin reorientation while the rare-earth contribution becomes significant only at much lower temperatures.

  5. 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.

  6. 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.

  7. M-Split: A Graphical User Interface to Analyze Multilayered Anisotropy from Shear Wave Splitting

    NASA Astrophysics Data System (ADS)

    Abgarmi, Bizhan; Ozacar, A. Arda

    2017-04-01

    Shear wave splitting analysis are commonly used to infer deep anisotropic structure. For simple cases, obtained delay times and fast-axis orientations are averaged from reliable results to define anisotropy beneath recording seismic stations. However, splitting parameters show systematic variations with back azimuth in the presence of complex anisotropy and cannot be represented by average time delay and fast axis orientation. Previous researchers had identified anisotropic complexities at different tectonic settings and applied various approaches to model them. Most commonly, such complexities are modeled by using multiple anisotropic layers with priori constraints from geologic data. In this study, a graphical user interface called M-Split is developed to easily process and model multilayered anisotropy with capabilities to properly address the inherited non-uniqueness. M-Split program runs user defined grid searches through the model parameter space for two-layer anisotropy using formulation of Silver and Savage (1994) and creates sensitivity contour plots to locate local maximas and analyze all possible models with parameter tradeoffs. In order to minimize model ambiguity and identify the robust model parameters, various misfit calculation procedures are also developed and embedded to M-Split which can be used depending on the quality of the observations and their back-azimuthal coverage. Case studies carried out to evaluate the reliability of the program using real noisy data and for this purpose stations from two different networks are utilized. First seismic network is the Kandilli Observatory and Earthquake research institute (KOERI) which includes long term running permanent stations and second network comprises seismic stations deployed temporary as part of the "Continental Dynamics-Central Anatolian Tectonics (CD-CAT)" project funded by NSF. It is also worth to note that M-Split is designed as open source program which can be modified by users for

  8. 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.

  9. First-principles determination of the in-plane interface magnetocrystalline anisotropy in (110) Co thin films and multilayers.

    NASA Astrophysics Data System (ADS)

    Kim, Miyoung; Zhong, Lieping; Freeman, A. J.

    1996-03-01

    In order to investigate possible in-plane magnetocrystalline anisotropy (MCA) in transition metal thin films, we have carried out first principles MCA calculations for fcc Co (110) in various environments: a free standing Co monolayer and Co/Cu multilayers. The full potential linearized augmented-plane-wave (FLAPW) method [1] was used to obtain semi-relativistic self-consistent charge densities within the local density approximation. Spin-orbit coupling was treated in a second variational manner and our newly developed state tracking and torque methods were adopted to accurately determine the MCA energy. We found a large in-plane anisotropy of the magnetocrystalline energy in the (110) orientation and a strong dependence of the in-plane MCA behavior on the structure. The calculated results and mechanism involved in the in-plane MCA are presented and discussed. Supported by the ONR (Grant No.N00014-94-1-0030) [1] E. Wimmer, H. Krakauer, M. Weinert and A. J. Freeman, Phys. Rev. B 24, 864 (1981)

  10. 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.

  11. Control of magnetic anisotropy and magnetic patterning of perpendicular Co/Pt multilayers by laser irradiation

    SciTech Connect

    Schuppler, C.; Habenicht, A.; Guhr, I.L.; Maret, M.; Leiderer, P.; Boneberg, J.; Albrecht, M.

    2006-01-02

    We report an approach to altering the magnetic properties of (111) textured Co/Pt multilayer films grown on sapphire (0001) substrates in a controlled way using single-pulse laser irradiation. The as-grown films reveal a strong perpendicular magnetic anisotropy induced by interfacial anisotropy. We show that laser irradiation can chemically mix the multilayer structure particularly at the interfaces, hence reducing the perpendicular magnetic anisotropy and coercivity in a controlled manner depending on laser fluence. As a result, perpendicular films can also be magnetically patterned into hard and soft magnetic regions using a regular two-dimensional lattice of polystyrene particles acting as an array of microlenses.

  12. Anisotropies of magnetic Compton profiles in Co /Pd multilayer system

    NASA Astrophysics Data System (ADS)

    Sakurai, H.; Ota, M.; Itoh, F.; Itou, M.; Sakurai, Y.; Koizumi, A.

    2006-02-01

    Anisotropies of spin-projected wave functions are measured on a Pd /Co multilayer system by measuring magnetic Compton profiles. The anisotropies of the wave functions are decomposed into the contributions of Co 3d states and Pd 4d states using an atomic model by a Hartree-Fock calculation assuming uniaxial (cylindrical) symmetry. Perpendicular anisotropy in Pd /Co multilayers is dominated by the anisotropy of Co 3d states; states with both magnetic quantum number ∣m∣=2 and ∣m∣=1 contribute.

  13. Layering and temperature-dependent magnetization and anisotropy of naturally produced Ni/NiO multilayers

    SciTech Connect

    Pappas, S. D.; Trachylis, D.; Velgakis, M. J.; Kapaklis, V.; Joensson, P. E.; Papaioannou, E. Th.; Delimitis, A.; Poulopoulos, P.; Fumagalli, P.; Politis, C.

    2012-09-01

    Ni/NiO multilayers were grown by magnetron sputtering at room temperature, with the aid of the natural oxidation procedure. That is, at the end of the deposition of each single Ni layer, air is let to flow into the vacuum chamber through a leak valve. Then, a very thin NiO layer ({approx}1.2 nm) is formed. Simulated x-ray reflectivity patterns reveal that layering is excellent for individual Ni-layer thickness larger than 2.5 nm, which is attributed to the intercalation of amorphous NiO between the polycrystalline Ni layers. The magnetization of the films, measured at temperatures 5-300 K, has almost bulk-like value, whereas the films exhibit a trend to perpendicular magnetic anisotropy (PMA) with an unusual significant positive interface anisotropy contribution, which presents a weak temperature dependence. The power-law behavior of the multilayers indicates a non-negligible contribution of higher order anisotropies in the uniaxial anisotropy. Bloch-law fittings for the temperature dependence of the magnetization in the spin-wave regime show that the magnetization in the multilayers decreases faster as a function of temperature than the one of bulk Ni. Finally, when the individual Ni-layer thickness decreases below 2 nm, the multilayer stacking vanishes, resulting in a dramatic decrease of the interface magnetic anisotropy and consequently in a decrease of the perpendicular magnetic anisotropy.

  14. Origin of perpendicular magnetic anisotropy in Co/Ni multilayers

    NASA Astrophysics Data System (ADS)

    Arora, M.; Hübner, R.; Suess, D.; Heinrich, B.; Girt, E.

    2017-07-01

    We studied the variation in perpendicular magnetic anisotropy of (111) textured Au /N ×[Co /Ni ]/Au films as a function of the number of bilayer repeats N . The ferromagnetic resonance and superconducting quantum interference device magnetometer measurements show that the perpendicular magnetic anisotropy of Co/Ni multilayers first increases with N for N ≤10 and then moderately decreases for N >10 . The model we propose reveals that the decrease of the anisotropy for N <10 is predominantly due to the reduction in the magnetoelastic and magnetocrystalline anisotropies. A moderate decrease in the perpendicular magnetic anisotropy for N >10 is due to the reduction in the magnetocrystalline and the surface anisotropies. To calculate the contribution of magnetoelastic anisotropy in the Co/Ni multilayers, in-plane and out-of-plane x-ray diffraction measurements are performed to determine the spacing between Co/Ni (111) and (220) planes. The magnetocrystalline bulk anisotropy is estimated from the difference in the perpendicular and parallel g factors of Co/Ni multilayers that are measured using the in-plane and out-of-plane ferromagnetic resonance measurements. Transmission electron microscopy has been used to estimate the multilayer film roughness. These values are used to calculate the roughness-induced surface and magnetocrystalline anisotropy coefficients as a function of N .

  15. 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.

  16. 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.

  17. Scattering anisotropy and giant magnetoresistance in magnetic multilayers

    SciTech Connect

    Binder, J.; Zahn, P.; Mertig, I.

    2001-06-01

    We present full ab initio calculations of giant magnetoresistance (GMR) in Co/Cu (001) multilayers including self-consistent impurity scattering potentials. Starting from density functional theory the electronic structure of the multilayer and the scattering at impurities are described by means of a new Green function method. It will be demonstrated that impurity scattering in magnetic multilayers is strongly anisotropic in comparison to impurity scattering in bulk systems. Concerning transport the anisotropy of scattering leads to a formation of highly conducting channels which give rise to short circuits and cause strong variation of GMR as a function of the impurity position in the multilayer. {copyright} 2001 American Institute of Physics.

  18. Perpendicular magnetic anisotropy in Fe/CeH 2 multilayers with reduced pair number

    NASA Astrophysics Data System (ADS)

    Münzenberg, M.; Lohstroh, W.; Dufour, C.; Bauer, Ph.; Felsch, W.

    1999-06-01

    In the multilayer system [Fe/CeH 2]× n a strong interface anisotropy causes a rotation of the magnetization direction out of the layer plane at a temperature TR. Measurements of the 57Fe Mössbauer spectra and of the magnetization curves by the magneto-optical Kerr effect on samples with a different number of bilayers n are presented which reveal that a contribution from the magnetostatic interaction between the domains adds to the interface anisotropy to stabilize the out-of-plane magnetization orientation; with increasing n, TR increases and the angle Θ between the average magnetization direction and the layer normal decreases.

  19. Magnetization reversal and magnetic anisotropy in patterned Co/Pd multilayer thin films

    SciTech Connect

    Smith, Darren; Parekh, Vishal; E, Chunsheng; Litvinov, Dmitri; Zhang Shishan; Donner, Wolfgang; Lee, T. Randall; Khizroev, Sakhrat

    2008-01-15

    (Co/Pd){sub N} multilayers exhibit high vertical magnetic anisotropy and have been extensively explored as recording medium candidates for high density magnetic recording applications. In this work (Co/Pd){sub N} multilayers are deposited by magnetron sputtering and patterned into large periodic arrays of 200 nm islands to enable controlled domain wall injection for quantitative comparison of magnetic anisotropy energies. Magnetic properties are correlated with x-ray photoelectron spectroscopy data, an approach commonly used to probe the binding energies and valence band positions. Confirming theoretical predictions, it is demonstrated that the degree of d-shell hybridization at Co/Pd interfaces directly correlated with the magnitude of magnetic anisotropy.

  20. Variable variance Preisach model for multilayers with perpendicular magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Franco, A. F.; Gonzalez-Fuentes, C.; Morales, R.; Ross, C. A.; Dumas, R.; Åkerman, J.; Garcia, C.

    2016-08-01

    We present a variable variance Preisach model that fully accounts for the different magnetization processes of a multilayer structure with perpendicular magnetic anisotropy by adjusting the evolution of the interaction variance as the magnetization changes. We successfully compare in a quantitative manner the results obtained with this model to experimental hysteresis loops of several [CoFeB/Pd ] n multilayers. The effect of the number of repetitions and the thicknesses of the CoFeB and Pd layers on the magnetization reversal of the multilayer structure is studied, and it is found that many of the observed phenomena can be attributed to an increase of the magnetostatic interactions and subsequent decrease of the size of the magnetic domains. Increasing the CoFeB thickness leads to the disappearance of the perpendicular anisotropy, and such a minimum thickness of the Pd layer is necessary to achieve an out-of-plane magnetization.

  1. Anisotropy constant and exchange coupling strength of perpendicularly magnetized CoFeB/Pd multilayers and exchange springs

    NASA Astrophysics Data System (ADS)

    Franco, A. F.; Gonzalez-Fuentes, C.; Åkerman, J.; Garcia, C.

    2017-04-01

    A model describing the ferromagnetic resonance of multilayer structures is used to characterize the interface anisotropy constant and interlayer exchange coupling strength associated to individual components of [CoFeB/Pd ] n multilayers with perpendicular magnetic anisotropy and [CoFeB/Pd ] 5/(CoFeB or Co) exchange spring structures by comparing with ferromagnetic resonance behavior measurements. We find that the effective perpendicular anisotropy increases with the number of repetitions of the multilayer, which we could explain only after accounting for a different anisotropy at the bottom repetition of the multilayer with perpendicular anisotropy. Similarly, the characterization of the exchange coupling in our structures was only possible after accounting for individual components, thus portraying the importance of using a multilayer model to properly describe the magnetic behavior and properties of a multilayer structure. We find that the perpendicular anisotropy constant in amorphous Pd/CoFeB/Pd structures increases slightly from 0.295 to 0.315 mJ /m2 when increasing the thickness of the CoFeB from 3 to 4 Å. Furthermore, we find that the exchange coupling in CoFeB/Pd(10 Å)/CoFeB structures decreases from 4.899 to 3.268 mJ /m2 when increasing the thickness of the CoFeB from 3 to 4 Å. Finally, we find that the magnitude of the anisotropy at Co/Pd interfaces is 65% larger than at CoFeB/Pd interfaces, and the exchange coupling at CoFeB/Pd/Co interfaces decreases approximately 30% when compared to a CoFeB/Pd/CoFeB structure.

  2. Enhancement of perpendicular magnetic anisotropy and anomalous hall effect in Co/Ni multilayers

    NASA Astrophysics Data System (ADS)

    Liu, Yiwei; Zhang, Jingyan; Jiang, Shaolong; Liu, Qianqian; Li, Xujing; Yu, Guanghua

    2016-12-01

    The perpendicular magnetic anisotropy (PMA) and the anomalous Hall effect (AHE) in Co/Ni multilayer were optimized by manipulating its interface structure (inducing HfO2 capping layer and Pt insertion) and post-annealing treatment. A strong PMA can be obtained in Co/Ni multilayers with HfO2 capping layer even after annealing at 400 °C. The heavy metal Hf may improve the interfacial spin-orbit coupling, which responsible for the enhanced PMA and high annealing stability. Moreover, the multilayer containing HfO2 capping layer also exhibited high saturation anomalous Hall resistivity through post-annealing, which is 0.85 μΩ cm after annealing at 375 °C, 211% larger than in the sample at deposited state which is only 0.27 μΩ cm. The enhancement of AHE is mainly attributed to the interface scattering through post-annealing treatment.

  3. Perpendicular magnetic anisotropy and microstructure properties of nanoscale Co/Au multilayers

    NASA Astrophysics Data System (ADS)

    Rizal, C.; Fullerton, E. E.

    2017-09-01

    We investigated the role of microstructure and Co layer thickness on the perpendicular magnetic anisotropy of as-deposited and annealed Ta (5 nm)/[Co (t Co)/Au (2 nm)]  ×  N  =  20 multilayers with 1  ⩽  t Co  ⩽  2 nm prepared using dc-magnetron sputtering. These multilayers were characterized using a vibrating sample magnetometer, a p-MOKE magnetometer and a microscopy magnetometer, small angle x-ray reflection (XRR), and wide angle x-ray diffraction (XRD) analysis. These multilayers demonstrated strong perpendicular magnetic anisotropy with their saturation magnetization close to the bulk magnetization of Co. Magnetization and magnetic anisotropy increased with annealing and this increase is directly linked to the strain relaxation and sharpening of the interfaces after annealing. Using XRR analysis before and after annealing, and fitting these XRR data, the multilayer periodicities are extracted and the refined layer thickness and surface roughness are determined. Using XRD analysis and fitting these XRD spectra, information regarding both the average lattice spacing of atoms and the strain developed on an individual layer were determined.

  4. Perpendicular magnetic anisotropy in amorphous ferromagnetic CoSiB/Pt multilayers.

    PubMed

    Hwang, J Y; Park, J S; Yim, H I; Kim, T W; Shin, D Y; Lee, S B

    2011-01-01

    Magnetic anisotropy properties of amorphous ferromagnetic CoSiB/Pt multilayers with perpendicular magnetic anisotropy (PMA, K(u)) were systematically investigated as a function of CoSiB layer thickness (t(coSiB)) and Pt layer thickness (t(Pt)). In two series of [CoSiB t(coSiB)Pt t(P1)]5 multilayers, the perpendicular coercivity (H(c)) increased to reach a maximum and then decreased with further increase in both t(coSiB) and t(Pt), due to intermixing of CoSiB/Pt interfaces. Particularly, using the amorphous soft magnetic CoSiB, the coercivity became very sensitive to the CoSiB thickness. These multilayer films exhibited a high K(u) of 2 x 10(6) erg/cc and a high H(c) of 360 Oe with marked squareness. It was found that even after annealing at 350 degrees C, the CoSiB/Pt multilayers had a high PMA and their H(c) increased.

  5. Depth-resolved magnetization reversal in nanoporous perpendicular anisotropy multilayers

    NASA Astrophysics Data System (ADS)

    Kirby, B. J.; Rahman, M. T.; Dumas, R. K.; Davies, J. E.; Lai, C. H.; Liu, Kai

    2013-01-01

    We have used polarized neutron reflectometry to study the field-dependent magnetizations of Co/Pt mulitlayers patterned via deposition onto nanoporous alumina hosts with varying pore aspect ratio. Despite the porosity and lack of long-range order, robust spin-dependent reflectivities are observed, allowing us to distinguish the magnetization of the surface multilayer from that of material in the pores. We find that as the pores become wider and shallower, the surface Co/Pt multilayers have progressively smaller high field magnetization and exhibit softer magnetic reversal—consistent with increased magnetic disorder and a reduction of the perpendicular anisotropy near the pore rims. These results reveal complexities of magnetic order in nanoporous heterostructures, and help pave the way for depth-resolved studies of complex magnetic heterostructures grown on prepatterned substrates.

  6. Unidirectional superscattering by multilayered cavities of effective radial anisotropy

    PubMed Central

    Liu, Wei; Lei, Bing; Shi, Jianhua; Hu, Haojun

    2016-01-01

    We achieve unidirectional forward superscattering by multilayered spherical cavities which are effectively radially anisotropic. It is demonstrated that, relying on the large effective anisotropy, the electric and magnetic dipoles can be tuned to spectrally overlap in such cavities, which satisfies the Kerker’s condition of simultaneous backward scattering suppression and forward scattering enhancement. We show that such scattering pattern shaping can be obtained in both all-dielectric and plasmonic multilayered cavities at different spectral positions, and believe that the mechanism we have revealed provides extra freedom for scattering shaping, which may play a significant role in many scattering related applications and also in optoelectronic devices made up of intrinsically anisotropic two dimensional materials. PMID:27708398

  7. 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.

  8. 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.

  9. Perpendicular magnetic anisotropy properties of CoFeB/Pd multilayers.

    PubMed

    Jung, Jong Ho; Lim, Sang Ho; Lee, Seong-Rae

    2011-07-01

    The perpendicular magnetic anisotropy (PMA) properties of CoFeB/Pd multilayers are investigated as functions of the thickness of the constituent layers of the multilayers and of the substrate type. A relatively strong PMA is formed at small CoFeB thicknesses of 0.3 and 0.5 nm over the entire Pd thickness range of 0.47 to 1.26 nm. At a fixed CoFeB thickness, the PMA tends to increase with increasing Pd thickness and this behavior can be attributed to the fact that the interface tends to become flatter and smoother at a higher Pd thicknesss, leading to a stronger surface anisotropy. A stronger PMA is observed for the glass substrate than for the MgO substrate. Since the thermal stress formed at the CoFeB layer is tensile for both the glass and MgO substrates, the magnetoelastic interactions suggest the possibility of forming a Co-Pd alloy with a negative saturation magnetostriction at the CoFeB/Pd interfaces.

  10. Ferromagnetic resonance measurements of (Co/Ni/Co/Pt) multilayers with perpendicular magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Sbiaa, R.; Shaw, J. M.; Nembach, H. T.; Bahri, M. Al; Ranjbar, M.; Åkerman, J.; Piramanayagam, S. N.

    2016-10-01

    Multilayers of [Co/Ni(t)/Co/Pt]×8 with varying Ni thickness were investigated for possible use as a free layer in magnetic tunnel junctions and spintronics devices. The thickness t of the Ni sub-layer was varied from 0.3 nm to 0.9 nm and the resulting magnetic properties were compared with (Co/Ni) and (Co/Pt) multilayers. As determined from magnetic force microscopy, magnetometry and ferromagnetic resonance measurements, all multilayers exhibited perpendicular magnetic anisotropy. Compared with (Co/Pt) multilayers, the sample with t of 0.9 nm showed almost the same anisotropy field of μ 0 H k   =  1.15 T but the damping constant was 40% lower. These characteristics make these multilayers attractive for spin torque based magnetoresistive devices with perpendicular anisotropy.

  11. 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.

  12. 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.

  13. Perpendicular magnetic anisotropy in Co-Pt granular multilayers

    NASA Astrophysics Data System (ADS)

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

    2012-09-01

    Magnetization hysteresis curves have been measured on Co granular multilayers, (Al2O3/Co/Pt)N (N = 1 and 25), with the applied magnetic field parallel and perpendicular to the substrate plane. In all samples perpendicular magnetic anisotropy was observed. For Co particles with average diameter 3 nm, the coercive field at low temperature is μ0HC = 0.5 T. HC decreases for increasing temperature and disappears at ≈200 K. A soft magnetic component is also present in all samples up to the freezing temperature Tf = 365 K. Co and Pt XMCD measurements at the L2,3 edges were performed, yielding to the orbital mL and spin mS contributions to the total magnetic moment of the system. These results, in addition to XANES ones, indicate the presence of CoxPt1-x alloy. Particles conformed of CoPt alloy, embedded in Pt and coupled magnetically by dipolar or RKKY interaction, may explain the phenomenology observed in these systems.

  14. 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

  15. Ferromagnetic resonance study of ion irradiated Co/Ni multilayers with perpendicular magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Beaujour, J.-M.; Kent, A.; Ravelosona, D.; Fullerton, E.; Samson, Y.; Beigne, C.

    2009-03-01

    Ferromagnetic resonance (FMR) spectroscopy was used to investigate the effect of helium ion-irradiation on the magnetic properties and the magnetization dynamics of Co/Ni multilayer films. The anisotropy in these materials is associated with interfaces, which can be systematically disordered with light ion-irradiation without inducing major structural changes to the films. [Pd/Co]x2|[8åNi/1.4åCo]x3 |Pd|Co|Pd| have been exposed to He^+ irradiation with fluence up to 10^15 ions/cm^2 [1]. FMR was conducted with a broad band coplanar waveguide up to 30 GHz. The resonance field and the FMR linewidth were determined as a function of frequency for dc magnetic fields in-plane, out-of-plane and for selected field angles. The perpendicular anisotropy decreases linearly with fluence, and at a particular fluence the direction of easy magnetization switches from perpendicular to in-plane. The Gilbert damping constant of the films irradiated at the higher and lower fluence is about the same: 0.03<=α<=0.04. However, the linewidth exhibits a non-monotonic dependence on fluence, with a maximum at intermediate fluence. We will discuss this effect as well as possible explanations in terms of the changes in interface structure as a function of fluence. [1] Stanescu et al., J. Appl. Phys. (2008).

  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. Magnetic anisotropy and spin reorientation effects in Gd/Fe and Gd/(FeCo) multilayers for high density magneto-optical recording

    NASA Astrophysics Data System (ADS)

    Stavrou, E.; Sbiaa, R.; Suzuki, T.; Knappmann, S.; Röll, K.

    2000-05-01

    We have investigated the anisotropy behavior and temperature dependent changes of the magnetic anisotropy in Gd/Fe and Gd/(FeCo) multilayers. The spin reorientation effects are very important for the super resolution readout in new methods for high-density magneto-optical recording. Gd/(Fe, Co) multilayered films are a good alternative to the common Gd(Fe, Co) alloy films, because the magnetic anisotropy and also spin reorientation effects can be comfortably adjusted by varying the interface and volume anisotropy components and the composition using experimental parameters such as the periodicity λ=tGd+tTM [tGd,tTM: the sublayer thicknesses of the Gd and transition metal Fe, FeCo (TM)] and the ratio of the sublayer thicknesses tGd/tTM. We have found the mechanisms for spin reorientation, which are explained qualitatively with a new model.

  18. 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.

  19. 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.

  20. 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.

  1. Exchange anisotropy in NiFe layers coupled with multilayered MnFe/MnFeCr (abstract)

    NASA Astrophysics Data System (ADS)

    Kung, Kenneth T.-Y.; Campbell, Richard T.

    1991-11-01

    The exchange anisotropy in a ferromagnetic NiFe layer coupled with an antiferromagnetic MnFe layer can be used to stabilize the single domain state of a magnetoresistive sensor,1 but this technology may be limited by the high corrosion sensitivity of MnFe. It is possible to improve the corrosion resistance of MnFe through impurity doping, e.g., MnFeCr with Cr concentrations of 3-12 at. %,2 but this technique will at the same time degrade the exchange anisotropy. In this work, we have investigated the exchange anisotropy in NiFe layers coupled with multilayered MnFe/MnFeCr. The samples had a configuration of glass substrates, followed by a NiFe (300 Å) layer, followed by a MnFe(x Å)/MnFeCr(y Å) multilayer, where the antiferromagnetic multilayer had either MnFe or MnFeCr interfacing with the NiFe and had a fixed total thickness of 240 Å. They were prepared by rf diode sputtering and, after a Ta (200 Å) protective layer deposition, were thermally cycled to a maximum temperature of 250 °C. The results can be summarized as follows: (1) The anisotropy energy, EUA, near the room temperature ranged from 0.03 to 0.10 erg/cm2; it was determined mostly by the antiferromagnetic layer (MnFe or MnFeCr) at the NiFe interface and was essentially independent of the rest of antiferromagnetic structure. (2) The critical temperature, TC, range from 90 to 160 °C; it was determined mostly by the relative amounts of MnFe and MnFeCr in the entire antiferromagnetic structure and not just at the NiFe interface. These results implied that, while one could improve the anisotropy energy at lower temperatures simply by improving the antiferromagnetic layer near the NiFe interface, to improve the anisotropy energy at higher temperatures one must improve the entire antiferromagnetic layer.

  2. Large enhancement of perpendicular magnetic anisotropy and high annealing stability by Pt insertion layer in (Co/Ni)-based multilayers

    NASA Astrophysics Data System (ADS)

    Chen, Xi; Li, Minghua; Yang, Kang; Jiang, Shaolong; Han, Gang; Liu, Qianqian; Yu, Guanghua

    2015-09-01

    We have investigated the influence of ultrathin Pt insertion layers on the perpendicular magnetic anisotropy (PMA) and annealing stability of Ta/Pt/(Co/Ni)×3/Co/Pt/Ta multilayered films. When the Pt layers were inserted at the Co/Ni interfaces, the PMA of the multilayered films decreased monotonically as the thickness of the Pt insertion layer (tPt) was increased. However, when the Pt layers were inserted at the Ni/Co interfaces, the PMA increased from 1.39 × 106 to 3.5 × 106 erg/cm3 as tPt increased from 0 to 10 Å. Moreover, the multilayered film containing 6-Å-thick Pt insertion layers that inserted at the Ni/Co interfaces exhibited the highest annealing stability for PMA, which was up to temperature of 480 °C. We hypothesize that the introduced Pt/Co interfaces, due to the Pt insertion layers, are responsible for the enhanced PMA and high annealing stability. This study is particularly important for perpendicularly magnetized spintronic devices that require high PMA and high annealing stability.

  3. Interface effects on the magnetic properties of exchange coupled Co/Fe multilayers studied by Brillouin light scattering

    NASA Astrophysics Data System (ADS)

    D'Orazio, F.; Lucari, F.; Carlotti, G.; Gubbiotti, G.; Carbucicchio, M.; Ruggiero, G.

    2001-05-01

    Exchange-coupled 5[Co ( x) /Fe (3 x) ]/Co ( x) with x=5, 10, 15 nm multilayers were grown by UHV electron-beam evaporation. The influence of the interface magnetic anisotropy and interlayer exchange interaction on the magnetic properties was studied by means of Brillouin light scattering from thermally excited spin waves. Both the Damon-Eshbach surface mode of the total multilayer and bulk standing modes are present in the BLS spectra. A careful study of spin waves frequency dependence on the applied magnetic field allowed the determination of the magnetic parameters of the Co/Fe multilayers.

  4. Unidirectional Anisotropy in Manganite Based Ferromagnetic-Antiferromagnetic Multilayers

    DTIC Science & Technology

    2000-01-01

    UNCLASSIFIED Defense Technical Information Center Compilation Part Notice ADPO 11814 TITLE: Unidirectional Anisotropy in Manganite Based...component part numbers comprise the compilation report: ADPO11800 thru ADP011832 UNCLASSIFIED UNIDIRECTIONAL ANISOTROPY IN MANGANITE BASED FERROMAGNETIC...Introduction In mixed valence manganites a large negative magnetoresistance (MR), termed colossal magnetoresistance [1] (CMR), can be obtained due to a

  5. Perpendicular magnetic anisotropy and temperature-dependent reorientation transition of the magnetization in CeH2/Fe multilayers

    NASA Astrophysics Data System (ADS)

    Schulte, O.; Klose, F.; Felsch, W.

    1995-09-01

    Magnetic anisotropies were investigated in a series of CeH2/Fe multilayers with a pronounced (111) texture by measurements of the magnetization between 4.2 and 300 K. The results reveal, together with 57Fe Mössbauer spectra measured previously, that in the ground state at low temperatures the magnetization is oriented perpendicular to the layer planes in a multidomain configuration, up to remarkably large Fe layer thicknesses. It is demonstrated in a phenomenological model that this appears as the result of a strong interface anisotropy in combination with a magnetostatic interaction between the domains in the Fe layers across the CeH2 layers, which overcome the shape anisotropy of the Fe layers. At a critical temperature TR, which decreases with both the Fe or CeH2 layer thicknesses tFe and tCeH, a transition from the out-of-plane to an in-plane orientation of the magnetization is observed. The present system is outstanding among other rare-earth/iron multilayers, because the reorientation transition occurs rather abruptly in a narrow temperature range.

  6. 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.

  7. Lack of dependence between intrinsic magnetic damping and perpendicular magnetic anisotropy in Cu(tCu)/[Ni/Co]N multilayers

    NASA Astrophysics Data System (ADS)

    Tang, Minghong; Li, Wei; Ren, Yang; Zhang, Zongzhi; Jin, Q. Y.

    2017-04-01

    The correlation between magnetic damping and perpendicular magnetic anisotropy has been investigated in Cu(tCu)/[Ni/Co]N multilayers by time-resolved magneto-optical Kerr effect. The uniaxial magnetic anisotropy constant Ku is varied in the range of 3.0-3.6 Merg/cm3 by tuning either multilayer repetition number N or Cu thickness tCu. It is found that the PMA strength Ku increases with the increase of N, while the damping constant α0 keeps nearly a constant of 0.025, implying the intrinsic damping is independent of the Ku tuned by N. In contrast, as tCu increases from 2.5 to 20 nm, the α0 value rises continuously up to 0.040, in spite of the rather weak enhancement in Ku and its non-monotonic variation behavior. We consider the constant α0 with N is due to the unchanged spin-orbit coupling strength at each Co/Ni interface, while the obvious enhancement in α0 with tCu results mainly from the increased degree of spin disordering at the rougher Cu/Ni interface.

  8. Effect of fast strain on Co/Pt multilayers with perpendicular anisotropy

    NASA Astrophysics Data System (ADS)

    Singh, Uday; Adenwalla, S.

    2013-09-01

    Materials possessing perpendicular anisotropy have applications in high density magnetic data storage technology. In this paper, we present initial attempts to measure the fast magnetization switching from out-of-plane to in-plane in perpendicular anisotropy Co/Pt multilayers. Interaction with surface acoustic waves (SAW) results in strain induced anisotropy changes in Co/Pt multilayers arising from the magnetostrictive properties of ferromagnetic Co, and changing the easy axis of magnetization. The strain amplitude required to overcome perpendicular magnetic anisotropy is close to 1%. Such large strains are achievable using annular interdigital transducers (AIDT), in which the electrodes follow the velocity curve of the piezoelectric substrate. When excited at the fundamental resonance frequency, SAW propagating towards the center undergo constructive interference and create an intense strain at the focal center. We successfully fabricated AIDT using photolithography with a fundamental resonance of 87.56 MHz. An elliptic structure of Co/Pt multilayers was deposited at the focal center using electron beam lithography (EBL) and magnetron sputtering. The magnetization of the elliptic patterned Co/Pt was measured using focused MOKE and magnetic force microscopy (MFM), confirming that the ellipse is in a single domain state with out of plane anisotropy. Preliminary attempts to measure the magnetization rotation arising from the strain waves did not show the expected magnetization rotation signature. Possible reasons for this are discussed.

  9. 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

    2016-06-14

    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.

  10. 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.

  11. 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

  12. Handling magnetic anisotropy and magnetoimpedance effect in flexible multilayers under external stress

    NASA Astrophysics Data System (ADS)

    Agra, K.; Bohn, F.; Mori, T. J. A.; Callegari, G. L.; Dorneles, L. S.; Correa, M. A.

    2016-12-01

    We investigate the dynamic magnetic response though magnetoimpedance effect of ferromagnetic flexible NiFe/Ta and FeCuNbSiB/Ta multilayers under external stress. We explore the possibility of handling magnetic anisotropy, and consequently the magnetoimpedance effect, of magnetostrictive multilayers deposited onto flexible substrates. We quantify the sensitivity of the multilayers under external stress by calculating the ratio between impedance variations and external stress changes, and show that considerable values can be reached by tuning the magnetic field, frequency, magnetostriction constant, and external stress. The results extend possibilities of application of magnetostrictive multilayers deposited onto flexible substrates when under external stress and place them as very attractive candidates as element sensor for the development of sensitive smart touch sensors.

  13. 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.

  14. Magnetic anisotropy at the buried CoO/Fe interface

    NASA Astrophysics Data System (ADS)

    Giannotti, D.; Hedayat, H.; Vinai, G.; Picone, A.; Calloni, A.; Berti, G.; Riva, M.; Bussetti, G.; Boschini, F.; Torelli, P.; Panaccione, G.; Carpene, E.; Dallera, C.; Finazzi, M.; Brambilla, A.

    2016-12-01

    Interfaces between antiferromagnetic CoO and ferromagnetic Fe are typically characterized by the development of Fe oxides. Recently, it was shown that the use of a proper ultra-thin Co buffer layer prevents the formation of Fe oxides [Brambilla et al., Appl. Surf. Sci. 362, 374 (2016)]. In the present work, we investigate the magnetic properties of such an interface, and we find evidence for an in-plane uniaxial magnetic anisotropy, which is characterized by a multijump reversal behavior in the magnetization hysteresis loops. X-ray photoemission spectroscopy and element-sensitive hysteresis loops reveal that the occurrence of such an anisotropy is a phenomenon developing at the very interface.

  15. Reversal and thermal stability of ordered moments in nano-rings of perpendicular anisotropy Co/Pd multilayers

    NASA Astrophysics Data System (ADS)

    Kaur, M.; Raju, M.; Varandani, D.; Gupta, Anurag; Senguttuvan, T. D.; Mehta, B. R.; Budhani, R. C.

    2015-07-01

    Magnetic properties of the ring array made with ultrathin (Pd-/Co-layer thickness ~0.5/0.25 nm) Co/Pd multilayers are reported. Systematic investigation of magnetization loops M(H) at varying temperatures (T = 3-300 K) and magnetic relaxations (at T = 300 K) were carried out in a plain film and ring arrays with different ring widths of 660, 500 and 340 nm. The M(H) loops of all the samples show anisotropy distribution, a reversal mechanism facilitated by nucleation of the reverse domain followed by pinning dependent domain wall motion, and a thermally stable remanant state with Ub/kT  >  250 (at T = 300 K, where Ub is the activation barrier). Both anisotropy distribution and pinning are found to increase in the nanostructures along with a precipitous rise of the reversal field below  ≈100 K. These results are discussed in terms of the presence of chemically sharp/disordered interface regions and inter-layer interactions in the Co/Pd multilayers.

  16. Strong Perpendicular Magnetic Anisotropy in CoFeB/Pd Multilayers

    NASA Astrophysics Data System (ADS)

    Jung, Jong Ho; Jeong, Boram; Lim, Sang Ho; Lee, Seong-Rae

    2010-02-01

    The strong perpendicular magnetic anisotropy (PMA), indicated by a large coercivity of 590 Oe, is obtained in CoFeB/Pd multilayers through a systematic study that involves using various substrates (Si, glass, sapphire, and MgO) and seed layers (Al and Ta) and also varying the thickness of the seed layer. The PMA is nearly independent of the substrate when Al is used as a seed layer, but the dependence increases significantly with increasing seed layer thickness. The behavior becomes rather complicated for the multilayers with a Ta seed layer, showing a large substrate dependence and a large seed layer thickness dependence.

  17. Accurate calculation of the transverse anisotropy of a magnetic domain wall in perpendicularly magnetized multilayers

    NASA Astrophysics Data System (ADS)

    Büttner, Felix; Krüger, Benjamin; Eisebitt, Stefan; Kläui, Mathias

    2015-08-01

    Bloch domain walls are the most common type of transition between two out-of-plane magnetized domains (one magnetized upwards, one downwards) in films with perpendicular magnetic anisotropy. The rotation of the spins of such domain walls in the plane of the film requires energy, which is described by an effective anisotropy, the so-called transverse or hard axis anisotropy K⊥. This anisotropy and the related Döring mass density of the domain wall are key parameters of the one-dimensional model to describe the motion of magnetic domain walls. In particular, the critical field strength or current density where oscillatory domain wall motion sets in (Walker breakdown) is directly proportional to K⊥. So far, no general framework is available to determine K⊥ from static characterizations such as magnetometry measurements. Here, we derive a universal analytical expression to calculate the transverse anisotropy constant for the important class of perpendicular magnetic multilayers. All the required input parameters of the model, such as the number of repeats, the thickness of a single magnetic layer, and the layer periodicity, as well as the effective perpendicular anisotropy, the saturation magnetization, and the static domain wall width are accessible by static sample characterizations. We apply our model to a widely used multilayer system and find that the effective transverse anisotropy constant is a factor of seven different from that when using the conventional approximations, showing the importance of using our analysis scheme. Our model is also applicable to domain walls in materials with Dzyaloshinskii-Moriya interaction (DMI). The accurate knowledge of K⊥ is needed to determine other unknown parameters from measurements, such as the DMI strength or the spin polarization of the spin current in current-induced domain wall motion experiments.

  18. Colloidal domain lithography in multilayers with perpendicular anisotropy: an experimental study and micromagnetic simulations.

    PubMed

    Kuświk, Piotr; Sveklo, Iosif; Szymański, Bogdan; Urbaniak, Maciej; Stobiecki, Feliks; Ehresmann, Arno; Engel, Dieter; Mazalski, Piotr; Maziewski, Andrzej; Jagielski, Jacek

    2012-11-30

    Currently, much attention is being paid to patterned multilayer systems in which there exists a perpendicular magnetic anisotropy, because of their potential applications in spintronics devices and in a new generation of magnetic storage media. To further improve their performance, different patterning techniques can be used, which render them suitable also for other applications. Here we show that He(+) 10 keV and Ar(+) 100 keV ion bombardment of (Ni(80)Fe(20)-2 nm/Au-2 nm/Co-0.6 nm/Au-2 nm)(10) multilayers through colloidal mask enables magnetic patterning of regularly arranged cylindrical magnetic domains, with perpendicular anisotropy, embedded in a non-ferromagnetic matrix or in a ferromagnetic matrix with magnetization oriented along the normal. These domains form an almost perfect two-dimensional hexagonal lattice with a submicron period and a large correlation length in a continuous and flat multilayer system. The magnetic anisotropy of these artificial domains remains unaffected by the magnetic patterning process, however the magnetization configuration of such a system depends on the magnetic properties of the matrix. The micromagnetic simulations were used to explain some of the features of the investigated patterned structures.

  19. 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.

  20. Exchange-biased spin valves with perpendicular magnetic anisotropy based on (Co/Pt) multilayers

    NASA Astrophysics Data System (ADS)

    Garcia, F.; Fettar, F.; Auffret, S.; Rodmacq, B.; Dieny, B.

    2003-05-01

    We have prepared spin valves exhibiting perpendicular magnetic anisotropy [perpendicular spin valves (PSVs)] by sputtering. These PSVs associate a "free" (Co/Pt) multilayer with a "pinned" (Co/Pt)/FeMn multilayer separated by various spacer materials (Pt, Cu, Al2O3). We carried out a comprehensive study of the magnetic and magnetotransport properties of the biased multilayers and of the complete spin valves. When the number of repeats in the (Co/Pt) exchange-biased multilayer is larger than 3, the samples present 100% remnant magnetization in the perpendicular configuration. The major hysteresis cycles exhibit two well-separated loops associated with the free and the exchange-biased (Pt/Co) multilayers. When optimized, the exchange-bias field can be larger than the coercivity of the pinned layer. Metallic PSVs with Cu spacers exhibit giant magnetoresistance but the amplitude is only of the order of 1% due to significant current shunting. In contrast, perpendicularly magnetized tunnel junctions are very promising.

  1. Interface dynamics and anisotropy effects in directional solidification

    NASA Astrophysics Data System (ADS)

    de Cheveigné, S.; Guthmann, C.

    1992-02-01

    A study of the dynamics of the cellular solid-liquid interface in directional solidification of dilute CBr{4} alloy has allowed us to observe a number of secondary instabilities (travelling states, optical modes, anomalous cells, etc.) some of which were well known and traditionally attributed to the effect of crystalline anisotropy. However, most of these instabilities are also observed in a hydrodynamic analog of directional solidification, directional viscous fingering (M. Rabaud, S. Michalland and Y. Couder, Phys. Rev. Lett. 64 (1990) 184). This analogy enables us to discuss the interplay of crystalline anisotropy and of the dynamics generic to one-dimensional systems in directional solidification. Une étude de la dynamique de l'interface cellulaire en solidification directionnelle d'un alliage binaire dilué de CBr4 nous a permis d'observer un certain nombre d'instabilités secondaires (propagation de cellules inclinées, modes optiques, cellules anormales, etc.) dont certaines étaient bien connues et traditionnellement attribuées à des effets de l'anisotropie cristalline. Cependant, la plupart de ces instabilités sont observables dans une expérience qui est l'analogue hydrodynamique de la solidification directionnelle, la digitation visqueuse dirigée ou instabilité de l'imprimeur (M. Rabaud, S. Michalland and Y. Couder, Phys. Rev. Lett. 64 (1990) 184). Cette analogie va nous permettre de discuter les rôles respectifs de l'anisotropie cristalline et de la dynamique propre aux systèmes uni-dimentionnels.

  2. Influence of interface exchange coupling in perpendicular anisotropy [Pt/Co]50/TbFe bilayers

    SciTech Connect

    Mangin, S.; Hauet, T.; Fischer, P.; Kim, D.H.; Kortright, J.B.; Chesnel, K.; Arenholz, E.; Fullerton, Eric E.

    2007-10-10

    We present the magnetization evolution of perpendicular anisotropy TbFe and [Co/Pt]{sub 50} thin films either in direct contact resulting in antiferromagnetic interfacial coupling or separated by a thick Pt layer. Magnetometry and x-ray magnetic circular dichroism spectroscopy determine the spatially averaged magnetic properties. Resonant magnetic x-ray small-angle scattering and magnetic soft X-ray transmission microscopy probed the domain configurations and correlations in the reversal processes. While the Co/Pt multilayer reverses by domain propagation, the TbFe magnetization reversal is found to be dominated either by coherent magnetization reversal processes or by lateral domain formation depending on the interface exchange coupling. In the presence of lateral domains, dipolar field induced domain replication phenomena are observed.

  3. Perpendicular Magnetic Anisotropy and Induced Magnetic Structures of Pt Layers in the Fe/Pt Multilayers Investigated by Resonant X-ray Magnetic Scattering

    NASA Astrophysics Data System (ADS)

    Lee, Mihee; Takechi, Ryota; Hosoito, Nobuyoshi

    2017-02-01

    Depth distribution of the magnetization induced in the paramagnetic Pt layers of Fe/Pt multilayers was investigated by resonant X-ray magnetic scattering (RXMS) near the Pt L3 absorption edge. Two samples with different perpendicular magnetic anisotropy (PMA) were chosen for RXMS measurements. The magnetic depth profile of the Pt layer was determined in the magnetic saturation state of the Fe magnetization with the sample of weak PMA. The magnetization process of the Pt layer was investigated with the sample of moderate PMA. It is found that the Pt atoms near the interface region have a perpendicular component of the induced magnetization even in the saturation state of the Fe magnetization, suggesting that the PMA of Fe/Pt multilayers originates from the Pt atoms near the interface region. Concerning the magnetization process, the induced Pt magnetization is not proportional to the Fe magnetization. This implies a complicated magnetizing mechanism of the Pt layer by the Fe magnetization.

  4. Magnetic anisotropies and magnetotransport in CeH2/Co multilayers

    NASA Astrophysics Data System (ADS)

    Nawrath, T.; Damaske, B.; Schulte, O.; Felsch, W.

    1997-02-01

    Measurements of the magnetization were performed between 4.2 and 300 K on a series of periodically stacked layers of cerium hydride and cobalt prepared by reactive ion-beam sputtering. X-ray reflectometry shows that the interfaces are sharp with a rms roughness of nominally one atomic layer. In the ground state at low temperatures, for Co-layer thicknesses up to 17 Å, the magnetization is spontaneously oriented perpendicular to the layer planes in a multidomain configuration. A phenomenological analysis of the measured magnetic anisotropy energy reveals that the out-of-plane orientation of the magnetic easy axis is the result of a strong interface anisotropy which overcomes the shape anisotropy of the Co layers and of an additional volume anisotropy. Possible mechanisms behind the surface and volume anisotropies are discussed. Between 50 and 100 K, the magnetization turns into the layer planes in a continuous transition. The saturation magnetization, the spin-wave parameter describing its temperature dependence and the anisotropy energy vary continuously through the transition from the crystalline fcc phase to the amorphous phase of the Co sublayers near 20 Å. This reveals the close relationship between the electronic configurations of amorphous and fcc Co. The magnetization measurements are supplemented by measurements of the anisotropic magnetoresistance and the extraordinary Hall effect. The extraordinary Hall coefficient shows contributions from skew scattering and side jump processes and scales with the ordinary electrical resistivity.

  5. Effect of deposition technique of Ni on the perpendicular magnetic anisotropy in Co/Ni multilayers

    NASA Astrophysics Data System (ADS)

    Akbulut, S.; Akbulut, A.; Özdemir, M.; Yildiz, F.

    2015-09-01

    The perpendicular magnetic anisotropy (PMA) of Si/Pt 3.5/(Co 0.3/Ni 0.6)n /Co 0.3/ Pt 3 (all thicknesses are nm) multilayers were investigated for two different sample sets by using ferromagnetic resonance (FMR) and magnetooptic Kerr effect (MOKE) techniques. In the first sample set all layers (buffer, cap, Co and Ni) were grown by magnetron sputtering technique while in the second sample set Ni sub-layers were grown by molecular beam epitaxy (MBE) at high vacuum. Apart from deposition technique of Ni, all other parameters like thicknesses and growth rates of each layers are same for both sample sets. Multilayers in these two sample sets display PMA in the as grown state until a certain value of bilayer repetition (n) and the strength of PMA decreases with increasing n. Magnetic easy axis's of the multilayered samples switched from film normal to the film plane when n is 9 and 5 for the first and second sample sets, respectively. The reason for that, PMA was decreased due to increasing roughness with increasing n. This was confirmed by X Ray Reflectivity (XRR) measurements for both sample sets. Moreover, in the first sample set coercive field values are smaller than the second sample set, which means magnetic anisotropy is lower than the latter one. This stronger PMA is arising due to existence of stronger Pt (111) and Co/Ni (111) textures in the second sample set.

  6. Magnetic tunnel junctions using Co/Ni multilayer electrodes with perpendicular magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Lytvynenko, Ia.; Deranlot, C.; Andrieu, S.; Hauet, T.

    2015-02-01

    Magnetic and magneto-transport properties of amorphous Al2O3-based magnetic tunnel junctions (MTJ) having two Co/Ni multilayer electrodes exhibiting perpendicular magnetic anisotropy (PMA) are presented. An additional Co/Pt multilayer is required to maintain PMA in the top Co/Ni electrode. Slight stacking variations lead to dramatic magnetic changes due to dipolar interactions between the top and bottom electrodes. Tunnel magneto-resistance (TMR) of up to 8% at 300 K is measured for the MTJ with two PMA electrodes. The TMR value increases when the top PMA electrode is replaced by an in-plane magnetized Co layer. These observations can be attributed to significant intermixing in the top Co/Ni electrode.

  7. Microwave-assisted magnetization reversal in a Co/Pd multilayer with perpendicular magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Nozaki, Yukio; Narita, Naoyuki; Tanaka, Terumitsu; Matsuyama, Kimihide

    2009-08-01

    Microwave-assisted magnetization reversal in a rectangle of a Co/Pd multilayer with a perpendicular magnetic anisotropy is examined using vector network analyzer ferromagnetic resonance (FMR) spectroscopy. A microwave field is applied along the in-plane direction of the rectangle together with a negative dc easy-axis field smaller than the coercive field. Broadening or splitting of the peak profile in the FMR spectrum suggesting the formation of multidomain structure appears after the microwave field is applied. The dominance of microwave-assisted nucleation of magnetization is supported by the frequency dependence of the probability with which the multidomain structure appears.

  8. Manipulation of superparamagnetic beads on patterned Au/Co/Au multilayers with perpendicular magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Jarosz, A.; Holzinger, D.; Urbaniak, M.; Ehresmann, A.; Stobiecki, F.

    2016-08-01

    The magnetophoresis of water-suspended 4 μm-diameter superparamagnetic beads above topographically patterned, sputter deposited Ti(4 nm)/Au(60 nm)/[Co(0.7 nm)/Au(1 nm)] × 3 multilayers with perpendicular magnetic anisotropy was investigated. The results impressively demonstrate that the magnetic stray field landscape above the stripe structure when superimposed with an external, slowly rotating, field enables the directed transport of magnetic beads across the stripe panel with velocities up to 12 μm s-1.

  9. Origin of anomalously high exchange field in antiferromagnetically coupled magnetic structures: Spin reorientation versus interface anisotropy

    NASA Astrophysics Data System (ADS)

    Ranjbar, M.; Piramanayagam, S. N.; Wong, S. K.; Sbiaa, R.; Song, W.; Tan, H. K.; Gonzaga, L.; Chong, T. C.

    2011-11-01

    Magnetization reorientation from in-plane to perpendicular direction, observed in Co thin film coupled antiferromagnetically to high perpendicular magnetic anisotropy (Co/Pd) multilayers, is studied systematically for Co thickness ranging from 0 to 2.4 nm. The sample with 0.75 nm thick Co showed an exchange coupling field (Hex) exceeding 15 kOe at room temperature and 17.2 kOe at 5 K. With an increase of Co thickness, Hex decreased as expected and beyond certain thickness, magnetization reorientation was not observed. Indeed, three regions were observed in the thickness dependence of magnetization of the thin layer; one in which the thin layer (in the thickness range up to 0.8 nm) had a perpendicular magnetic anisotropy due to interface effects and antiferromagnetic coupling, another in which the thin layer (0.9-1.2 nm) magnetization had no interface or crystallographic anisotropy but was reoriented in the perpendicular direction due to antiferromagnetic coupling, and the third (above 1.2 nm) in which the magnetization was in-plane. In addition, Hall effect measurements were carried out to observe the anomalous and planar Hall voltages and to quantify the perpendicular and in-plane components of magnetization. The sample with thicker Co layer (2.4 nm) showed an in-plane component of magnetization, whereas the sample with 0.75 nm Co showed no in-plane component. The high value of Hex observed in 0.75 nm Co samples can have important implications in spintronics and bit patterned media.

  10. High-frequency magnetoimpedance in multilayer thin films with longitudinal and transverse anisotropy

    NASA Astrophysics Data System (ADS)

    de Cos, D.; Lepalovskij, V. N.; Kurlyandskaya, G. V.; García-Arribas, A.; Barandiarán, J. M.

    Giant magnetoimpedance (GMI) effect in NiFe (150 nm)/Cu (500 nm)/NiFe (150 nm) multilayers with longitudinal and transverse induced magnetic anisotropy was studied at frequencies of 300 kHz-3 GHz. Several sensitive elements were built in a single "chip" configuration. At low and intermediate frequencies the GMI displays a single peak at zero-field for samples with longitudinal and two peaks for the samples with transverse anisotropy. Above 500 MHz the observed behaviour in both cases can be explained by the apparition of the ferromagnetic resonance (FMR). Regarding the performance of the sample, the maximum GMI sensitivity values achieved in case of longitunal anisotropy are 6%/Oe from the single peak to the saturation field at 500 MHz (quasistatic regime), and 12%/Oe from the FMR peaks to zero-field at 1.12 GHz (dynamic regime). Sensitivity values achieved in case of transverse anisotropy are 31%/Oe from the single peak to the saturation field at 70 MHz and 17%/Oe from the FMR peaks to zero-field at 0.8 GHz. Small variations of GMI ratio and field sensitivity for different sensitive elements built in a single "chip" confirm the possibility to use this design for multi-analyte detector construction.

  11. Perpendicular magnetic anisotropy at transition metal/oxide interfaces and applications

    NASA Astrophysics Data System (ADS)

    Dieny, B.; Chshiev, M.

    2017-04-01

    Spin electronics is a rapidly expanding field stimulated by a strong synergy between breakthrough basic research discoveries and industrial applications in the fields of magnetic recording, magnetic field sensors, nonvolatile memories [magnetic random access memories (MRAM) and especially spin-transfer-torque MRAM (STT-MRAM)]. In addition to the discovery of several physical phenomena (giant magnetoresistance, tunnel magnetoresistance, spin-transfer torque, spin-orbit torque, spin Hall effect, spin Seebeck effect, etc.), outstanding progress has been made on the growth and nanopatterning of magnetic multilayered films and nanostructures in which these phenomena are observed. Magnetic anisotropy is usually observed in materials that have large spin-orbit interactions. However, in 2002 perpendicular magnetic anisotropy (PMA) was discovered to exist at magnetic metal/oxide interfaces [for instance Co (Fe )/alumina ]. Surprisingly, this PMA is observed in systems where spin-orbit interactions are quite weak, but its amplitude is remarkably large—comparable to that measured at Co /Pt interfaces, a reference for large interfacial anisotropy (anisotropy˜1.4 erg /cm2=1.4 mJ /m2 ). Actually, this PMA was found to be very common at magnetic metal/oxide interfaces since it has been observed with a large variety of amorphous or crystalline oxides, including AlOx, MgO, TaOx, HfOx, etc. This PMA is thought to be the result of electronic hybridization between the oxygen and the magnetic transition metal orbit across the interface, a hypothesis supported by ab initio calculations. Interest in this phenomenon was sparked in 2010 when it was demonstrated that the PMA at magnetic transition metal/oxide interfaces could be used to build out-of-plane magnetized magnetic tunnel junctions for STT-MRAM cells. In these systems, the PMA at the CoFeB /MgO interface can be used to simultaneously obtain good memory retention, thanks to the large PMA amplitude, and a low write current

  12. Giant enhancement of the controllable in-plane anisotropy of biased isotropic noncentrosymmetric materials with epsilon-negative multilayers

    NASA Astrophysics Data System (ADS)

    Valagiannopoulos, C. A.; Tsitsas, N. L.; Lakhtakia, A.

    2017-02-01

    Giant in-plane anisotropy can be exhibited by a finitely thick periodic multilayer comprising bilayers of an isotropic noncentrosymmetric material and a non-dissipative isotropic medium of negative permittivity, when a dc electric field is applied in the thickness direction. Compared to a homogeneous layer of the noncentrosymmetric material with the same thickness as the periodic multilayer, the latter exhibits an effective in-plane anisotropy that can be three orders larger in magnitude. This enhancement gets more substantial at higher frequencies and is electrically controllable. The incorporation of dissipation reduces the enhancement of the effective in-plane anisotropy, which nevertheless remains significant. We expect the finitely thick periodic multilayer to be useful as a polarization transformer or a modulator in the terahertz regime fully controllable via external dc bias.

  13. Magnetic tunnel junctions using Co/Pt multilayered free layers with perpendicular magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Machida, K.; Furukawa, K.; Nakayama, T.; Funabashi, N.; Aoshima, K.; Kuga, K.; Kikuchi, H.; Ishibashi, T.; Shimidzu, N.

    2011-07-01

    Co/Pt multilayered films with perpendicular magnetic anisotropy have a large magneto-optical Kerr effect. To use the films with a submicron magneto-optical light modulator driven by spin transfer switching, we fabricated two types of magnetic tunnel junctions (MTJs) with Co/Pt multilayered films for the free layers. One is an fcc-based MTJ, another is a bcc-based MTJ with CoFeB/MgO/CoFeB junction. The fcc-based MTJ with a Ag buffer layer on the bottom electrode showed a large coercive force of the pinned layer, a large Kerr rotation angle of 0.3 degree in the free layer and a tunnel magnetoresistance (TMR) ratio of 3.8%. In the CoFeB/MgO/CoFeB junction, an X-ray diffraction pattern of an MgO layer showed a large MgO(002)-orientation. However, the TMR ratio was less than 3 %. An MTJ with a Ta buffer layer between the CoFeB layer and the Co/Pt multilayered films in the free layer was prepared. The Ta buffer was used to alleviate a lattice mismatch between bcc-CoFeB/MgO/CoFeB and fcc-Co/Pt multilayer. The peak intensity of the MgO(002)-orientation was increased up to 2 times. This result suggests that the crystalline texture of the bcc-CoFeB/MgO/CoFeB junction is strongly influenced by the fcc-Co/Pt multilayered films.

  14. Perpendicular Magnetic Anisotropy in Ultrathin Co/Ni Multilayer Films Studies with Ferromagnetic Resonance and Magnetic X-Ray Microspectroscopy

    DTIC Science & Technology

    2012-06-28

    fields (approx 1 T) the Py magnetization will rotate out of the film plane and may effect the FMR measurement of the Co9Ni multilayer . However, no or...REPORT Perpendicular magnetic anisotropy in ultrathin Co|Ni multilayer films studied with ferromagnetic resonance and magnetic x-ray microspectroscopy...14. ABSTRACT 16. SECURITY CLASSIFICATION OF: Ferromagnetic resonance ( FMR ) spectroscopy, x-ray magnetic circular dichroism (XMCD) spectroscopy and

  15. Tuning the perpendicular magnetic anisotropy of co-based layers in multilayered systems.

    PubMed

    Angelakeris, M; Papaioannou, E Th; Poulopoulos, P; Kopsidis, M; Kalogirou, O; Flevaris, N K

    2010-09-01

    The combination of Pt with Co either in alloy or in multilayer form is widely studied among the potential magnetic media for ultrahigh density magnetic recording. On the other hand the combination of Co with Cr in alloy form is currently providing commercial magnetic media. In an effort to further exploit and benefit from both systems, we fabricated Co(1-x)Cr(x)/Pt multilayers with two adjustable parameters. The first one is the Cr concentration on CoCr layer (x = 0, 5, 30), which modulates segregation effects on Co grains, thus tunes macroscopic magnetic features such as saturation magnetization and coercive field. The second one is the small layer thickness (< or = 0.6 nm) that affects interlayer coupling, perpendicular magnetic anisotropy and magnetization enhancement through spin polarization of Pt atoms in a ferromagnetic environment. The X-ray diffraction patterns verified the existence of multilayered structures following a preferable face-centered-cubic stacking. The Pt thickness and Cr concentration are found to significantly affect the macroscopic magnetic behavior. It is remarkable the fact that, samples present perpendicular anisotropy that scales with Pt thickness and temperature, even in the case of significant Cr concentration (30% in the alloy) when ferromagnetic behavior is expected to diminish according to relevant studies in alloys and in bulk films. Such an effect may be attributed to spin-polarization of Pt interlayers and was evidenced by X-ray magnetic circular dichroism. The spin-polarization of Pt is also the drive for the strong magneto-optic enhancement in the ultra-violet region between 4.5 and 5 eV shown by magnetooptic Kerr spectroscopy.

  16. Catalytic polyelectrolyte multilayers at the bipolar membrane interface.

    PubMed

    Abdu, Said; Sricharoen, Kittikun; Wong, John E; Muljadi, Eko S; Melin, Thomas; Wessling, Matthias

    2013-11-13

    Bipolar membranes are laminated anion and cation exchange membranes that split water at their interface very efficiently upon application of an electric field. This paper investigates the layer-by-layer (LbL) deposition of polyelectrolyte multilayers, as a tool to introduce molecularly thin catalyst groups at this interface of bipolar membranes. The bipolar membranes were prepared by first modifying an anion exchange membrane by consecutive dipping LbL assembly, then casting a thin highly charged intermediate layer followed by casting a cation exchange layer. The results reveal that polyelectrolytes of higher charge density coated on the anion exchange layer yield better performance. Several parameters of the LbL interface deposition were varied. Out of the investigated LbL assembly parameters, ionic strength and number of layers have shown the largest influence on catalytic activity as well as ionic selectivity. The membrane with two bilayers of poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) and poly(ethyleneimine) (PEI), where the PEI was prepared in 0.5 M NaCl, gave rise to the best performance. Surprisingly, detailed data analysis at low electrical potential suggests that the interface layers of a bipolar membrane play a major role in its permselectivity. Previously, only the bulk thickness of the anion and cation exchange membrane was assumed to influence the bipolar membrane selectivity.

  17. Quenching and temperature dependence of perpendicular magnetic anisotropy of Pt/Co multilayers

    NASA Astrophysics Data System (ADS)

    Xu, Yonggang; Zhao, Xiaolin; Lv, Meng; Yu, Guolin; Dai, Ning; Chu, Junhao

    2015-04-01

    Magnetic metallic multilayers separated by nonmagnetic metal films are of great importance in magnetoelectronics and spintronics, due to their capacity of giving rise to giant magneto-resistance as well as the electric field control of ferromagnetism. Co/Pt multilayers are one of the typical platforms that own perpendicular magnetic anisotropy which can be tuned in various ways. Since previous investigations focus on the anomalous Hall(transverse) resistivity which characterizes the magnetization of the multilayers, much less attention has been paid to the longitudinal resistivity. In this work, we find that the longitudinal resistivity also gives rich phenomena that need further theoretical treatment. We have grown two Co/Pt multilayer structures that have different spacings between neighboring ferromagnetic layers. The one with smaller spacing shows a superparamagnetic behavior in its Hall resistivity even at a temperature as low as 1.5 K, but the longitudinal resistivity shows a well established hysteresis. The other sample shows square hysteresis in the Hall resistivity at all available temperatures up to 300 K, while the longitudinal resistivity gives no significant signals because they are mostly engulfed in the noises. The corresponding temperature dependence of the coercive field are also different. While the former gives an approximately exponential function of the temperature T, the latter can be divided to two zones, each of which can be characterized by a lnTs dependence, where s is not necessarily an integer. Such distinct features may be deeply related to the microstructures as well as the magnon scattering, which require further investigations.

  18. 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.

  19. Spin-orbital coupling induced four-fold anisotropy distribution during spin reorientation in ultrathin Co/Pt multilayers

    NASA Astrophysics Data System (ADS)

    Yang, Qu; Wang, Xinjun; Peng, Bin; Li, Chunlei; Zhou, Ziyao; Yan, Yuan; Zhou, Hongtao; Zhang, Yijun; Zhao, Shishun; Ren, Wei; Ye, Zuo-Guang; Sun, Nian X.; Liu, Ming

    2017-01-01

    In this work, we synthesized (Co(t)/Pt)3 multilayers and quantitatively determined thickness and temperature dependence of spin reorientation transition (SRT) and perpendicular magnetic anisotropy (PMA) using ferromagnetic resonance measurement. The critical thickness for PMA switching as well as tremendous magnetic anisotropy change up to 645 Oe once the temperature varies from 25 °C to -153 °C are demonstrated. More interestingly, a four-fold symmetry of magnetic anisotropy was found to be prominent during the SRT. By conducting magnetic simulation with involving high order energy term, we highly related this phenomenon to the strong spin-orbital coupling, which is considered to be the major energy term to tip the balance between the surface anisotropy and shape anisotropy. These results provide an opportunity for better understanding the transition behaviors which is essential for PMA structure preparation and their related devices.

  20. Tailoring of multilayer interfaces by pulsed laser irradiation

    NASA Astrophysics Data System (ADS)

    Luby, S.; Majkova, E.

    2005-07-01

    Multilayers (MLs) consisting of a few nm thick alternating layers of two different materials are broadly used in soft X-ray optics and in giant magnetoresistance (GMR) sensors. The efficiency of ML-based devices depends on the quality and thermal stability of the interfaces, which must be sharp at the nm scale. It is shown that, using heating with excimer laser pulses of 30 ns and fluence of approximately 0.1 J cm -2, the diffusion length for one laser pulse in the above mentioned MLs is in the region of nanometers, i.e. it closely matches the thickness of the ML sublayers. Therefore, pulsed laser induced diffusion can be used for controlled manipulation and tailoring of ML interface properties. Depending on the miscibility or immiscibility of the ML material combinations, the interfaces could be intermixed or even sharpened, which is attributed to the backdiffusion process. These phenomena are demonstrated for various combinations of ML building layers, like W/Si, Co/Ag, Fe/W and Co/W. The experimental samples were analyzed by X-ray reflectivity and X-ray diffuse scattering, combined with TEM.

  1. 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.

  2. Dependence of perpendicular magnetic anisotropy and hall resistivity on Pd-layer thickness in CoSiB/Pd multilayer

    NASA Astrophysics Data System (ADS)

    Jung, Sol; Yim, Haein; Kim, Sung Yong

    2015-08-01

    We investigated the perpendicular magnetic anisotropy and the Hall resistivity of CoSiB/Pd multilayers. The CoSiB/Pd multilayers consisted of CoSiB (7-Å thickness) and Pd (Pd thickness t Pd = 10, 12, 14, 16, 18, and 20 Å), and a CoSiB/Pd bilayer was stacked five times. The coercivity shows oscillating values between tPd = 12 Å and t Pd = 20 Å. The value of the saturation magnetization increased between t Pd = 10 Å and t Pd = 12 Å and then decreased after t Pd = 12 Å. The perpendicular magnetic anisotropy constant depended on the thickness of Pd-layer and the values repeatedly increased and decreased. All CoSiB/Pd multilayers exhibited a positive Hall effect, and the Hall resistivity was not proportional to the magnetic moment.

  3. Control of magnetic domains in Co/Pd multilayered nanowires with perpendicular magnetic anisotropy.

    PubMed

    Noh, Su Jung; Miyamoto, Yasuyoshi; Okuda, Mitsunobu; Hayashi, Naoto; Kim, Young Keun

    2012-01-01

    Magnetic domain wall (DW) motion induced by spin transfer torque in magnetic nanowires is of emerging technological interest for its possible applications in spintronic memory or logic devices. Co/Pd multilayered magnetic nanowires with perpendicular magnetic anisotropy were fabricated on the surfaces of Si wafers by ion-beam sputtering. The nanowires had different sized widths and pinning sites formed by an anodic oxidation method via scanning probe microscopy (SPM) with an MFM tip. The magnetic domain structure was changed by an anodic oxidation method. To discover the current-induced DW motion in the Co/Pd nanowires, we employed micromagnetic modeling based on the Landau-Lifschitz-Gilbert (LLG) equation. The split DW motions and configurations due to the edge effects of pinning site and nanowire appeared.

  4. Angle-dependent X-ray magnetic circular dichroism study of enhanced perpendicular magnetic anisotropy in hybrid [CoO/Pd]2[Co/Pd]7 multilayers

    NASA Astrophysics Data System (ADS)

    Kim, D. H.; Lee, Eunsook; Kim, Hyun Woo; Seong, Seungho; Yang, Seung-Mo; Park, Hae-Soo; Hong, JinPyo; Kim, Younghak; Kim, J.-Y.; Kang, J.-S.

    2017-06-01

    We have investigated the angle-dependent orbital and spin magnetic moments of the [Co/Pd] multilayer (ML) films with intervening CoO layers under annealing by employing angle-dependent soft X-ray magnetic circular dichroism (XMCD). After annealing, the orbital magnetic moments of Co ions are found to be enhanced, with the maximum values along the perpendicular direction of [Co/Pd] ML, providing evidence for the origin of the improved perpendicular magnetic anisotropy (PMA) being the interface spin-orbit coupling. The induced Pd polarization was observed after annealing, demonstrating the strong Co-Pd hybridization arising from the Co-Pd alloy formation near the interface. The angle-dependent coercivity follows the 1 / cosθ behavior, suggesting that the magnetization reversal in the hysteresis curve in [Co/Pd] ML occurs mainly through the pinning mechanism.

  5. 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.

  6. 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.

  7. Tuning the Magnetic Anisotropy at a Molecule-Metal Interface

    NASA Astrophysics Data System (ADS)

    Bairagi, K.; Bellec, A.; Repain, V.; Chacon, C.; Girard, Y.; Garreau, Y.; Lagoute, J.; Rousset, S.; Breitwieser, R.; Hu, Yu-Cheng; Chao, Yen Cheng; Pai, Woei Wu; Li, D.; Smogunov, A.; Barreteau, C.

    2015-06-01

    We demonstrate that a C60 overlayer enhances the perpendicular magnetic anisotropy of a Co thin film, inducing an inverse spin reorientation transition from in plane to out of plane. The driving force is the C60/Co interfacial magnetic anisotropy that we have measured quantitatively in situ as a function of the C60 coverage. Comparison with state-of-the-art ab initio calculations show that this interfacial anisotropy mainly arises from the local hybridization between C60 pz and Co dz2 orbitals. By generalizing these arguments, we also demonstrate that the hybridization of C60 with a Fe(110) surface decreases the perpendicular magnetic anisotropy. These results open the way to tailor the interfacial magnetic anisotropy in organic-material-ferromagnet systems.

  8. Tuning the Magnetic Anisotropy at a Molecule-Metal Interface.

    PubMed

    Bairagi, K; Bellec, A; Repain, V; Chacon, C; Girard, Y; Garreau, Y; Lagoute, J; Rousset, S; Breitwieser, R; Hu, Yu-Cheng; Chao, Yen Cheng; Pai, Woei Wu; Li, D; Smogunov, A; Barreteau, C

    2015-06-19

    We demonstrate that a C(60) overlayer enhances the perpendicular magnetic anisotropy of a Co thin film, inducing an inverse spin reorientation transition from in plane to out of plane. The driving force is the (60)/Co interfacial magnetic anisotropy that we have measured quantitatively in situ as a function of the (60) coverage. Comparison with state-of-the-art ab initio calculations show that this interfacial anisotropy mainly arises from the local hybridization between (60) p(z) and Co d(z(2)) orbitals. By generalizing these arguments, we also demonstrate that the hybridization of (60) with a Fe(110) surface decreases the perpendicular magnetic anisotropy. These results open the way to tailor the interfacial magnetic anisotropy in organic-material-ferromagnet systems.

  9. Ferromagnetic resonance study of Co/Pd/Co/Ni multilayers with perpendicular anisotropy irradiated with helium ions

    SciTech Connect

    Beaujour, J.-M. L.; Kent, A. D.; Tudosa, I.; Ravelosona, D.; Fullerton, E. E.

    2011-02-01

    We present a ferromagnetic resonance (FMR) study of the effect of helium ion irradiation on the magnetic anisotropy, the linewidth and the Gilbert damping of a Co/Ni multilayer coupled to Co/Pd bilayers. The perpendicular magnetic anisotropy decreases linearly with He ion fluence, leading to a transition to in-plane magnetization at a critical fluence of 5x10{sup 14} ions/cm{sup 2}. We find that the damping is nearly independent of fluence but the FMR linewidth at fixed frequency has a maximum near the critical fluence, indicating that the inhomogeneous broadening of the FMR line is a nonmonotonic function of the He ion fluence. Based on an analysis of the angular dependence of the FMR linewidth, the inhomogeneous broadening is associated with spatial variations in the magnitude of the perpendicular magnetic anisotropy. These results demonstrate that ion irradiation may be used to systematically modify the magnetic anisotropy and distribution of magnetic anisotropy parameters of Co/Pd/Co/Ni multilayers for applications and basic physics studies.

  10. Ferromagnetic resonance study of Co/Pd/Co/Ni multilayers with perpendicular anisotropy irradiated with helium ions

    NASA Astrophysics Data System (ADS)

    Beaujour, J.-M. L.; Kent, A. D.; Ravelosona, D.; Tudosa, I.; Fullerton, E. E.

    2011-02-01

    We present a ferromagnetic resonance (FMR) study of the effect of helium ion irradiation on the magnetic anisotropy, the linewidth and the Gilbert damping of a Co/Ni multilayer coupled to Co/Pd bilayers. The perpendicular magnetic anisotropy decreases linearly with He ion fluence, leading to a transition to in-plane magnetization at a critical fluence of 5×1014 ions/cm2. We find that the damping is nearly independent of fluence but the FMR linewidth at fixed frequency has a maximum near the critical fluence, indicating that the inhomogeneous broadening of the FMR line is a nonmonotonic function of the He ion fluence. Based on an analysis of the angular dependence of the FMR linewidth, the inhomogeneous broadening is associated with spatial variations in the magnitude of the perpendicular magnetic anisotropy. These results demonstrate that ion irradiation may be used to systematically modify the magnetic anisotropy and distribution of magnetic anisotropy parameters of Co/Pd/Co/Ni multilayers for applications and basic physics studies.

  11. 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.

  12. Ferromagnetic resonance linewidth and damping in perpendicular-anisotropy magnetic multilayers thin films

    NASA Astrophysics Data System (ADS)

    Beaujour, Jean-Marc

    2010-03-01

    Transition metal ferromagnetic films with perpendicular magnetic anisotropy (PMA) have ferromagnetic resonance (FMR) linewidths that are one order of magnitude larger than soft magnetic materials, such as pure iron (Fe) and permalloy (NiFe) thin films. We have conducted systematic studies of a variety of thin film materials with perpendicular magnetic anisotropy to investigate the origin of the enhanced FMR linewidths, including Ni/Co and CoFeB/Co/Ni multilayers. In Ni/Co multilayers the PMA was systematically reduced by irradiation with Helium ions, leading to a transition from out-of-plane to in-plane easy axis with increasing He ion fluence [1,2]. The FMR linewidth depends linearly on frequency for perpendicular applied fields and increases significantly when the magnetization is rotated into the film plane with an applied in-plane magnetic field. Irradiation of the film with Helium ions decreases the PMA and the distribution of PMA parameters, leading to a large reduction in the FMR linewidth for in-plane magnetization. These results suggest that fluctuations in the PMA lead to a large two magnon scattering contribution to the linewidth for in-plane magnetization and establish that the Gilbert damping is enhanced in such materials (α˜0.04, compared to α˜0.002 for pure Fe) [2]. We compare these results to those on CoFeB/Co/Ni and published results on other thin film materials with PMA [e.g., Ref. 3]. [1] D. Stanescu et al., J. Appl. Phys. 103, 07B529 (2008). [2] J-M. L. Beaujour, D. Ravelosona, I. Tudosa, E. Fullerton, and A. D. Kent, Phys. Rev. B RC 80, 180415 (2009). [3] N. Mo, J. Hohlfeld, M. ulIslam, C. S. Brown, E. Girt, P. Krivosik, W. Tong, A. Rebel, and C. E. Patton, Appl. Phys. Lett. 92, 022506 (2008). *Research done in collaboration with: A. D. Kent, New York University, D. Ravelosona, Institut d'Electronique Fondamentale, UMR CNRS 8622, Universit'e Paris Sud, E. E. Fullerton, Center for Magnetic Recording Research, UCSD, and supported by NSF

  13. Dielectric Anisotropy of the GaP /Si (001 ) Interface from First-Principles Theory

    NASA Astrophysics Data System (ADS)

    Kumar, Pankaj; Patterson, Charles H.

    2017-06-01

    First-principles calculations of the dielectric anisotropy of the GaP /Si (001 ) interface are compared to the anisotropy extracted from reflectance measurements on GaP thin films on Si(001) [O. Supplie et al., Phys. Rev. B 86, 035308 (2012), 10.1103/PhysRevB.86.035308]. Optical excitations from two states localized in several Si layers adjacent to the interface result in the observed anisotropy of the interface. The calculations show excellent agreement with experiment only for a gapped interface with a P layer in contact with Si and show that a combination of theory and experiment can reveal localized electronic states and the atomic structure at buried interfaces.

  14. Multivalent-Counterion-Induced Surfactant Multilayer Formation at Hydrophobic and Hydrophilic Solid-Solution Interfaces.

    PubMed

    Penfold, Jeffrey; Thomas, Robert K; Li, Peixun; Xu, Hui; Tucker, Ian M; Petkov, Jordan T; Sivia, Devinderjit S

    2015-06-23

    Surface multilayer formation from the anionic-nonionic surfactant mixture of sodium dodecyl dioxyethylene sulfate, SLES, and monododecyl dodecaethylene glycol, C12E12, by the addition of multivalent Al(3+) counterions at the solid-solution interface is observed and characterized by neutron reflectivity, NR. The ability to form surface multilayer structures on hydrophobic and hydrophilic silica and cellulose surfaces is demonstrated. The surface multilayer formation is more pronounced and more well developed on the hydrophilic and hydrophobic silica surfaces than on the hydrophilic and hydrophobic cellulose surfaces. The less well developed multilayer formation on the cellulose surfaces is attributed to the greater surface inhomogeneities of the cellulose surface which partially inhibit lateral coherence and growth of the multilayer domains at the surface. The surface multilayer formation is associated with extreme wetting properties and offers the potential for the manipulation of the solid surfaces for enhanced adsorption and control of the wetting behavior.

  15. Electric-Field Modulation of Interface Magnetic Anisotropy and Spin Reorientation Transition in (Co/Pt)3/PMN-PT Heterostructure.

    PubMed

    Sun, Ying; Ba, You; Chen, Aitian; He, Wei; Wang, Wenbo; Zheng, Xiaoli; Zou, Lvkuan; Zhang, Yijun; Yang, Qu; Yan, Lingjia; Feng, Ce; Zhang, Qinghua; Cai, Jianwang; Wu, Weida; Liu, Ming; Gu, Lin; Cheng, Zhaohua; Nan, Ce-Wen; Qiu, Ziqiang; Wu, Yizheng; Li, Jia; Zhao, Yonggang

    2017-03-29

    We report electric-field control of magnetism of (Co/Pt)3 multilayers involving perpendicular magnetic anisotropy with different Co-layer thicknesses grown on Pb(Mg,Nb)O3-PbTiO3 (PMN-PT) FE substrates. For the first time, electric-field control of the interface magnetic anisotropy, which results in the spin reorientation transition, was demonstrated. The electric-field-induced changes of the bulk and interface magnetic anisotropies can be understood by considering the strain-induced change of magnetoelastic energy and weakening of Pt 5d-Co 3d hybridization, respectively. We also demonstrate the role of competition between the applied magnetic field and the electric field in determining the magnetization of the sample with the coexistence phase. Our results demonstrate electric-field control of magnetism by harnessing the strain-mediated coupling in multiferroic heterostructures with perpendicular magnetic anisotropy and are helpful for electric-field modulations of Dzyaloshinskii-Moriya interaction and Rashba effect at interfaces to engineer new functionalities.

  16. Interface-engineered spin-dependent transport in perpendicular Co/Pt multilayers

    NASA Astrophysics Data System (ADS)

    Jiang, Shao-Long; Yang, Guang; Teng, Jiao; Guo, Qi-Xun; Li, Lei-Lei; Yu, Guang-Hua

    2016-11-01

    The improvement of anomalous Hall effect (AHE) has been obtained through the introduction of a Ta metallic layer at the Co/MgO interface in perpendicular [Pt/Co]3/MgO multilayers. It is exhibited that the saturation anomalous Hall resistivity is 42% larger than that in Co/Pt multilayers without Ta insertion. More meaningfully, thermally stable AHE feature is gained in perpendicular [Pt/Co]3/Ta/MgO multilayers despite Co-Pt interdiffusion. The AHE is enhanced for sample [Pt/Co]3/Ta/MgO after annealing, mainly due to the enhancement of the side-jump and intrinsic contributions.

  17. Domain structure and perpendicular magnetic anisotropy in CoFe/Pd multilayers using off-axis electron holography

    NASA Astrophysics Data System (ADS)

    Zhang, Desai; Shaw, Justin M.; Smith, David J.; McCartney, Martha R.

    2015-08-01

    Multilayers of Co90Fe10/Pd with different bilayer thicknesses, have been deposited by dc-magnetron sputtering on thermally oxidized Si wafers. Transmission electron microscopy showed that the highly textured crystalline films had columnar structure, while scanning transmission electron microscopy and atomic force microscopy respectively indicated some layer waviness and surface roughness. The magnetic domain structure and perpendicular magnetic anisotropy (PMA) of the Co90Fe10/Pd multilayers were investigated by off-axis electron holography and magnetic force microscopy. The Co90Fe10 layer thickness was the primary factor determining the magnetic domain size and the perpendicular magnetization: both decreased as the thickness increased. The strongest PMA was observed in the sample with the thinnest magnetic layer of 0.45 nm.

  18. Seed layer impact on structural and magnetic properties of [Co/Ni] multilayers with perpendicular magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Liu, Enlong; Swerts, J.; Devolder, T.; Couet, S.; Mertens, S.; Lin, T.; Spampinato, V.; Franquet, A.; Conard, T.; Van Elshocht, S.; Furnemont, A.; De Boeck, J.; Kar, G.

    2017-01-01

    [Co/Ni] multilayers with perpendicular magnetic anisotropy (PMA) have been researched and applied in various spintronic applications. Typically, the seed layer material is studied to provide the desired face-centered cubic (fcc) texture to the [Co/Ni] to obtain PMA. The integration of [Co/Ni] in back-end-of-line processes also requires the PMA to survive post-annealing. In this paper, the impact of NiCr, Pt, Ru, and Ta seed layers on the structural and magnetic properties of [Co(0.3 nm)/Ni(0.6 nm)] multilayers is investigated before and after annealing. The multilayers were deposited in-situ on different seeds via physical vapor deposition at room temperature. The as-deposited [Co/Ni] films show the required fcc(111) texture on all seeds, but PMA is only observed on Pt and Ru. In-plane magnetic anisotropy is obtained on NiCr and Ta seeds, which is attributed to strain-induced PMA loss. PMA is maintained on all seeds after post-annealing up to 400 °C. The largest effective perpendicular anisotropy energy ( KUeff≈2 ×105 J/m3) after annealing is achieved on the NiCr seed. The evolution of PMA upon annealing cannot be explained by further crystallization during annealing or strain-induced PMA, nor can the observed magnetization loss and the increased damping after annealing. Here, we identify the diffusion of the non-magnetic materials from the seed into [Co/Ni] as the major driver of the changes in the magnetic properties. By selecting the seed and post-annealing temperature, the [Co/Ni] can be tuned in a broad range for both PMA and damping.

  19. Interface induced uniaxial magnetic anisotropy in amorphous CoFeB films on AlGaAs(001).

    PubMed

    Hindmarch, A T; Kinane, C J; MacKenzie, M; Chapman, J N; Henini, M; Taylor, D; Arena, D A; Dvorak, J; Hickey, B J; Marrows, C H

    2008-03-21

    We demonstrate an isolated magnetic interface anisotropy in amorphous CoFeB films on (Al)GaAs(001), similar to that in epitaxial films but without a magnetocrystalline anisotropy term. The direction of the easy axis corresponds to that due to the interfacial interaction proposed for epitaxial films. We show that the anisotropy is determined by the relative orbital component of the atomic magnetic moments. Charge transfer is ruled out as the origin of the interface anisotropy, and it is postulated that the spin-orbit interaction in the semiconductor is crucial in determining the magnetic anisotropy.

  20. Perpendicular magnetic anisotropy and the reorientation transition of the magnetization in CeH2/Fe multilayers probed by x-ray magnetic circular dichroism

    NASA Astrophysics Data System (ADS)

    Arend, M.; Felsch, W.; Krill, G.; Delobbe, A.; Baudelet, F.; Dartyge, E.; Kappler, J.-P.; Finazzi, M.; San Miguel-Fuster, A.; Pizzini, S.; Fontaine, A.

    1999-02-01

    The transition of the magnetization of multilayers [CeH2(x Å)/Fe(16 Å)]×n, x=10, 16, 25, from planar to perpendicular orientation at low temperatures is explained on a microscopic basis by performing angle- and temperature-dependent measurements of x-ray magnetic circular dichroism at the 2p absorption edge of Fe and at the 2p and 3d absorption edges of Ce. The 3d orbital magnetic moment in the Fe sublayers is considerably enhanced with respect to bulk bcc Fe and distinctly larger parallel to the layer normal than perpendicular to it. The Ce 4f states in these structures are well localized. The 4f magnetic moment is oriented along the layer normal due to a strong single-ion anisotropy resulting from crystal-field effects. The spin-split 3d states of Fe induce magnetic order on the Ce 5d states via hybridization and spin-orbit coupling, even on ions more distant from the interface. By intra-atomic 5d-4f exchange coupling the 4f states become magnetically polarized, with increasing strength toward low temperature. Together with the 5d-mediated 4f-3d coupling and the crystal-field induced single-ion 4f anisotropy this leads to a perpendicular orientation of the Fe 3d moment at low temperature. Hence the Ce 4f states are the motor of the reorientation transition of the multilayer magnetization. The 4f-5d exchange interaction in the hydrided Ce sublayers affects dramatically the spectral shape of the dichroic Ce 5d spectra and, at low temperature, the ratio of the integrated signals at the L2 and L3 edges.

  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.

  2. Extreme magnetic anisotropy and multiple superconducting transition signatures in a [Nb(23 nm)/Ni(5 nm)] 5 multilayer

    NASA Astrophysics Data System (ADS)

    De Long, L. E.; Kryukov, S. A.; Joshi, Amish G.; Xu, Wentao; Bosomtwi, A.; Kirby, B. J.; Fitzsimmons, M. R.

    2008-04-01

    We have applied polarized neutron reflectometry, and novel SQUID and vibrating reed magnetometry to probe a [Nb(23 nm)/Ni(5 nm)]5 multilayer (ML) whose superconducting state magnetic anisotropy is dominated by confined (in-plane) supercurrents in DC magnetic fields, H, applied nearly parallel to the ML plane. The upper critical field exhibits abrupt shifts (0.1-0.6 K) in near-parallel fields, but is field-independent for μ0H < 0.8 T when the ML is exactly aligned with the DC field, indicating suppression of orbital pairbreaking and the possible presence of unconventional superconducting pairing states.

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

    SciTech Connect

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

    2016-06-27

    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- B{sub 4}C 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-B{sub 4}C 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. 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.

  5. Phase anisotropy measurements in multilayer dielectric laser mirrors during their manufacture process and corrections introduced in the produced lasers

    NASA Astrophysics Data System (ADS)

    Klochko, Alexander I.; Likholit, Nikolaj I.

    2004-02-01

    In this paper on the basis of the development and manufacture experience of two-mode lasers, i.e. two-frequency laser with linear orthogonal polarizations of generated waves (used in heterodyne interferometry) and four-frequency ring lasers with linear orthogonal mode polarizations (used in differential laser gyros) described and analyzed are: a new measurement and control method of multilayer dielectric mirrors phase anisotropy during the deposition (by analyzing the mirror surface-reflected two-frequency radiation with linear orthogonal components), block diagram of control measurement device based on the two-frequency laser used in the vacuum-evaporation plant as well as a measurement signal shaping algorithm and the proposed measurement method accuracy characteristics. The correction methods of multilayer dielectric mirrors phase anisotropy (and laser orthogonally polarized waves difference beat frequency) used in the manufacture proces of two-mode lasers (linear and ring) are reviewed. At the stage of vacuum technological processing of the laser, soldered to a vacuum-exhaust station (or after its cutting off from the station) a predetermined generated wave beat frequency by using a special SHF mirror processing is achieved as well as mirror phase anisoptropy stabilization and drift decrease of the relevant beat frequency of the orthogonally polarized waves during laser operation is provided.

  6. 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.

  7. Magnetic anisotropy in multilayer nanogranular films (Co40Fe40B20)50(SiO2)50/α-Si:H

    NASA Astrophysics Data System (ADS)

    Denisova, E. A.; Komogortsev, S. V.; Iskhakov, R. S.; Chekanova, L. A.; Balaev, A. D.; Kalinin, Yu. E.; Sitnikov, A. V.

    2017-10-01

    Macroscopic and local magnetic anisotropy of [CoFeB-SiO2/α-Si:H]60 multilayer films was studied in comparison with that for the thick CoFeB-SiO2 granular films. The volume fraction of magnetic component Co40Fe40B20 is ranged from 0.34 to 0.70. In the multilayer films the magnetic layer and silicon spacer thicknesses are 2.5÷4.5 nm and 3.5 nm correspondingly. The magnetization curves and ferromagnetic resonance measurements were used to determining magnetic anisotropy energy constants. The main contribution to the local magnetic anisotropy energy constant is found to be from surface magnetic anisotropy of magnetic granules. It is found that the magnetic percolation point of multilayer films (XC 40) is shifted in comparison with that in granular films (XC 30). Surface magnetic anisotropy energy constants of multilayer films with different X evaluated from the surface modes of spin-wave resonance are in the range 0.5

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

    DOE PAGES

    Burcklen, C.; Soufli, R.; Gullikson, E.; ...

    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

  9. 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.

  10. Cr/B{sub 4}C multilayer mirrors: Study of interfaces and X-ray reflectance

    SciTech Connect

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

    2016-03-28

    We present an experimental study of the effect of layer interfaces on the x-ray reflectance in Cr/B{sub 4}C 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 B{sub 4}C-on-Cr interface, which we modeled with a 1–1.5 nm thick interfacial layer. Reflectance measurements in the vicinity of the Cr L{sub 2,3} absorption edge demonstrate fine structure that is not predicted by simulations using the currently tabulated refractive index (optical constants) values for Cr.

  11. Effect of oxygen migration on magnetic anisotropy and damping constant in perpendicular Ta/CoFeB/Gd/MgO/Ta multilayers

    NASA Astrophysics Data System (ADS)

    Yang, Guang; Zhang, Jing-Yan; Jiang, Shao-Long; Dong, Bo-Wen; Wang, Shou-Guo; Liu, Jia-Long; Zhao, Yun-Chi; Wang, Chao; Sun, Young; Yu, Guang-Hua

    2017-02-01

    By inserting a Gd layer with strong oxygen-affinitive property, the effect of interfacial oxygen migration on the perpendicular magnetic anisotropy (PMA) and damping constant was investigated in perpendicular Ta/CoFeB/Gd/MgO/Ta multilayers. The overoxidation of CoFeB was greatly suppressed by inserting a thin Gd layer at CoFeB/MgO interface, leading to an O-poor status at interface. Different oxygen migration behavior in samples without and with Gd was observed during the thermal annealing. By optimizing Gd thickness, the effective damping constant of 0.029 and 0.037 was obtained with 0.6 nm Gd layer in out-of-plane and in-plane configuration, respectively. This value was decreased by 70% and 46% with respect to that without Gd layer. More importantly, the PMA can be well maintained when Gd thickness was increased to 1.2 nm. This effective modification of magnetic properties based on oxygen migration provides a promising pathway for spintronic applications.

  12. Dispersive effects on the multi-layer porous media flows with permeable and impermeable interfaces

    NASA Astrophysics Data System (ADS)

    Daripa, Prabir; Gin, Craig

    2016-11-01

    We investigate dispersive effects on the linear stability of multi-layer porous media flow models of enhanced oil recovery for two different types of interfaces: permeable and impermeable interfaces. Results presented are relevant for the design of smarter interfaces in the available parameter space of Capillary number, Peclet number, longitudinal and transverse dispersion and the viscous profile of the middle layer. The stabilization capacity of each of these two interfaces is explored numerically and conditions for complete dispersive stabilization are identified for each of these two types of interfaces. Several key results will be presented including our finding that for most values of the flow parameters, permeable interfaces suppress flow instability more than impermeable interfaces. Time permitting, full simulation results will also be presented. NSF Grant # DMS-1522782 and QNRF NPRP Grant 08-777-1-141.

  13. First-principles investigation of magnetocrystalline anisotropy at the L 21 full Heusler |MgO interfaces and tunnel junctions

    NASA Astrophysics Data System (ADS)

    Vadapoo, Rajasekarakumar; Hallal, Ali; Yang, Hongxin; Chshiev, Mairbek

    2016-09-01

    Magnetocrystalline anisotropy at Heusler alloy |MgO interfaces has been studied using first-principles calculations. It has been found that Co-terminated Co2FeAl |MgO interfaces show perpendicular magnetic anisotropy up to 1.31 mJ/m2, while those with FeAl termination exhibit in-plane magnetic anisotropy. Atomic layer-resolved analysis indicates that the origin of perpendicular magnetic anisotropy in Co2FeAl |MgO interfaces can be attributed to the out-of-plane orbital contributions of interfacial Co atoms. At the same time, Co2MnGe and Co2MnSi interfaced with MgO tend to favor in-plane magnetic anisotropy for all terminations.

  14. Magnetic Ultrathin Films: Multilayers and Surfaces, Interfaces and Characterization

    DTIC Science & Technology

    1993-04-01

    deduce for fields near the cusp field HIiI iL S... """ :• 2" 7 4..... 126 J1 + 2J2 =- -- d •2 (6) 2KI( (HI - -Il where b2 - (7) and 2A/Ms 2KI1 (H I + M s...with minimal cost in anisotropy and exchange energy. This effect of spin-reorientation as the temperature is swept through the bulk Curie temperature is...University, Department of Physics and Astronomy, Baltimore , Maryland 21218 In the study of thin films and surfaces as well as the examination of superlattices

  15. Roles of L10 ordering in controlling the magnetic anisotropy and coercivity of (111)-oriented CoPt ultrathin continuous layers in CoPt/AlN multilayer films

    NASA Astrophysics Data System (ADS)

    Cai, Wupeng; Shi, Ji; Nakamura, Yoshio; Liu, Wei; Yu, Ronghai

    2011-10-01

    Chemical ordering of (111)-oriented CoPt ultrathin continuous layers in CoPt/AlN multilayer structure has been investigated. It is found that upon thermal annealing at 600 °C, CoPt layers undergo ordering transformation even when the CoPt layers are as thin as 2 nm. The degree of ordering increases with increasing the layer thickness. For the 600 °C annealed CoPt/AlN multilayer film with 2 nm thick CoPt layers, due to the ordering, out-of-plane coercivity is increased to 3330 Oe, while large perpendicular magnetic anisotropy constant of 8.1 × 106 erg/cm3 is exhibited. These coercivity and anisotropy energy are appropriate for the practical use as magnetic recording media. It is clear that for such a structure, ordering transformation does not impair the perpendicular magnetic anisotropy induced by the interface and magnetoelastic effects. The easy axis of magnetization still lies in the layer normal direction, i.e., [111] direction, although for L10 structure it is supposed to lie in the [001] direction. But L10 ordering does contribute to the enhancement of coercivity.

  16. 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.

  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

    2016-05-24

    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.

  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. Formation of Magnetic Anisotropy by Lithography

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    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.

  20. 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.

  1. Anisotropy and roughness of the solid-liquid interface of BCC Fe.

    PubMed

    Sun, Yongli; Wu, Yongquan; Lu, Xiuming; Li, Rong; Xiao, Junjiang

    2015-02-01

    Melting point T m and kinetic coefficient μ (a proportional constant between the interfacial velocity ν and undercooling ΔT), along with the structural roughness of the solid-liquid interface for body centered cubic (BCC) Fe were calculated by molecular dynamics (MD) simulation. All simulations applied the Sutton-Chen potential, and adopted average bond orientational order (ABOO) parameters together with Voronoi polyhedron method to characterize atomic structure and calculate atomic volume. Anisotropy of T m was found through about 20~40 K decreasing from [100] to [110] and continuously to [111]. Anisotropy of μ with three low index orientations was found as: μ s,[100] > > μ s,[110] > μ s,[111] for solidifying process and μ m,[100] > > μ m,[111] > μ m,[110] for melting process. Slight asymmetry between melting and solidifying was discovered from that the ratios of μ m/μ s are all slightly larger than 1. To explain these, interfacial roughness R int and area ratio S/S 0 (ratio of realistic interfacial area S and the ideal flat cross-sectional area S 0) were defined to verify the anisotropy of interfacial roughness under different supercoolings/superheatings. The results indicated interfacial roughness anisotropies were approximately [100] > [111] > [110]; the interface in melting process is rougher than that in solidifying process; asymmetry of interfacial roughness was larger when temperature deviation ΔT was larger. Anisotropy and asymmetry of interfacial roughness fitted the case of kinetic coefficient μ very well, which could give some explanations to the anisotropies of T m and μ.

  2. 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.

  3. Effect of the number of interfaces on the magnetic properties of [SnO2/Cu-Zn ferrite] multilayer

    NASA Astrophysics Data System (ADS)

    Saipriya, S.; Kurian, Joji; Singh, R.

    2012-04-01

    The [SnO2/Cu-Zn ferrite (CZF)]n (n = 5, 10, 15, and 20) multilayer (ML) were deposited by rf-magnetron sputtering to study their magnetic properties. The magnetization and ferromagnetic resonance (FMR) measurements were undertaken to understand the effect of interfaces on the magnetic properties of these ML. FMR signal line shape changes from asymmetric to symmetric as n increases. The FMR signal peak to peak intensity, FMR linewidth, effective and saturation magnetization and coercivity exhibit oscillations as a function of n. In the parallel configuration the resonance field increases with increase in n, presumably due to the decrease in the active layer to dead layer thickness ratio. The interlayer coupling is strong in the ML with n = 5 leading to the formation of spin waves. The ML interlayer coupling and anisotropy decreases with increasing n. The oscillatory behavior of the magnetic properties can be ascribed to the nonmonotonic variations in the structure and the geometry of the interfaces.

  4. High frequency characteristics of NiO/(FeCo/NiO) 10 multilayers with exchange anisotropy

    NASA Astrophysics Data System (ADS)

    Chen, Jihong; Tang, Dongming; Li, Yuwei; Zhang, Baoshan; Yang, Yi; Lu, Mu; Lu, Huaixian

    2010-10-01

    [NiO/Fe 65Co 35] 10 exchange-coupled multilayer films for high frequency applications are fabricated, and their static magnetic property and microwave permeability are studied systematically. Both exchange bias field and ferromagnetic resonance frequency of the multilayers increase with decreasing Fe 65Co 35 thickness, which means that the microwave properties such as permeability and FMR frequency can be controlled by changing Fe 65Co 35 thickness in the exchange-coupled films. Ferromagnetic resonance frequencies beyond 7 GHz of the films are measured and reported for the first time.

  5. Thermally enhanced perpendicular magnetic anisotropy behaviors of ultrathin [Co/Pd]n multilayers via NiOx capping layer

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    We report the enhanced perpendicular magnetic anisotropy (PMA) features of ultrathin [Co/Pd]3 multilayers (MLs) employing a NiOx insertion layer at high annealing temperatures. Thermally enhanced PMA in [Co/Pd]3/NiOx (capping layer) MLs were achieved at a specific capping layer thickness, while no PMA responses were observed for a NiOx (buffer layer)/[Co/Pd]3 ML, regardless of NiOx thickness. X-ray diffraction observations, including rocking curves, identified the relatively different crystalline characteristics of the NiOx capping and buffer layers. Origin of the enhanced PMAs of [Co/Pd]3 MLs containing a NiOx capping layer is described based on the NiOx capping effect possibly providing additional Co/Oxide i-PMA under high-temperature annealing.

  6. Precise in situ etch depth control of multilayered III−V semiconductor samples with reflectance anisotropy spectroscopy (RAS) equipment

    PubMed Central

    Kleinschmidt, Ann-Kathrin; Barzen, Lars; Strassner, Johannes; Doering, Christoph; Bock, Wolfgang; Wahl, Michael; Kopnarski, Michael

    2016-01-01

    Reflectance anisotropy spectroscopy (RAS) equipment is applied to monitor dry-etch processes (here specifically reactive ion etching (RIE)) of monocrystalline multilayered III–V semiconductors in situ. The related accuracy of etch depth control is better than 16 nm. Comparison with results of secondary ion mass spectrometry (SIMS) reveals a deviation of only about 4 nm in optimal cases. To illustrate the applicability of the reported method in every day settings for the first time the highly etch depth sensitive lithographic process to form a film lens on the waveguide ridge of a broad area laser (BAL) is presented. This example elucidates the benefits of the method in semiconductor device fabrication and also suggests how to fulfill design requirements for the sample in order to make RAS control possible. PMID:28144528

  7. 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/B4C) 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-B4C) and conjugate-component (Ru-C and Cu-C) multilayers on the normal incidence reflectance and long term stability of the mirrors are presented.

  8. 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.

  9. Electronic effects at interfaces in Cu - Cr, Mo, Ta, Re Multilayers

    SciTech Connect

    Barbee, T W; Bello, A F; Klepeis, J E; Van Buuren, T

    1999-06-28

    In this study we characterize electronic effects in short-period ({approx}20 {angstrom}) metallic multilayer films in which 40% of the atoms are at an interface using near-edge (L{sub 3,2}) x-ray absorption. This study investigates Cu/TM where TM = Cr, MO, W, Ta, Re. These immiscible elemental pairs are ideal to study as they form no compounds and exhibit terminal solid solubility. An interest in the charge transfer between elements in alloys and compounds has led to studies using x-ray absorption as described above. Near edge x-ray absorption fine structure (NEXAFS), a technique used for analyzing x-ray absorption near the absorption edge of the element, is especially suited to study the amount of unoccupied states in the conduction band of a metal. The d-metals spectra show large peaks at the absorption edges called ''white lines.'' These are due to the unoccupied d-states just above the Fermi level in these metals. A study of the white lines in the 3d metals show that as the d-band is increasingly occupied the white lines decrease in intensity. Starting with Ti (3d{sup 2} 4s{sup 2}), which has an almost empty d-band and shows strong white lines, the white-line intensities decrease across the Periodic Chart to Cu (3d{sup 10} 4s{sup 1}), which has a full d-band and no white lines. Systematic measurement of the L{sub 3,2} absorption spectra of bulk elemental Cu and Cu in the Cu/TM multilayers enabled measurement of the charge transfer. NEXAFS on metallic multilayers has received less attention than alloys because of the difficulty in synthesizing multilayers with controllability up to the monolayer level and because there is little difference between the signal from the bulk and from longer period (> 30 {angstrom}) multilayers. For high-quality short period multilayers, however, the difference is clear. This is highlighted in a study of short period Co/Cu multilayers, where the electronic density of states of Cu in Cu/Co greatly differed from that of bulk Cu. The

  10. Spin dynamics and magnetic anisotropies at the Fe/GaAs(001) interface

    SciTech Connect

    Kardasz, B.; Montoya, E. A.; Eyrich, C.; Girt, E.; Heinrich, B.

    2011-04-01

    20Au/(d)Fe/GaAs(001) structures were deposited using molecular beam epitaxy, where Fe thickness d = (5...90) atomic layers. Interface anisotropies were investigated using the in-plane angular dependence of ferromagnetic resonance (FMR). Intrinsic and extrinsic contributions to magnetic damping were investigated using FMR linewidth ({Delta}H) measurements at 9, 24, 36, and 72 GHz (in-plane configuration) and 9, 24, and 36 GHz (perpendicular configuration). The in-plane cubic and uniaxial perpendicular anisotropies were well described by the bulk and interface contributions indicating that the Fe films have a high lattice coherence and high critical Curie temperature T{sub c}. The in-plane uniaxial anisotropy is more complex and will be discussed in detail. The frequency dependence of {Delta}H(f) was analyzed using the Gilbert damping, two magnon scattering, and long range magnetic inhomogeneity contributions. The thickness dependence of the Gilbert damping parameter {alpha} was found to be well described by the bulk and interface terms.

  11. Hetero interface and twin boundary mediated strengthening in nano-twinned Cu//Ag multilayered materials.

    PubMed

    Zheng, Yonggang; Li, Qian; Zhang, Jiayong; Ye, Hongfei; Zhang, Hongwu; Shen, Luming

    2017-10-13

    Based on molecular dynamics simulations, tensile mechanical properties and plastic deformation mechanisms of nano-twinned Cu//Ag multilayered materials are investigated in this work. Simulation results show that, due to the stronger strengthening effect of the twin boundary than both the cube-on-cube and hetero-twin interfaces between Cu and Ag layers, the strength increases with the increase of layer thickness for nano-twinned Cu//Ag multilayered materials with a constant twin spacing, while it decreases with the increase of layer thickness for twin-free ones. The strength of hetero-twin multilayered materials is higher than that of the cube-on-cube samples due to the different hetero interfacial configurations. The confined layer slip of dislocation is found to be the dominant plastic deformation mechanism for twin-free hetero-twin multilayered materials and the strength versus twin spacing in nano-twinned samples follows the conventional Hall-Petch relationship. These findings will shed light on the understanding of the plastic deformation mechanisms and the fabrication of high strength nano-twinned multilayered metallic materials.

  12. Hetero interface and twin boundary mediated strengthening in nano-twinned Cu//Ag multilayered materials

    NASA Astrophysics Data System (ADS)

    Zheng, Yonggang; Li, Qian; Zhang, Jiayong; Ye, Hongfei; Zhang, Hongwu; Shen, Luming

    2017-10-01

    Based on molecular dynamics simulations, tensile mechanical properties and plastic deformation mechanisms of nano-twinned Cu//Ag multilayered materials are investigated in this work. Simulation results show that, due to the stronger strengthening effect of the twin boundary than both the cube-on-cube and hetero-twin interfaces between Cu and Ag layers, the strength increases with the increase of layer thickness for nano-twinned Cu//Ag multilayered materials with a constant twin spacing, while it decreases with the increase of layer thickness for twin-free ones. The strength of hetero-twin multilayered materials is higher than that of the cube-on-cube samples due to the different hetero interfacial configurations. The confined layer slip of dislocation is found to be the dominant plastic deformation mechanism for twin-free hetero-twin multilayered materials and the strength versus twin spacing in nano-twinned samples follows the conventional Hall–Petch relationship. These findings will shed light on the understanding of the plastic deformation mechanisms and the fabrication of high strength nano-twinned multilayered metallic materials.

  13. 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.

  14. 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%.

  15. Ultrahigh Energy Storage Performance of Lead-Free Oxide Multilayer Film Capacitors via Interface Engineering.

    PubMed

    Sun, Zixiong; Ma, Chunrui; Liu, Ming; Cui, Jin; Lu, Lu; Lu, Jiangbo; Lou, Xiaojie; Jin, Lei; Wang, Hong; Jia, Chun-Lin

    2017-02-01

    Ultrahigh energy storage density of 52.4 J cm(-3) with optimistic efficiency of 72.3% is achieved by interface engineering of epitaxial lead-free oxide multilayers at room temperature. Moreover, the excellent thermal stability of the performances provides solid basis for widespread applications of the thin film systems in modern electronic and power modules in harsh working environments. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Effect of dry air on interface smoothening in reactive sputter deposited Co/Ti multilayer

    NASA Astrophysics Data System (ADS)

    Biswas, A.; Porwal, A.; Bhattacharya, Debarati; Prajapat, C. L.; Ghosh, Arnab; Nand, Mangla; Nayak, C.; Rai, S.; Jha, S. N.; Singh, M. R.; Bhattacharyya, D.; Basu, S.; Sahoo, N. K.

    2017-09-01

    Top surface roughness and interface roughness are one of the key elements which determine the performance of X-ray and neutron thin film multilayer devices. It has been observed that by mixing air with argon in sputtering ambience during deposition of Co layers, polarized neutron reflectivity (PNR) of Co/Ti supermirror polarizers can be improved substantially. Cross-sectional HRTEM measurement reveals that sharper interfaces in the supermirror can be achieved in case of deposition of the multilayer under mixed ambience of argon and air. In order to investigate this interface modification mechanism further, in this communication two sets of tri-layer Co/Ti/Co samples and 20-layer Co/Ti periodic multilayer samples have been prepared; in one set all the layers are deposited only under argon ambience and in the other set, Co layers are deposited under a mixed ambience of argon and air. These samples have been characterized by measuring specular and non-specular X-ray reflectivities (GIXR) with X-rays of 1.54 Å wavelength and polarized neutron reflectivity (PNR) with neutron of 2.5 Å wavelength at grazing angle of incidence. It has been observed that the X-ray and neutron specular reflectivities at Bragg peaks of 20 layer periodic multilayer increase when Co layers are deposited under mixed ambience of argon and air. The detail information regarding the effect of air on the interfaces and magnetic properties has been obtained by fitting the measured spectra. The above information has subsequently been supplemented by XRD and magnetic measurements on the samples. XPS and XANES measurements have also been carried out to investigate whether cobalt oxide or cobalt nitride layers are being formed due to use of air in sputtering ambience.

  17. Role of varying interface conditions on the eddy current response from cracks in multilayer structures

    NASA Astrophysics Data System (ADS)

    Cherry, Aaron; Knopp, Jeremy; Aldrin, John C.; Sabbagh, Harold A.; Boehnlein, Thomas; Mooers, Ryan

    2013-01-01

    There is a need to improve the understanding of the role of interface conditions on eddy current inspections for cracks in multilayer aircraft structures. This paper presents initial experimental and simulated results studying the influence of gaps and contact conditions between two plates with a notch in the second layer. Simulations show an amplification of the eddy current signal for a subsurface notch adjacent to an air gap as opposed to a submerged notch in a solid plate.

  18. Interface-induced anisotropy and the nematic glass/gel state in jammed aqueous Laponite suspensions.

    PubMed

    Shahin, A; Joshi, Yogesh M; Ramakrishna, S Anantha

    2011-12-06

    Aqueous suspensions of Laponite, a system composed of disklike nanoparticles, are found to develop optical birefringence over several days, well after the suspensions solidified because of jamming. The optical anisotropy is particularly enhanced near the air-Laponite suspension interface over length scales of several millimeters, which is beyond 5 orders of magnitude larger than the particle length scale, suggestive of large-scale ordering influenced by the interface. The orientational order increases with time and is always greater for higher concentration of salt, higher concentration of Laponite, and higher temperatures of the suspension. Although weakly birefringent, Laponite suspensions covered by paraffin oil do not show any enhancement in optical anisotropy near the interface compared to that in the bulk. We suggest that the expedited structure formation near the air interface propagating progressively inside the sample is responsible for the observed behavior. We discuss the observed nematic ordering in the context of glass-like and gel-like microstructure associated with aqueous Laponite suspensions.

  19. Magnetic field induced chirality in Ho/Y multilayers with gradually decreasing anisotropy

    NASA Astrophysics Data System (ADS)

    Tarnavich, V.; Tartakovskaya, E.; Chetverikov, Yu.; Golub, V.; Lott, D.; Chernenkov, Yu.; Devishvili, A.; Ukleev, V.; Kapaklis, V.; Oleshkevych, A.; Fedorov, V.; Bairamukov, V.; Vorobiev, A.; Grigoriev, S.

    2017-07-01

    Metal rare-earth magnetic/nonmagnetic Ho/Y superlattice structures possess a coherent spin helix propagating through many superlattice layer repetitions. An external magnetic field applied in the film plane induces a nonzero average chirality of the helices. It is shown that the direction of the applied in-plane field can modify the value and sign of the chirality parameter γ . The dependence of γ on the relative angle of applied field during the field-cooling procedure has an oscillatory character and can be described by simple sinusoidal function with π periodicity. The experimental finding is discussed from the point of view of an interbalance between Zeeman energy, magnetocrystalline anisotropy, and induced uniaxial anisotropy.

  20. Topological defects and misfit strain in magnetic stripe domains of lateral multilayers with perpendicular magnetic anisotropy.

    PubMed

    Hierro-Rodriguez, A; Cid, R; Vélez, M; Rodriguez-Rodriguez, G; Martín, J I; Álvarez-Prado, L M; Alameda, J M

    2012-09-14

    Stripe domains are studied in perpendicular magnetic anisotropy films nanostructured with a periodic thickness modulation that induces the lateral modulation of both stripe periods and in-plane magnetization. The resulting system is the 2D equivalent of a strained superlattice with properties controlled by interfacial misfit strain within the magnetic stripe structure and shape anisotropy. This allows us to observe, experimentally for the first time, the continuous structural transformation of a grain boundary in this 2D magnetic crystal in the whole angular range. The magnetization reversal process can be tailored through the effect of misfit strain due to the coupling between disclinations in the magnetic stripe pattern and domain walls in the in-plane magnetization configuration.

  1. Nonlinear electric field effect on perpendicular magnetic anisotropy in Fe/MgO interfaces

    NASA Astrophysics Data System (ADS)

    Xiang, Qingyi; Wen, Zhenchao; Sukegawa, Hiroaki; Kasai, Shinya; Seki, Takeshi; Kubota, Takahide; Takanashi, Koki; Mitani, Seiji

    2017-10-01

    The electric field effect on magnetic anisotropy was studied in an ultrathin Fe(0 0 1) monocrystalline layer sandwiched between Cr buffer and MgO tunnel barrier layers, mainly through post-annealing temperature and measurement temperature dependences. A large coefficient of the electric field effect of more than 200 fJ (Vm)‑1 was observed in the negative range of electric field, as well as an areal energy density of perpendicular magnetic anisotropy (PMA) of around 600 µJ m‑2. More interestingly, nonlinear behavior, giving rise to a local minimum around  +100 mV nm‑1, was observed in the electric field dependence of magnetic anisotropy, being independent of the post-annealing and measurement temperatures. The insensitivity to both the interface conditions and the temperature of the system suggests that the nonlinear behavior is attributed to an intrinsic origin such as an inherent electronic structure in the Fe/MgO interface. The present study can contribute to the progress in theoretical studies, such as ab initio calculations, on the mechanism of the electric field effect on PMA.

  2. Multilayering of Surfactant Systems at the Air-Dilute Aqueous Solution Interface.

    PubMed

    Thomas, Robert K; Penfold, Jeffrey

    2015-07-14

    In the last 15 years there have been a number of observations of surfactants adsorbed at the air-water interface with structures more complicated than the expected single monolayer. These observations, mostly made by neutron or X-ray reflectivity, show structures varying from the usual monolayer to monolayer plus one or two additional bilayers to multilayer adsorption at the surface. These observations have been assembled in this article with a view to finding some common features between the very different systems and to relating them to aspects of the bulk solution phase behavior. It is argued that multilayering is primarily associated with wetting or prewetting of the air-water interface by phases in the bulk system, whose structures depend on an overall attractive force between the constituent units. Two such phases, whose formation is assumed to be partially driven by strong specific ion binding, are a concentrated lamellar phase that forms at low concentrations and a swollen lamellar phase that is not space-filling. Multilayering phenomena at the air-water interface then offer a delicate and easy means of studying the finer details of the incompletely understood attraction that leads to these two phases, as well as an interesting new means of self-assembling surface structures. In addition, multilayering is often associated with unusual wetting characteristics. Examples of systems discussed, and in some cases their bulk phase behavior, include surfactants with multivalent metal counterions, surfactants with oligomers and polymers, surfactant with hydrophobin, dichain surfactants, lung surfactant, and the unusual system of ethanolamine and stearic acid. Two situations where the air-water surface is deliberately held out of equilibrium are also assessed for features in common with the steady-state/equilibrium observations.

  3. Effect of annealing on the magnetic tunnel junction with Co/Pt perpendicular anisotropy ferromagnetic multilayers

    NASA Astrophysics Data System (ADS)

    Wang, Yi.; Wang, W. X.; Wei, H. X.; Zhang, B. S.; Zhan, W. S.; Han, X. F.

    2010-05-01

    Perpendicular magnetic tunnel junctions (pMTJs) with tunneling magnetoresistance (TMR) as high as 14.7% at room temperature were fabricated. The continuous film and pMTJs with Co/Pt multilayer magnetic electrodes and AlOx tunnel barrier were annealed at different temperatures and the effect of annealing on their properties was investigated. The hysteresis loops and X-ray reflectivity measurement show that the interdiffusion of Co and Pt atoms is slight when annealed below 523 K. However, the patterned magnetic tunnel junction gets TMR ratio from 12.3% to the maximum value of 14.7% after annealing at 483 K for 1 h.

  4. Anisotropy of the optical and magneto-optical response of Au/Co/Au/Cu multilayers grown on vicinal Si (111) surfaces

    NASA Astrophysics Data System (ADS)

    Cheikh-Rouhou, W.; Sampaio, L. C.; Bartenlian, B.; Beauvillain, P.; Brun, A.; Ferré, J.; Georges, P.; Jamet, J.-P.; Mathet, V.; Stupakewicz, A.

    2002-05-01

    The optical and magneto-optical second harmonic reflectivity response of Au/Co/Au/Cu multilayers grown on vicinal Si (111) substrates has been studied. These azimuthal optical non-linear experiments check the uniaxial character of the crystallinity of the Au buffer layer and the magnetic behavior of the ultrathin Co films in the metallic multilayer. They clearly show the strong dependence of the growth parameters and the misorientation of the vicinal surface on the SHG reflectivity signals. This uniaxial behavior is also correlated to linear MOKE experiments on the magnetic anisotropy with an easy magnetization axis parallel to the step edges.

  5. 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

    2015-12-09

    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.

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

    PubMed

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

    2015-10-12

    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.

  7. 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

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

    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.

  9. Domain wall motion in ultrathin Co70Fe30/Pd multilayer nanowires with perpendicular anisotropy

    NASA Astrophysics Data System (ADS)

    Meng, Zhaoliang; He, Shikun; Qiu, Jinjun; Zhou, Tiejun; Han, Guchang; Teo, Kie-Leong

    2016-02-01

    We report the investigation of spin polarized current induced domain wall (DW) displacement in the perpendicularly magnetized nanowires patterned on ultrathin CoFe/Pd multilayer films by anomalous Hall-effect measurement. We find that DWs can be driven to propagate in the nanowire by the threshold current density (Jth) as low as 5.2 × 1010 A/m2 under a bias field H = 115 Oe. The spin-torque efficiency ɛ = (1.68 ± 0.09) × 10-14 T.m2/A is derived by measuring the effective field (HJ) generated by the pulsed current as well as through the dependency of Jth on H from the DW depinning field experiment. Our result indicates that the current induced DW motion is essentially dominated by the non-adiabatic spin transfer torque effect and the non-adiabaticity factor β is estimated to be as high as 0.96 ± 0.04.

  10. Dependence of interface roughness and diffuseness of Cu-Co electrodeposited multilayers on electrochemical additives

    NASA Astrophysics Data System (ADS)

    Merkourakis, Spyridon; Hÿtch, Martin J.; Chassaing, Elisabeth; Walls, Michael G.; Leprince-Wang, Yamin

    2003-09-01

    We examine the effect of two organic additives, sds and saccharin, and also the effect of the solution pH on the interface properties of Cu/Co nanolayers, produced by pulsed electrodeposition from a single aqueous bath. Quantitative Fresnel fringe transmission electron microscopy is applied to cross-sectional samples of the layers. The widths of their respective interfaces as well as the widths of individual Cu and Co layers are determined via comparison with computer simulations. These initial results are further numerically treated to yield information about the separate contributions of interdiffusion and roughness to total interface widths. Conclusions on the behavior of these organic additives are considered in the light of the giant magnetoresistance properties of the multilayers, as reported in previous work.

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

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

    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.

  12. 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.

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

    NASA Astrophysics Data System (ADS)

    Młyńczak, E.; Luches, P.; Valeri, S.; Korecki, J.

    2013-06-01

    The magnetic and structural properties of NiO/Fe epitaxial bilayers grown on MgO(001) were studied using magnetooptic Kerr effect (MOKE) and conversion electron Mössbauer 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 57Fe-CEMS. An iron oxide phase (Fe3+4Fe2+1O7), as thick as 31 Å, 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.

  14. 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.

  15. 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.

  16. 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.

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

    NASA Astrophysics Data System (ADS)

    Tan, Aik Jun; Bauer, Uwe; Beach, Geoffrey; Beach Group Team

    2015-03-01

    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, but these changes required elevated temperature and a voltage dwell time on the order of minutes. Here, we examine magneto-ionic switching in ultrathin Co/GdOx films with perpendicular anisotropy, in which the the GdOx gate dielectric acts as an oxygen ion conductor. We examine the switching efficiency as a function of GdOx layer thickness and electrode geometry, and show that the voltage, operating temperature, and switching timescale can be significantly reduced by optimizing the GdOx thickness and defect structure. We demonstrate reversible toggling of magnetic properties for >50 cycles, and correlate the magnetic switching behavior with changes in the electrical properties of the GdOx.

  18. 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.

  19. 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.

  20. Employing soft x-ray resonant magnetic scattering to study domain sizes and anisotropy in Co/Pd multilayers

    NASA Astrophysics Data System (ADS)

    Bagschik, Kai; Frömter, Robert; Bach, Judith; Beyersdorff, Björn; Müller, Leonard; Schleitzer, Stefan; Berntsen, Magnus Hârdensson; Weier, Christian; Adam, Roman; Viefhaus, Jens; Schneider, Claus Michael; Grübel, Gerhard; Oepen, Hans Peter

    2016-10-01

    It is demonstrated that the magnetic diffraction pattern of the isotropic disordered maze pattern is well described utilizing a gamma distribution of domain sizes in a one-dimensional model. From the analysis, the mean domain size and the shape parameter of the distribution are obtained. The model reveals an average domain size that is significantly different from the value that is determined from the peak position of the structure factor in reciprocal space. As a proof of principle, a wedge-shaped (Cot Å/Pd10 Å)8 multilayer film, that covers the thickness range of the spin-reorientation transition, has been used. By means of soft x-ray resonant magnetic scattering (XRMS) and imaging techniques the thickness-driven evolution of the magnetic properties of the cobalt layers is explored. It is shown that minute changes of the domain pattern concerning domain size and geometry can be investigated and analyzed due to the high sensitivity and lateral resolution of the XRMS technique. The latter allows for the determination of the magnetic anisotropies of the cobalt layers within a thickness range of a few angstroms.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Asymmetric interaction of point defects and heterophase interfaces in ZrN/TaN multilayered nanofilms

    NASA Astrophysics Data System (ADS)

    Lao, Yuanxia; Hu, Shuanglin; Shi, Yunlong; Deng, Yu; Wang, Fei; Du, Hao; Zhang, Haibing; Wang, Yuan

    2017-01-01

    Materials with a high density of heterophase interfaces, which are capable of absorbing and annihilating radiation-induced point defects, can exhibit a superior radiation tolerance. In this paper, we investigated the interaction behaviors of point defects and heterophase interfaces by implanting helium atoms into the ZrN/TaN multilayered nanofilms. It was found that the point defect-interface interaction on the two sides of the ZrN/TaN interface was asymmetric, likely due to the difference in the vacancy formation energies of ZrN and TaN. The helium bubbles could migrate from the ZrN layers into the TaN layers through the heterophase interfaces, resulting in a better crystallinity of the ZrN layers and a complete amorphization of the TaN layers. The findings provided some clues to the fundamental behaviors of point defects near the heterophase interfaces, which make us re-examine the design rules of advanced radiation-tolerant materials.

  6. Asymmetric interaction of point defects and heterophase interfaces in ZrN/TaN multilayered nanofilms

    PubMed Central

    Lao, Yuanxia; Hu, Shuanglin; Shi, Yunlong; Deng, Yu; Wang, Fei; Du, Hao; Zhang, Haibing; Wang, Yuan

    2017-01-01

    Materials with a high density of heterophase interfaces, which are capable of absorbing and annihilating radiation-induced point defects, can exhibit a superior radiation tolerance. In this paper, we investigated the interaction behaviors of point defects and heterophase interfaces by implanting helium atoms into the ZrN/TaN multilayered nanofilms. It was found that the point defect-interface interaction on the two sides of the ZrN/TaN interface was asymmetric, likely due to the difference in the vacancy formation energies of ZrN and TaN. The helium bubbles could migrate from the ZrN layers into the TaN layers through the heterophase interfaces, resulting in a better crystallinity of the ZrN layers and a complete amorphization of the TaN layers. The findings provided some clues to the fundamental behaviors of point defects near the heterophase interfaces, which make us re-examine the design rules of advanced radiation-tolerant materials. PMID:28053307

  7. Asymmetric interaction of point defects and heterophase interfaces in ZrN/TaN multilayered nanofilms.

    PubMed

    Lao, Yuanxia; Hu, Shuanglin; Shi, Yunlong; Deng, Yu; Wang, Fei; Du, Hao; Zhang, Haibing; Wang, Yuan

    2017-01-05

    Materials with a high density of heterophase interfaces, which are capable of absorbing and annihilating radiation-induced point defects, can exhibit a superior radiation tolerance. In this paper, we investigated the interaction behaviors of point defects and heterophase interfaces by implanting helium atoms into the ZrN/TaN multilayered nanofilms. It was found that the point defect-interface interaction on the two sides of the ZrN/TaN interface was asymmetric, likely due to the difference in the vacancy formation energies of ZrN and TaN. The helium bubbles could migrate from the ZrN layers into the TaN layers through the heterophase interfaces, resulting in a better crystallinity of the ZrN layers and a complete amorphization of the TaN layers. The findings provided some clues to the fundamental behaviors of point defects near the heterophase interfaces, which make us re-examine the design rules of advanced radiation-tolerant materials.

  8. Human collagen-based multilayer scaffolds for tendon-to-bone interface tissue engineering.

    PubMed

    Kim, Beob Soo; Kim, Eun Ji; Choi, Ji Suk; Jeong, Ji Hoon; Jo, Chris Hyunchul; Cho, Yong Woo

    2014-11-01

    The natural tendon-to-bone region has a gradient in structure and composition, which is translated into a spatial variation of chemical, physical, and biological properties. This unique transitional tissue between bone and tendon is not normally recreated during natural bone-to-tendon healing. In this study, we have developed a human collagen-based multilayer scaffold mimicking the tendon-to-bone region. The scaffold consists of four different layers with the following composition gradient: (a) a tendon layer composed of collagen; (b) an uncalcified fibrocartilage layer composed of collagen and chondroitin sulfate; (c) a calcified fibrocartilage layer composed of collagen and less apatite; (d) a bone layer composed of collagen and apatite. The chemical, physical, and mechanical properties of the scaffold were characterized by a scanning electron microscope, porosimeter, universal tensile machine, Fourier transform infrared spectrometer, energy dispersive X-ray analysis apparatus, and thermogravimetric analysis apparatus. The multilayer scaffold provided a gradual transition of the physical, chemical, and mechanical environment and supported the adhesion and proliferation of human fibroblasts, chondrocytes, and osteoblasts toward each corresponding matrix. Overall, our results suggest the feasibility of a human collagen-based multilayer scaffold for regeneration of hard-to-soft interface tissues. © 2014 Wiley Periodicals, Inc.

  9. 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

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

    PubMed

    Wu, Shujie; Chen, Yonghai; Yu, Jinling; Gao, Hansong; Jiang, Chongyun; Huang; Zhang, Yanhua; Wei, Yang; Ma, Wenquan

    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 D 2d to C 2v . IPOA has been observed in the (001) plane along [110] and [1[Formula: see text]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.

  11. Interface effects on perpendicular magnetic anisotropy for molecular-capped cobalt ultrathin films

    NASA Astrophysics Data System (ADS)

    Zhang, Xianmin; Mizukami, Shigemi; Kubota, Takahide; Oogane, Mikihiko; Naganuma, Hiroshi; Ando, Yasuo; Miyazaki, Terunobu

    2011-10-01

    The perpendicular magnetic anisotropy (PMA) of cobalt (0.5-1.8 nm) films capped separately by pentacene (Pc), fullerene (C60), and 8-hydroxyquinoline-aluminum (Alq3) are investigated. For all three series, the thickness of Co is around 0.7 nm for maximum out-of-plane coercivity. It is found that the coercivity of C60-capped films is nearly equal to that for Alq3-capped samples, although both are smaller than for Pc-capped films. The different interface effects of Co/molecules are discussed to explain this observation. This work highlights the PMA of ferromagnetic metal, which can be markedly infected depending on the nature of organic molecule.

  12. 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.

  13. 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.

  14. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

    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.

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

    SciTech Connect

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

    2016-08-08

    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.

  17. 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.

  18. Simulated vibrational sum frequency generation from a multilayer thin film system with two active interfaces.

    PubMed

    O'Brien, Daniel B; Massari, Aaron M

    2013-04-21

    In the field of surface-specific vibrational sum frequency generation spectroscopy (VSFG) on organic thin films, optical interferences combined with the two-interface problem presents a challenge in terms of qualitative assessment of the data and quantitative modeling. The difficulty is amplified when considering systems comprised of more than a single material thin film layer. Recently, in our lab we have developed a generalized model that describes thin film interference in interface-specific nonlinear optical spectroscopies from arbitrary multilayer systems. Here, we apply the model to simulate VSFG spectra from the simplest multilayer: a system of two thin films, one of which is an organic small molecule and the other is a dielectric layer on a semiconductor substrate system where we idealize that the organic interfaces are equally VSFG active. Specifically, we consider the molecule N,N'-dioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C8) deposited on a silicon wafer with a thermally grown oxide dielectric. We present results for the four polarization experiments that sample the nonzero nonlinear susceptibility elements of macroscopically centrosymmetric materials (ssp, sps, pss, and ppp) and in two mIR frequency windows (the imide carbonyl stretches around 1680 cm(-1) and the alkyl stretches around 2900 cm(-1)) as a function of both thin film thicknesses with fixed input beam angles. We use frequency dependent refractive indices for all materials. The goal is to illustrate some of the intricacies contained in the intensity data of such systems. Of particular interest is the effect of the relative polar orientation of modes at the interfaces and the possibility of designing a system where the collected signal is exclusively attributable to a single interface. Our calculations indicate that in order to unambiguously identify the relative polar orientation one must experimentally vary an additional system parameter such as thin film thickness or input beam angle

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

    SciTech Connect

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

    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 (optical constants) values for Cr.

  20. 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.

  1. 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.

  2. 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.

  3. Potential of SPR sensors based on multilayer interfaces with gold and LHM for biosensing applications

    NASA Astrophysics Data System (ADS)

    Cherifi, Abdellatif; Bouhafs, Benamar

    2017-09-01

    Recently, the subject on "plasmonics" has received significant attention in designing surface plasmon resonance (SPR) sensors. In order to achieve extremely high-sensitivity sensing, multilayered configurations based on a variety of active materials and dielectrics have been exploited. In this work, a novel SPR sensor is proposed and investigated theoretically. The structure, analyzed in attenuated total reflection (ATR), consists of multilayer interfaces between gold and a metamaterial (LHM) separated by an analyte layer as a sensing medium. By interchanging between gold and LHM, under the effect of the refractive index (RI) of analyte set to be in the range of 1.00 to 1.99, the sharp peak reflectivity at the SPR angle takes two opposite behaviors predicted from the transfer matrix method. At the threshold value of 1.568 of the refractive index of analyte and when the LHM is the outer medium, the layered structure exhibits a giant sharp peak located at 43° of intensity up to 105 due to the Goos-Hànchen effect. With respect to the refractive index (RI) change and thickness of analyte, the characteristics (intensity, resonance condition, and quality factor) of the SPR mode, which make the proposed device have the potential for biosensing applications, have been analytically modelized.

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

    SciTech Connect

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

    2016-06-15

    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, K{sub i}, is maximized at an annealing temperature 225{sup ∘}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.

  5. X-ray dynamical diffraction from multilayer Laue lenses with rough interfaces

    SciTech Connect

    Yan Hanfei

    2009-04-15

    A modeling approach for x-ray dynamical diffraction from multilayer Laue lenses (MLLs) with rough interfaces is developed. Although still based on the principle of the distorted-wave Born approximation (DWBA), this model is formulated from the perspective of the physical scattering process, very different from the conventional DWBA formalism. Using this model, one can study x-ray scattering from rough interfaces in the regime of Fresnel diffraction and in the case of absorptive samples, for example, x-ray dynamical diffraction from MLLs with rough interfaces, which is hard to handle in the framework of the conventional DWBA. Theoretical simulations for various MLLs with rough interfaces are conducted. It is found that interfacial roughness results in a decrease in the local diffraction intensity, where the attenuation factor is a function of the root-mean-square (rms) roughness versus the local zone width ratio. This study shows that if all zones possess an identical rms roughness value that is less than half of the outmost MLL zone width, the focal broadening effect due to roughness is almost unnoticeable, provided that the mean position of the interface does not deviate from the required zone plate law. A further study shows that uncorrelated interfacial roughness can be treated the same as interfacial diffusion, in which case a roughness factor similar to the ''Debye-Waller factor'' can be used, and the pseudo-Fourier coefficients of the susceptibility function for an MLL [H. F. Yan et al., Phys. Rev. B 76, 115438 (2007)] have to be multiplied by this factor.

  6. Harnessing second-order optical nonlinearities at interfaces in multilayer silicon-oxy-nitride waveguides

    NASA Astrophysics Data System (ADS)

    Logan, Dylan F.; Alamin Dow, Ali B.; Stepanov, Dmitri; Abolghasem, Payam; Kherani, Nazir P.; Helmy, Amr S.

    2013-02-01

    We demonstrate multi-layer silicon-oxy-nitride (SiON) waveguides as a platform for broadband tunable phase-matching of second-order nonlinear interactions arising at material interfaces. Second-harmonic generation (SHG) is measured with a 2 ps pulsed pump of 1515-1535 nm wavelength, where 6 nW power is generated by an average pump power of 30 mW in a 0.92 mm long device. The wavelength acceptance bandwidth of the SHG is as broad as 20 nm due to the low material dispersion of SiON waveguides. The waveguide structure provides a viable method for utilizing second order nonlinearity for light generation and manipulation in silicon photonic circuits.

  7. 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

  8. Interface and temperature dependent magnetic properties of 57Fe/Ti/Co multilayers

    NASA Astrophysics Data System (ADS)

    Jain, Vishal; Lakshmi, N.; Sudheesh, V. D.; Jain, Vivek Kumar; Reddy, V. R.; Venugopalan, K.; Gupta, Ajay

    2014-09-01

    The effect of thermal annealing on the interface of 57Fe/Ti/Co multilayer and associated changes in microstructure, hyperfine field and bulk magnetic properties such as saturation magnetization, coercivity and squareness has been studied by X-ray diffraction, X-ray reflectivity, conversion electron Mössbauer spectroscopy and vibrating sample magnetometry. With increase in annealing temperature, interdiffusion leads to an increase in the roughness, hyperfine fields and coercivity along with a decrease in saturation magnetization. Annealing at 823 K leads to the formation of a FeCo phase along with the precipitation of Ti. The electrical resistivity (ρ) of the as-deposited sample decreases on annealing and hence the thermal coefficient of resistance (TCR) goes from negative to positive on annealing the samples. All samples show Curie temperature in excess of 723 K.

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

    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.

  10. Enhancement of electric-field-induced change of magnetic anisotropy by interface engineering of MgO magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Bonaedy, Taufik; Choi, Jun Woo; Jang, Chaun; Min, Byoung-Chul; Chang, Joonyeon

    2015-06-01

    Electric-field-induced modification of magnetic anisotropy is studied using tunnel magnetoresistance of the Co40Fe40B20/ MgO/ Co40Fe40B20 and Co40Fe40B20/ Hf (0.08 nm)/ MgO/ Co40Fe40B20 magnetic tunnel junctions. In both systems, the interfacial perpendicular magnetic anisotropy is increased with increasing electron density at the MgO interface. A quantitative comparison between the two systems reveals that the change of magnetic anisotropy energy with electric field is significantly enhanced in Co40Fe40B20/ Hf/ MgO/ Co40Fe40B20 compared to Co40Fe40B20/ MgO/ Co40Fe40B20. The sub-monolayer Hf insertion at the Co40Fe40B20/MgO interface turns out to be critical to the enhanced electric field control of the magnetic anisotropy, indicating the interface sensitive nature of the effect.

  11. 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.

  12. 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

  13. ADM guidance-Ceramics: all-ceramic multilayer interfaces in dentistry.

    PubMed

    Lohbauer, Ulrich; Scherrer, Susanne S; Della Bona, Alvaro; Tholey, Michael; van Noort, Richard; Vichi, Alessandro; Kelly, J Robert; Cesar, Paulo F

    2017-06-01

    This guidance document describes the specific issues involved in dental multilayer ceramic systems. The material interactions with regard to specific thermal and mechanical properties are reviewed and the characteristics of dental tooth-shaped processing parameters (sintering, geometry, thickness ratio, etc.) are discussed. Several techniques for the measurement of bond quality and residual stresses are presented with a detailed discussion of advantages and disadvantages. In essence no single technique is able to describe adequately the all-ceramic interface. Invasive or semi-invasive methods have been shown to distort the information regarding the residual stress state while non-invasive methods are limited due to resolution, field of focus or working depth. This guidance document has endeavored to provide a scientific basis for future research aimed at characterizing the ceramic interface of dental restorations. Along with the methodological discussion it is seeking to provide an introduction and guidance to relatively inexperienced researchers. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  14. Interdiffusion in epitaxial ultrathin Co2FeAl/MgO heterostructures with interface-induced perpendicular magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Wen, Zhenchao; Hadorn, Jason Paul; Okabayashi, Jun; Sukegawa, Hiroaki; Ohkubo, Tadakatsu; Inomata, Koichiro; Mitani, Seiji; Hono, Kazuhiro

    2017-01-01

    The interfacial atomic structure of epitaxial ultrathin Co2FeAl/MgO(001) heterostructures, which is related to the interface-induced perpendicular magnetic anisotropy (PMA), was investigated using scanning transmission electron microscopy, energy dispersive X-ray spectroscopy, and X-ray magnetic circular dichroism. Al atoms from the Co2FeAl layer significantly interdiffused into MgO, forming an Al-deficient Co-Fe-Al/Mg-Al-O structure near the Co2FeAl/MgO interface. This atomic replacement may have enhanced the PMA, which is consistent with the observed large perpendicular orbital magnetic moments of Fe atoms at the interface. This work suggests that control of interdiffusion at ferromagnet/barrier interfaces is critical for designing an interface-induced PMA system.

  15. Effect of the number of interfaces on the magnetic properties of [SnO{sub 2}/Cu-Zn ferrite] multilayer

    SciTech Connect

    Saipriya, S.; Kurian, Joji; Singh, R.

    2012-04-01

    The [SnO{sub 2}/Cu-Zn ferrite (CZF)]{sub n} (n = 5, 10, 15, and 20) multilayer (ML) were deposited by rf-magnetron sputtering to study their magnetic properties. The magnetization and ferromagnetic resonance (FMR) measurements were undertaken to understand the effect of interfaces on the magnetic properties of these ML. FMR signal line shape changes from asymmetric to symmetric as n increases. The FMR signal peak to peak intensity, FMR linewidth, effective and saturation magnetization and coercivity exhibit oscillations as a function of n. In the parallel configuration the resonance field increases with increase in n, presumably due to the decrease in the active layer to dead layer thickness ratio. The interlayer coupling is strong in the ML with n = 5 leading to the formation of spin waves. The ML interlayer coupling and anisotropy decreases with increasing n. The oscillatory behavior of the magnetic properties can be ascribed to the nonmonotonic variations in the structure and the geometry of the interfaces.

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

    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.

  17. 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.

  18. 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.

  19. SHG anisotropy in Au/Co/Au/Cu/vicinal Si(1 1 1)

    NASA Astrophysics Data System (ADS)

    Cheikh-Rouhou, W.; Sampaio, L. C.; Bartenlian, B.; Beauvillain, P.; Brun, A.; Ferré, J.; Georges, P.; Jamet, J.-P.; Mathet, V.; Stupakewicz, Andrei

    2002-02-01

    The second harmonic generation (SHG) reflectivity on magnetic multilayers is a very sensitive technique to reveal the crystallography of buried interfaces. We have used the azimuthal anisotropy of SHG to demonstrate that the vicinal character of Si(1 1 1) substrate is duplicated in the metallic multilayer Au/Co/Au/Cu. The magnetic properties of these multilayers as anisotropy and magneto-optic polar Kerr rotation were studied by linear magneto-optic effects in correlation with SHG experiments, by varying the Co and Au buffer thicknesses as well as the Cu buffer deposition condition.

  20. 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

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

    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 Ni50.0Zr50.0 alloy 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.

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

    DOE PAGES

    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

  3. 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.

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

    SciTech Connect

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

    2016-04-04

    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.

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

    SciTech Connect

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

    2016-07-28

    Interfacial atomic diffusion, reaction, and formation of microstructure in nanoscale level are investigated in W/B{sub 4}C 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 B{sub 4}C 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.

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

    PubMed

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

    2015-09-21

    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.

  7. 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.

  8. 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

  9. 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

  10. Crystallography of Co/Pt multilayers and nanostructures

    SciTech Connect

    Zhang, Bing; Krishnan, K.M.; Farrow, R.F.C.

    1992-04-01

    Atomically engineered nanostructures and multilayers of Co/Pt exhibit strong perpendicular anisotropy. This unique property, that determines their potential as a magneto-optic recording media, is dependent on a variety of microstructural parameters that include the overall crystallography, thickness of the layers, orientation, defect formation, interface reactions etc. A series of Co/Pt multilayer samples with different thickness of the Co layer were studied by electron diffraction. It has been determined that the Co layers persists in the fcc structure up to a thickness of 50 {Angstrom}. As the thickness is varied fmm 3{Angstrom} to 50{Angstrom} in the multilayers, the Co film gradually relaxed to its bulk lattice parameter. (111) twinning and lattice strain at the interfaces between Pt and Co layers are also observed. The symmetry forbidden reflections observed at 1/3 (224) positions in (111) zone diffraction patterns of the multilayer are due to (111) twinning and compositional modulations along the multilayer growth direction.

  11. Thermally enhanced perpendicular magnetic anisotropy behaviors of ultrathin [Co/Pd]{sub n} multilayers via NiO{sub x} capping layer

    SciTech Connect

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

    2015-06-01

    We report the enhanced perpendicular magnetic anisotropy (PMA) features of ultrathin [Co/Pd]{sub 3} multilayers (MLs) employing a NiO{sub x} insertion layer at high annealing temperatures. Thermally enhanced PMA in [Co/Pd]{sub 3}/NiO{sub x} (capping layer) MLs were achieved at a specific capping layer thickness, while no PMA responses were observed for a NiO{sub x} (buffer layer)/[Co/Pd]{sub 3} ML, regardless of NiO{sub x} thickness. X-ray diffraction observations, including rocking curves, identified the relatively different crystalline characteristics of the NiO{sub x} capping and buffer layers. Origin of the enhanced PMAs of [Co/Pd]{sub 3} MLs containing a NiO{sub x} capping layer is described based on the NiO{sub x} capping effect possibly providing additional Co/Oxide i-PMA under high-temperature annealing.

  12. Structural, magnetic, and magneto-optical properties of nanocrystalline face centered cubic Co70Cr30/Pt multilayers with perpendicular magnetic anisotropy.

    PubMed

    Papaioannou, E Th; Angelakeris, M; Poulopoulos, P; Tsiaoussis, I; Rüdt, C; Fumagalli, P; Flevaris, N K

    2007-12-01

    Co70Cr30 alloyed layers are combined with extremely thin Pt layers in order to produce novel face-centered-cubic multilayered films to be considered as a potential perpendicular magnetic recording medium. The films were grown on Si, glass and polyimide substrates by e-beam evaporation at a temperature slightly higher than room temperature. The multilayered structure of the films was verified by X-ray diffraction experiments. Plane-view transmission electron microscopy images have revealed the formation of very small grains in the range of 7-9 nm. Hysteresis loops as a function of temperature were recorded via the magneto-optic Kerr effect in the polar geometry configuration. The system exhibits perpendicular magnetic anisotropy, which enhances with decreasing temperature. Hysteresis loops with a squareness of 1 and a coercivity of 1.45 kOe were obtained at 10 K. Furthermore, complete magneto-optic spectra of the films are recorded, showing a strong magneto-optic enhancement in the ultraviolet region at around 4.5 eV.

  13. 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.

  14. Modified magnetic anisotropy at LaCoO3/La0.7Sr0.3MnO3 interfaces

    NASA Astrophysics Data System (ADS)

    Cabero, M.; Nagy, K.; Gallego, F.; Sander, A.; Rio, M.; Cuellar, F. A.; Tornos, J.; Hernandez-Martin, D.; Nemes, N. M.; Mompean, F.; Garcia-Hernandez, M.; Rivera-Calzada, A.; Sefrioui, Z.; Reyren, N.; Feher, T.; Varela, M.; Leon, C.; Santamaria, J.

    2017-09-01

    Controlling magnetic anisotropy is an important objective towards engineering novel magnetic device concepts in oxide electronics. In thin film manganites, magnetic anisotropy is weak and it is primarily determined by the substrate, through induced structural distortions resulting from epitaxial mismatch strain. On the other hand, in cobaltites, with a stronger spin orbit interaction, magnetic anisotropy is typically much stronger. In this paper, we show that interfacing La0.7Sr0.3MnO3 (LSMO) with an ultrathin LaCoO3 (LCO) layer drastically modifies the magnetic anisotropy of the manganite, making it independent of the substrate and closer to the magnetic isotropy characterizing its rhombohedral structure. Ferromagnetic resonance measurements evidence a tendency of manganite magnetic moments to point out-of-plane suggesting non collinear magnetic interactions at the interface. These results may be of interest for the design of oxide interfaces with tailored magnetic structures for new oxide devices.

  15. 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)

  16. A first-principles study on magnetocrystalline anisotropy at interfaces of Fe with non-magnetic metals

    NASA Astrophysics Data System (ADS)

    Miura, Yoshio; Tsujikawa, Masahito; Shirai, Masafumi

    2013-06-01

    Magnetocrystalline anisotropy (MCA) of Fe(001) interfaces with various non-magnetic metals (Hf, Zr, Ti, Ta, Nb, V, Ir, Rh, Pt, Pd, Au, Ag, Cu, and Zn) was investigated by first-principles calculations. We found that Fe interfaces with non-magnetic metals with fully occupied d states tend to show perpendicular MCA. The spin-orbit coupling in interfacial Fe atoms plays an important role in perpendicular MCA. Conversely, Fe interfaces with non-magnetic metals with partially occupied d states exhibit in-plane MCA. The Hf/Fe(001) interface shows an exceptionally large perpendicular MCA energy of 1.5 mJ/m2, which corresponds to that of the MgO/Fe(001) interface. In these cases, contributions from interfacial Fe atoms to MCA are relatively small, and the large spin-orbit coupling of non-magnetic atoms is the primary contribution to MCA. We conclude that formation of Hf/Fe(001) interfaces will enhance the perpendicular magnetization of MgO/CoFeB-based magnetic tunnel junctions.

  17. Enhanced interface perpendicular magnetic anisotropy in Ta|CoFeB|MgO using nitrogen doped Ta underlayers

    NASA Astrophysics Data System (ADS)

    Sinha, Jaivardhan; Hayashi, Masamitsu; Kellock, Andrew J.; Fukami, Shunsuke; Yamanouchi, Michihiko; Sato, Hideo; Ikeda, Shoji; Mitani, Seiji; Yang, See-hun; Parkin, Stuart S. P.; Ohno, Hideo

    2013-06-01

    We show that the magnetic characteristics of Ta|CoFeB|MgO magnetic heterostructures are strongly influenced by doping the Ta underlayer with nitrogen. In particular, the saturation magnetization drops upon doping the Ta underlayer, suggesting that the doped underlayer acts as a boron diffusion barrier. In addition, the thickness of the magnetic dead layer decreases with increasing nitrogen doping. Surprisingly, the interface magnetic anisotropy increases to ˜1.8 erg/cm2 when an optimum amount of nitrogen is introduced into the Ta underlayer. These results show that nitrogen doped Ta serves as a good underlayer for spintronic applications including magnetic tunnel junctions and domain wall devices.

  18. Complex, multilayered azimuthal anisotropy beneath Tibet: evidence for co-existing channel flow and pure-shear crustal thickening

    NASA Astrophysics Data System (ADS)

    Agius, Matthew R.; Lebedev, Sergei

    2017-09-01

    Of the two debated, end-member models for the late-Cenozoic thickening of Tibetan crust, one invokes 'channel flow' (rapid viscous flow of the mid-lower crust, driven by topography-induced pressure gradients and transporting crustal rocks eastward) and the other 'pure shear' (faulting and folding in the upper crust, with viscous shortening in the mid-lower crust). Deep-crustal deformation implied by each model is different and would produce different anisotropic rock fabric. Observations of seismic anisotropy can thus offer a discriminant. We use broad-band phase-velocity curves-each a robust average of tens to hundreds of measurements-to determine azimuthal anisotropy in the entire lithosphere-asthenosphere depth range and constrain its amplitude. Inversions of the differential dispersion from path pairs, region-average inversions and phase-velocity tomography yield mutually consistent results, defining two highly anisotropic layers with different fast-propagation directions within each: the middle crust and the asthenosphere. In the asthenosphere beneath central and eastern Tibet, anisotropy is 2-4 per cent and has an NNE-SSW fast-propagation azimuth, indicating flow probably driven by the NNE-ward, shallow-angle subduction of India. The distribution and complexity of published shear wave splitting measurements can be accounted for by the different anisotropy in the mid-lower crust and asthenosphere. The estimated splitting times that would be accumulated in the crust alone are 0.25-0.8 s; in the upper mantle-0.5-1.2 s, depending on location. In the middle crust (20-45 km depth) beneath southern and central Tibet, azimuthal anisotropy is 3-5 and 4-6 per cent, respectively, and its E-W fast-propagation directions are parallel to the current extension at the surface. The rate of the extension is relatively low, however, whereas the large radial anisotropy observed in the middle crust requires strong alignment of mica crystals, implying large finite strain and

  19. Growth of perpendicularly magnetized thin films on a polymer buffer and voltage-induced change of magnetic anisotropy at the MgO|CoFeB interface

    NASA Astrophysics Data System (ADS)

    Lam, D. D.; Bonell, F.; Shiota, Y.; Miwa, S.; Nozaki, T.; Tamura, E.; Mizuochi, N.; Shinjo, T.; Suzuki, Y.; Yuasa, S.

    2015-06-01

    We show that perpendicularly magnetized thin films can be grown onto polyimide, a potentially flexible substrate. With polar Kerr magnetometry, we demonstrate that the coercive field of CoFeB thin film can be modulated by applying a back gate voltage. Our proposed multi-layered structure is suitable for surface-sensitive measurements of the voltage-induced change in anisotropy, and could be used to realize flexible spintronics devices.

  20. 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.

  1. Chemical and magnetic interface properties of tunnel junctionswith co2mnsi/co2fesi multilayer electrode showing large tunnelingmagnetoresistance

    SciTech Connect

    Schmalhorst, J.; Ebke, D.; Sacher, M.D.; Liu, N.; Thomas, A.; Reiss, G.; Hutten, A.; Arenholz, E.

    2007-01-01

    Transport, as well as chemical and magnetic interface properties of two kinds of magnetic tunnel junctions (MTJs) with Co{sub 2}FeSi electrode, Al-O barrier, and Co-Fe counter electrode, are investigated. For junctions with Co{sub 2}FeSi single-layer electrodes, a tunnel magnetoresistance of up to 52% is found after optimal annealing for an optimal Al thickness of 1.5 nm, whereas the room temperature bulk magnetization of the Co{sub 2}FeSi film reaches only 75% of the expected value. By using a [Co{sub 2}MnSi/Co{sub 2}FeSi]{sub x10} multilayer electrode, the magnetoresistance can be increased to 114%, corresponding to a large spin polarization of 0.74, and the full bulk magnetization is reached. For Al thickness smaller than 1 nm, the TMR of both kinds of MTJs decreases rapidly to zero. On the other hand, for 2- to 3-nm-thick Al, the TMR decreases only slowly. The Al thickness dependence of the TMR is directly correlated to the element-specific magnetic moments of Fe and Co at the Co{sub 2}FeSi/Al-O interface for all Al thickness. Especially, for optimal Al thickness and annealing, the interfacial Fe moment of the single-layer electrode is about 20% smaller than for the multilayer electrode, indicating smaller atomic disorder at the barrier interface for the latter MTJ.

  2. On the possible effect of Hall currents and anisotropy of the thermal conductivity on the plasma flow in heliospheric interface

    NASA Astrophysics Data System (ADS)

    Baranov, Vladimir

    Under physical conditions of cosmic plasma the cyclotron frequency of electrons is almost always much greater than the frequency of their collisions. In particular, this inequality is fulfilled in the heliospheric interface. In this case the effect of magnetic field gives rise to the anisotropy of transport coefficients (viscosity, thermal-and electro-conductivities). It is shown in our presentation, that the most important dissipative process in the heliospheric interface is thermal conduction along the magnetic field lines because the Peclet number determining this process is quite small. It means that its effect has to be definitely taken into account in the energy equation at theoretical modelling. Hall currents, which arise due to the electro-conductivity anisotropy, determine the dispersion processes. The effect of Hall currents on the principle of the freezing-in magnetic field and on a wave propagation is discussed. In particular, it is shown that the interplanetary magnetic field can penetrate through the heliopause into the interstellar plasma even if it is the tangential discontinuity. The value of this penetration is estimated.

  3. Influence of thickness variation on perpendicular magnetic anisotropy features of the [co/pt]n multilayer frame.

    PubMed

    Lee, Ja Bin; An, Gwang Guk; Yang, Seung Mo; Hong, Jin Pyo

    2014-11-01

    We report the structural and magnetic properties of a [Co/Pt] multilayer matrix as a function of Pt thickness. Increasing Pt thickness allows for the formation of a well-aligned fcc (111) CoPt3 structure in a [Co/Pt]n multilayer geometry, where the clear appearance of main (111) peak of CoPt3 measured using the X-ray diffraction patterns was confirmed. High-resolution transmission electron microscopy images, along with the corresponding fast Fourier transform patterns displayed the ordered structure with clear 6-fold symmetric diffraction spots. The c/a lattice constant ratio of 0.949 was calculated by utilizing the XRD and, demonstrating the presence of a well-aligned CoPt3 structure. The Pt thickness-dependent saturation magnetization (M(s)) values for the in- and out-of-plane M-H hysteresis loops obtained by vibrating sample magnetometer measurements showed distinctly opposite trends. The increase in the out-of-plane M(s) value with increasing Pt thickness seems to originate from the enhanced perpendicular orbital moment of the proper CoPt3 structure.

  4. Interface-roughening phase diagram of the three-dimensional Ising model for all interaction anisotropies from hard-spin mean-field theory.

    PubMed

    Cağlar, Tolga; Berker, A Nihat

    2011-11-01

    The roughening phase diagram of the d=3 Ising model with uniaxially anisotropic interactions is calculated for the entire range of anisotropy, from decoupled planes to the isotropic model to the solid-on-solid model, using hard-spin mean-field theory. The phase diagram contains the line of ordering phase transitions and, at lower temperatures, the line of roughening phase transitions, where the interface between ordered domains roughens. Upon increasing the anisotropy, roughening transition temperatures settle after the isotropic case, whereas the ordering transition temperature increases to infinity. The calculation is repeated for the d=2 Ising model for the full range of anisotropy, yielding no roughening transition.

  5. Effect of annealing conditions on the perpendicular magnetic anisotropy of Ta/CoFeB/MgO multilayers

    NASA Astrophysics Data System (ADS)

    Liu, Yan; Hao, Liang; Cao, Jiangwei

    2016-04-01

    Films with a structure of Ta (5 nm)/Co20Fe60B20 (0.8-1.5 nm)/MgO (1 nm)/Ta (1 nm) were deposited on Corning glass substrates by magnetron sputtering. The as-deposited films with CoFeB layer thickness from 0.8 to 1.3 nm show perpendicular magnetic anisotropy (PMA). After annealing at a proper temperature, the PMA of the films can be enhanced remarkably. A maximum effective anisotropy field of up to 9 kOe was obtained for 1.0- and 1.1-nm-thick CoFeB layers annealed at an optimum temperature of 300 °C. A 4-kOe magnetic field was applied during annealing to study its effect on the PMA of the CoFeB layers. The results confirmed that applying a perpendicular magnetic field during annealing did not improve the maximum PMA of the films, but it did enhance the PMA of the thinner films at a lower annealing temperature.

  6. Temperature dependent coercivity crossover in pseudo-spin-valve magnetic tunnel junctions with perpendicular anisotropy

    NASA Astrophysics Data System (ADS)

    Feng, G.; Wu, H. C.; Feng, J. F.; Coey, J. M. D.

    2011-07-01

    We report the temperature dependent collapse of tunnel magnetoresistance (TMR) in perpendicular anisotropy magnetic tunnel junctions (pMTJs) with AlOx barriers and (Co/Pt)3 multilayer electrodes, due to the coercivity crossover of the top and bottom (Co/Pt)3 stacks. The different temperature dependence of two (Co/Pt)3 stacks in pMTJs is mainly caused by the additional perpendicular anisotropy created at interface between the ferromagnetic electrode and the AlOx barrier.

  7. 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.

  8. 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.

  9. 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.

  10. Ultrathin Co-O oxide layer-driven perpendicular magnetic anisotropy in a CoO/[Co/Pd]m multilayer matrix upon annealing

    NASA Astrophysics Data System (ADS)

    Chung, Woo Seong; Yang, Seung Mo; Kim, Tae Whan; Hong, Jin Pyo

    2016-11-01

    Ferromagnetic/noble metal multilayer (ML) frames are expected to serve as reliable building blocks in a variety of perpendicular magnetic anisotropy (PMA) based spintronic devices. However, ultrathin ML matrices are highly susceptible to unintended reduction of electron spin polarization in the as-grown or annealed states and often require a large repeat number. Here, we introduce a simple approach to achieve thermally stable PMA in ultrathin [Co/Pd]3 MLs involving the incorporation of an ultrathin CoO capping layer. The thickness and oxygen content of the CoO layer are critical parameters to achieve enhanced PMA in ultrathin [Co/Pd]3/CoO MLs post-annealed up to 400 °C. An extensive analysis of structural features identified that robust PMA characteristics in [Co/Pd]3/CoO MLs are linked with thermally activated oxygen atom diffusion leading to structural reconfiguration upon annealing. The possible origin of the enhanced PMA in our [Co/Pd]3/CoO ML samples after high-temperature annealing is discussed, thereby enabling their use in future spintronic-related devices.

  11. Ultrathin Co-O oxide layer-driven perpendicular magnetic anisotropy in a CoO/[Co/Pd]m multilayer matrix upon annealing.

    PubMed

    Chung, Woo Seong; Yang, Seung Mo; Kim, Tae Whan; Hong, Jin Pyo

    2016-11-25

    Ferromagnetic/noble metal multilayer (ML) frames are expected to serve as reliable building blocks in a variety of perpendicular magnetic anisotropy (PMA) based spintronic devices. However, ultrathin ML matrices are highly susceptible to unintended reduction of electron spin polarization in the as-grown or annealed states and often require a large repeat number. Here, we introduce a simple approach to achieve thermally stable PMA in ultrathin [Co/Pd]3 MLs involving the incorporation of an ultrathin CoO capping layer. The thickness and oxygen content of the CoO layer are critical parameters to achieve enhanced PMA in ultrathin [Co/Pd]3/CoO MLs post-annealed up to 400 °C. An extensive analysis of structural features identified that robust PMA characteristics in [Co/Pd]3/CoO MLs are linked with thermally activated oxygen atom diffusion leading to structural reconfiguration upon annealing. The possible origin of the enhanced PMA in our [Co/Pd]3/CoO ML samples after high-temperature annealing is discussed, thereby enabling their use in future spintronic-related devices.

  12. Ultrathin Co-O oxide layer-driven perpendicular magnetic anisotropy in a CoO/[Co/Pd]m multilayer matrix upon annealing

    PubMed Central

    Chung, Woo Seong; Yang, Seung Mo; Kim, Tae Whan; Hong, Jin Pyo

    2016-01-01

    Ferromagnetic/noble metal multilayer (ML) frames are expected to serve as reliable building blocks in a variety of perpendicular magnetic anisotropy (PMA) based spintronic devices. However, ultrathin ML matrices are highly susceptible to unintended reduction of electron spin polarization in the as-grown or annealed states and often require a large repeat number. Here, we introduce a simple approach to achieve thermally stable PMA in ultrathin [Co/Pd]3 MLs involving the incorporation of an ultrathin CoO capping layer. The thickness and oxygen content of the CoO layer are critical parameters to achieve enhanced PMA in ultrathin [Co/Pd]3/CoO MLs post-annealed up to 400 °C. An extensive analysis of structural features identified that robust PMA characteristics in [Co/Pd]3/CoO MLs are linked with thermally activated oxygen atom diffusion leading to structural reconfiguration upon annealing. The possible origin of the enhanced PMA in our [Co/Pd]3/CoO ML samples after high-temperature annealing is discussed, thereby enabling their use in future spintronic-related devices. PMID:27886211

  13. Engineering the magnetic coupling and anisotropy at the molecule-magnetic surface interface in molecular spintronic devices

    NASA Astrophysics Data System (ADS)

    Campbell, Victoria E.; Tonelli, Monica; Cimatti, Irene; Moussy, Jean-Baptiste; Tortech, Ludovic; Dappe, Yannick J.; Rivière, Eric; Guillot, Régis; Delprat, Sophie; Mattana, Richard; Seneor, Pierre; Ohresser, Philippe; Choueikani, Fadi; Otero, Edwige; Koprowiak, Florian; Chilkuri, Vijay Gopal; Suaud, Nicolas; Guihéry, Nathalie; Galtayries, Anouk; Miserque, Frederic; Arrio, Marie-Anne; Sainctavit, Philippe; Mallah, Talal

    2016-12-01

    A challenge in molecular spintronics is to control the magnetic coupling between magnetic molecules and magnetic electrodes to build efficient devices. Here we show that the nature of the magnetic ion of anchored metal complexes highly impacts the exchange coupling of the molecules with magnetic substrates. Surface anchoring alters the magnetic anisotropy of the cobalt(II)-containing complex (Co(Pyipa)2), and results in blocking of its magnetization due to the presence of a magnetic hysteresis loop. In contrast, no hysteresis loop is observed in the isostructural nickel(II)-containing complex (Ni(Pyipa)2). Through XMCD experiments and theoretical calculations we find that Co(Pyipa)2 is strongly ferromagnetically coupled to the surface, while Ni(Pyipa)2 is either not coupled or weakly antiferromagnetically coupled to the substrate. These results highlight the importance of the synergistic effect that the electronic structure of a metal ion and the organic ligands has on the exchange interaction and anisotropy occurring at the molecule-electrode interface.

  14. Engineering the magnetic coupling and anisotropy at the molecule–magnetic surface interface in molecular spintronic devices

    PubMed Central

    Campbell, Victoria E.; Tonelli, Monica; Cimatti, Irene; Moussy, Jean-Baptiste; Tortech, Ludovic; Dappe, Yannick J.; Rivière, Eric; Guillot, Régis; Delprat, Sophie; Mattana, Richard; Seneor, Pierre; Ohresser, Philippe; Choueikani, Fadi; Otero, Edwige; Koprowiak, Florian; Chilkuri, Vijay Gopal; Suaud, Nicolas; Guihéry, Nathalie; Galtayries, Anouk; Miserque, Frederic; Arrio, Marie-Anne; Sainctavit, Philippe; Mallah, Talal

    2016-01-01

    A challenge in molecular spintronics is to control the magnetic coupling between magnetic molecules and magnetic electrodes to build efficient devices. Here we show that the nature of the magnetic ion of anchored metal complexes highly impacts the exchange coupling of the molecules with magnetic substrates. Surface anchoring alters the magnetic anisotropy of the cobalt(II)-containing complex (Co(Pyipa)2), and results in blocking of its magnetization due to the presence of a magnetic hysteresis loop. In contrast, no hysteresis loop is observed in the isostructural nickel(II)-containing complex (Ni(Pyipa)2). Through XMCD experiments and theoretical calculations we find that Co(Pyipa)2 is strongly ferromagnetically coupled to the surface, while Ni(Pyipa)2 is either not coupled or weakly antiferromagnetically coupled to the substrate. These results highlight the importance of the synergistic effect that the electronic structure of a metal ion and the organic ligands has on the exchange interaction and anisotropy occurring at the molecule–electrode interface. PMID:27929089

  15. Engineering the magnetic coupling and anisotropy at the molecule-magnetic surface interface in molecular spintronic devices.

    PubMed

    Campbell, Victoria E; Tonelli, Monica; Cimatti, Irene; Moussy, Jean-Baptiste; Tortech, Ludovic; Dappe, Yannick J; Rivière, Eric; Guillot, Régis; Delprat, Sophie; Mattana, Richard; Seneor, Pierre; Ohresser, Philippe; Choueikani, Fadi; Otero, Edwige; Koprowiak, Florian; Chilkuri, Vijay Gopal; Suaud, Nicolas; Guihéry, Nathalie; Galtayries, Anouk; Miserque, Frederic; Arrio, Marie-Anne; Sainctavit, Philippe; Mallah, Talal

    2016-12-08

    A challenge in molecular spintronics is to control the magnetic coupling between magnetic molecules and magnetic electrodes to build efficient devices. Here we show that the nature of the magnetic ion of anchored metal complexes highly impacts the exchange coupling of the molecules with magnetic substrates. Surface anchoring alters the magnetic anisotropy of the cobalt(II)-containing complex (Co(Pyipa)2), and results in blocking of its magnetization due to the presence of a magnetic hysteresis loop. In contrast, no hysteresis loop is observed in the isostructural nickel(II)-containing complex (Ni(Pyipa)2). Through XMCD experiments and theoretical calculations we find that Co(Pyipa)2 is strongly ferromagnetically coupled to the surface, while Ni(Pyipa)2 is either not coupled or weakly antiferromagnetically coupled to the substrate. These results highlight the importance of the synergistic effect that the electronic structure of a metal ion and the organic ligands has on the exchange interaction and anisotropy occurring at the molecule-electrode interface.

  16. Band alignment of ZnO/multilayer MoS2 interface determined by x-ray photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Liu, Xinke; Zhang, Yuan; Liu, Qiang; He, Jiazhu; Chen, Le; Li, Kuilong; Jia, Fang; Zeng, Yuxiang; Lu, Youming; Yu, Wenjie; Zhu, Deliang; Liu, Wenjun; Wu, Jing; He, Zhubing; Ang, Kah-Wee

    2016-08-01

    The energy band alignment between ZnO and multilayer (ML)-MoS2 was characterized using high-resolution x-ray photoelectron spectroscopy. The ZnO film was deposited using an atomic layer deposition tool, and ML-MoS2 was grown by chemical vapor deposition. A valence band offset (VBO) of 3.32 eV and a conduction band offset (CBO) of 1.12 eV were obtained for the ZnO/ML-MoS2 interface without any treatment. With CHF3 plasma treatment, a VBO and a CBO across the ZnO/ML-MoS2 interface were found to be 3.54 eV and 1.34 eV, respectively. With the CHF3 plasma treatment, the band alignment of the ZnO/ML-MoS2 interface has been changed from type II or staggered band alignment to type III or misaligned one, which favors the electron-hole pair separation. The band alignment difference is believed to be dominated by the down-shift in the core level of Zn 2p or the interface dipoles, which is caused by the interfacial layer rich in F.

  17. Band alignment of ZnO/multilayer MoS{sub 2} interface determined by x-ray photoelectron spectroscopy

    SciTech Connect

    Liu, Xinke E-mail: liuwj@szu.edu.cn; He, Jiazhu; Chen, Le; Li, Kuilong; Jia, Fang; Zeng, Yuxiang; Lu, Youming; Zhu, Deliang; Liu, Wenjun E-mail: liuwj@szu.edu.cn; Zhang, Yuan; Liu, Qiang; Yu, Wenjie; Wu, Jing; He, Zhubing; Ang, Kah-Wee

    2016-08-15

    The energy band alignment between ZnO and multilayer (ML)-MoS{sub 2} was characterized using high-resolution x-ray photoelectron spectroscopy. The ZnO film 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 3.32 eV and a conduction band offset (CBO) of 1.12 eV were obtained for the ZnO/ML-MoS{sub 2} interface without any treatment. With CHF{sub 3} plasma treatment, a VBO and a CBO across the ZnO/ML-MoS{sub 2} interface were found to be 3.54 eV and 1.34 eV, respectively. With the CHF{sub 3} plasma treatment, the band alignment of the ZnO/ML-MoS{sub 2} interface has been changed from type II or staggered band alignment to type III or misaligned one, which favors the electron-hole pair separation. The band alignment difference is believed to be dominated by the down-shift in the core level of Zn 2p or the interface dipoles, which is caused by the interfacial layer rich in F.

  18. Strong perpendicular magnetic anisotropy energy density at Fe alloy/HfO2 interfaces

    NASA Astrophysics Data System (ADS)

    Ou, Yongxi; Ralph, D. C.; Buhrman, R. A.

    2017-05-01

    We report on the perpendicular magnetic anisotropy (PMA) behavior of heavy metal (HM)/Fe alloy/MgO thin film heterostructures when an ultrathin HfO2 passivation layer is inserted between the Fe alloy and MgO. This is accomplished by depositing one to two atomic layers of Hf onto the Fe alloy before the subsequent rf sputter deposition of the MgO layer. This Hf layer is fully oxidized during the subsequent deposition of the MgO layer, as confirmed by X-ray photoelectron spectroscopy measurements. The HfO2 insertion generates a strong interfacial perpendicular anisotropy energy density without any post-fabrication annealing treatment, for example, 1.7 erg / cm 2 for the Ta/Fe60Co20B20/HfO2/MgO heterostructure. We also demonstrate PMA even in Ni80Fe20/HfO2/MgO structures for low-damping, low-magnetostriction Ni80Fe20 thin films. Depending on the choice of the HM, further enhancements of the PMA can be realized by thermal annealing to at least 400 o C . We show that ultra-thin HfO2 layers offer a range of options for enhancing the PMA properties of magnetic heterostructures for spintronics applications.

  19. On the origin of perpendicular magnetic anisotropy in strained Fe-Co(-X) films

    NASA Astrophysics Data System (ADS)

    Reichel, L.; Edström, A.; Pohl, D.; Rusz, J.; Eriksson, O.; Schultz, L.; Fähler, S.

    2017-02-01

    Very high magnetic anisotropies have been theoretically predicted for strained Fe-Co(-X) and indeed several experiments on epitaxial thin films seemed to confirm strain induced anisotropy enhancement. This study presents a critical analysis of the different contributions to perpendicular anisotropy: volume, interface and surface anisotropies. Tracing these contributions, thickness series of single layer films as well as multilayers with Au-Cu buffers/interlayers of different lattice parameters have been prepared. The analysis of their magnetic anisotropy reveals a negligible influence of the lattice parameter of the buffer. Electronic effects, originating from both, the Au-Cu interface and the film surface, outrange the elastic effects. Surface anisotropy, however, exceeds the interface anisotropy by more than a factor of three. A comparison with results from density functional theory suggests, that the experimentally observed strong perpendicular surface anisotropy originates from a deviation from an ideal oxide-free surface. Accordingly, tailored Fe-Co-X/oxide interfaces may open a route towards high anisotropy in rare-earth free materials.

  20. Metallic multilayers at the nanoscale

    SciTech Connect

    Jankowski, A.F.

    1994-11-01

    The development of multilayer structures has been driven by a wide range of commercial applications requiring enhanced material behaviors. Innovations in physical vapor deposition technologies, in particular magnetron sputtering, have enabled the synthesis of metallic-based structures with nanoscaled layer dimensions as small as one-to-two monolayers. Parameters used in the deposition process are paramount to the Formation of these small layer dimensions and the stability of the structure. Therefore, optimization of the desired material properties must be related to assessment of the actual microstructure. Characterization techniques as x-ray diffraction and high resolution microscopy are useful to reveal the interface and layer structure-whether ordered or disordered crystalline, amorphous, compositionally abrupt or graded, and/or lattice strained Techniques for the synthesis of metallic multilayers with subnanometric layers will be reviewed with applications based on enhancing material behaviors as reflectivity and magnetic anisotropy but with emphasis on experimental studies of mechanical properties.

  1. Anisotropies in thermal Casimir interactions: ellipsoidal colloids trapped at a fluid interface.

    PubMed

    Noruzifar, Ehsan; Oettel, Martin

    2009-05-01

    We study the effective interaction between two ellipsoidal particles at the interface of two fluid phases which are mediated by thermal fluctuations of the interface. In this system the restriction of the long-ranged interface fluctuations by particles gives rise to fluctuation-induced forces which are equivalent to interactions of Casimir type and which are anisotropic in the interface plane. Since the position and the orientation of the colloids with respect to the interface normal may also fluctuate, this system is an example of the Casimir effect with fluctuating boundary conditions. In the approach taken here, the Casimir interaction is rewritten as the interaction between fluctuating multipole moments of an auxiliary charge-density-like field defined on the area enclosed by the contact lines. These fluctuations are coupled to fluctuations of multipole moments of the contact line position (due to the possible position and orientational fluctuations of the colloids). We obtain explicit expressions for the behavior of the Casimir interaction at large distances for arbitrary ellipsoid aspect ratios. If colloid fluctuations are suppressed, the Casimir interaction at large distances is isotropic, attractive, and long ranged (double logarithmic in the distance). If, however, colloid fluctuations are included, the Casimir interaction at large distances changes to a power law in the inverse distance and becomes anisotropic. The leading power is 4 if only vertical fluctuations of the colloid center are allowed, and it becomes 8 if also orientational fluctuations are included.

  2. 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

  3. 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.

  4. 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.

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

    DOE PAGES

    Hachtel, Jordan A.; Sachan, Ritesh; Mishra, Rohan; ...

    2015-09-03

    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. In this paper, 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 complicatedmore » systems. Finally, we demonstrate, using NiSi2/Si heterostructures, that by varying the relative volume fractions of interface and bulk, we can tune the spectral range of the heterostructure absorption.« less

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

    SciTech Connect

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

    2015-09-03

    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. In this paper, 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. Finally, we demonstrate, using NiSi2/Si heterostructures, that by varying the relative volume fractions of interface and bulk, we can tune the spectral range of the heterostructure absorption.

  7. 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.

  8. Gilbert damping in single and multilayer ultrathin films: role of interfaces in nonlocal spin dynamics.

    PubMed

    Urban, R; Woltersdorf, G; Heinrich, B

    2001-11-19

    Unique features of the Gilbert damping in magnetic multilayers were investigated by ferromagnetic resonance (FMR) using magnetic single and double layer structures prepared by molecular beam epitaxy. The FMR linewidth for the Fe films in the double layer structures was larger than the FMR linewidth in the single Fe films having the same thickness. The additional FMR linewidth scaled inversely with the film thickness, and increased linearly with increasing microwave frequency. These results demonstrate that a transfer of electron angular momentum between the magnetic layers leads to additional relaxation torques.

  9. 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.

  10. Natural nanomorphous Ni/NiO magnetic multilayers: structure and magnetism of the high-Ar pressure series.

    PubMed

    Pappas, S D; Delimitis, A; Kapaklis, V; Papaioannou, E Th; Poulopoulos, P; Trachylis, D; Velgakis, M J; Politis, C

    2014-08-01

    Natural nanomorphous Ni/NiO multilayers have exhibited interesting magnetic properties, such as an unusual positive surface anisotropy and perpendicular magnetic anisotropy. Most attention has been paid to multilayers prepared by radio frequency magnetron sputtering under relatively low (3 x 10(-3) mbar) Ar pressure. Here we report on the correlation between structural and magnetic properties for a new series of multilayers, prepared under relatively high (3 x 10(-2) mbar) Ar pressure. The crystalline Ni individual layer thickness ranges between 5-8 nm. The amorphous NiO layer thickness is constant, about 1.1 nm thick. X-ray reflectivity showed that in some of the multilayers the high-order Bragg peaks become broader and diminish quickly. Cross-section transmission electron microscopy reveals that this occurs because the first bilayers are formed in accordance to the growth conditions, while the ones near the top are vanished. Despite the deterioration of the interface quality, all samples show tendency for perpendicular magnetic anisotropy even for large bilayer thickness of about 9 nm. Similar tendency is observed even by a 330 nm thick non-multilayered Ni film grown under the same conditions. This observation reveals the important role of strain and magnetoelastic anisotropy as a source of perpendicular magnetic anisotropy in the Ni/NiO multilayers.

  11. Perpendicular magnetic anisotropy at lattice-matched Co2FeAl/MgAl2O4(001) epitaxial interfaces

    NASA Astrophysics Data System (ADS)

    Sukegawa, Hiroaki; Hadorn, Jason Paul; Wen, Zhenchao; Ohkubo, Tadakatsu; Mitani, Seiji; Hono, Kazuhiro

    2017-03-01

    We report perpendicular magnetic anisotropy (PMA) induced at Co2FeAl/MgAl2O4(001) epitaxial interfaces prepared by magnetron sputtering and post-oxidation of MgAl layers. A PMA energy density of more than 4 Merg/cm3 for 1-nm-thick Co2FeAl layers and an effective interface PMA energy density of 1.6 erg/cm2 were achieved by controlling the interfacial oxidation states through fine-tuning of oxidation processes and annealing temperature. Cross-sectional scanning transmission electron microscopy imaging revealed a lattice-matched Co2FeAl/MgAl2O4 interface, which may be responsible for the large PMA energy due to a reduction of the bulk anisotropy contribution.

  12. A novel route to prepare a multilayer system via the combination of interface-mediated catalytic chain transfer polymerization and thiol-ene click chemistry.

    PubMed

    Zengin, Adem; Caykara, Tuncer

    2017-05-01

    Herein, we have designed a novel multilayer system composed of poly(methyl methacrylate) [poly(MMA)] brush, biotin, streptavidin and protein-A on a silicon substrate to attach onanti-immunoglobulin G (anti-IgG). poly(MMA) brush with vinyl end-group was first synthesized by the interface-mediated catalytic chain transfer polymerization. The brush was then modified with cysteamine molecules to generate the polymer chains with amine end-group via a thiol-ene click chemistry. The amine end-groups of poly(MMA) chains were also modified with biotin units to ensure selective connection points for streptavidin molecules. Finally, a multilayer system on the silicon substrate was formed by using streptavidin and protein-A molecules, respectively. This multilayer system was employed to attach anti-IgG molecules in a highly oriented manner and provide anti-IgG molecular functional configuration on the multilayer. High reproducibility of the amount of anti-IgG adsorption and homogeneous anti-IgG adsorption layer on the silicon surface could be provided by this multilayer system. The multilayer system with protein A may be opened the door for designing an efficient immunoassay protein chip.

  13. Interface induced out-of-plane magnetic anisotropy in magnetoelectric BiFeO3-BaTiO3 superlattices

    NASA Astrophysics Data System (ADS)

    Lazenka, Vera; Jochum, Johanna K.; Lorenz, Michael; Modarresi, Hiwa; Gunnlaugsson, Haraldur P.; Grundmann, Marius; Van Bael, Margriet J.; Temst, Kristiaan; Vantomme, André

    2017-02-01

    Room temperature magnetoelectric BiFeO3-BaTiO3 superlattices with strong out-of-plane magnetic anisotropy have been prepared by pulsed laser deposition. We show that the out-of-plane magnetization component increases with the increasing number of double layers. Moreover, the magnetoelectric voltage coefficient can be tuned by varying the number of interfaces, reaching a maximum value of 29 V/cm Oe for the 20×BiFeO3-BaTiO3 superlattice. This enhancement is accompanied by a high degree of perpendicular magnetic anisotropy, making the latter an ideal candidate for the next generation of data storage devices.

  14. Interface and growth-mode characterization of Ce/Fe and CeH≊2/Fe multilayers by x-ray diffraction and Rutherford backscattering spectroscopy

    NASA Astrophysics Data System (ADS)

    Klose, F.; Steins, M.; Kacsich, T.; Felsch, W.

    1993-07-01

    The detailed structural characterization of ion beam sputtered Ce/Fe and CeH≊2/Fe multilayers offers the possibility for a better understanding of their magnetic properties. In the case of the Ce/Fe multilayers the extension of the interface, as one of the most important features, is determined to 5-7 Å by means of Monte Carlo simulations of the small-angle x-ray scattering diagrams. Below a critical thickness of ≊24 Å Fe grows in an amorphous structure. Here the interface extension is enhanced. In contrast all CeH≊2/Fe multilayers show nearly abrupt interfaces. X-ray scattering experiments at higher angles in reflection and transmission mode provide information about the crystal structure, the texture, and the lateral dimensions of the grains in the samples. Depths profiles of the multilayers are generated by Rutherford backscattering spectroscopy, which confirm the well-ordered periodic structures. Surprisingly indications of an island-like growth mode of the Fe layers onto the Ce and CeH≊2 layers could be resolved by using this procedure.

  15. Origin of variation of shift field via annealing at 400°C in a perpendicular-anisotropy magnetic tunnel junction with [Co/Pt]-multilayers based synthetic ferrimagnetic reference layer

    NASA Astrophysics Data System (ADS)

    Honjo, H.; Ikeda, S.; Sato, H.; Watanebe, T.; Miura, S.; Nasuno, T.; Noguchi, Y.; Yasuhira, M.; Tanigawa, T.; Koike, H.; Muraguchi, M.; Niwa, M.; Ito, K.; Ohno, H.; Endoh, T.

    2017-05-01

    We investigated properties of perpendicular-anisotropy magnetic tunnel junctions (p-MTJs) with [Co/Pt]-multilayer based synthetic ferrimagnetic reference (SyF) layer at elevated annealing temperature Ta from 350°C to 400°C. Shift field HS defined as center field of minor resistance versus magnetic field curve of the MTJs increased with increase of Ta from 350°C to 400°C. The variation of HS is attributed to the variation of saturation magnetic moment in the SyF reference layer. Cross sectional energy dispersive X-ray spectroscopy analysis revealed that Fe element of CoFeB in the reference layer diffuses to Co/Pt multilayers in the SyF reference layer.

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

    SciTech Connect

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

    2015-02-15

    We examine highly stable perpendicular magnetic anisotropy (PMA) features of [Co/Pd]{sub 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.

  17. 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.

  18. Thermal stability of antiferromagnetically coupled multilayers with Ru/Co and Cu/Co interfaces

    NASA Astrophysics Data System (ADS)

    Bal, K.; van den Berg, H. A. M.; Deck, D.; Rasing, Th.

    2001-11-01

    The long-term thermal stability of the hard artificial antiferromagnetic subsystem (AAF) found in giant magnetoresistance (GMR) and tunnel magnetoresistance sensors based on Cu/Co/Ru/Co/Cu has been investigated using the complete sensor stack as well as of selected single layers. A striking asymmetry between both types of Co layers in the single Co layer samples with respect to magnetic and transport properties is observed, which show a different dynamics for each upon annealing. Directly after deposition, the Co/Ru interface is stronger mixed as compared to the Ru/Co interface, due to difference in sputter energies and order of growth. The different behavior upon annealing has been interpreted by the difference in concentration gradients and lattice mismatch at the interfaces. Despite the strong mixing found at the Co/Ru interface, the impact on the characteristics of the AAF, like the GMR signal and the rigidity is limited. Several causes, like the cohesion in the AAF induced by its Co seed layer on the Cu and the limited availability of Ru, are pointed out as likely origins of the improved stability of the AAF as compared to the single Co layers. Possibilities to even further improve the rigidity by carefully matching of anneal procedure and layer thicknesses are discussed.

  19. 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).

  20. Interface coupling and growth rate measurements in multilayer Rayleigh-Taylor instabilities

    NASA Astrophysics Data System (ADS)

    Adkins, Raymond; Shelton, Emily M.; Renoult, Marie-Charlotte; Carles, Pierre; Rosenblatt, Charles

    2017-06-01

    Magnetic levitation was used to measure the growth rate Σ vs wave vector k of a Rayleigh-Taylor instability in a three-layer fluid system, a crucial step in the elucidation of interface coupling in finite-layer instabilities. For a three-layer (low-high-low density) system, the unstable mode growth rate decreases as both the height h of the middle layer and k are reduced, consistent with an interface coupling ∝e-k h . The ratios of the three-layer to the established two-layer growth rates are in good agreement with those of classic linear stability theory, which has long resisted verification in that configuration.

  1. 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.

  2. 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.

  3. Interface effects on an ultrathin Co film in multilayers based on the organic semiconductor Alq3

    NASA Astrophysics Data System (ADS)

    Sidorenko, A. A.; Pernechele, C.; Lupo, P.; Ghidini, M.; Solzi, M.; De Renzi, R.; Bergenti, I.; Graziosi, P.; Dediu, V.; Hueso, L.; Hindmarch, A. T.

    2010-10-01

    The effect of the AlOx barrier thickness on magnetic and morphological properties of Ta/Co/(AlOx)/Alq3/Si hybrid structures was systematically studied by means of atomic force microscopy, superconducting quantum interference device magnetometry, and nuclear magnetic resonance (NMR). All used techniques pointed out that the barrier thickness of 2 nm is required to obtain a magnetically good cobalt layer on top of Alq3. C59o NMR measurements revealed that the AlOx barrier gives rise to the formation of an interface layer with "defective" cobalt favoring growth of "bulk" cobalt with good magnetic properties.

  4. Phase segregation of sulfonate groups in Nafion interface lamellae, quantified via neutron reflectometry fitting techniques for multi-layered structures.

    PubMed

    DeCaluwe, Steven C; Kienzle, Paul A; Bhargava, Pavan; Baker, Andrew M; Dura, Joseph A

    2014-08-21

    Neutron reflectometry analysis methods for under-determined, multi-layered structures are developed and used to determine the composition depth profile in cases where the structure is not known a priori. These methods, including statistical methods, sophisticated fitting routines, and coupling multiple data sets, are applied to hydrated and dehydrated Nafion nano-scaled films with thicknesses comparable to those found coating electrode particles in fuel cell catalyst layers. These results confirm the lamellar structure previously observed on hydrophilic substrates, and demonstrate that for hydrated films they can accurately be described as layers rich in both water and sulfonate groups alternating with water-poor layers containing an excess of fluorocarbon groups. The thickness of these layers increases slightly and the amplitude of the water volume fraction oscillation exponentially decreases away from the hydrophilic interface. For dehydrated films, the composition oscillations die out more rapidly. The Nafion-SiO2 substrate interface contains a partial monolayer of sulfonate groups bonded to the substrate and a large excess of water compared to that expected by the water-to-sulfonate ratio, λ, observed throughout the rest of the film. Films that were made thin enough to truncate this lamellar region showed a depth profile nearly identical to thicker films, indicating that there are no confinement or surface effects altering the structure. Comparing the SLD profile measured for films dried at 60 °C to modeled composition profiles derived by removing water from the hydrated lamellae suggests incomplete re-mixing of the polymer groups upon dehydration, indicated limited polymer mobility in these Nafion thin films.

  5. Interface metallization and electrical characterization of Ta-Pt multilayers on n-type SiC

    NASA Astrophysics Data System (ADS)

    Yang, H.; Peng, T. H.; Wang, W. J.; Wang, W. Y.; Chen, X. L.

    2008-12-01

    A multilayered metallization Ta/Pt/Ta has been developed for obtaining low resistance ohmic contact to n-type SiC. The electrical, chemical and microstructural properties of the contacts are studied. It is observed that the conducting behavior is rectifying in the as-deposited state, whereas becomes ohmic upon annealing above 900 °C for 5 min in an Ar ambient, resulting in a typical specific contact resistance as low as 10 -4 Ω cm 2 range corresponding to a doping level of 2 × 10 18 cm -3. The Auger electron spectroscopy (AES) and X-ray diffraction analysis results indicate that platinum atoms migrate towards SiC to form platinum silicides in intimate contact with SiC substrate. While the C atoms released from the SiC interface interact with out-diffused Ta atoms to form TaC at the contact surface. The addition of Ta into the Pt metallization scheme serves to reduce the residual carbon left behind from SiC dissociation and Pt-silicides formation, thus could lead to improvement of the thermal and electrical stability. Ta/Pt/Ta metallization on n-SiC is an effective method to realize ohmic contact.

  6. Ferromagnetic resonance study of interface coupling for spin waves in narrow NiFe/Ru/NiFe multilayer nanowires

    NASA Astrophysics Data System (ADS)

    Lupo, P.; Haghshenasfard, Z.; Cottam, M. G.; Adeyeye, A. O.

    2016-12-01

    A systematic investigation is presented for the magnetization dynamics in trilayer nanowires, consisting of two permalloy (Ni80Fe20 ) layers separated by a nonmagnetic Ru spacer layer. The width of the wires ranges from 90 to 190 nm. By varying the Ru thickness between 0.7 and 2.0 nm, the interlayer coupling can be effectively controlled, modifying the corresponding magnetic ground state and the spin-wave dynamics. By contrast with previous work on coupled trilayer nanowires with larger widths (270 nm and more), the focus here is on nanowire arrays where the strong shape anisotropy competes with the Ruderman-Kittel-Kasuya-Yosida interactions and biquadratic exchange interactions across the Ru interface, as well as dipolar interactions and Zeeman energy. As a result, the spin-wave spectrum is found to be drastically modified. Ferromagnetic resonance and hysteresis loop measurements are reported over a wide range of applied magnetic fields, showing that the overall magnetization alignment between the permalloy layers may be parallel, antiparallel, or in a spin-flop state, depending on the overall interlayer coupling. The experimental results for different stripe widths are successfully analyzed using a microscopic dipole-dipole theory and micromagnetic simulations.

  7. Role of top and bottom interfaces of a Pt/Co/AlOx system in Dzyaloshinskii-Moriya interaction, interface perpendicular magnetic anisotropy, and magneto-optical Kerr effect

    NASA Astrophysics Data System (ADS)

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

    2017-03-01

    We investigate the role of top and bottom interfaces in inversion symmetry-breaking Pt/Co/AlOx systems by inserting ultra-thin Cu layers. Wedge-type ultrathin Cu layers (0-0.5 nm) are introduced between Pt/Co or Co/AlOx interfaces. Interface sensitive physical quantities such as the interfacial Dzyaloshinskii-Moriya interaction (iDMI) energy density, the interfacial perpendicular magnetic anisotropy (iPMA), and the magneto-optical Kerr effects (MOKE) are systematically measured as a function of Cu-insertion layer thickness. We find that the Cu-insertion layer in the bottom interface (Pt/Co) plays a more important role in iDMI, PMA, and MOKE. In contrast, the top interface (Co/AlOx) noticeably contributes to only PMA, while its contributions to iDMI and MOKE enhancement are less significant. Although the PMA mainly comes from the bottom interface (Pt/Co), the Cu-insertion layers of all interfaces (Pt/Co, Co/AlOx) influence PMA. For iDMI, only the Cu-insertion layer in the bottom interface exerts SOC suppression which leads iDMI energy to decrease rapidly.

  8. Enhancement of voltage-controlled magnetic anisotropy through precise control of Mg insertion thickness at CoFeB|MgO interface

    NASA Astrophysics Data System (ADS)

    Li, Xiang; Fitzell, Kevin; Wu, Di; Karaba, C. Ty; Buditama, Abraham; Yu, Guoqiang; Wong, Kin L.; Altieri, Nicholas; Grezes, Cecile; Kioussis, Nicholas; Tolbert, Sarah; Zhang, Zongzhi; Chang, Jane P.; Khalili Amiri, Pedram; Wang, Kang L.

    2017-01-01

    We studied the impact of different insertion layers (Ta, Pt, and Mg) at the CoFeB|MgO interface on voltage-controlled magnetic anisotropy (VCMA) effect and other magnetic properties. Inserting a very thin Mg layer of 0.1-0.3 nm yielded a VCMA coefficient of 100 fJ/V-m, more than 3 times higher than the average values of around 30 fJ/V-m reported in Ta|CoFeB|MgO-based structures. Ta and Pt insertion layers also showed a small improvement, yielding VCMA coefficients around 40 fJ/V-m. Electrical, magnetic, and X-ray diffraction results reveal that a Mg insertion layer of around 1.2 nm gives rise to the highest perpendicular magnetic anisotropy, saturation magnetization, as well as the best CoFe and MgO crystallinity. Other Mg insertion thicknesses give rise to either under- or over-oxidation of the CoFe|MgO interface; a strong over-oxidation of the CoFe layer leads to the maximum VCMA effect. These results show that precise control over the Mg insertion thickness and CoFe oxidation level at the CoFeB|MgO interface is crucial for the development of electric-field-controlled perpendicular magnetic tunnel junctions with low write voltage.

  9. Reduction of thermal conductivity in MnSi{sub 1.7} multi-layered thin films with artificially inserted Si interfaces

    SciTech Connect

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

    2016-08-08

    We report a lowered lattice thermal conductivity in nm-scale MnSi{sub 1.7}/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 MnSi{sub 1.7} and Si. By applying the above nanostructures, we reduced the lattice thermal conductivity down to half that of bulk MnSi{sub 1.7}/Si composite materials. The obtained value of 1.0 W/K m is the experimentally observed minimum in MnSi{sub 1.7}-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 MnSi{sub 1.7}/Si interfaces in the multilayers.

  10. Growth and characterization of sputtered BSTO/BaM multilayers

    NASA Astrophysics Data System (ADS)

    Srinath, S.; Frey, N. A.; Heindl, R.; Srikanth, H.; Coffey, K. R.; Dudney, N. J.

    2005-05-01

    Multilayers of Ba0.5Sr0.5TiO3 (BSTO) and BaFe12O19 (BaM), with tunable permeability and permittivity are attractive systems for radio frequency and microwave applications. We have grown multilayers of BSTO and BaM using magnetron sputtering on Al2O3 substrates. Film growth conditions such as sputtering parameters were optimized to obtain high quality multilayers. X-ray diffraction established that both BSTO and BaM were formed and cross-sectional SEM studies showed sharp interfaces between BSTO and BaM layers. Magnetization showed a large coercivity (˜2000Oe ) consistent with the hexaferrite component. The hysteresis loops also revealed the distinct influence of magnetocrystalline and shape anisotropies at different temperatures.

  11. Growth and Characterization of Sputtered BSTO/BaM Multilayers

    SciTech Connect

    Srinath, S.; Frey, N. A.; Heindl, R.; Srikanth, H.; Coffey, K. R.; Dudney, Nancy J

    2005-01-01

    Multilayers of Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} (BSTO) and BaFe{sub 12}O{sub 19} (BaM), with tunable permeability and permittivity are attractive systems for radio frequency and microwave applications. We have grown multilayers of BSTO and BaM using magnetron sputtering on Al{sub 2}O{sub 3} substrates. Film growth conditions such as sputtering parameters were optimized to obtain high quality multilayers. X-ray diffraction established that both BSTO and BaM were formed and cross-sectional SEM studies showed sharp interfaces between BSTO and BaM layers. Magnetization showed a large coercivity ( {approx}2000 Oe) consistent with the hexaferrite component. The hysteresis loops also revealed the distinct influence of magnetocrystalline and shape anisotropies at different temperatures.

  12. 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.

  13. Pd Layer Thickness Dependence of Tunnel Magnetoresistance Properties in CoFeB/MgO-Based Magnetic Tunnel Junctions with Perpendicular Anisotropy CoFe/Pd Multilayers

    NASA Astrophysics Data System (ADS)

    Mizunuma, Kotaro; Yamanouchi, Michihiko; Ikeda, Shoji; Sato, Hideo; Yamamoto, Hiroyuki; Gan, Hua-Dong; Miura, Katsuya; Hayakawa, Jun; Matsukura, Fumihiro; Ohno, Hideo

    2011-02-01

    The authors investigated tunnel magnetoresistance (TMR) properties in [CoFe/Pd]-multilayer/CoFeB/MgO/CoFeB/[Pd/CoFe]-multilayer magnetic tunnel junctions (MTJs) having two different Pd layer thicknesses. By reducing the Pd layer thickness from 1.2 to 0.2 nm, the TMR ratio was enhanced from 7 to 101% at the annealing temperature (Ta) of 300 °C. The thin Pd layers resulted in high residual B concentration in the CoFeB layer after high-Ta annealing and in the suppression of crystallization of the CoFeB layer from the fcc(111)-Pd layer side.

  14. Spin reorientation transition in Fe/CeH2 multilayers probed by soft X-ray resonant magnetic scattering

    NASA Astrophysics Data System (ADS)

    Dürr, H. A.; Münzenberg, M.; Felsch, W.; Dhesi, S. S.

    The magnetic domain configurations of Fe 3d spins in Fe/CeH2 multilayers were measured by soft X-ray resonant magnetic scattering. The interface region could be probed by setting up X-ray standing waves due to the multilayer periodicity. By resolving first- and second-order magnetic scattering contributions, we show that the latter probe directly the magneto-crystalline anisotropy which is dominated by the Fe interface layers causing a spin reorientation transition when the temperature is lowered.

  15. Effect of heavy-metal insertions at Fe/MgO interfaces on electric-field-induced modification of magnetocrystalline anisotropy

    NASA Astrophysics Data System (ADS)

    Nakamura, K.; Nomura, T.; Pradipto, A.-M.; Nawa, K.; Akiyama, T.; Ito, T.

    2017-05-01

    Magnetocrystalline anisotropy (MCA) at Fe/MgO interfaces with insertions of 3d (Co, Ni), 4d (Ru, Rh, Pd), and 5d (Os, Ir, Pt) elements in external electric fields was investigated from first-principles calculations. The MCA energy and the electric-field-induced MCA modification dramatically depend on the inserted elements. Large MCA modification may be achieved by heavy-metal insertions, in which the strength of spin-orbit coupling of inserted elements and the position of the Fermi level relative to d band level play key roles.

  16. Perpendicular magnetic anisotropy at the interface between ultrathin Fe film and MgO studied by angular-dependent x-ray magnetic circular dichroism

    SciTech Connect

    Okabayashi, J.; Koo, J. W.; Mitani, S.; Sukegawa, H.; Takagi, Y.; Yokoyama, T.

    2014-09-22

    Interface perpendicular magnetic anisotropy (PMA) in ultrathin Fe/MgO (001) has been investigated using angular-dependent x-ray magnetic circular dichroism (XMCD). We found that anisotropic orbital magnetic moments deduced from the analysis of XMCD contribute to the large PMA energies, whose values depend on the annealing temperature. The large PMA energies determined from magnetization measurements are related to those estimated from the XMCD and the anisotropic orbital magnetic moments through the spin-orbit interaction. The enhancement of anisotropic orbital magnetic moments can be explained mainly by the hybridization between the Fe 3d{sub z}{sup 2} and O 2p{sub z} states.

  17. Effect of antiferromagnetic interfacial coupling on spin-wave resonance frequency of multi-layer film

    NASA Astrophysics Data System (ADS)

    Qiu, Rong-ke; Cai, Wei

    2017-08-01

    We investigate the spin-wave resonance (SWR) frequency in a bicomponent bilayer and triple-layer films with antiferromagnetic or ferromagnetic interfacial couplings, as function of interfacial coupling, surface anisotropy, interface anisotropy, thickness and external magnetic field, using the linear spin-wave approximation and Green's function technique. The microwave properties for multi-layer magnetic film with antiferromagnetic interfacial coupling is different from those for multi-layer magnetic film with ferromagnetic interfacial coupling. For the bilayer film with antiferromagnetic interfacial couplings, as the lower (upper) surface anisotropy increases, only the SWR frequencies of the odd (even) number modes increase. The lower (upper) surface anisotropy does not affect the SWR frequencies of the even (odd) number modes. For the multi-layer film with antiferromagnetic interfacial coupling, the SWR frequency of modes m = 1, 3 and 4 decreases while that of mode m = 2 increases with increasing thickness of the film within a proper parameter region. The present results could be useful in enhancing our fundamental understanding and show the method to enhance and adjust the SWR frequency of bicomponent multi-layer magnetic films with antiferromagnetic or ferromagnetic interfacial coupling.

  18. Correlation between the optical performance of TiO2-Ag-TiO2 multilayers and the interface roughness between the layers

    NASA Astrophysics Data System (ADS)

    von Blanckenhagen, Bernhard; Tonova, Diana

    2005-09-01

    Ag-dielectric multilayers are widely used in the production of heat reflecting filters, induced transmission filters, beam splitters, etc. The performance of such coatings in the visible part of the spectrum is sometimes strongly influenced by a plasmon absorption in the Ag-layer or a surface plasmon absorption in the Ag-dielectric interfaces. The strength of the plasmon absorption is very sensitive to the layer structure, the light polarization and the angle of incidence. As a result, the target specifications for reflection and transmission are not reached easily. We investigate PVD-deposited TiO2-Ag-TiO2 multilayers by means of optical reflection and transmission and Grazing Incidence X-ray Reflectometry (GIXR). The GIXR-method yields the individual layers thicknesses and the interface roughness. Some of the coatings have a broad absorption peak between 500 and 400nm that cannot be modeled using the bulk dielectric function of Ag. The magnitude of the absorption peak is correlated with the measured roughness of the TiO2-Ag interfaces. The analysis of the results shows the critical parameters for the deposition process.

  19. 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.

  20. Electronic interaction and bipolar resistive switching in copper oxide-multilayer graphene hybrid interface: Graphene as an oxygen ion storage and blocking layer

    NASA Astrophysics Data System (ADS)

    Singh, Bharti; Mehta, B. R.; Govind, Feng, X.; Müllen, Klaus

    2011-11-01

    This study reports a bipolar resistive switching device based on copper oxide (CuO)-multilayer graphene (MLG) hybrid interface in complete contrast to the ohmic and rectifying characteristics of junctions based on individual MLG and CuO layers. The observed shift and the occurrence of additional O1s, Cu2p, and C1s core level peaks indicate electronic interaction at the hybrid interfacial layer. Large changes in the resistive switching parameters on changing the ambient conditions from air to vacuum establish the important role of MLG as oxygen ion storage and blocking layer towards the observed resistive switching effect.

  1. 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.

  2. Interfacial effects in multilayers

    SciTech Connect

    Barbee, T.W., Jr.

    1998-04-01

    Interfacial structure and the atomic interactions between atoms at interfaces in multilayers or nano-laminates have significant impact on the physical properties of these materials. A technique for the experimental evaluation of interfacial structure and interfacial structure effects is presented and compared to experiment. In this paper the impact of interfacial structure on the performance of x-ray, soft x-ray and extreme ultra-violet multilayer optic structures is emphasized. The paper is concluded with summary of these results and an assessment of their implications relative to multilayer development and the study of buried interfaces in solids in general.

  3. Interfacial effects in multilayers

    SciTech Connect

    Barbee, T W

    1999-06-28

    There are many physical characterization approaches which evaluate a limited set of structural elements in multilayers: they study a single interface; they study a single layer of material; they study a very small sample of a multilayer. On a broader basis, the interference phenomena on which the performance of x-ray optic multilayers is based integrates over the full area/volume of the multilayer illuminated. In order to gain understanding of the impact of imperfections on multilayer performance it is necessary to develop an experimental approach that provides detailed information about the effects of interfaces in the multilayer obtained when the multilayer is being applied in a manner directly related to application. Additionally, it is also of interest to determine the breadth of application of any such experimental approach to the general study of interfaces in solids. The primary goal in this research was to develop an experimental methodology to quantitatively characterize both the physical and electronic characteristics of interfaces in multilayer structures. The approach was to fabricate multilayers from three elements so that one monolayer or less thick ''marker layers'' were selectively deposited on a given set interfaces in the multilayer. These ''marker layers'' could then interrogated by scattering and fluorescence techniques for their distribution, for their atomic arrangements relative to the thicker layers and for their electronic state at the interfaces as affected by the thicker layer materials. WC/C multilayers with one monolayer (2.33 {angstrom}) of tantalum at the WC on C and the C on WC interfaces were fabricated and studied. Ta was selected as the marker layer material as its L{sub 3} absorption edge is at 9879 eV, more than 300 eV less than the W L{sub 3} edge at 10200 eV. Reflectivities at 9850 eV, 9879 eV and 9950 eV were measured: Ta layers standing wave fluorescence on the multilayer Bragg peak at these energies and fluorescence EXAFS

  4. 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.

  5. FANTEN: a new web-based interface for the analysis of magnetic anisotropy-induced NMR data.

    PubMed

    Rinaldelli, Mauro; Carlon, Azzurra; Ravera, Enrico; Parigi, Giacomo; Luchinat, Claudio

    2015-01-01

    Pseudocontact shifts (PCSs) and residual dipolar couplings (RDCs) arising from the presence of paramagnetic metal ions in proteins as well as RDCs due to partial orientation induced by external orienting media are nowadays routinely measured as a part of the NMR characterization of biologically relevant systems. PCSs and RDCs are becoming more and more popular as restraints (1) to determine and/or refine protein structures in solution, (2) to monitor the extent of conformational heterogeneity in systems composed of rigid domains which can reorient with respect to one another, and (3) to obtain structural information in protein-protein complexes. The use of both PCSs and RDCs proceeds through the determination of the anisotropy tensors which are at the origin of these NMR observables. A new user-friendly web tool, called FANTEN (Finding ANisotropy TENsors), has been developed for the determination of the anisotropy tensors related to PCSs and RDCs and has been made freely available through the WeNMR ( http://fanten-enmr.cerm.unifi.it:8080 ) gateway. The program has many new features not available in other existing programs, among which the possibility of a joint analysis of several sets of PCS and RDC data and the possibility to perform rigid body minimizations.

  6. 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.

  7. An accurate and fast forward model of three-dimensional electromagnetic wave scattering in a layered structure with multilayer rough interfaces

    NASA Astrophysics Data System (ADS)

    Wu, Chao; Zhang, Xiaojuan; Fang, Guangyou; Shi, Jiancheng; Liu, Shiyin

    2015-03-01

    We develop an accurate and fast forward model for calculating the compact closed-form high-order perturbative solutions of the problem of three-dimensional (3-D) radiation and propagation electromagnetic fields in a layered structure with multilayer rough interfaces. The proposed method for the fast forward model is first demonstrated by strictly theoretical formulas derivation in the framework of classical small perturbation method (SPM) without other else approximation and equivalent process. The kernel functions of high order are proposed for calculating the radar cross sections with more efficiency and clear physical meanings for better use in practice. What is more, we give the clear physical interpretation of the first-order fully polarimetric electromagnetic wave scattering mechanism in the layered structure with multilayer rough interfaces. The proposed forward model is necessary to insure a successful inversion process. Furthermore, the high-order SPM solutions derived by employing the proposed method are validated with existing methods and numerical results. Finally, we study the performance of the high-order fully polarimetric electromagnetic wave scattering according to the numerical results and analyze the scattering enhancement phenomena.

  8. Scaling of anomalous Hall effect in Ta/CoFeB/MgAl2O4/Ta multilayers

    NASA Astrophysics Data System (ADS)

    Wu, Yong; Zhang, Qimeng; Meng, Kangkang; Chen, Jikun; Xu, Xiaoguang; Miao, Jun; Jiang, Yong

    2017-06-01

    The anomalous Hall effect (AHE) is studied in Ta/CoFeB/MgAl2O4/Ta multilayers with different thicknesses of MgAl2O4 (t), which causes in-plane magnetic anisotropy (IMA) for t = 1.0 nm and perpendicular magnetic anisotropy (PMA) for t ≥ 1.2 nm. Conventional scaling was demonstrated to be not inadequate in our case. The origin of the AHE in Ta/CoFeB/MgAl2O4/Ta multilayers is mainly an extrinsic mechanism. The contribution of skew scattering (SS) is unneglectable, and both the SS and side jump are enhanced when the magnetic anisotropy changes from IMA to PMA, indicating that the oxidation at the interface of CoFeB/MgAl2O4 has a dominant influence on the AHE.

  9. 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.

  10. 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.

  11. Stabilization of phospholipid multilayers at the air-water interface by compression beyond the collapse: a BAM, PM-IRRAS, and molecular dynamics study.

    PubMed

    Saccani, J; Castano, S; Beaurain, F; Laguerre, M; Desbat, B

    2004-10-12

    Compression beyond the collapse of phospholipid monolayers on a modified Langmuir trough has revealed the formation of stable multilayers at the air-water interface. Those systems are relevant new models for studying the properties of biological membranes and for understanding the nature of interactions between membranes and peptides or proteins. The collapse of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), 1,2-di[cis-9-octadecenoyl]-sn-glycero-3-[phospho-l-serine] (DOPS), 1,2-di[cis-9-octadecenoyl]-sn-glycero-3-phosphocholine (DOPC), and 1,2-di[cis-9-octadecenoyl]-sn-glycero-3-[phospho-1-rac-glycerol] (DOPG) monolayers has been investigated by isotherm measurements, Brewster angle microscopy (BAM), and polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS). In the cases of DMPC and DOPS, the collapse of the monolayers revealed the formation of bilayer and trilayer structures, respectively. The DMPC bilayer stability has been analyzed also by a molecular dynamics study. The collapse of the DOPC and DOPG systems shows a different behavior, and the Brewster angle microscopy reveals the formation of luminous bundles, which can be interpreted as diving multilayers in the subphase.

  12. Element-specific characterization of the interface magnetism in [Co{sub 2}MnGe/Au]{sub n} multilayers by x-ray resonant magnetic scattering

    SciTech Connect

    Grabis, J.; Bergmann, A.; Nefedov, A.; Westerholt, K.; Zabel, H.

    2005-07-01

    The magnetism of the ferromagnetic half-metallic Heusler compounds at the interface with other metals, insulators, and semiconductors is a critical issue when judging the prospects for these materials to be used in future spintronic devices. We study the interface magnetism of the ferromagnetic half metal Co{sub 2}MnGe in a high-quality [Co{sub 2}MnGe/Au]{sub 50} multilayer by x-ray resonant magnetic reflectivity using circularly polarized x-ray radiation in the energy range of the Co and Mn L{sub 2,3} edges. An analysis of the magnetic part of the reflectivity at the superlattice Bragg peaks allows a precise determination of the magnetization profile within the Co{sub 2}MnGe layers. We find that the profile is definitely different for Mn and Co spins and asymmetric with respect to the growth direction. At room temperature nonferromagnetic interface layers exist with a thickness of about 0.45 nm at the bottom and 0.3 nm at the top of the Co{sub 2}MnGe layers. Additionally, the comparison of the nonresonant and resonant magnetic diffuse scattering reveals that the correlated structural and magnetic roughness are almost identical, the corresponding length scale being the in-plane crystallite size.

  13. Structural and magnetic properties of evaporated nanostructured Fe/V multilayers.

    PubMed

    Duc, N H; Lechevallier, L; Fnidiki, A; Danh, T M; Teillet, J; Bencok, P; Heckmann, O; Gibaud, A; Hazra, S; Hricovini, K

    2002-04-01

    The structural and magnetic properties of the evaporated Fe/V multilayers with a fixed V-layer thickness (tV = 1.5 nm) and variable Fe layer thicknesses (0.75 nm < or = tFe < or = 6 nm) have been studied by X-ray reflectivity and high-angle X-ray diffraction, conversion-electron Mössbauer spectrometry, and vibrating sample magnetometry. The results show that multilayers are formed with a broad Fe/V interface and pure crystalline bcc-Fe layers in the center of the individual subsystems. The Fe spin orientation is aligned in the film plane in the individual centers as well in the interfacial regions. The interfacial anisotropy constant Ks was estimated to be equal to 0.04 mJ/m2. This parallel magnetic anisotropy is discussed in terms of reduced symmetry effects on the hybridized 3d states.

  14. 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.

  15. Multiscale micromagnetism of Co-Pd multilayers

    NASA Astrophysics Data System (ADS)

    Manchanda, P.; Skomski, R.; Sahota, P. K.; Franchin, M.; Fangohr, H.; Kashyap, A.

    2012-04-01

    The interplay between atomic and micromagnetic effects in Co-Pd multilayers is investigated by model calculations and numerical simulations. By minimizing the total exchange energy, an effective exchange stiffness is obtained. The stiffness depends on the superlattice periodicity, on the wave vector of the magnetization variation, and on the exchange coupling through the Pd, which is calculated from first principles (J = 7.66 mJ/m2). The net magnetic anisotropy, Keff = 0.71 MJ/m3, which is also obtained from first principles, contains two parts, namely the Pd-Co interface anisotropy Kif = 0.45 mJ/m2 and the bulk anisotropy KCo = -0.28 MJ/m3 of the strained fcc Co. For vertical and lateral magnetization variations, we find domain-wall thicknesses of 5.1 nm and 6.9 nm and domain-wall energies of 5.94 mJ/m2 and 6.66 mJ/m2, respectively.

  16. 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.

  17. Multi-layer magnetism and thermal stability in perpendicular magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Singh, Amritpal

    Thermal stability is one of the critical issues for applications of nano-magnets for spin-logic applications. Our work is focused on the thermal stability in perpendicular magnetic tunnel junctions (p-MTJs) for MRAM and STT-RAM purposes. Most of the research so far has been focused on p-MTJs based on CoFeB/MgO interfacial anisotropy as the sandwich structures with bcc ferromagnetic electrodes and MgO spacer have large magnetoresistance. It has been demonstrated that this interfacial anisotropy by itself is not sufficient to reduce the p-MTJ diameter down to 20 nm. To overcome this problem, we have proposed and investigated hard-soft composite structures: [Co/Pt multilayers]/ (non-magnetic element) /CoFeB/MgO, to control the perpendicular magnetic anisotropy (PMA) of the CoFeB soft layer by exchange coupling with Co/Pt multilayers having bulk anisotropy. Ta has been studied as the first non-magnetic insertion element, since it helps in crystallization of CoFeB by absorbing the B. The other elements studied as insertions are V and Zr, since they have low damping constants. A micromagnetic model has been set up on the basis of experimental results and ab-initio calculations to study the effect of insertion thickness and damping parameter on switching current density and switching time. To understand the mechanism of CoFeB/MgO interfacial anisotropy, low temperature scaling of interface anisotropy (Ks(T)) and saturation magnetization (M s(T)) is measured, since at low temperature (T), Ks(T) vs Ms(T) scaling is sensitive to the details of the anisotropy mechanism. For the first time, we experimentally show that for CoFeB/MgO, Ks(T) scales as Ms(T) 2.2, hence indicating the two-ion type anisotropy as the dominant mechanism.

  18. Structure of interfaces in GaN/AlN and Ge/Si multilayered heterosystems by XAFS spectroscopy

    NASA Astrophysics Data System (ADS)

    Erenburg, S. B.; Trubina, S. V.; Zhuravlev, K. S.; Malin, T. V.; Zinovyev, V. A.; Dvurechenskii, A. V.; Kuchinskaya, P. A.; Kvashnina, K. O.

    2016-11-01

    III-nitride heterostructures in the form of multilayered quantum wells (MQWs) or quantum dots (QDs) and interacting Ge QDs (“quantum molecules”) are promising candidates for high-speed intersubband (ISB) optical devices relying on the quantum confinement of electrons. Microstructural parameters (interatomic distances, coordination numbers, and Debye-Waller factors) were determined by means of EXAFS spectroscopy based on the Synchrotron Radiation, and the relationship between the variations in these parameters and the morphology of superlattices and symmetric assembles of QDs were established. The EXAFS technique has been used to study the local structure of thin hexagonal GaN/AlN MQWs grown by ammonia MBE at different temperatures. It is shown that the heterointerface intermixing leads to a decrease in the Ga-Al interatomic distance and the Ga-Ga coordination number in MQWs. The degree of intermixing in the boundary layers rises from 30% to 40% with increase of the growth temperature from 795 to 895 °C. It was found that in the first phase of quantum molecules growth Ge atoms concentration is 25%. With further growth (deposition of the base layers) Ge concentration increases up to 35-45%, depending on the temperature (from 610 to 550 °C) of deposition.

  19. Probing the interface of doped isotopically mixed helium droplets by the directional anisotropy of interatomic Coulombic decay.

    PubMed

    Kryzhevoi, Nikolai V; Mateo, David; Pi, Martí; Barranco, Manuel; Cederbaum, Lorenz S

    2013-11-07

    Interatomic Coulombic decay (ICD) represents an efficient electronic relaxation mechanism of an ionized or an excited system embedded in an environment. The type of this environment and its size have a great impact on the ICD performance. It is stressed that ICD is sensitive to the arrangement of neighboring atoms when the initially created vacancy has a polarization direction. This is demonstrated in the present paper for the case of a 3p-ionized Ca surrounded by He atoms. Useful explicit expressions are derived for the ICD widths which show that the neighbors located along the polarization direction of the ionized orbital have the largest contribution to the ICD rate. By comparison with ab initio results for small clusters, we also show that in a helium environment, the pairwise approximation represents a reliable approach for computing ICD widths. Using this approximation and the density distribution of the helium atoms obtained within density functional theory, we explore ICD in large isotopically mixed helium droplets doped with Ca. A special emphasis is given to the difference between the ICD widths for the Ca3p orbitals directed perpendicular and parallel to the droplet surface. Depending on the size and isotopic composition of the droplet, Ca resides in the interfacial layer between the (4)He core and the (3)He outer shell. Hence, ICD studies in these droplets may provide valuable information on the properties of this interface.

  20. Wedged multilayer Laue Lens.

    SciTech Connect

    Conley, R.; Liu, C.; Qian, J.; Kewish, C. M.; Macrander, A. T.; Yan, H.; Kang, H. C.; Maser, J.; Stephenson, G. B.

    2008-05-01

    A multilayer Laue lens (MLL) is an x-ray focusing optic fabricated from a multilayer structure consisting of thousands of layers of two different materials produced by thin-film deposition. The sequence of layer thicknesses is controlled to satisfy the Fresnel zone plate law and the multilayer is sectioned to form the optic. An improved MLL geometry can be created by growing each layer with an in-plane thickness gradient to form a wedge, so that every interface makes the correct angle with the incident beam for symmetric Bragg diffraction. The ultimate hard x-ray focusing performance of a wedged MLL has been predicted to be significantly better than that of a nonwedged MLL, giving subnanometer resolution with high efficiency. Here, we describe a method to deposit the multilayer structure needed for an ideal wedged MLL and report our initial deposition results to produce these structures.

  1. Multilayer Dye Aggregation at Dye/TiO2 Interface via π…π Stacking and Hydrogen Bond and Its Impact on Solar Cell Performance: A DFT Analysis

    PubMed Central

    Zhang, Lei; Liu, Xiaogang; Rao, Weifeng; Li, Jingfa

    2016-01-01

    Multilayer dye aggregation at the dye/TiO2 interface of dye-sensitized solar cells is probed via first principles calculations, using p-methyl red azo dye as an example. Our calculations suggest that the multilayer dye aggregates at the TiO2 surface can be stabilized by π…π stacking and hydrogen bond interactions. Compared with previous two-dimensional monolayer dye/TiO2 model, the multilayer dye aggregation model proposed in this study constructs a three-dimensional multilayer dye/TiO2 interfacial structure, and provides a better agreement between experimental and computational results in dye coverage and dye adsorption energy. In particular, a dimer forms by π…π stacking interactions between two neighboring azo molecules, while one of them chemisorbs on the TiO2 surface; a trimer may form by introducing one additional azo molecule on the dimer through a hydrogen bond between two carboxylic acid groups. Different forms of multilayer dye aggregates, either stabilized by π…π stacking or hydrogen bond, exhibit varied optical absorption spectra and electronic properties. Such variations could have a critical impact on the performance of dye sensitized solar cells. PMID:27767196

  2. Multilayer Dye Aggregation at Dye/TiO2 Interface via π…π Stacking and Hydrogen Bond and Its Impact on Solar Cell Performance: A DFT Analysis

    NASA Astrophysics Data System (ADS)

    Zhang, Lei; Liu, Xiaogang; Rao, Weifeng; Li, Jingfa

    2016-10-01

    Multilayer dye aggregation at the dye/TiO2 interface of dye-sensitized solar cells is probed via first principles calculations, using p-methyl red azo dye as an example. Our calculations suggest that the multilayer dye aggregates at the TiO2 surface can be stabilized by π…π stacking and hydrogen bond interactions. Compared with previous two-dimensional monolayer dye/TiO2 model, the multilayer dye aggregation model proposed in this study constructs a three-dimensional multilayer dye/TiO2 interfacial structure, and provides a better agreement between experimental and computational results in dye coverage and dye adsorption energy. In particular, a dimer forms by π…π stacking interactions between two neighboring azo molecules, while one of them chemisorbs on the TiO2 surface; a trimer may form by introducing one additional azo molecule on the dimer through a hydrogen bond between two carboxylic acid groups. Different forms of multilayer dye aggregates, either stabilized by π…π stacking or hydrogen bond, exhibit varied optical absorption spectra and electronic properties. Such variations could have a critical impact on the performance of dye sensitized solar cells.

  3. 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.

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

    PubMed

    Franco, A F; Kachkachi, H

    2013-08-07

    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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. Magnetic metallic multilayers

    SciTech Connect

    Hood, Randolph Quentin

    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.

  10. Magnetic multilayers on nanospheres.

    PubMed

    Albrecht, Manfred; Hu, Guohan; Guhr, Ildico L; Ulbrich, Till C; Boneberg, Johannes; Leiderer, Paul; Schatz, Günter

    2005-03-01

    Thin-film technology is widely implemented in numerous applications. Although flat substrates are commonly used, we report on the advantages of using curved surfaces as a substrate. The curvature induces a lateral film-thickness variation that allows alteration of the properties of the deposited material. Based on this concept, a variety of implementations in materials science can be expected. As an example, a topographic pattern formed of spherical nanoparticles is combined with magnetic multilayer film deposition. Here we show that this combination leads to a new class of magnetic material with a unique combination of remarkable properties: The so-formed nanostructures are monodisperse, magnetically isolated, single-domain, and reveal a uniform magnetic anisotropy with an unexpected switching behaviour induced by their spherical shape. Furthermore, changing the deposition angle with respect to the particle ensemble allows tailoring of the orientation of the magnetic anisotropy, which results in tilted nanostructure material.

  11. Anisotropy in geometrically rough structure of ice prismatic plane interface during growth: Development of a modified six-site model of H2O and a molecular dynamics simulation.

    PubMed

    Nada, Hiroki

    2016-12-28

    This paper presents a modified version of the six-site model of H2O [H. Nada and J. P. J. M. van der Eerden, J. Chem. Phys. 118, 7401 (2003)]. Although the original six-site model was optimized by assuming the cut-off of the Coulomb interaction at an intermolecular distance of 10 Å, the modified model is optimized by using the Ewald method for estimating the Coulomb interaction. Molecular dynamics (MD) simulations of an ice-water interface suggest that the melting point of ice at 1 atm in the modified model is approximately 274.5 K, in good agreement with the real melting point of 273.15 K. MD simulations of bulk ice and water suggest that the modified model reproduces not only the structures and density curves of ice and water, but also the diffusion coefficient of water molecules in water near the melting point at 1 atm. Using the modified model, a large-scale MD simulation of the growth at an ice-water interface of the prismatic plane is performed to elucidate the anisotropy in the interface structure during growth. Simulation results indicate that the geometrical roughness of the ice growth front at the interface is greater in the c-axis direction than in the direction normal to the c-axis when it is analyzed along the axes parallel to the prismatic plane. In addition, during the growth at the interface, the transient appearance of specific crystallographic planes, such as a {202¯1} pyramidal plane, occurs preferentially at the ice growth front. The effect of different ensembles with different simulation systems on the anisotropy in the interface structure is also investigated.

  12. Anisotropy in geometrically rough structure of ice prismatic plane interface during growth: Development of a modified six-site model of H2O and a molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Nada, Hiroki

    2016-12-01

    This paper presents a modified version of the six-site model of H2O [H. Nada and J. P. J. M. van der Eerden, J. Chem. Phys. 118, 7401 (2003)]. Although the original six-site model was optimized by assuming the cut-off of the Coulomb interaction at an intermolecular distance of 10 Å, the modified model is optimized by using the Ewald method for estimating the Coulomb interaction. Molecular dynamics (MD) simulations of an ice-water interface suggest that the melting point of ice at 1 atm in the modified model is approximately 274.5 K, in good agreement with the real melting point of 273.15 K. MD simulations of bulk ice and water suggest that the modified model reproduces not only the structures and density curves of ice and water, but also the diffusion coefficient of water molecules in water near the melting point at 1 atm. Using the modified model, a large-scale MD simulation of the growth at an ice-water interface of the prismatic plane is performed to elucidate the anisotropy in the interface structure during growth. Simulation results indicate that the geometrical roughness of the ice growth front at the interface is greater in the c-axis direction than in the direction normal to the c-axis when it is analyzed along the axes parallel to the prismatic plane. In addition, during the growth at the interface, the transient appearance of specific crystallographic planes, such as a {20 2 ¯ 1 } pyramidal plane, occurs preferentially at the ice growth front. The effect of different ensembles with different simulation systems on the anisotropy in the interface structure is also investigated.

  13. Magnetic domain patterns on strong perpendicular magnetization of Co/Ni multilayers as spintronics materials: I. Dynamic observations.

    PubMed

    Suzuki, Masahiko; Kudo, Kazue; Kojima, Kazuki; Yasue, Tsuneo; Akutsu, Noriko; Diño, Wilson Agerico; Kasai, Hideaki; Bauer, Ernst; Koshikawa, Takanori

    2013-10-09

    Materials with perpendicular magnetic anisotropy can reduce the threshold current density of the current-induced domain wall motion. Co/Ni multilayers show strong perpendicular magnetic anisotropy and therefore it has become a highly potential candidate of current-induced domain wall motion memories. However, the details of the mechanism which stabilizes the strong perpendicular magnetization in Co/Ni multilayers have not yet been understood. In the present work, the evolution of the magnetic domain structure of multilayers consisting of pairs of 2 or 3 monolayers (ML) of Ni and 1 ML of Co on W(110) was investigated during growth with spin-polarized low-energy electron microscopy. An interesting phenomenon, that the magnetic domain structure changed drastically during growth, was revealed. In the early stages of the growth the magnetization alternated between in-plane upon Co deposition and out-of-plane upon Ni deposition. The change of the magnetization direction occurred within a range of less than 0.2 ML during Ni or Co deposition, with break-up of the existing domains followed by growth of new domains. The Ni and Co thickness at which the magnetization direction switched shifted gradually with the number of Co/Ni pairs. Above 3-4 Co/Ni pairs it stayed out-of-plane. The results indicate clearly that the Co-Ni interfaces play the important role of enhancing the perpendicular magnetic anisotropy.

  14. US-Japan Seminar on Magnetic Multilayered Structures Held in Kauai, Hawaii on 15-17 May 1992

    DTIC Science & Technology

    1992-05-17

    films as media for magneto-optical data storage has been motivated by their strong perpendicular magnetic anisotropy , favorable wavelength dependence...the underlying fundamental mechanism responsible for perpendicular magnetic anisotropy in metallic multilayers remains unexplained. This is due, in

  15. Optimization of perpendicular anisotropy of Ta-inserted double CoFeB/MgO interface MTJ's for STT-MRAM

    NASA Astrophysics Data System (ADS)

    Clark, Billy D.; Paul, Soumalya; Schwarm, Samuel C.; Singh, Amritpal; Natarajarathinam, Anusha; Gupta, Subhadra

    2016-01-01

    Ta inserts in double magnetic tunnel junctions have been shown to induce perpendicular magnetic anisotropy. We fabricated the central layers of a CoFeB/MgO based double magnetic tunnel junction with a Ta insertion layer between the free layers of the magnetic tunnel junctions. The thickness of the Ta insert and CoFeB layer were varied from 0.5 to 1.1 nm and 0.9 to 1.7 nm respectively, to find which minimum thickness of Ta will induce perpendicular anisotropy in the MTJ. FMR studies were performed to measure the interfacial anisotropy Ku,i. We demonstrated that the most effective stack minimized the CoFeB thickness while maximizing the Ta thickness. This was balanced with the need to keep both CoFeB layers from decoupling or becoming magnetically dead.

  16. 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.

  17. 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

  18. Magnetic domain patterns on strong perpendicular magnetization of Co/Ni multilayers as spintronics materials: II. Numerical simulations.

    PubMed

    Kudo, Kazue; Suzuki, Masahiko; Kojima, Kazuki; Yasue, Tsuneo; Akutsu, Noriko; Diño, Wilson Agerico; Kasai, Hideaki; Bauer, Ernst; Koshikawa, Takanori

    2013-10-02

    Magnetic domains in ultrathin films form domain patterns, which strongly depend on the magnetic anisotropy. The magnetic anisotropy in Co/Ni multilayers changes with the number of layers. We provide a model to simulate the experimentally observed domain patterns. The model assumes a layer-dependent magnetic anisotropy. With the anisotropy parameter estimated from experimental data, we reproduce the magnetic domain patterns.

  19. 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}.

  20. Solution pH and oligoamine molecular weight dependence of the transition from monolayer to multilayer adsorption at the air-water interface from sodium dodecyl sulfate/oligoamine mixtures.

    PubMed

    Halacheva, S S; Penfold, J; Thomas, R K; Webster, J R P

    2013-05-14

    Neutron reflectivity and surface tension have been used to investigate the solution pH and oligoamine molecular weight dependence of the adsorption of sodium dodecyl sulfate (SDS)/oligoamine mixtures at the air-water interface. For diethylenetriamine, triamine, or triethylenetetramine, tetramine mixed with SDS, there is monolayer adsorption at pH 7 and 10, and multilayer adsorption at pH 3. For the slightly higher molecular weight tetraethylenepentamine, pentamine, and pentaethylenehexamine, hexamine, the adsorption is in the form of a monolayer at pH 3 and multilayers at pH 7 and 10. Hence, there is a pH driven transition from monolayer to multilayer adsorption, which shifts from low pH to higher pH as the oligoamine molecular weight increases from tetramine to pentamine. This results from the relative balance between the electrostatic attraction between the SDS and amine nitrogen group which decreases as the charge density decreases with increasing pH, the ion-dipole interaction between the amine nitrogen and SDS sulfate group which is dominant at higher pH, and the hydrophobic interalkyl chain interaction between bound SDS molecules which changes with oligoamine molecular weight.

  1. 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.

  2. Magnetic studies of Co/Ag multilayers

    NASA Astrophysics Data System (ADS)

    Krishnan, R.; Cagan, V.; Porte, M.; Tessier, M.

    1990-01-01

    Co/Ag multilayers have been prepared by evaporation in UHV. For a Co layer thickness below about 2 nm some increase in the magnetization above that of the bulk and a strong uniaxial anisotropy are observed. The latter is considered to be of surface origin.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Structure and magnetic properties of Co/Pd multilayers prepared on porous nanotubular TiO2 substrate

    NASA Astrophysics Data System (ADS)

    Maximenko, A.; Marszałek, M.; Fedotova, J.; Zarzycki, A.; Zabila, Y.; Kupreeva, O.; Lazarouk, S.; Kasiuk, J.; Zavadski, S.

    2017-07-01

    We used porous nanotubular templates of TiO2 for fabrication of Co/Pd antidot arrays with strong perpendicular magnetic anisotropy. The morphology of porous multilayers followed the features of the initial template demonstrating a pronounced relief consisting of the cells with periodic pores with small inclination. We confirmed the formation of Co0.4Pd0.6 alloy at the Co/Pd interface. We observed the conservation of perpendicular magnetic anisotropy in the Co/Pd porous film with coercive field HC = 2.7 kOe, enhanced with respect to the continuous film due to the pinning of magnetic moments on the nanopore edges. From angular dependence of the coercive field HC we deduced the change of the magnetization reversal mechanism from domain wall motion in the continuous film to the predominantly coherent rotation mechanism in the porous film.

  8. 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

  9. Anomalous magnetoresistance in Fibonacci multilayers.

    SciTech Connect

    Machado, L. D.; Bezerra, C. G.; Correa, M. A.; Chesman, C.; Pearson, J. E.; Hoffmann, A.

    2012-01-01

    We theoretically investigated magnetoresistance curves in quasiperiodic magnetic multilayers for two different growth directions, namely, [110] and [100]. We considered identical ferromagnetic layers separated by nonmagnetic layers with two different thicknesses chosen based on the Fibonacci sequence. Using parameters for Fe/Cr multilayers, four terms were included in our description of the magnetic energy: Zeeman, cubic anisotropy, bilinear coupling, and biquadratic coupling. The minimum energy was determined by the gradient method and the equilibrium magnetization directions found were used to calculate magnetoresistance curves. By choosing spacers with a thickness such that biquadratic coupling is stronger than bilinear coupling, unusual behaviors for the magnetoresistance were observed: (i) for the [110] case, there is a different behavior for structures based on even and odd Fibonacci generations, and, more interesting, (ii) for the [100] case, we found magnetic field ranges for which the magnetoresistance increases with magnetic field.

  10. 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.

  11. 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.

  12. Polar Vibration Spectra of Interface and Surface Optical Phonons and Their FRÖHLICH Electron-Phonon Interactions in Freestanding Symmetrical and Asymmetrical Wurtzite GaN/Ga1-xAlxN Multi-Layer Heterostructures

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Shi, Jun-Jie

    Under the dielectric continuum model and Loudon's uniaxial crystal model, by adopting the transfer matrix method, the dispersion properties of the interface optical (IO) and surface optical (SO) phonon modes and their couplings with electrons in multi-layer coupling wurtzite quantum wells (QWs) are deduced and analyzed via the method of electrostatic potential expanding. Numerical calculations on a freestanding symmetrical wurtzite QW and an asymmetrical wurtzite QW have been performed. Results reveal that, in general, there are four branches of IO and two branches of SO phonon modes in the systems. The dispersions of these IO and SO phonon modes are obvious only when the free two-dimensional phonon wave number kt parallel to the heterostructure interfaces is small. The degenerating behavior for these phonon modes has been clearly observed for small kt. When kt is relatively large, with the increase in kt, the frequencies of the IO and SO phonon modes converge to some definite limiting frequencies in corresponding wurtzite single planar heterostructure. This feature have been analyzed in depth from the mathematical and physical viewpoints. The calculations of electron-phonon coupling function show that, the electrostatic potential distribution of the IO and SO mode in freestanding symmetrical wurtzite QW is either symmetrical or is antisymmetrical; but that in freestanding asymmetrical wurtzite QW is neither symmetrical nor is antisymmetric. The calculation also shows that the SO modes and the short wavelength phonon modes play a more important role in the electron-phonon interaction.

  13. Multilayer Thin Film Sensors for Damage Diagnostics

    NASA Astrophysics Data System (ADS)

    Protasov, A. G.; Gordienko, Y. G.; Zasimchuk, E. E.

    2006-03-01

    The new innovative approach to damage diagnostics within the production and maintenance/servicing procedures in industry is proposed. It is based on the real-time multiscale monitoring of the smart-designed multilayer thin film sensors of fatigue damage with the standard electrical input/output interfaces which can be connected to the embedded and on-board computers. The multilayer thin film sensors supply information about the actual unpredictable deformation damage, actual fatigue life, strain localization places, damage spreading, etc.

  14. 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.

  15. Significantly improved charge collection and interface injection in 3D BiVO4 based multilayered core-shell nanowire photocatalysts.

    PubMed

    Zhang, Zemin; Li, Yunxia; Jiang, Xiao; Han, Weihua; Xie, Mingzheng; Wang, Fangcong; Xie, Erqing

    2017-09-11

    It is challenging to design a photocatalyst with high-efficiency light absorption, charge separation and even high-efficiency charge transfer. Here, we report a demonstration by utilizing a three-dimensional multilayered core-shell nanowire array (rGO-ITO@BiVO4) as the composite photocatalyst. The core-shell structure can shorten the length of charge transfer and enhance light absorption through multireflection. RGO with defects can work as the charge transfer medium to improve the hole injection from semiconductor to electrolyte. Associated with the above effects, the Co-pi electrocatalyst modified rGO-ITO@BiVO4 photocatalyst yields a photocurrent of about 6.0 mA cm(-2) at 0.6 V vs. Ag/AgCl. Transient-state surface photovoltage measurement shows that the rGO layer can prolong the lifetime of the photogenerated holes through π-π interactions, so that more holes can participate in the water oxidation reaction.

  16. Transfer-printing of active layers to achieve high quality interfaces in sequentially deposited multilayer inverted polymer solar cells fabricated in air

    PubMed Central

    Vohra, Varun; Anzai, Takuya; Inaba, Shusei; Porzio, William; Barba, Luisa

    2016-01-01

    Abstract Polymer solar cells (PSCs) are greatly influenced by both the vertical concentration gradient in the active layer and the quality of the various interfaces. To achieve vertical concentration gradients in inverted PSCs, a sequential deposition approach is necessary. However, a direct approach to sequential deposition by spin-coating results in partial dissolution of the underlying layers which decreases the control over the process and results in not well-defined interfaces. Here, we demonstrate that by using a transfer-printing process based on polydimethylsiloxane (PDMS) stamps we can obtain increased control over the thickness of the various layers while at the same time increasing the quality of the interfaces and the overall concentration gradient within the active layer of PSCs prepared in air. To optimize the process and understand the influence of various interlayers, our approach is based on surface free energy, spreading parameters and work of adhesion calculations. The key parameter presented here is the insertion of high quality hole transporting and electron transporting layers, respectively above and underneath the active layer of the inverted structure PSC which not only facilitates the transfer process but also induces the adequate vertical concentration gradient in the device to facilitate charge extraction. The resulting non-encapsulated devices (active layer prepared in air) demonstrate over 40% increase in power conversion efficiency with respect to the reference spin-coated inverted PSCs. PMID:27877901

  17. Transfer-printing of active layers to achieve high quality interfaces in sequentially deposited multilayer inverted polymer solar cells fabricated in air.

    PubMed

    Vohra, Varun; Anzai, Takuya; Inaba, Shusei; Porzio, William; Barba, Luisa

    2016-01-01

    Polymer solar cells (PSCs) are greatly influenced by both the vertical concentration gradient in the active layer and the quality of the various interfaces. To achieve vertical concentration gradients in inverted PSCs, a sequential deposition approach is necessary. However, a direct approach to sequential deposition by spin-coating results in partial dissolution of the underlying layers which decreases the control over the process and results in not well-defined interfaces. Here, we demonstrate that by using a transfer-printing process based on polydimethylsiloxane (PDMS) stamps we can obtain increased control over the thickness of the various layers while at the same time increasing the quality of the interfaces and the overall concentration gradient within the active layer of PSCs prepared in air. To optimize the process and understand the influence of various interlayers, our approach is based on surface free energy, spreading parameters and work of adhesion calculations. The key parameter presented here is the insertion of high quality hole transporting and electron transporting layers, respectively above and underneath the active layer of the inverted structure PSC which not only facilitates the transfer process but also induces the adequate vertical concentration gradient in the device to facilitate charge extraction. The resulting non-encapsulated devices (active layer prepared in air) demonstrate over 40% increase in power conversion efficiency with respect to the reference spin-coated inverted PSCs.

  18. Magnetic multilayer structure

    DOEpatents

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

    2017-03-21

    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.

  19. Magnetic multilayer structure

    SciTech Connect

    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.

  20. 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.

  1. Microstructure and magnetism in barium strontium titanate (BSTO)-barium hexaferrite (BaM) multilayers

    SciTech Connect

    Frey, N.A.; Heindl, R.; Srinath, S.; Srikanth, H. . E-mail: sharihar@cas.usf.edu; Dudney, N.J.

    2005-08-11

    High quality multilayers of barium ferrite (BaM) and barium strontium titanate (BSTO) were grown in optimized conditions on thermally oxidized Si(1 0 0) and Al{sub 2}O{sub 3} substrates using magnetron sputtering. As-grown films were amorphous and different annealing procedures were explored to stabilize crystalline phases. BSTO and BaM phases were identified using X-ray diffraction and cross-sectional scanning electron micrographs showed sharp interfaces between BSTO and BaM layers. Magnetic hysteresis loops obtained at various temperatures and field orientations showed a large coercivity ({approx}2500 Oe) consistent with the hard magnetic hexaferrite component. Hysteresis loops also revealed the distinct influence of magnetocrystalline and shape anisotropies at different temperature ranges.

  2. 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.

  3. 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.

  4. Perpendicular magnetic anisotropy of two-dimensional Rashba ferromagnets

    NASA Astrophysics Data System (ADS)

    Kim, Kyoung-Whan; Lee, Kyung-Jin; Lee, Hyun-Woo; Stiles, M. D.

    2016-11-01

    We compute the magnetocrystalline anisotropy energy within two-dimensional Rashba models. For a ferromagnetic free-electron Rashba model, the magnetic anisotropy is exactly zero regardless of the strength of the Rashba coupling, unless only the lowest band is occupied. For this latter case, the model predicts in-plane anisotropy. For a more realistic Rashba model with finite band width, the magnetic anisotropy evolves from in-plane to perpendicular and back to in-plane as bands are progressively filled. This evolution agrees with first-principles calculations on the interfacial anisotropy, suggesting that the Rashba model captures energetics leading to anisotropy originating from the interface provided that the model takes account of the finite Brillouin zone. The results show that the electron density modulation by doping or an external voltage is more important for voltage-controlled magnetic anisotropy than the modulation of the Rashba parameter.

  5. 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.

  6. Atomic scale structure investigations of epitaxial Fe/Cr multilayers

    NASA Astrophysics Data System (ADS)

    Kąc, M.; Morgiel, J.; Polit, A.; Zabila, Y.; Marszałek, M.

    2014-06-01

    Fe/Cr multilayers were deposited by molecular beam epitaxy on the MgO(1 0 0) substrate. Structural properties of the samples were analyzed by low energy electron diffraction, high resolution transmission electron microscopy (HRTEM), as well as by X-ray reflectivity, conversion electron Mössbauer spectroscopy (CEMS) and Auger electron spectroscopy. Investigations revealed multilayered system built of well-ordered Fe and Cr thin films with (1 0 0) orientation. A high geometrical perfection of the system, i.e. planar form of interfaces and reproducible thickness of layers, was also proven. Fe/Cr interface roughness was determined to be 2-3 atomic layers. CEMS studies allowed to analyze at atomic scale the structure of buried Fe/Cr interfaces, as well as to distinguish origin of interface roughness. Roughnesses resulting from interface corrugations and from the Fe-Cr interdiffusion at interfaces were observed. Fe/Cr multilayers showed strong antiferromagnetic coupling of Fe layers.

  7. Multilayer scaffolds in orthopaedic tissue engineering.

    PubMed

    Atesok, Kivanc; Doral, M Nedim; Karlsson, Jon; Egol, Kenneth A; Jazrawi, Laith M; Coelho, Paulo G; Martinez, Amaury; Matsumoto, Tomoyuki; Owens, Brett D; Ochi, Mitsuo; Hurwitz, Shepard R; Atala, Anthony; Fu, Freddie H; Lu, Helen H; Rodeo, Scott A

    2016-07-01

    The purpose of this study was to summarize the recent developments in the field of tissue engineering as they relate to multilayer scaffold designs in musculoskeletal regeneration. Clinical and basic research studies that highlight the current knowledge and potential future applications of the multilayer scaffolds in orthopaedic tissue engineering were evaluated and the best evidence collected. Studies were divided into three main categories based on tissue types and interfaces for which multilayer scaffolds were used to regenerate: bone, osteochondral junction and tendon-to-bone interfaces. In vitro and in vivo studies indicate that the use of stratified scaffolds composed of multiple layers with distinct compositions for regeneration of distinct tissue types within the same scaffold and anatomic location is feasible. This emerging tissue engineering approach has potential applications in regeneration of bone defects, osteochondral lesions and tendon-to-bone interfaces with successful basic research findings that encourage clinical applications. Present data supporting the advantages of the use of multilayer scaffolds as an emerging strategy in musculoskeletal tissue engineering are promising, however, still limited. Positive impacts of the use of next generation scaffolds in orthopaedic tissue engineering can be expected in terms of decreasing the invasiveness of current grafting techniques used for reconstruction of bone and osteochondral defects, and tendon-to-bone interfaces in near future.

  8. Mechanical Anisotropy of Ankyrin Repeats

    PubMed Central

    Lee, Whasil; Zeng, Xiancheng; Rotolo, Kristina; Yang, Ming; Schofield, Christopher J.; Bennett, Vann; Yang, Weitao; Marszalek, Piotr E.

    2012-01-01

    Red blood cells are frequently deformed and their cytoskeletal proteins such as spectrin and ankyrin-R are repeatedly subjected to mechanical forces. While the mechanics of spectrin was thoroughly investigated in vitro and in vivo, little is known about the mechanical behavior of ankyrin-R. In this study, we combine coarse-grained steered molecular dynamics simulations and atomic force spectroscopy to examine the mechanical response of ankyrin repeats (ARs) in a model synthetic AR protein NI6C, and in the D34 fragment of native ankyrin-R when these proteins are subjected to various stretching geometry conditions. Our steered molecular dynamics results, supported by AFM measurements, reveal an unusual mechanical anisotropy of ARs: their mechanical stability is greater when their unfolding is forced to propagate from the N-terminus toward the C-terminus (repeats unfold at ∼60 pN), as compared to the unfolding in the opposite direction (unfolding force ∼ 30 pN). This anisotropy is also reflected in the complex refolding behavior of ARs. The origin of this unfolding and refolding anisotropy is in the various numbers of native contacts that are broken and formed at the interfaces between neighboring repeats depending on the unfolding/refolding propagation directions. Finally, we discuss how these complex mechanical properties of ARs in D34 may affect its behavior in vivo. PMID:22404934

  9. Exchange bias properties of [Co/CoO]n multilayers

    NASA Astrophysics Data System (ADS)

    Öztürk, M.; Sınır, E.; Demirci, E.; Erkovan, M.; Öztürk, O.; Akdoǧan, N.

    2012-11-01

    In this study, the exchange bias properties of four polycrystalline multilayer stack samples of antiferromagnetic (AF) CoO and ferromagnetic (FM) Co in the form of [CoO/Co]n with n = 1, 2, 3, and 5 are reported. The samples were grown on top of Si (001) substrates by using magnetron sputtering method. X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) were used to determine the structural properties of the samples. XPS measurements of cobalt oxide layer revealed the coexistence of different phases in cobalt oxide as CoO and Co3O4, the latter of which lowers the blocking temperature. The blocking temperature is also affected by the finite size scaling effects observed in AF layers. In-plane ferromagnetic resonance (FMR) measurements revealed uniaxial in-plane magnetic anisotropy for the samples. Low temperature vibrating sample magnetometer measurements provided exchange bias with a stepwise character. Observed steps are believed to be due to magnetization reversals of individual FM layers with varying thicknesses, each of which is pinned through two interfaces from above and below with two AFM layers, except the uppermost FM Co layer with a single AFM neighbor.

  10. Spin wave resonance and relaxation in microwave magnetic multilayer structures and devices

    NASA Astrophysics Data System (ADS)

    Wu, Cheng

    The continuous and increasing demand for higher frequency magnetic microwave structures triggered a tremendous development in the field of magnetization dynamics over the past decade. In order to develop smaller and faster devices, more efforts are required to achieve a better understanding of the complex magnetization precessional dynamics, the magnetization anisotropy, and the sources of spin scattering at the nanoscale. This thesis presents measurements of magnetic precession and relaxation dynamics in multilayer ferromagnetic films of CoFe/PtMn/CoFe in both frequency and time domain. First, we conducted the ferromagnetic resonance (FMR) measurements for samples with the ferromagnetic CoFe layer thicknesses varying from 10 A to 500 A. The magnetic anisotropic parameters were determined by rotating the field aligned axis with respect to the spectral field in the configurations of both in-plane and out-of-plane. Moreover, we identified a high-order standing spin wave in our spectra and found a "critical angle" in the multilayer samples. We included an effective surface anisotropy field to describe our results. This allows us to determine the exchange interaction stiffness in the CoFe layers. Next, we performed pump-probe Magneto-Optical Kerr Effect experiments in the multilayer films. Three precession modes were observed in the Voigt geometry. The modes are assigned to the exchange-dominated spin wave excitations and the non-homogeneous dipole mode. We developed a comprehensive model of the magnetic eigenmodes and their coupling to light to gain accurate values of the exchange, bulk and surface anisotropy constants. The results are consistent with those from the FMR measurements. Finally, the measured resonance linewidths of CoFe/PtMn/CoFe films were analyzed by the thickness dependence of the CoFe layers. We discussed the contribution of the Gilbert damping, two magnon scattering, as well as surface and interface to the FMR linewidth and concluded the two magnon

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

    PubMed

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

    2014-06-17

    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.

  12. Interdiffusion in W/Si Multilayers with Boron Carbide Interlayers

    SciTech Connect

    Potdar, Satish; Gupta, M.; Gupta, A.; Schneider, M.; Stahn, J.

    2011-07-15

    W/Si multilayers with B{sub 4}C as a diffusion barrier were deposited using ion beam sputtering technique. It was found that incorporation of B{sub 4}C at both interfaces of Si enhances the reflectivity of the multilayer. Though the interface of W/Si or W/B{sub 4}C has been studied in literature, what happens at Si/B{sub 4}C interfaces is largely unknown. This is primarily due to absence of contrast between Si/B{sub 4}C for x-rays. For neutrons there is significant contrast between Si and B{sub 4}C, therefore we used neutron reflectivity to study thermal stability of Si/B{sub 4}C multilayers. It was found that up to an annealing temperature of 573 K, the multilayer remains intact however at higher temperature interdiffusion starts.

  13. 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.

  14. Magneto-optical enhancement in Pt/(Ni 1- xCo x) multilayers

    NASA Astrophysics Data System (ADS)

    Krishnan, R.; Nývlt, M.; Prosser, V.; Seddat, M.; Smetana, Z.; Tessier, M.; Višňovský, Š.

    1995-07-01

    Magneto-optical (MO) polar Kerr rotation (PKR) and ellipticity (PKE) spectra of Pt/(Ni 1- x) multilayers with x = O, 0.3 and 1 nm prepared by evaporation under ultrahigh-vacuum conditions were studied. The thickness of the Pt layer was kept between 1.5 and 2 nm, and that of the ({Ni 1- xCo x}) alloy layer, tNi 1-xCox, was 0.45 and 1.4 nm Layers formed at the Pt—magnetic layer interfaces give rise to a surface-induced perpendicular magnetic anisotropy (PMA) and to an enhancement of PKR in the near-UV spectral region. Because the Curie temperature Tc is close to 300 K for x = O a clear manifestation of these effects in the Ni/Pt system required cooling to low temperatures. The possibility to optimize the characteristics, like PMA, TC and the amplitude and position of the PKR peak in the spectra by proper choices of x, tPt and tPt and tNi 1- xCox makes Pt/(Ni 1- xCo x) multilayers interesting for the realization of MO storage media capable of working in blue light.

  15. Skyrmions in thin-film multilayers with interfacially-induced Dzyaloshinskii-Moriya interaction observed by MFM

    NASA Astrophysics Data System (ADS)

    Bacani, Mirko; Marioni, Miguel A.; Schwenk, Johannes; Romer, Sara; Zhao, Xue; Guiller, Alexandre; Hug, Hans J.

    By proper selection of interfaces in thin-film multilayers one can separately engineer the anisotropy, magnetization and Dzyaloshinskii-Moriya interaction (DMI), which is useful in the design of skyrmion materials. We use high-sensitivity, high-resolution magnetic force microscopy (MFM) in various applied magnetic fields to image the micromagnetic structures in multilayers based on symmetric-interface stacks of Pt/Co/Pt and asymmetric ones of Pt/Co/Ir. The former have domain sizes of several microns, whereas the latter show considerably smaller domain sizes. These are (246 +/-40) nm independently of the demagnetization process used. We attribute the lower domain size to a net DMI. The calculated DMI in the asymmetric case is too small to support a skyrmion phase, but isolated skyrmions can exist. MFM experiments reveal skyrmions with a diameter below 50 nm, when the field is reduced from positive saturation. In negative fields these skyrmions are either incorporated into expanding domains or burst into a larger domain. Local DMI constants estimated from the bursting fields agree well with the average DMI constant. Our work demonstrates that MFM can detect skyrmions in thin films, and can help accelerate research in this field.

  16. 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.

  17. Control and enhancement of structural and magnetic properties of Co/Pd multilayer by seeded epitaxy

    NASA Astrophysics Data System (ADS)

    Chihaya, Hiroaki; Kamiko, Masao; Kuzumaki, Toru; Yamamoto, Ryoichi

    2006-07-01

    Effects of Co seed layer on the structural and magnetic properties of Co/Pd multilayers have been studied. Reflection high-energy electron diffraction measurements showed a possible control of the crystal orientation of Pd buffer layer from polycrystalline to face-centered cubic (111) orientation when using Co seed layer. Additionally, atomic force microscopy observations confirmed the ability of Co seed layer to flatten the Pd buffer layer drastically. In fact, the usage of Co seed layer has decreased the root-mean-square roughness from 2.3 to 0.23 nm. As for controlling the structural properties of Pd buffer layer, the effective perpendicular magnetic anisotropy constant was enhanced, mainly by the improvement of surface anisotropy. Electronic states of α-Al 2O 3(0001)/metal interface obtained by electron energy loss spectroscopy proved that these differences were the fruit of the interaction between the metal layer and oxygen atoms on the Al 2O 3(0001) surface.

  18. Multilayer ionic polymer transducer

    NASA Astrophysics Data System (ADS)

    Akle, Barbar J.; Leo, Donald J.

    2003-07-01

    A transducer consisting of multiple layers of ionic polymer material is developed for applications in sensing, actuation, and control. The transducer consists of two to four individual layers each approximately 200 microns thick. The transducers are connected in parallel to minimize the electric field requirements for actuation. The tradeoff in deflection and force can be controlled by controlling the mechanical constraint at the interface. Packaging the transducer in an outer coating produces a hard constraint between layers and reduces the deflection with a force that increases linearly with the number of layers. This configuration also increases the bandwidth of the transducer. Removing the outer packaging produces an actuator that maintains the deflection of a single layer but has an increased force output. This is obtained by allowing the layers to slide relative to one another during bending. Experiments on transducers with one to three layers are performed and the results are compared to Newbury"s equivalent circuit model, which was modified to accommodate the multilayer polymers. The modification was performed on four different boundary conditions, two electrical the series and the parallel connection, and two mechanical the zero interfacial friction and the zero slip on the interface. Results demonstrate that the largest obstacle to obtaining good performance is water transport between the individual layers. Water crossover produces a near short circuit electrical condition and produces feedthrough between actuation layers and sensing layers. Electrical feedthrough due to water crossover eliminates the ability to produce a transducer that has combined sensing and actuation properties. Eliminating water crossover through good insulation enables the development of a small (5 mm x 30 mm) transducer that has sensing and actuation bandwidth on the order of 100 Hz.

  19. Surface and interface magnetism in nanostructures and thin films

    NASA Astrophysics Data System (ADS)

    Frey, Natalie A.

    Nanostructured systems composed of two or more technologically important materials are useful for device applications and intriguing for the new fundamental physics they may display. Magnetism at the nanoscale is dominated by size and surface effects which combined with other media lead to new spin dynamics and interfacial coupling phenomena. These new properties may prove to be useful for optimizing sensors and devices, increasing storage density for magnetic media, as well as for biomedical applications such as drug delivery, MRI contrast enhancement, and hyperthermia treatment for cancer. In this project we have examined the surface and interface magnetism of composite nanoparticles and multilayer thin films by using conventional DC magnetization and AC susceptibility as well as transverse susceptibility, a method for directly probing the magnetic anisotropy of materials. Au and Fe3O4 synthesized together into three different nanoparticle configurations and ranging in size for 60 nm down to 9nm are used to study how the size, shape, and interfaces affect the most fundamental properties of magnetism in the Au-Fe3O 4 system. The findings have revealed ways in which the magnetic properties can be enhanced by tuning these parameters. We have shown that by changing the configurations of the Au and Fe3O4 particles, exotic behavior can be observed such as a large increase in anisotropy field (H K ranging from 435 Oe to 1650 Oe) and the presence of exchange bias. Multilayer thin films have been studied as well which combine the important classes of ferromagnetic and ferroelectric materials. In one case, barium hexaferrite/barium strontium titanate thin films, the anisotropic behavior of the ferromagnet is shown to change due to the introduction of the secondary material. In the other example, CrO2/Cr2O3 bilayers, exchange coupling is observed as Cr2O3 is an antiferromagnet as well as a ferroelectric. This coupling is manifest as a uniaxial anisotropy rather than the

  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. Domain walls in antiferromagnetically coupled multilayer films.

    PubMed

    Hellwig, Olav; Berger, Andreas; Fullerton, Eric E

    2003-11-07

    We report experimentally observed magnetic domain-wall structures in antiferromagnetically coupled multilayer films with perpendicular anisotropy. Our studies reveal a first-order phase transition from domain walls with no net moment to domain walls with ferromagnetic cores. The transition originates from the competition between dipolar and exchange energies, which we tune by means of layer thickness. Although observed in a synthetic antiferromagnetic system, such domain-wall structures may be expected to occur in A-type antiferromagnets with anisotropic exchange coupling.

  2. Progressive magnetic softening of ferromagnetic layers in multilayer ferromagnet-nonmagnet systems and the role of granularity

    NASA Astrophysics Data System (ADS)

    Sahu, Siddharth S.; Siva, Vantari; Pradhan, Paresh C.; Nayak, Maheswar; Senapati, Kartik; Sahoo, Pratap K.

    2017-06-01

    We report a study of the structural and magnetic behavior of the topmost magnetic layer in a ferromagnet-nonmagnet (Co-Au) multilayer system. Glancing angle X-ray diffraction measurements performed on a series of multilayers showed a gradual decrease in the grain size of the topmost magnetic layer with the increasing number of bilayers. Concurrently, the magnetic hardness and magneto-crystalline anisotropy of the top Co layer were found to decrease, as observed by magneto-optical Kerr effect measurements. This magnetic softening has been discussed in the light of Herzer's random anisotropy model. Micromagnetic simulations of the multilayer system also corroborated these observations.

  3. 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.

  4. Nanoconstriction spin-Hall oscillator with perpendicular magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Divinskiy, B.; Demidov, V. E.; Kozhanov, A.; Rinkevich, A. B.; Demokritov, S. O.; Urazhdin, S.

    2017-07-01

    We experimentally study spin-Hall nano-oscillators based on [Co/Ni] multilayers with perpendicular magnetic anisotropy. We show that these devices exhibit single-frequency auto-oscillations at current densities comparable to those for in-plane magnetized oscillators. The demonstrated oscillators exhibit large magnetization precession amplitudes, and their oscillation frequency is highly tunable by the electric current. These features make them promising for applications in high-speed integrated microwave circuits.

  5. Fabrication of multilayer nanowires

    SciTech Connect

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

    2016-05-06

    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. Modeling elastic anisotropy in strained heteroepitaxy.

    PubMed

    Dixit, Gopal Krishna; Ranganathan, Madhav

    2017-09-20

    Using a continuum evolution equation, we model the growth and evolution of quantum dots in the heteroepitaxial Ge on Si(0 0 1) system in a molecular beam epitaxy unit. We formulate our model in terms of evolution due to deposition, and due to surface diffusion which is governed by a free energy. This free energy has contributions from surface energy, curvature, wetting effects and elastic energy due to lattice mismatch between the film and the substrate. In addition to anisotropy due to surface energy which favors facet formation, we also incorporate elastic anisotropy due to an underlying crystal lattice. The complicated elastic problem of the film-substrate system subjected to boundary conditions at the free surface, interface and the bulk substrate is solved by perturbation analysis using a small slope approximation. This permits an analysis of effects at different orders in the slope and sheds new light on the observed behavior. Linear stability analysis shows the early evolution of the instability towards dot formation. The elastic anisotropy causes a change in the alignment of dots in the linear regime, whereas the surface energy anisotropy changes the dot shapes at the nonlinear regime. Numerical simulation of the full nonlinear equations shows the evolution of the surface morphology. In particular, we show, for parameters of the [Formula: see text] [Formula: see text] on Si(0 0 1), the surface energy anisotropy dominates the shapes of the quantum dots, whereas their alignment is influenced by the elastic energy anisotropy. The anisotropy in elasticity causes a further elongation of the islands whose coarsening is interrupted due to [Formula: see text] facets on the surface.

  7. Modeling elastic anisotropy in strained heteroepitaxy

    NASA Astrophysics Data System (ADS)

    Krishna Dixit, Gopal; Ranganathan, Madhav

    2017-09-01

    Using a continuum evolution equation, we model the growth and evolution of quantum dots in the heteroepitaxial Ge on Si(0 0 1) system in a molecular beam epitaxy unit. We formulate our model in terms of evolution due to deposition, and due to surface diffusion which is governed by a free energy. This free energy has contributions from surface energy, curvature, wetting effects and elastic energy due to lattice mismatch between the film and the substrate. In addition to anisotropy due to surface energy which favors facet formation, we also incorporate elastic anisotropy due to an underlying crystal lattice. The complicated elastic problem of the film-substrate system subjected to boundary conditions at the free surface, interface and the bulk substrate is solved by perturbation analysis using a small slope approximation. This permits an analysis of effects at different orders in the slope and sheds new light on the observed behavior. Linear stability analysis shows the early evolution of the instability towards dot formation. The elastic anisotropy causes a change in the alignment of dots in the linear regime, whereas the surface energy anisotropy changes the dot shapes at the nonlinear regime. Numerical simulation of the full nonlinear equations shows the evolution of the surface morphology. In particular, we show, for parameters of the Ge0.25 Si0.75 on Si(0 0 1), the surface energy anisotropy dominates the shapes of the quantum dots, whereas their alignment is influenced by the elastic energy anisotropy. The anisotropy in elasticity causes a further elongation of the islands whose coarsening is interrupted due to < 1 0 5 > facets on the surface.

  8. Detection of Seismic Anisotropy From Low-Frequency Earthquakes: Eastern Shikoku

    NASA Astrophysics Data System (ADS)

    Ishise, M.; Nishida, K.

    2015-12-01

    In this study, we detected seismic anisotropy from low-frequency earthquakes (LFEs) by the JMA (Nishide et al., 2000) during a tremor episodes at the plate interface of the PHS slab beneath eastern Shikoku, southwest Japan by S-wave splitting analysis (e.g., Ando et al., 1983). We applied this method for the isolated phases of LFEs, which are regarded as S-waves and used by hypocenter determination. In this method seismic anisotropy is represented by polarization direction of fast S-wave (direction of anisotropy) and delay time between two S-waves. In order to examine the difference between anisotropy within the subducting plate and around the plate interface, we also investigated anisotropy of slab earthquakes, which occurred within the slab. Furthermore, we measured anisotropy of crustal earthquakes in order to evaluate anisotropy near receiver, because anisotropy obtained by S-wave splitting analysis is strongly affected by anisotropy in shallow crust and often masked by it. We used filtered seismograms (2-8 Hz) at stations of Hi-net deployed by NIED in all the analyses. Results of S-wave splitting analyses of LFEs showed that the directions of anisotropy are tend to be orientated in the East-West-trending direction and the delay times are 0.2-0.4 sec. The delay times of LFEs are larger than those of slab earthquakes and crustal earthquakes (~ 0.2 s), suggesting a possibility that there exists a unique anisotropy in the source regions of LFEs. However, the direction of anisotropy is similar to crust anisotropy in the study area, implying that the anisotropy of LFE might be masked by crustal anisotropy. In order to rigorously discuss anisotropy around the source region, we have to remove the effect of the anisotropy in the crust.

  9. Magnetic domain and domain wall in Co/Pt multilayer

    NASA Astrophysics Data System (ADS)

    Talapatra, A.; Mohanty, J.

    2016-05-01

    We report systematic micromagnetic investigation of formation of magnetic domains in perpendicularly magnetized Co/Pt multilayer with the variation in magnetic anisotropy and stack thickness. The lowering of anisotropy makes the domain wall broader and domain formation less efficient. Domain sizeincreases with increasing thickness of the stack to minimize the stray field energy.The minimization of energy of the system due to domain formation makes the M-H loop narrower whereas, lower stack thickness results in a wider loop. The magnetization reversalin this system occurs due tothe nucleation and growth of reverse domains.

  10. Enhancement of anomalous Nernst effects in metallic multilayers free from proximity-induced magnetism

    NASA Astrophysics Data System (ADS)

    Uchida, Ken-ichi; Kikkawa, Takashi; Seki, Takeshi; Oyake, Takafumi; Shiomi, Junichiro; Qiu, Zhiyong; Takanashi, Koki; Saitoh, Eiji

    2015-09-01

    The anomalous Nernst effect (ANE) has been investigated in alternately stacked multilayer films comprising paramagnetic and ferromagnetic metals. We found that the ANE is enhanced by increasing the number of the paramagnet/ferromagnet interfaces and keeping the total thickness of the films constant, and that the enhancement appears even in the absence of magnetic proximity effects; similar behavior was observed not only in Pt/Fe multilayers but also in Au/Fe and Cu/Fe multilayers free from proximity ferromagnetism. This universal enhancement of the ANE in metallic multilayers suggests the presence of unconventional interface-induced thermoelectric conversion in the Fe films attached to the paramagnets.

  11. Multilayer thin film thermoelectrics produced by sputtering

    SciTech Connect

    Wagner, A.V.; Foreman, R.J.; Summers, L.J.; Barbee, T.W. Jr.; Farmer, J.C.

    1995-06-19

    In this work we explore the possibility of achieving bulk electrical properties in single layer sputter deposited films grown epitaxially on (111) oriented BaF{sub 2} substrates. There are a number of sputter deposition parameters that can be varied in order to optimize the film quality. It is important to understand the effect of varying the deposition temperature, Ar sputtering gas pressure, and the substrate bias. We will consider only Bi and Bi{sub 0.86}Sb{sub 0.14} films in this paper. These materials were chosen since they have the same simple structure, two different band gaps and do not change significantly either in physical or electrical properties with small amounts of cross contamination. We will also present our work on multilayer thermoelectrics made of Bi and Bi{sub 0.86}Sb{sub 0.14} layers. There has been considerable interest in this multilayer structure in the literature. Theoretical calculations of the band structure and interface states of these multilayer structures have been made by Mustafaev and Agassi et al. respectively [6,7]. Experimentally Yoshida et al. have examined similar multilayer structures grown by MBE as well as Bi/Sb multilayer samples in which report an anomalous thermoelectric power [8].

  12. Modular, Multilayer Perceptron

    NASA Technical Reports Server (NTRS)

    Cheng, Li-Jen; Liu, Tsuen-Hsi

    1991-01-01

    Combination of proposed modular, multilayer perceptron and algorithm for its operation recognizes new objects after relatively brief retraining sessions. (Perceptron is multilayer, feedforward artificial neural network fully connected and trained via back-propagation learning algorithm.) Knowledge pertaining to each object to be recognized resides in subnetwork of full network, therefore not necessary to retrain full network to recognize each new object.

  13. In-Plane Optical Anisotropy of Layered Gallium Telluride.

    PubMed

    Huang, Shengxi; Tatsumi, Yuki; Ling, Xi; Guo, Huaihong; Wang, Ziqiang; Watson, Garrett; Puretzky, Alexander A; Geohegan, David B; Kong, Jing; Li, Ju; Yang, Teng; Saito, Riichiro; Dresselhaus, Mildred S

    2016-09-27

    Layered gallium telluride (GaTe) has attracted much attention recently, due to its extremely high photoresponsivity, short response time, and promising thermoelectric performance. Different from most commonly studied two-dimensional (2D) materials, GaTe has in-plane anisotropy and a low symmetry with the C2h(3) space group. Investigating the in-plane optical anisotropy, including the electron-photon and electron-phonon interactions of GaTe is essential in realizing its applications in optoelectronics and thermoelectrics. In this work, the anisotropic light-matter interactions in the low-symmetry material GaTe are studied using anisotropic optical extinction and Raman spectroscopies as probes. Our polarized optical extinction spectroscopy reveals the weak anisotropy in optical extinction spectra for visible light of multilayer GaTe. Polarized Raman spectroscopy proves to be sensitive to the crystalline orientation of GaTe, and shows the intricate dependences of Raman anisotropy on flake thickness, photon and phonon energies. Such intricate dependences can be explained by theoretical analyses employing first-principles calculations and group theory. These studies are a crucial step toward the applications of GaTe especially in optoelectronics and thermoelectrics, and provide a general methodology for the study of the anisotropy of light-matter interactions in 2D layered materials with in-plane anisotropy.

  14. In-plane optical anisotropy of layered gallium telluride

    DOE PAGES

    Huang, Shengxi; Tatsumi, Yuki; Ling, Xi; ...

    2016-08-16

    Layered gallium telluride (GaTe) has attracted much attention recently, due to its extremely high photoresponsivity, short response time, and promising thermoelectric performance. Different from most commonly studied two-dimensional (2D) materials, GaTe has in-plane anisotropy and a low symmetry with the C2h3 space group. Investigating the in-plane optical anisotropy, including the electron–photon and electron–phonon interactions of GaTe is essential in realizing its applications in optoelectronics and thermoelectrics. In this work, the anisotropic light-matter interactions in the low-symmetry material GaTe are studied using anisotropic optical extinction and Raman spectroscopies as probes. Our polarized optical extinction spectroscopy reveals the weak anisotropy in opticalmore » extinction spectra for visible light of multilayer GaTe. Polarized Raman spectroscopy proves to be sensitive to the crystalline orientation of GaTe, and shows the intricate dependences of Raman anisotropy on flake thickness, photon and phonon energies. Such intricate dependences can be explained by theoretical analyses employing first-principles calculations and group theory. Furthermore, these studies are a crucial step toward the applications of GaTe especially in optoelectronics and thermoelectrics, and provide a general methodology for the study of the anisotropy of light-matter interactions in 2D layered materials with in-plane anisotropy.« less

  15. In-plane optical anisotropy of layered gallium telluride

    SciTech Connect

    Huang, Shengxi; Tatsumi, Yuki; Ling, Xi; Guo, Huaihong; Wang, Ziqiang; Watson, Garrett; Puretzky, Alexander A.; Geohegan, David B.; Kong, Jing; Li, Ju; Yang, Teng; Saito, Riichiro; Dresselhaus, Mildred S.

    2016-08-16

    Layered gallium telluride (GaTe) has attracted much attention recently, due to its extremely high photoresponsivity, short response time, and promising thermoelectric performance. Different from most commonly studied two-dimensional (2D) materials, GaTe has in-plane anisotropy and a low symmetry with the C2h3 space group. Investigating the in-plane optical anisotropy, including the electron–photon and electron–phonon interactions of GaTe is essential in realizing its applications in optoelectronics and thermoelectrics. In this work, the anisotropic light-matter interactions in the low-symmetry material GaTe are studied using anisotropic optical extinction and Raman spectroscopies as probes. Our polarized optical extinction spectroscopy reveals the weak anisotropy in optical extinction spectra for visible light of multilayer GaTe. Polarized Raman spectroscopy proves to be sensitive to the crystalline orientation of GaTe, and shows the intricate dependences of Raman anisotropy on flake thickness, photon and phonon energies. Such intricate dependences can be explained by theoretical analyses employing first-principles calculations and group theory. Furthermore, these studies are a crucial step toward the applications of GaTe especially in optoelectronics and thermoelectrics, and provide a general methodology for the study of the anisotropy of light-matter interactions in 2D layered materials with in-plane anisotropy.

  16. In-plane optical anisotropy of layered gallium telluride

    SciTech Connect

    Huang, Shengxi; Tatsumi, Yuki; Ling, Xi; Guo, Huaihong; Wang, Ziqiang; Watson, Garrett; Puretzky, Alexander A.; Geohegan, David B.; Kong, Jing; Li, Ju; Yang, Teng; Saito, Riichiro; Dresselhaus, Mildred S.

    2016-08-16

    Layered gallium telluride (GaTe) has attracted much attention recently, due to its extremely high photoresponsivity, short response time, and promising thermoelectric performance. Different from most commonly studied two-dimensional (2D) materials, GaTe has in-plane anisotropy and a low symmetry with the C2h3 space group. Investigating the in-plane optical anisotropy, including the electron–photon and electron–phonon interactions of GaTe is essential in realizing its applications in optoelectronics and thermoelectrics. In this work, the anisotropic light-matter interactions in the low-symmetry material GaTe are studied using anisotropic optical extinction and Raman spectroscopies as probes. Our polarized optical extinction spectroscopy reveals the weak anisotropy in optical extinction spectra for visible light of multilayer GaTe. Polarized Raman spectroscopy proves to be sensitive to the crystalline orientation of GaTe, and shows the intricate dependences of Raman anisotropy on flake thickness, photon and phonon energies. Such intricate dependences can be explained by theoretical analyses employing first-principles calculations and group theory. Furthermore, these studies are a crucial step toward the applications of GaTe especially in optoelectronics and thermoelectrics, and provide a general methodology for the study of the anisotropy of light-matter interactions in 2D layered materials with in-plane anisotropy.

  17. Origin of perpendicular magnetic anisotropy in epitaxial Pd /Co /Pd (111 ) trilayers

    NASA Astrophysics Data System (ADS)

    Davydenko, A. V.; Kozlov, A. G.; Ognev, A. V.; Stebliy, M. E.; Samardak, A. S.; Ermakov, K. S.; Kolesnikov, A. G.; Chebotkevich, L. A.

    2017-02-01

    Perpendicular magnetic anisotropy in epitaxial Pd /Co /Pd (111 ) trilayered films grown on Si(111) substrate was investigated. Contributions to perpendicular magnetic anisotropy from the bottom and top Co/Pd interfaces were deduced by replacement of Pd layers by Cu layers and comparative analysis of the magnetic anisotropy in the samples. Perpendicular magnetic anisotropy in Pd/Co/Pd films was induced both by interface electronic effects and by stress caused by lattice mismatch between Pd and Co. Due to asymmetry of the stress in the Co film, the contribution to magnetic anisotropy induced by the bottom Co/Pd interface was stronger than that induced by the top Pd/Co interface. The energy of the perpendicular magnetic anisotropy and asymmetrical contributions from the bottom Co/Pd and top Pd/Co interfaces to anisotropy in Pd/Co/Pd trilayers strongly depend on the thickness of the bottom and top Pd layers and may be precisely controlled. The roughness of the interfaces does not have a large influence on the energy of perpendicular magnetic anisotropy in this system.

  18. 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.

  19. 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.

  20. Growth of Co Nanomagnet Arrays with Enhanced Magnetic Anisotropy

    PubMed Central

    Fernández, Laura; Ilyn, Maxim; Magaña, Ana; Vitali, Lucia; Ortega, José Enrique

    2016-01-01

    A trigon structure formed by submonolayer gadolinium deposition onto Au(111) is revealed as a robust growth template for Co nanodot arrays. Scanning Tunneling Microscopy and X‐Ray Magnetic Circular Dichroism measurements evidence that the Co nanoislands behave as independent magnetic entities with an out‐of‐plane easy axis of anisotropy and enhanced magnetic anisotropy values, as compared to other self‐organized Co nanodot superlattices. The large strain induced by the lattice mismatch at the interface between Co and trigons is discussed as the main reason for the increased magnetic anisotropy of the nanoislands. PMID:27711268

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

    PubMed

    Li, Junwen; Haney, Paul M

    2016-07-18

    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 n̂. We find an in-plane uniaxial anisotropy in the ẑ × n̂ direction, where ẑ 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 α(4) 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, n̂ 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.

  2. Determination of the distribution of transverse magnetic anisotropy in thin films from the second harmonic of Kerr signal

    NASA Astrophysics Data System (ADS)

    García-Arribas, A.; Fernández, E.; Orue, I.; Barandiaran, J. M.

    2013-09-01

    We describe a method to determine the magnetic anisotropy distribution in thin films based on Kerr magnetometry, well adapted for single micro- and nanostructures. When the sample is excited by an ac field of small amplitude, for each value of a longitudinal dc field H, the second harmonic of the Kerr signal gives the contribution of the corresponding transverse anisotropy field Hk=H to the anisotropy distribution. The method is tested on a Permalloy-based multilayer microstructure, revealing two anisotropy contributions, one of them deviated from the perfect transverse direction. This confirms and extends a previous characterization performed by far more sophisticated methods.

  3. 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.

  4. Determination of spin pumping as a source of linewidth in sputtered Co90Fe10/Pd multilayers by use of broadband ferromagnetic resonance spectroscopy

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

    We performed a systematic study of damping in Co90Fe10/Pd multilayers by use of broadband (1-60 GHz) ferromagnetic resonance (FMR) spectroscopy in the perpendicular geometry. The data were fitted with the conventional Landau-Lifshitz equation in conjunction with an inhomogeneous contribution to linewidth ΔH0. Samples were prepared with net perpendicular anisotropy field values ranging from -0.5 to +1.2 T. ΔH0 shows a dependence on the perpendicular anisotropy, though the Landau-Lifshitz damping parameter α, which ranged from 0.016 to 0.04, exhibits no trend as a function of anisotropy. We explain the wide variation of α as a result of spin pumping from Co90Fe10 into adjacent nonmagnetic layers. We use a quantitative model for spin pumping that includes the intrinsic spin-mixing conductance at the Co90Fe10/Pd interface and the spin-diffusion length of Pd, which were experimentally measured at room temperature to be (1.07 ± 0.13) × 1019 m-2 and 8.6 ± 1.0 nm, respectively. We quantitatively show how α is enhanced by spin pumping through an FMR investigation of individual Pd/CoFe/Pd, and Pd/CoFe/Pd/CoFe/Pd layer structures.

  5. Film stress studies and the multilayer laue lens project.

    SciTech Connect

    Liu, C.; Conley, R.; Macrander, A. T.; X-Ray Science Division

    2006-01-01

    A Multilayer Laue Lens (MLL) is a new type of linear zone plate, made by sectioning a planar depth-graded multilayer and used in Laue transmission diffraction geometry, for nanometer-scale focusing of hard x-rays. To produce an MLL, a depth-graded multilayer consisting of thousands of layers with a total thickness of tens of microns is needed. Additionally, the multilayer wafer has to be sectioned and polished to a thickness of {approx}10 to 25 microns to yield a diffracting grating to focus x-rays. The multilayers must have both low stress and good adhesion to survive the subsequent cutting and polishing processes, as well as sharp interfaces and accurate layer placement. Several partial MLLs using WSi{sub 2}/Si multilayers with precise zone-plate structures have been successfully fabricated. A W/Si multilayer with the same structure, however, cracked and peeled off from the Si substrate after it was grown. Here we report results of our film stress studies of dc magnetron-sputtered WSi{sub 2}, W, and Mo thin films and WSi{sub 2}/Si, W/Si, and Mo/Si multilayers grown on Si(100) substrates. The stress measurements were carried out using a stylus profiler to measure the curvatures of 2-inch-diameter, 0.5-mm-thick Si(100) wafers before and after each coating. The physical origins of the stress and material properties of these systems will be discussed.

  6. Magnetic anisotropies in GaAs/Fe(001) structures

    NASA Astrophysics Data System (ADS)

    Kardasz, Bartek; Mosendz, Oleksandr; Heinrich, Bret; Przybylski, Marek; Kirschner, Jiirgen

    2010-01-01

    Fe ultrathin films on GaAs(001) substrates were prepared by thermal deposition (TD) and pulse laser deposition (PLD) using MBE. Conversion electron Mössbauer spectroscopy (CEMS) was employed to investigate the atomic arrangement of Fe at the GaAs(001) interface. The magnetic anisotropies were studied by FMR. They have strong interface and bulk contributions which undergo several transitions with increasing film thickness. The most pronounced effect was observed in the in-plane interface uniaxial anisotropy Kint||,u. Kint||,u=0.10 ergs/cm2 for the TD films thinner than 30ML. For thicker samples it decreased to Kint||,u=0.03 ergs/cm2 which is equal to that for the PLD samples. It will be shown that these transitions in magnetic anisotropies are driven by B1 and B2 magneto-elastic energies.

  7. Resonant Raman spectroscopy of twisted multilayer graphene

    NASA Astrophysics Data System (ADS)

    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

    2014-11-01

    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.

  8. 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.

  9. Emergent magnetism at transition-metal-nanocarbon interfaces.

    PubMed

    Al Ma'Mari, Fatma; Rogers, Matthew; Alghamdi, Shoug; Moorsom, Timothy; Lee, Stephen; Prokscha, Thomas; Luetkens, Hubertus; Valvidares, Manuel; Teobaldi, Gilberto; Flokstra, Machiel; Stewart, Rhea; Gargiani, Pierluigi; Ali, Mannan; Burnell, Gavin; Hickey, B J; Cespedes, Oscar

    2017-05-30

    Charge transfer at metallo-molecular interfaces may be used to design multifunctional hybrids with an emergent magnetization that may offer an eco-friendly and tunable alternative to conventional magnets and devices. Here, we investigate the origin of the magnetism arising at these interfaces by using different techniques to probe 3d and 5d metal films such as Sc, Mn, Cu, and Pt in contact with fullerenes and rf-sputtered carbon layers. These systems exhibit small anisotropy and coercivity together with a high Curie point. Low-energy muon spin spectroscopy in Cu and Sc-C60 multilayers show a quick spin depolarization and oscillations attributed to nonuniform local magnetic fields close to the metallo-carbon interface. The hybridization state of the carbon layers plays a crucial role, and we observe an increased magnetization as sp(3) orbitals are annealed into sp(2)-π graphitic states in sputtered carbon/copper multilayers. X-ray magnetic circular dichroism (XMCD) measurements at the carbon K edge of C60 layers in contact with Sc films show spin polarization in the lowest unoccupied molecular orbital (LUMO) and higher π*-molecular levels, whereas the dichroism in the σ*-resonances is small or nonexistent. These results support the idea of an interaction mediated via charge transfer from the metal and dz-π hybridization. Thin-film carbon-based magnets may allow for the manipulation of spin ordering at metallic surfaces using electrooptical signals, with potential applications in computing, sensors, and other multifunctional magnetic devices.

  10. Engineering aspects of multilayer piezoceramic actuators

    NASA Astrophysics Data System (ADS)

    Golovnin, V. A.; Kaplunov, I. A.; Ivanova, A. I.; Grechishkin, R. M.

    2013-12-01

    With the increasing demand for multilayer ceramic chip components a full understanding of the co-firing of ceramics with metal electrodes becomes important. In the present work the processing of a piezoelectric monolithic actuator by stacking and cofiring Ag-Pd electroded tape cast layers was studied. The inter-diffusion and microstructure of the co-fired interface of PZT ferroelectrics and Ag-Pd metal electrode were examined by scanning electron microscopy (SEM) and energy-dispersive microanalysis. No strong structural distortions and interdiffusion were observed at the co-fired ceramic-electrode interface.

  11. 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.

  12. 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.

  13. Mechanism of tailored magnetic anisotropy in amorphous Co68Fe24Zr8 thin films

    NASA Astrophysics Data System (ADS)

    Fu, Yu; Barsukov, I.; Meckenstock, R.; Lindner, J.; Raanaei, H.; Hjörvarsson, B.; Farle, M.

    2014-02-01

    The mechanism of tailored magnetic anisotropy in amorphous Co68Fe24Zr8 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/m3. 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.

  14. Anisotropy across Superplume Boundaries

    NASA Astrophysics Data System (ADS)

    Cottaar, S.; Romanowicz, B. A.

    2011-12-01

    Sdiff data sets are presented for paths that run parallel to the African and the Pacific superplume boundaries. Objective clustering of waveforms illustrates sharp changes across these boundaries. The African plume shows a sharp offset in travel times in the SHdiff phase, while a more gradual offset towards slower arrivals is seen in the case of the Pacific superplume. Additionally, Pdiff phases display no offset around the African plume and a weak one around the Pacific plume. Here we focus mainly on another striking feature observed in both cases: outside of the superplume the Sdiff particle motion is strongly elliptical, but becomes linear within the superplume (first noticed by To et al. 2005 in the African superplume case). For the African plume we argue that these observations of delayed SV at large distances (~120 degrees) are indicative of the occurrence of azimuthal anisotropy. The SV arrivals have similar polarity as SH, opposite from what their radiation pattern predicts. Azimuthal anisotropy causes SH energy to be converted to SV (Maupin, 1994), explaining the travel time, polarity and amplitude. Forward modeling through different isotropic and anisotropic models supports this statement, although there are trade-offs between direction and magnitude of azimuthal anisotropy. The strong elliptical particle motions are also observed outside the Pacific plume, but at shorter distances (95-105 degrees). Elliptical motions can occur in the absence of anisotropy when strong velocity deviations or layering occurs close to the CMB, which, based on velocity profiles with depth in global tomographic models would be more likely within the superplume rather than on the fast side. The elliptical particle motions here can be modelled with a simple transverse isotropic model with VSH>VSV, but azimuthal anisotropy cannot be ruled out. The complexities within the Pacific superplume, including strong amplitude drop and existence of a post-cursor, are likely caused by an

  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. 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.

  17. Theory of magnetoelectric effects in multilayer composites

    NASA Astrophysics Data System (ADS)

    Bichurin, M. I.; Petrov, V. M.; Srinivasan, G.

    2002-03-01

    A theoretical model is presented for magnetoelectric (ME) effects in bilayer and multilayer composites. Early models are based on ideal interface or the absence of friction, conditions that are not satisfied in real materials [1]. In addition, one needs to understand our recent observations showing considerable discrepancy between data on ME voltage coefficients in bilayer and multilayer composites [2]. A novel approach to take into account the actual boundary conditions in multilayer composites is proposed. An averaging method is used for deriving effective material parameters in composites. With the modified boundary conditions and the effective material parameters, we obtain expressions for ME voltage coefficients for multilayers. The estimated ME coupling constants are compared with data for lithium ferrite-lead zirconate titanate (PZT) and nickel ferrite-PZT composites. - work supported by a grant from the NSF (DMR-0072144) 1. G. Harshe, J.O. Dougherty, and R. E. Newnham, Int. J. Appl. Electromagn. Mater. 4, 145 (1993). 2. G. Srinivasan, E. T. Rasmussen, J. Gallegos, R. Srinivasan, Yu. I. Bokhan, and V. M. Laletin, Phys. Rev. B 64, 214408 (2001).

  18. Microstructures and mechanical properties of sputtered Cu/Cr multilayers

    SciTech Connect

    Misra, A.; Kung, H.; Mitchell, T.E.; Jervis, T.R.; Nastasi, M.

    1998-03-01

    The microstructures and mechanical properties of Cu/Cr multilayers prepared by sputtering onto {l_brace}100{r_brace} Si substrates at room temperature are presented. The films exhibit columnar grain microstructures with nanoscale grain sizes. The interfaces are planar and abrupt with no intermixing, as expected from the phase diagram. The multilayers tend to adopt a Kurdjumov-Sachs (KS) orientation relationship: {l_brace}110{r_brace}Cr // {l_brace}111{r_brace}Cu, <111>Cr // <110>Cu. The hardness of the multilayered structures, as measured by nanoindentation, increase with decreasing layer thickness for layer thicknesses ranging from 200 nm to 50 nm, whereas for lower thicknesses the hardness of the multilayers is independent of the layer thickness. Dislocation-based models are used to interpret the variation of hardness with layer periodicity. The possible effects of factors such as grain size within the layers, density and composition of films and residual stress in the multilayers are highlighted. Comparisons are made to the mechanical properties of sputtered polycrystalline Cu/Nb multilayers which, like Cu/Cr, exhibit sharp fcc/bcc interfaces with no intermixing and a KS orientation relationship, but have a small shear modulus mismatch.

  19. Tailored magnetic anisotropy in an amorphous trilayer

    NASA Astrophysics Data System (ADS)

    Fu, Yu; Barsukov, I.; Raanaei, H.; Spasova, M.; Lindner, J.; Meckenstock, R.; Farle, M.; Hjörvarsson, B.

    2011-06-01

    An amorphous Co68Fe24Zr8(3 nm)/Al70Zr30(3 nm)/Co68Fe24Zr8(3 nm) trilayer system has been investigated using in-plane and out-of-plane angular dependent ferromagnetic resonance at different frequencies. The in-plane magnetic anisotropy is uniaxial, retaining its value of (2.9 ± 0.1) × 103 J/m3 for each magnetic layer, whereas its direction was tailored independently in an arbitrary manner by applying an external magnetic field during the film deposition. The perpendicular anisotropy constant, supposed to reflect the interface quality, is nearly identical for both layers. Furthermore, the magnetic layers act independently upon each other due to the absence of interlayer coupling.

  20. Applications of multilayer optics

    NASA Astrophysics Data System (ADS)

    Wang, Zhanshan; Zhu, Jingtao; Mu, Baozhong; Zhang, Zhong; Wang, Fengli; Xu, Jing; Li, Wenbin; Chen, Lingyan

    2010-11-01

    Recent development of multilayer mirror and its applications in extreme ultraviolet (EUV), soft X-ray ranges in China was reviewed in this paper. Three types of multilayer mirrors were developed with special performance for dense plasma diagnostics, EUV astronomical observation. Firstly, dual-periodic W/B 4C multilayer mirror was designed for Kirkpatrick-Baez (K-B) microscopy working at TiKα line (4.75 keV), which is highly reflective both at hard X-ray (CuKα line at 8.05 keV) and soft X-ray (4.75 keV). Using this mirror, the K-B system can be aligned conveniently in air using hard X-ray instead of in vacuum. The second mirror is aperiodic Mg/SiC multilayer, also a bi-functional mirror with high reflectivity for He-II emission line (30.4 nm) but suppressing He-I emission line (58.4 nm) in astronomy observation, which will replace the traditional combination of periodic multilayer and the fragile film filter. This will be more safe in satellite launching. The third mirror is Mo/Si periodic multilayer, depositing on a parabolic substrate with diameter of 230 mm, which is designed for EUV telescope for imaging of solar corona by selecting Fe-XII emission (19.5 nm). The uniformity of lateral layer thickness distribution is within ±0.3% along the diameter of mirror, measured by X-ray reflectometry. The measured peak reflectivity is 42% at the wavelength of 19.5 nm. All these multilayer mirrors were prepared by using magnetron sputtering system in our group.

  1. Magnetic-plasmonic multilayered nanorods

    NASA Astrophysics Data System (ADS)

    Thumthan, Orathai

    Multilayered nanorods which consist of alternating magnetic layers separated by Au layers combine two distinctive properties, magnetic properties and surface plasmonic resonance (SPR) properties into one nano-entity. Their magnetic properties are tunable by changing the layer thickness, varying from single domain to superparamagnetic state. Superparamagnetic is a key requirement for magnetic nanoparticles for bioapplications. Superparamagnetic nanoparticles exhibit high magnetic moments at low applied magnetic field while retain no magnetic moments when magnetic field is removed preventing them from aggregation due to magnetic attraction. Au layers in the nanorods provide anchorage sites for functional group attachment. Also, Au nanodisks exhibit SPR properties. The SPR peak can be tuned from 540 nm to 820 nm by controlling the thickness of magnetic segments while keeping Au thickness constant. In this research, there are three types of multilayered nanorod have been fabricated: Au/NiFe nanorods, Au/Fe nanorods, and Au/Co nanorods. These magnetic nanorods were fabricated by templated electrodeposition into the channels in Anodic Aluminum Oxide (AAO) membrane. The setup for AAO fabrication was developed as a part of this research. Our fabricated AAO membrane has channels with a diameter ranging from 40nm to 80 nm and a thickness of 10um to 12um. Magnetic properties of nanorods such as saturation field, saturation moment, coercivity and remanence are able to manipulate through their shape anisotropy. The magnetization will be easier in long axis rather than short axis of particle. In addition, Au nanodisks in the nanorod structure are not only serving as anchorage sites for functional groups but also provide SPR properties. Under irradiation of light Au nanodisks strongly absorb light at SPR frequency which ranging from 540 nm to 820 nm by controlling the thickness of magnetic segments while keeping Au thickness constant. The SPR tunability of nanorods in near

  2. Robust isothermal electric switching of interface magnetization: A route to voltage-controlled spin electronics

    NASA Astrophysics Data System (ADS)

    He, Xi; Wang, Yi; Wu, Ning; Shi, Siqi; Caruso, A.; Vescovo, E.; Belashchenko, Kirill D.; Dowben, Peter; Binek, Christian

    2010-03-01

    Promising spintronic device concepts utilize the electric control of magnetic interfaces. We present compelling evidence of a roughness-insensitive and electrically controllable ferromagnetic state at the (0001) surface of antiferromagnetic chromia. If this ferromagnetic surface is placed in close proximity with a ferromagnetic Co/Pd multilayer film, exchange coupling across a Pd interlayer induces an electrically controllable unidirectional anisotropy in the Co/Pd film. This electrically controlled exchange bias effect allows for reversible isothermal shifting of the global hysteresis loop of the Co/Pd film along the magnetic field axis from negative to positive values. Supported by NSF through Career DMR-0547887, by NRI, by NSF MRSEC, and by the NRC/NRI supplement. K.D.B. is a Cottrell Scholar of Research Corporation.

  3. 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.

  4. Structural and magnetic properties of Cr/Sb multilayers

    NASA Astrophysics Data System (ADS)

    Dohnomae, H.; Shintaku, K.; Nakayama, N.; Shinjo, T.

    Cr/Sb multilayered films take two types of structures - epitaxial superlattice and non-epitaxial multilayer - depending on the thickness of Cr layer ( dCr) and substrate temperature during deposition ( Ts). The epitaxial superlattices were formed when dCr ≤ 2Å and Ts = 90°C; Cr and Sb reacted into a NiAs-type compound CrSb, and furthermore deposited Sb grew epitaxially on the CrSb layer. With other deposition parameters, non-epitaxial Cr/Sb multilayers were formed, in which Cr layers are polycrystalline or amorphous-like but Sb layers are crystalline and [00.1] oriented. The reactivities of Cr/Sb interfaces greatly affect the film quality. Magnetic properties are also dependent on the degree of compound formation. The epitaxial CrSb/Sb superlattices show a ferromagnetic feature at 5 K, whereas the non-epitaxial Cr/Sb multilayers show a paramagnetic feature.

  5. Swelling Behavior of Blended Multilayer Thin Films Using Neutron Reflectivity.

    NASA Astrophysics Data System (ADS)

    Akgun, Bulent; Satija, Sushil; Kim, Hosub; Char, Kookheon

    2008-03-01

    Surface structure and swelling behavior of polyelectrolyte multilayer films of poly (allylamine hydrochloride) (PAH)/poly(sodium 4-styrenesulfonate) (PSS):poly(methacrylic acid) (PMAA) have been studied using X-ray and neutron reflectivity (NR). Samples have been prepared either using spin-assisted self assembly or dip coating. Swelling measurements were done in a chamber by using saturated salt solutions. PSS:PMAA blend composition was varied from pure PSS to pure PMAA to investigate the effect of strong polyelectrolyte on the swelling of the multilayer film. Multilayer films prepared by spin assisted deposition yields well defined films with much smooth interfaces than the films prepared by dip coating. NR results showed that incorporation of strong polyelectrolyte, PSS, into the multilayer decreases the swelling capacity of the film.

  6. 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.

  7. Study of Co/Pd multilayers as a candidate material for next generation magnetic media

    SciTech Connect

    Hu Bing; Amos, Nissim; Tian Yuan; Butler, John; Khizroev, Sakhrat; Litvinov, Dmitri

    2011-02-01

    We report a combinatorial synthesis study on the magnetic properties of sputter-deposited Co/Pd multilayers with high perpendicular anisotropy and high remnant squareness for magnetic media applications such as magnetic logic systems, bit patterned media, magneto-optical recording, and multilevel three-dimensional (3D) magnetic media. The perpendicular magnetic anisotropy in the multilayers originates from the interfacial anisotropy of the alloylike structure. The deposition conditions and subsequent microstructures of the multilayers are critical factors to determine the magnetic properties of the media. We investigated the dependence of the magnetic properties on the thickness of Co and Pd layers the number of Co/Pd bilayers. For instance, we found that a 0.26-nm-thick layer of Co would produce the highest coercivity value if paired with a 0.55-nm-thick Pd layer. Our results revealed that an Ar{sup +} milling could significantly increase the coercivity of the multilayer media. Further, we discovered that we could control the deposition pressure to achieve either granular or continuous media morphologies corresponding to exchange-coupled or decoupled grains, respectively. Finally, we used the combinatorial synthesis to tailor multilayers' properties to engineer a eight-level three-layer 3D media.

  8. 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.

  9. Antiferromagnetic coupling in soft amorphous ferromagnet/semiconductor multilayers

    NASA Astrophysics Data System (ADS)

    Velez, Maria

    2005-03-01

    Antiferromagnetic coupling between ferromagnetic layers separated by nonmagnetic metallic interlayers has been intensively studied due to the fundamental and technological interest in such behaviour. In this work, the presence of antiferromagnetic (AF) coupling has been investigated in multilayers where the nonmagnetic interlayers are not metallic but semiconducting. The analyzed samples are amorphous (CoxSi1-x)5 nm /(Si)d multilayers obtained by co-sputtering on Si substrates, and the Si layer thickness has been varied in the range 1 nm < d < 15 nm. X-ray diffraction analysis has shown that the multilayered structure is well defined. The individual (CoxSi1-x)5 nm ferromagnetic layer presents an uniaxial anisotropy and a soft magnetic behaviour (with coercivity smaller than 1 Oe for fields applied along its easy axis), being suitable to detect the possible AF coupling in the multilayer. Magneto-optical kerr effect and alternating gradient magnetometry measurements have revealed that these multilayers do present AF coupling at room temperature for d < 8 nm. Moreover, the magnetic field required to switch between antiparallel and parallel configurations is as low as 3 Oe and varies slightly with the Si layer thickness [1]. [1] C. Quiros et al., Phys. Rev. B (in press)

  10. Enhancement of perpendicular magnetic anisotropy in FeB free layers using a thin MgO cap layer

    NASA Astrophysics Data System (ADS)

    Kubota, Hitoshi; Ishibashi, Shota; Saruya, Takeshi; Nozaki, Takayuki; Fukushima, Akio; Yakushiji, Kay; Ando, Koji; Suzuki, Yoshishige; Yuasa, Shinji

    2012-04-01

    We prepared magnetic tunnel junction films with PtMn/CoFe/Ru/CoFeB/MgO tunnel barrier/FeB free layer/MgO cap layer/Ta multilayers using sputtering and measured magnetic and magnetoresistive properties of the films at room temperature. The magnetization curves of the FeB plane film measured under perpendicular-to-plane magnetic fields showed much smaller saturation fields (Hs) than those expected from the demagnetizing field. Hs decreased from 4 to 0.4 kOe with increasing MgO cap layer thickness. The small Hs is due to the perpendicular magnetic anisotropy (PMA) induced at both MgO barrier-FeB and FeB-MgO cap interfaces. After microfabrication, the small free layer cells having a 1.6 nm thick MgO cap layer showed a magnetization easy axis in the perpendicular-to-plane direction. By inducing PMA from both upper and lower interfaces, we can stabilize the magnetization of the relatively thick (2 nm) FeB free layer in the perpendicular-to-plane direction.

  11. 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.

  12. Tetragonal and cubic zirconia multilayered ceramic constructs created by EPD.

    PubMed

    Mochales, Carolina; Frank, Stefan; Zehbe, Rolf; Traykova, Tania; Fleckenstein, Christine; Maerten, Anke; Fleck, Claudia; Mueller, Wolf-Dieter

    2013-02-14

    The interest in electrophoretic deposition (EPD) for nanomaterials and ceramics production has widely increased due to the versatility of this technique to effectively combine different materials in unique shapes and structures. We successfully established an EPD layering process with submicrometer sized powders of Y-TZP with different mol percentages of yttrium oxide (3 and 8%) and produced multilayers of alternating tetragonal and cubic phases with a clearly defined interface. The rationale behind the design of these multilayer constructs was to optimize the properties of the final ceramic by combining the high mechanical toughness of the tetragonal phase of zirconia together with the high ionic conductivity of its cubic phase. In this work, a preliminary study of the mechanical properties of these constructs proved the good mechanical integrity of the multilayered constructs obtained as well as crack deflection in the interface between tetragonal and cubic zirconia layers.

  13. 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.

  14. 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.

  15. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

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

  17. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

    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.

  19. 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

  20. 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.

  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.

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

    PubMed

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

    2016-02-04

    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. 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.

  4. Exchange bias properties of [Co/CoO]{sub n} multilayers

    SciTech Connect

    Oeztuerk, M.; S Latin-Small-Letter-Dotless-I n Latin-Small-Letter-Dotless-I r, E.; Demirci, E.; Erkovan, M.; Oeztuerk, O.; Akdogan, N.

    2012-11-01

    In this study, the exchange bias properties of four polycrystalline multilayer stack samples of antiferromagnetic (AF) CoO and ferromagnetic (FM) Co in the form of [CoO/Co]{sub n} with n = 1, 2, 3, and 5 are reported. The samples were grown on top of Si (001) substrates by using magnetron sputtering method. X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) were used to determine the structural properties of the samples. XPS measurements of cobalt oxide layer revealed the coexistence of different phases in cobalt oxide as CoO and Co{sub 3}O{sub 4}, the latter of which lowers the blocking temperature. The blocking temperature is also affected by the finite size scaling effects observed in AF layers. In-plane ferromagnetic resonance (FMR) measurements revealed uniaxial in-plane magnetic anisotropy for the samples. Low temperature vibrating sample magnetometer measurements provided exchange bias with a stepwise character. Observed steps are believed to be due to magnetization reversals of individual FM layers with varying thicknesses, each of which is pinned through two interfaces from above and below with two AFM layers, except the uppermost FM Co layer with a single AFM neighbor.

  5. Effect of Mo capping layers thickness on the perpendicular magnetic anisotropy in MgO/CoFeB based top magnetic tunnel junction structure

    NASA Astrophysics Data System (ADS)

    Liu, Yi; Zhu, Kai-Gui; Zhong, Hui-Cai; Zhu, Zheng-Yong; Yu, Tao; Ma, Su-De

    2016-11-01

    A detailed study of the magnetic characterizations of the top structure MgO/CoFeB/Mo is presented. The samples show strong perpendicular magnetic anisotropy (PMA) when the thickness of CoFeB is 0.9 nm and 1.1 nm. The saturation magnetic moment and interface anisotropy constant are 1566 emu/cm3 and 3.75 erg/cm2, respectively. The magnetic dead layer (MDL) is about 0.23 nm in this system. Furthermore, strong capping layer thickness dependence is also observed. The strong PMA of 1.1 nm CoFeB only exists in a Mo cap layer thickness window of 1.2-2 nm. To maintain PMA, the metal layer could not be too thin or thick in these multilayers. The oxidation and diffusion of the metal capping layer should be respectively responsibility for the degradation of PMA in these thin or thick metal capping layer samples. Project supported by the National Fundamental Research Program of China (Grant No. 2011CB921804) and Beijing Key Subject Foundation of Condensed Matter Physics, China (Grant No. 0114023).

  6. Multilayer Perceptrons for Classification

    DTIC Science & Technology

    1992-03-01

    retention/ separation rates fu, input to force projection models. The second application concerns the classification of Armor Piercing Incendiary (API...Air Force pilot reten- tion/ separation rates for input to force projection models. The second application concerns the classification of Armor...methodologies for predicting pilot retention/ separation rates for input to personnel inventory projection models were e::plored. Specifically, the multilayer

  7. Modeling multilayer woven fabrics

    NASA Astrophysics Data System (ADS)

    Åström, J. A.; Mäkinen, J. P.; Timonen, J.

    2001-07-01

    A numerical algorithm for nonlinear elastic relaxation of a multilayer woven fabric is introduced and tested. The equilibrium solutions are compared with real samples. An excellent result is obtained in spite of two simplifications: Bending stiffness of the fibers and friction between the fibers are both neglected. The numerical simulation is very fast and cost efficient in the search for optimal fabrics.

  8. Uniaxial anisotropy and its manipulation in amorphous Co68Fe24Zr8 thin films (invited)

    NASA Astrophysics Data System (ADS)

    Fu, Yu; Barsukov, I.; Meckenstock, R.; Lindner, J.; Zhai, Y.; Hjörvarsson, B.; Farle, M.

    2014-05-01

    We have proven that the growth of Co68Fe24Zr8 layers under external field yields a uniaxial anisotropy, defined by the direction of the field. No magnetic coupling is present between Co68Fe24Zr8 layers when separated by a 3 nm of Al70Zr30. The anisotropy axis can therefore be manipulated at will and the direction can be tailored, layer by layer in multilayers, by the choice of the direction of the applied field during growth. The g-factor (2.13) and the anisotropy constant, obtained from ferromagnetic resonance, support the existence of short-range order. The relation between the temperature dependences of magnetic anisotropy and magnetization are partially captured by Callen-Callen power law.

  9. First-principle description of magnonic PdnFem multilayers

    SciTech Connect

    Manchanda, P; Sahota, PK; Skomski, R; Kumar, PSA; Kashyap, A

    2011-04-01

    Ab-initio calculations are used to determine the parameters that determine magnonic band structure of PdnFem multilayers (n = 2, m <= 8). We obtain the layer-resolved magnetization, the exchange coupling, and the magnetic anisotropy of the Pd-Fe structures. The Fe moment is 3.0 mu(B) close to the Pd layers and 2.2 mu(B) in the middle of the Fe layers. An intriguing but not usually considered aspect is that the elemental Pd is nonmagnetic, similar to Cu spacer layers in other multilayer systems. This leads to a pre-asymptotic ferromagnetic coupling through the Pd (about 40 mJ/m(2)). Furthermore, the Pd acquires a small moment due to spin polarization by neighboring Fe atoms, which translates into magnetic anisotropy. The anisotropies are large, in the range typical for L1(0) structures, which is beneficial for high-frequency applications. (C) 2011 American Institute of Physics. [doi:10.1063/1.3556763

  10. Seismic anisotropy of the Victoria Land region, Antarctica

    NASA Astrophysics Data System (ADS)

    Salimbeni, S.; Pondrelli, S.; Danesi, S.; Morelli, A.

    2010-07-01

    We present shear wave splitting results obtained from the analysis of core-refracted teleseismic phases recorded by permanent and temporary seismographic stations located in the Victoria Land region (Antarctica). We use an eigenvalue technique to isolate the rotated and shifted shear wave particle motion, to determine the best splitting parameters. Average values show clearly that dominant fast axis direction is NE-SW oriented, in accordance with previous measurements obtained around this zone. Only two stations, OHG and STAR, show different orientations, with N-S and NNW-SSE main directions. On the basis of the periodicity of single shear wave splitting measurements with respect to backazimuths of events under study, we infer the presence of lateral and vertical changes in the deep anisotropy direction. To test this hypothesis we model waveforms using a cross-convolution technique for the cases of one and two anisotropic layers. We obtain a significant improvement on the misfit in the double layer case for the two stations. For stations where a multilayer structure does not fit, we investigate lateral anisotropy changes at depth through Fresnel zone computation. We find that anisotropy beneath the Transantarctic Mountains (TAM) is considerably different from that beneath the Ross Sea. This feature influences the measurement distribution for the two permanent stations TNV and VNDA. Our results show a dominant NE-SW direction over the entire region, however other anisotropy directions are present and maybe interpreted in the context of regional tectonics.

  11. Oscillatory spin transport in spin Hall multilayers

    NASA Astrophysics Data System (ADS)

    Barsukov, Igor; Gonçalves, A. M.; Soledade, P.; Passos, C. A. C.; Costa, M.; Souza-Neto, N. M.; Garcia, F.; Lee, H. K.; Smith, A.; Tretiakov, O.; Krivorotov, I. N.; Sampaio, L. C.

    We study multilayers of sputtered Pt/(d)Cu/Py as a function of the Cu thickness d using ferromagnetic resonance (FMR). The FMR linewidth reveals a linear dependence on the frequency with negligible inhomogeneous contribution. The Gilbert damping falls smoothly with increasing d, but presents a strong superimposed oscillation with a period of ~1.5nm. We attribute this behavior to RKKY-like spin transport in the confinement of the Cu layer. The induced perpendicular anisotropy due to the proximity effect shows a similar behavior. We evaluate the induced magnetic moment on Pt using x-ray magnetic circular dichroism and find that it decreases with increasing Cu thickness smoothly. Again, we see oscillations of the magnetic moment and show that the oscillatory spin transport affects proximity induced magnetism in Pt. We extend our study to multilayer systems with increased oxidation levels and with out-of-plane crystal texture, in order to investigate the effects of disorder and electron's k-vectors that are responsible for the oscillatory spin transport.

  12. Edge-modulated perpendicular magnetic anisotropy in [Co/Pd]n and L10-FePt thin film wires

    NASA Astrophysics Data System (ADS)

    Zhang, Jinshuo; Ho, Pin; Currivan-Incorvia, Jean Anne; Siddiqui, Saima A.; Baldo, Marc A.; Ross, Caroline A.

    2015-11-01

    Thickness modulation at the edges of nanostructured magnetic thin films is shown to have important effects on their perpendicular magnetic anisotropy. Thin film wires with tapered edges were made from [Co/Pd]20 multilayers or L10-FePt films using liftoff with a double-layer resist. The effect of edge taper on the reversal process was studied using magnetic force microscopy and micromagnetic modeling. In [Co/Pd]20, the anisotropy was lower in the tapered edge regions which switched at a lower reverse field compared to the center of the wire. The L10-FePt wires showed opposite behavior with the tapered regions exhibiting higher anisotropy.

  13. A thermodynamic model for solid state amorphization: Application to Ni-Ti multilayers of different microstructures

    SciTech Connect

    Boettger, A.; Benedictus, R.; Mittemeijer, E.J.

    1997-07-01

    On the basis of an assessment of both the phase-formation energies and the energies of interfaces and grain boundaries the driving force for solid state amorphization (SSA) in crystalline Ni crystalline Ti and amorphous Ni- crystalline Ti multilayers was calculated. It followed that the structure of the interfaces and grain boundaries, and thus their energies is of crucial importance for the occurrence (or not) of SSA. The SSA behavior of the two types of Ni-Ti multilayers upon annealing was investigated using X-ray diffraction and (high resolution) transmission electron microscopy. The crystalline Ni-crystalline Ti multilayers showed SSA at both the Ni-Ti interfaces and the Ti grain boundaries. The amorphous Ni-crystalline Ti multilayers exhibited SSA at the Ti grain boundaries only. These observations agree with the predictions from the thermodynamic model.

  14. Delamination of isotropic and orthotropic multi-layers

    NASA Astrophysics Data System (ADS)

    Narayan, Shri Hari

    Inter-layer debonding or delamination is a prevalent damage phenomenon in multi-layered components in applications such as coatings, microelectronics, parts made by layered manufacturing methods and resin matrix composites. A common thread in these applications is the existence of multi-layered configurations with interfaces which are potential sites for damage initiation and growth in the form of interfacial cracks. In this thesis, fundamental concepts until now used in analyzing debonding between isotropic bimaterials are extended to the study of interfacial delamination in multi-layer configurations. The thesis is divided into two main sections. In the first section, focus is on the use of energy release rate quantities within the framework of interfacial fracture mechanics, to predict susceptibility to delamination of two-dimensional isotropic multi-layers under residual stress. Bounds on energy release rates are obtained analytically for two generic isotropic multi-layer configurations and numerical results are presented for a number of cases, verifying theoretical predictions. In the second section, effort is centered on developing interfacial fracture mechanics methods for application to debonding in resin-matrix composites which can be modeled as orthotropic multi-layers. Two specific issues are addressed, namely those of: (i) extracting non-oscillatory measures of mode mix from oscillatory models and (ii) designation of mode mix in composite debonding problems. The methods are developed for application to resin-matrix composites; however, the scope is not limited to composites but any orthotropic interfacial fracture problem.

  15. 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.

  16. Anisotropy determination in epitaxial Sm-Co/Fe exchange springs

    SciTech Connect

    Pechan, Michael J.; Teng, Nienchtze; Stewart, Jason-Dennis; Hilt, J. Zachary; Fullerton, Eric E.; Jiang, J. S.; Sowers, C. H.; Bader, S. D.

    2000-05-01

    We report in-plane anisotropy in epitaxial Sm-Co(x)/Fe(y) bilayers as determined by ferromagnetic resonance (FMR). Four samples, (x,y)=(35,30) and (20, 20) nm each on MgO (110) and (100) substrates, have been prepared via magnetron sputtering. The two substrate orientations result in twofold and fourfold Sm-Co symmetry respectively, with the Sm-Co c-axis in-plane. Magnetization curves indicate elastic exchange spring Fe behavior in reversing fields up to the Sm-Co switching fields (6 and 8 kG at room temperature in the (35, 30) and (20, 20) nm films, respectively). 35 GHz in-plane FMR measurements were made in order to map the crystalline anisotropy of the Fe layer as well as the induced anisotropy from the exchange coupling to the Sm-Co layer. The twofold Sm-Co samples exhibit a clear superposition of the near fourfold Fe crystal field anisotropy (530 Oe) and the unidirectional exchange-bias anisotropy ({approx_equal}650 Oe) arising from the Fe/Sm-Co interface. The crystalline Fe anisotropy in the fourfold Sm-Co samples is less well defined, presumably due to poorer epitaxy of the Fe layer for this orientation. (c) 2000 American Institute of Physics.

  17. COBE anisotropy from supercluster gas

    NASA Technical Reports Server (NTRS)

    Hogan, Craig J.

    1992-01-01

    It is suggested that the microwave background anisotropy detected by the COBE DMR might be dominated not by the direct gravitational effect of primordial fluctuations in the last scattering surface, but by scattering off of moving electrons in optically thin, nearby superclusters. Hot diffuse clouds of ionized gas created during supercluster collapse produce Sunyaev-Zel'dovich and Doppler background anisotropy whose properties may closely mimic those of primordial anisotropy in current data. Strategies for and difficulties in separating the effects are discussed, based on the anisotropy spectrum, autocorrelation, correlation with galaxy catalogs, X-ray emission, and integrated spectral distortions.

  18. Interfacial magnetism of Ce/Fe and CeH ˜2/Fe multilayers studied by 57Fe Mössbauer spectroscopy

    NASA Astrophysics Data System (ADS)

    Bauer, Ph.; Klose, F.; Schulte, O.; Felsch, W.

    1994-11-01

    The distribution of the magnetic hyperfine fields and the magnetic anisotropy of Ce/Fe and CeH ˜2/Fe multilayers have been studied by Mössbauer spectroscopy between 4.2 and 300 K. The extension of the Ce-Fe interaction defining a 'magnetic interface' exceeds the structural extension of the interface and is more than two times larger at the Ce/Fe than at the CeH ˜2/Fe interface. This is proposed to be a consequence of a strong hybridization between the Ce-5d and Fe-3d states that is suppressed by hydrogenation. From the relative intensity of the Mössbauer lines we show that for the CeH ˜2/Fe system with sufficiently thin Fe layers the orientation of the spontaneous magnetization is perpendicular to the film plane at low temperatures and switches to a parallel alignment at higher temperatures in a sharp transition. In contrast, the Ce/Fe system is spontaneously magnetized in the film plane.

  19. Relationship among petrofabric, magnetic anisotropy and seismic anisotropy in dunite

    NASA Astrophysics Data System (ADS)

    Hirt, A. M.; Wang, Q.; Biedermann, A. R.

    2012-04-01

    Physical anisotropies in rocks arise from the preferred alignment of the rock's constituents, which include mineral grains, organic matter or pore space. Different physical properties will be affected to a greater or lesser extent by these various factors. The anisotropy of magnetic susceptibility (AMS) is dependent on mineral orientation, particularly of minerals with high susceptibility and strong intrinsic anisotropy. Seismic anisotropy will also be controlled predominantly by mineral texture for rocks deformed at high pressure, where pore space or cracks are closed. During high-temperature ductile flow of the upper mantle, peridotite will develop a permanent deformation texture, which will be responsible for its physical anisotropies. Olivine develops characteristic crystal-preferred orientations (CPO) under different thermal-mechanical conditions. In this study we examine the relationship among mineral texture, magnetic anisotropy and seismic anisotropy of dunites from the Western Gneiss Region, Norway. Because dunite consists of > 90% olivine, the intrinsic magnetic anisotropy of single crystals of olivine is also investigated. AMS was measured with a high-field torsion magnetometer at room temperature and 77 K, in order to separate the paramagnetic sub-fabric from the total anisotropy. Our results indicate that olivine has a prolate anisotropy, in which the minimum, intermediate, and maximum axes of susceptibility correspond to the [010], [100] and [001] axes of olivine, respectively; this is partially contrary to an earlier investigation by Belley et al. (2009, EPSL, 284, 516-526). The degree of anisotropy increases by a factor of 7.1 - 8.2 at 77 K, and the shape becomes more triaxial. The CPO of olivine was measured using electron backscatter diffraction technique or X-ray texture goniometry. Although olivine grains in the samples develop two fabric types, namely [100](010) or [001](010), there is the same very good agreement between the orientation of the

  20. 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

  1. Nano-sized Adsorbate Structure Formation in Anisotropic Multilayer System

    NASA Astrophysics Data System (ADS)

    Kharchenko, Vasyl O.; Kharchenko, Dmitrii O.; Yanovsky, Vladimir V.

    2017-05-01

    In this article, we study dynamics of adsorbate island formation in a model plasma-condensate system numerically. We derive the generalized reaction-diffusion model for adsorptive multilayer system by taking into account anisotropy in transfer of adatoms between neighbor layers induced by electric field. It will be found that with an increase in the electric field strength, a structural transformation from nano-holes inside adsorbate matrix toward separated nano-sized adsorbate islands on a substrate is realized. Dynamics of adsorbate island sizes and corresponding distributions are analyzed in detail. This study provides an insight into details of self-organization of adatoms into nano-sized adsorbate islands in anisotropic multilayer plasma-condensate systems.

  2. Reactive Functionalized Multilayer Polymers in Coextrusion Process

    NASA Astrophysics Data System (ADS)

    Lamnawar, Khalid; Maazouz, Abderrahim

    2007-04-01

    Coextrusion technologies are commonly used to produce multilayered composite sheets or films with a large range of applications. The contrast of rheological properties between layers can lead to interfacial instabilities during flow. Important theoretical and experimental advances have been made during the last decades on the stability of compatible and incompatible polymers using a mechanical approach. The present study deals with the influence of this affinity on interfacial instabilities for functionalized incompatible polymers between the neighboring layers. Polyamide (PA6)/Polyethylene-grafted (GMA) or pure PE were studied with different viscosity and elasticity ratios. We have experimentally confirmed, in this case, that the weak disturbance can be predicted by considering an interphase of non-zero thickness (corresponding to interdiffusion/reaction zone) instead of a purely geometrical interface between the two reactive layers. As a first step, rheological behavior of multilayer coextruded cast films was investigated to probe: (i) the competition between polymer/polymer interdiffusion and the interfacial reaction and (ii) the influence of the interphase. The contribution of this one effect has been studied along with the increase of the number of layers. The results show that the variation in dynamic modulus of the multilayer system reflects both diffusion and chemical reaction. Finally, and in order to quantify the contribution of the effect of the interface/interphase with a specific interfacial area, an expression was developed to take into account the interphase triggered between the neighboring layers and allowed us to estimate its thickness at a specific welding time and shear rate. As the second step, we formulate an experimental strategy to optimize the process by listing the different parameters controlling the stability of the reactive multilayer flows. The plastic films of two, three and five layers were coextruded in symmetrical and asymmetrical

  3. 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

  4. 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.

  5. Multilayer Optical Learning Networks

    NASA Astrophysics Data System (ADS)

    Wagner, Kelvin; Psaltis, Demetri

    1987-08-01

    In this paper we present a new approach to learning in a multilayer optical neural network which is based on holographically interconnected nonlinear Fabry-Perot etalons. The network can learn the interconnections that form a distributed representation of a desired pattern transformation operation. The interconnections are formed in an adaptive and self aligning fashion, as volume holographic gratings in photorefractive crystals. Parallel arrays of globally space integrated inner products diffracted by the interconnecting hologram illuminate arrays of nonlinear Fabry-Perot etalons for fast thresholding of the transformed patterns. A phase conjugated reference wave interferes with a backwards propagating error signal to form holographic interference patterns which are time integrated in the volume of the photorefractive crystal in order to slowly modify and learn the appropriate self aligning interconnections. A holographic implementation of a single layer perceptron learning procedure is presented that can be extendept ,to a multilayer learning network through an optical implementation of the backward error propagation (BEP) algorithm.

  6. Multilayer ceramic actuator commercialization

    NASA Astrophysics Data System (ADS)

    Ritter, Andrew P.

    1995-05-01

    AVX is the largest US manufacturer of multilayer ceramic capacitors, producing 10's of millions per day. Multilayer ceramic actuators are manufactured using virtually identical fabrication methods. Fabrication from this ceramic tape allows tremendous latitude in device shape, size and material choice. This paper will discuss several different actuator configurations-including stacks, plates and chips- with respect to performance and cost tradeoffs. Virtually all developing smart material applications are 'technology driven,' however the widespread availability of devices at commercial scale relies on 'market pull' to achieve a balance of high annualized volumes and low cost. Given sufficient demand, devices can be produced such that the raw materials themselves dominate the unit cost. Generalized price-volume-performance relationships for the different actuator configurations can both guide system designers and focus long-term component development efforts.

  7. Multilayers of zinc-blende half-metals with semiconductors

    NASA Astrophysics Data System (ADS)

    Mavropoulos, Ph; Galanakis, I.; Dederichs, P. H.

    2004-06-01

    We report on first-principles calculations for multilayers of zinc-blende half-metallic ferromagnets CrAs and CrSb with III-V and II-VI semiconductors, in the [001] orientation. We examine the ideal and tetragonalized structures, as well as the case of an intermixed interface. We find that, as a rule, half-metallicity can be conserved throughout the heterostructures, provided that the character of the local coordination and bonding is not disturbed. We describe a mechanism operative at the interfaces with semiconductors that can also give a non-integer spin moment per interface transition atom, and derive a simple rule for evaluating it.

  8. 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.

  9. Multilayer structures as negative refractive and left-handed materials.

    PubMed

    Chui, S T; Chan, C T; Lin, Z F

    2006-02-15

    We examine multilayer structures as negative refractive index and left-handed materials, and find that for one polarization there is a wide range (≈90°) of incident angle within which negative refraction will occur. This comes about because the group velocity and the Poynting vector have a large component parallel to the layers, no matter what the angle of incidence of the incoming radiation is. This behaviour in turn comes from the large anisotropy of the phase velocities. If one of the components is a ferromagnetic metal, the system can be a left-handed material above the ferromagnetic resonance frequency.

  10. High temperature interface superconductivity

    DOE PAGES

    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

  11. High temperature interface superconductivity

    SciTech Connect

    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, 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.

  12. 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.

  13. Electromechanical transduction in multilayer ionic transducers

    NASA Astrophysics Data System (ADS)

    Akle, Barbar; Leo, Donald J.

    2004-10-01

    A transducer consisting of multiple layers of ionic polymer material is developed for applications in sensing, actuation and control. A multilayer transducer is fabricated by layering individual transducers on top of one another. Each multilayer transducer consists of two to four individual layers each approximately 200 µm thick. The electrical characteristics of the transducers can be varied by connecting the layers in either a parallel arrangement or a series arrangement. The tradeoff in deflection and force is obtained by controlling the mechanical constraint at the interface. Packaging the transducer in an outer coating produces a hard constraint between layers and reduces the deflection with a force that increases linearly with the number of layers. This configuration also increases the bandwidth of the transducer. Removing the outer packaging produces an actuator that maintains the deflection of a single layer with an increased force output. This is obtained by allowing the layers to slide relative to one another during bending. Experiments on transducers with one to three layers are performed and the results are compared to an equivalent circuit model which was modified to accommodate multilayer transducers. The modification is performed on four different boundary conditions: two electrical, the series and the parallel connection, and two mechanical, the zero interfacial friction and the zero slip on the interface. Expressions for blocked force, free deflection, and electrical impedance of the transducer are developed in terms of fundamental material parameters, transducer geometry, and the number of individual layers. The trends in the transducer response are validated using experiments on transducers with multiple polymer layers.

  14. Electronic structure and phase composition of dielectric interlayers in multilayer amorphous nanostructure [(CoFeB)60C40/SiO2]200

    NASA Astrophysics Data System (ADS)

    Domashevskaya, E. P.; Builov, N. S.; Terekhov, V. A.; Barkov, K. A.; Sitnikov, V. G.

    2017-01-01

    The multilayer amorphous nanostructure [(CoFeB)60C40/SiO2]200 of alternating composite and dielectric layers was obtained by ion-beam sputtering on a rotating pyroceramic substrate of two targets, one of which was a Co40Fe40B20 metal alloy plate with graphite inserts. The dielectric interlayers of SiO2 were sputtered from a quartz plate (second target). The thicknesses of bilayers of the multilayered nanostructure (MNS) (6 nm), consisting of metal-carbon composite layers (CoFeB)60C40 approximately 4 nm in thickness and a silicon oxide dielectric interlayers with a thickness of approximately 2 nm, were determined by small-angle diffraction. The results of experimental layer-by-layer study without destroying the MNS by ultrasoft X-ray spectroscopy (USXES) showed a significant deviation of the stoichiometric composition of the dielectric interlayers from stoichiometry sputtered quartz towards decreasing oxygen concentration with the formation of SiO1.3 suboxide. As a result of simulation of the Si L 2,3 spectra of silicon using reference spectra of known phases, the concentration of the silicon suboxide phase in the amorphous dielectric interlayers reaches about half of the interlayer content, the second half of which is accounted for SiO 2 dioxide. A "shielding" effect of carbon in the metal layers is manifested in the absence of silicide formation at the interfaces of the multilayer structure under study and should help to increase the anisotropy of their electromagnetic properties.

  15. Determination of exchange and rotational anisotropies in IrMn /Fe(t)/IrMn exchange coupled structures using dynamic and static techniques: Application to microwave devices

    NASA Astrophysics Data System (ADS)

    Kuanr, Bijoy K.; Maat, Stefan; Chandrashekariaih, S.; Veerakumar, V.; Camley, R. E.; Celinski, Z.

    2008-04-01

    We determined the exchange anisotropy and rotational anisotropy of IrMn(7 nm)/Fe(t=3-20 nm)/IrMn(7 nm) exchange-biased structures using conventional ferromagnetic resonance (FMR) and network analyzer FMR (NA-FMR). Compared to single Fe layer films of identical thickness, we observe an isotropic downward shift and an angular variation of the FMR resonance field in the multilayer structures. The isotropic shift originates from the rotational anisotropy, while the angular variation originates from the exchange anisotropy. Both exchange anisotropy and rotational anisotropy increase with decreasing Fe thickness in the exchange-biased structures. The isotropic downward shift of the resonance field translates to an upward shift of the resonance frequency, and can be used to boost the operational frequency of microwave devices (bandpass/stop filters) by several gigahertz.

  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. 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.

  18. Evolution of magnetic properties and domain structures in Co/Ni multilayers

    NASA Astrophysics Data System (ADS)

    Su, Xianpeng; Jin, Tianli; Wang, Ying; Ren, Yang; Wang, Lianwen; Bai, Jianmin; Cao, Jiangwei

    2016-11-01

    Co/Ni multilayers with different layer thicknesses and repetition numbers were fabricated by magnetron sputtering. The films with appropriate Co and Ni layer thicknesses show strong perpendicular magnetic anisotropy. The results of magnetic force microscopy indicate that the films show a maze domain in the demagnetization state and that the domain width decreases with increasing layer thickness and repetition number. The magnetostatic and domain wall energies of the film stack were calculated on the basis of an irregular maze domain pattern. The results suggest that the magnetostatic energy is the main reason for the variation of the domain width in Co/Ni multilayers.

  19. 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.

  20. Tailoring magnetism in CoNi films with perpendicular anisotropy by ion irradiation

    SciTech Connect

    Stanescu, D.; Ravelosona, D.; Mathet, V.; Chappert, C.; Samson, Y.; Beigne, C.; Gierak, J.; Bouhris, E.; Fullerton, E. E.

    2008-04-01

    This paper reports on the influence of ion irradiation on the magnetic properties of Co/Ni multilayers with perpendicular magnetic anisotropy (PMA). This material is a very promising candidate for ultrahigh density spintronic applications since it exhibits high polarization and low damping parameters. We show that PMA can be tailored in a controlled way by using uniform He{sup +} ion irradiation or focused Ga{sup +} ion beam.

  1. A molecular dynamics study of growth anisotropy in Al melt

    NASA Astrophysics Data System (ADS)

    Men, H.

    2016-01-01

    In this paper, we investigated the growth kinetics and physical origin of the anisotropy at the (1 1 1), (1 1 0) and (1 0 0) interfaces in the growth of Al, using molecular dynamics (MD) simulations. The simulation results reveal that the growth is usually involved in slight adjustment of the atomic positions at the interfaces during the solidification, and the pronounced atomic ordering at the interface may facilitate the in-layer displacement and z-displacement (z-displacement involves the motion between layers) of the atoms during the solidification. The stacking fault island that previous authors proposed isn’t observed in this study, and the occurrence of stacking fault island may be not a general mechanism for the slow growth of the (1 1 1) interface. The (1 1 0) and (1 0 0) interfaces may be reconstructed and become rougher than the (1 1 1) interface, and this might be the physical origin of the growth anisotropy in the fcc metals.

  2. Dependence of Magnetic Properties of Co/Pt Multilayers on Deposition Temperature of Pt Buffer Layers

    NASA Astrophysics Data System (ADS)

    Shiomi, Shigeru; Nishimura, Tomotaka; Kobayashi, Tadashi; Masuda, Morio

    1993-04-01

    A 15-nm-thick Pt buffer layer was deposited on a glass slide at temperature Ts(Ptbuf) ranging from 30 to 300°C by e-gun evaporation. Following the cooling in vacuum to ambient temperature, Co and Pt layers have been alternately deposited on it. Very large perpendicular anisotropy and coercivity have been obtained at Ts(Ptbuf) higher than 200°C. The (111) preferred orientation of the Co/Pt multilayer as well as the Pt buffer layer became more pronounced with elevating Ts(Ptbuf), to which the enhancement of perpendicular anisotropy with elevating Ts(Ptbuf) might be ascribable.

  3. Enhanced conductivity along lateral homojunction interfaces of atomically thin semiconductors

    NASA Astrophysics Data System (ADS)

    Jia, Ying; Stanev, Teodor K.; Lenferink, Erik J.; Stern, Nathaniel P.

    2017-06-01

    Energy band realignment at the interfaces between materials in heterostructures can give rise to unique electronic characteristics and non-trivial low-dimensional charge states. In a homojunction of monolayer and multilayer MoS2, the thickness-dependent band structure implies the possibility of band realignment and a new interface charge state with properties distinct from the isolated layers. In this report, we probe the interface charge state using scanning photocurrent microscopy and gate-dependent transport with source-drain bias applied along the interface. Enhanced photoresponse observed at the interface is attributed to band bending. The effective conductivity of a material with a monolayer-multilayer interface of MoS2 is demonstrated to be higher than that of independent monolayers or multilayers of MoS2. A classic heterostructure model is constructed to interpret the electrical properties at the interface. Our work reveals that the band engineering at the transition metal dichalcogenides monolayer/multilayer interfaces can enhance the longitudinal conductance and field-effect mobility of the composite monolayer and multilayer devices.

  4. Magnetism and magnetic anisotropy of antiferromagnetic NiMn

    NASA Astrophysics Data System (ADS)

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

    2000-03-01

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

  5. 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

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

    DOE PAGES

    Guggenmos, Alexander; Radünz, Stefan; Rauhut, Roman; ...

    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

  7. 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.

  8. Multilayer Mg-Stainless Steel Sheets, Microstructure, and Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Inoue, Junya; Sadeghi, Alireza; Kyokuta, Nobuhiko; Ohmori, Toshinori; Koseki, Toshihiko

    2017-05-01

    Different multilayer Mg AZ31 and SS304L steel sheet combinations were prepared with different volume fractions of Mg. Isolated stress-strain curves of the Mg layers showed significant improvements in the strength and elongation of multilayer samples. Results indicated that in the most extreme situation with the lowest Mg volume fraction ( V f = 0.39), the ultimate strength was increased by 25 pct to 370 MPa and the elongation was improved by 70 pct to 0.34. Investigation of the fracture surface showed that failure occurs by the coalescence of cracks close to the interface region. The improved strength of the multilayer samples was due to the combined effect of surface crack prevention by the steel layer and the higher work-hardening rate caused by the possible increased activity of non-basal systems. It is suggested that the stronger work-hardening behavior and the enhanced activity of non-basal systems in the multilayer samples were due to the formation of new stress components in the transverse direction. The larger the volume fraction of steel in the multilayer, the longer the distance remaining unstrained before the UTS.

  9. Multilayer Mg: Stainless Steel Sheets, Microstructure, and Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Inoue, Junya; Sadeghi, Alireza; Kyokuta, Nobuhiko; Ohmori, Toshinori; Koseki, Toshihiko

    2017-02-01

    Different multilayer Mg AZ31 and SS304L steel sheet combinations were prepared with different volume fractions of Mg. Isolated stress-strain curves of the Mg layers showed significant improvements in the strength and elongation of multilayer samples. Results indicated that in the most extreme situation with the lowest Mg volume fraction (V f = 0.39), the ultimate strength was increased by 25 pct to 370 MPa and the elongation was improved by 70 pct to 0.34. Investigation of the fracture surface showed that failure occurs by the coalescence of cracks close to the interface region. The improved strength of the multilayer samples was due to the combined effect of surface crack prevention by the steel layer and the higher work-hardening rate caused by the possible increased activity of non-basal systems. It is suggested that the stronger work-hardening behavior and the enhanced activity of non-basal systems in the multilayer samples were due to the formation of new stress components in the transverse direction. The larger the volume fraction of steel in the multilayer, the longer the distance remaining unstrained before the UTS.

  10. Thermal conductivity reduction in Si-isotope-multilayers

    NASA Astrophysics Data System (ADS)

    Bachmann, M.; Czerner, M.; Heiliger, C.

    2014-12-01

    We employ the atomistic Green's function (AGF) formalism to investigate phonon transport in silicon isotope multilayers. Since we use the AGF method, we can distinguish between coherent scattering at isotope multilayers and incoherent phonon-phonon scattering. Our investigations show that there are two different regimes for coherent scattering at isotope multilayers: the periodic regime, with periodically arranged layers, and a random regime, with layers of different thicknesses. The phonon scattering is stronger in the random regime, whereas in the periodic regime the phonon scattering rapidly saturates with the number of layers. Even though the phonon scattering in the random regime is stronger than in the periodic regime, the resulting thermal resistance in both regimes is much lower than the one obtained by combining the interfaces of the multilayer incoherently. We also found that the periodic regime is sensitive to small deviations. A small deviation from the perfect periodic arrangement leads to the behavior of the random regime. These deviations are so small that it is extremely difficult to actually grow perfect periodic isotope multilayers and observe the periodic regime experimentally.

  11. Osseointegration of a hydroxyapatite-coated multilayered mesh stem.

    PubMed

    Kusakabe, Hiroshi; Sakamaki, Toyonori; Nihei, Kotaro; Oyama, Yasuo; Yanagimoto, Shigeru; Ichimiya, Masaru; Kimura, Jun; Toyama, Yoshiaki

    2004-07-01

    A new type of porous coating for hip prostheses called "multilayered mesh" was tested under weight-bearing conditions. The surface of the stem is constructed of titanium mesh produced by etching. The hip stems of hydroxyapatite (HA)-coated multilayered mesh and conventional beads were implanted into canine right hips, and animals were killed 3, 6 and 10 weeks and 6 and 12 months after implantation. Shear strength between the implant and the bone was evaluated by the push-out test. Bone ingrowth was calculated from backscattered electron imaging-scanning electron microscopy (BEI-SEM) images of transverse sections. Toluidine blue stained sections and the BEI-SEM images were evaluated histologically. The break sites of the specimens after the push-out test were evaluated on BEI-SEM images of longitudinal sections. The mean push-out strength of the HA-coated multilayered mesh samples was greater than that of the beads-coated samples every time tested, and the HA-coated multilayered mesh implants had significantly stronger push-out strength at 3 and 6 weeks (p<0.05). The strength of the HA-coated multilayered mesh implants was even greater at 6 and 12 months, whereas the strength of the beads-coated samples decreased. The HA-coated multilayered mesh implants showed significantly higher percentages of bone ingrowth than the beads-coated implants every time tested, except at 6 months (p<0.05). At 6 and 12 months, the bone ingrowth data for the HA-coated multilayered mesh implants increased, whereas it decreased for the beads-coated implants. The new bone formation had reached the bottom of the porous area of the HA-coated multilayered mesh surface by 3 weeks, but not had reached the bottom of the conventional beads surface. At 6 and 12 months, the smaller pores of the bead surface stopped the thickening of trabecular bone, and at 12 months, the break sites were at the bone-implant interface of the bead surface, whereas they were on the bone side of the HA

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. Anisotropy in solid inflation

    NASA Astrophysics Data System (ADS)

    Bartolo, Nicola; Matarrese, Sabino; Peloso, Marco; Ricciardone, Angelo

    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(phi)F2 model, which also allows for anisotropic inflation thanks to a suitable coupling between the inflaton phi 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(phi)F2 model.

  17. 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).

  18. Analysis of oxygen induced anisotropy crossover in Pt/Co/MOx trilayers

    NASA Astrophysics Data System (ADS)

    Manchon, A.; Ducruet, C.; Lombard, L.; Auffret, S.; Rodmacq, B.; Dieny, B.; Pizzini, S.; Vogel, J.; Uhlíř, V.; Hochstrasser, M.; Panaccione, G.

    2008-08-01

    Extraordinary Hall effect and x-ray spectroscopy measurements have been performed on a series of Pt/Co/MOx trilayers (M =Al, Mg, Ta, etc.) in order to investigate the role of oxidation in the onset of perpendicular magnetic anisotropy at the Co/MOx interface. It is observed that varying the plasma oxidation time modifies the magnetic properties of the Co layer, inducing a magnetic anisotropy crossover from in plane to out of plane. We focused on the influence of plasma oxidation on Pt/Co/AlOx perpendicular magnetic anisotropy. The interfacial electronic structure is analyzed via x-ray photoelectron spectroscopy measurements. It is shown that the maximum of out-of-plane magnetic anisotropy corresponds to the appearance of a significant density of Co-O bondings at the Co/AlOx interface.

  19. 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.

  20. 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.

  1. Multilayer heat insulator

    SciTech Connect

    Iwabuchi, S.; Matsui, K.

    1982-04-06

    The invention relates to multilayer heat insulators wherein gasimpermeable layers each made of a metal foil of one member selected from the group consisting of aluminum, nickel and stainless steel and gas-containing layers each made of at least one member selected from the group consisting of glass fiber, asbestos fiber, mineral fiber, ceramic fiber, carbon fiber, silica powder, alumina powder and zirconia powder in the form of wool, paper or mat are laminated alternately so that the same layers do not contact each other. The thickness of the gasimpermeable layer is 10 to 20 mu m, the thickness of the gascontaining layer is 0.3 to 1.8 mm and its porosity is 0.98 to 95 to make the thermal conductivity of this lamina multilayer heat insulator about 0.02 kcal/mh0 C (2000 C) so that the behavior of the contained gas may be as small as possible, the thermal conduction may be prevented and the heat insulating performance may be improved.

  2. 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.

  3. Studies of the magnetic structure at the ferromagnet - antiferromagnet interface

    SciTech Connect

    Scholl, A.; Nolting, F.; Stohr, J.; Luning, J.; Seo, J.W.; Locquet, J.-P.; Anders, S.; Ohldag, H.; Padmore, H.A.

    2001-01-02

    Antiferromagnetic layers are a scientifically challenging component in magneto-electronic devices such as magnetic sensors in hard disk heads, or magnetic RAM elements. In this paper we show that photo-electron emission microscopy (PEEM) is capable of determining the magnetic structure at the interface of ferromagnets and antiferromagnets with high spatial resolution (down to 20 nm). Dichroism effects at the L edges of the magnetic 3d transition metals, using circularly or linearly polarized soft x-rays from a synchrotron source, give rise to a magnetic image contrast. Images, acquired with the PEEM2 experiment at the Advanced Light Source, show magnetic contrast for antiferromagnetic LaFeO{sub 3}, microscopically resolving the magnetic domain structure in an antiferromagnetically ordered thin film for the first time. Magnetic coupling between LaFeO{sub 3} and an adjacent Co layer results in a complete correlation of their magnetic domain structures. From field dependent measurements a unidirectional anisotropy resulting in a local exchange bias of up to 30 Oe in single domains could be deduced. The elemental specificity and the quantitative magnetic sensitivity render PEEM a perfect tool to study magnetic coupling effects in multi-layered thin film samples.

  4. Deformation-induced nanoscale mixing reactions in Cu/Ni and Ag/Pd multilayers

    SciTech Connect

    Wang, Z.; Perepezko, J. H.

    2013-11-04

    During the repeated cold rolling of Cu/Ni and Ag/Pd multilayers, a solid solution forms at the interfaces as nanoscale layer structure with a composition that replicates the overall multilayer composition. The interfacial mixing behavior was investigated by means of X-ray diffraction and scanning transmission electron microscopy. During deformation induced reaction, the intermixing behavior of the Cu/Ni and Ag/Pd multilayers is in contrast to thermally activated diffusion behavior. This distinct behavior can provide new kinetic pathways and offer opportunities for microstructure control that cannot be achieved by thermal processing.

  5. Permalloy-FeMn exchange-biased multilayers grown on flexible substrates for microwave applications

    NASA Astrophysics Data System (ADS)

    Phuoc, Nguyen N.; Xu, Feng; Ma, Yungui; Ong, C. K.

    2009-09-01

    Permalloy-FeMn multilayers deposited onto flexible substrates oriented for wide-band absorber applications were fabricated using RF sputtering deposition. The ferromagnetic resonance (FMR) frequency was tuned by changing the thickness of the Permalloy layers. Plural FMR frequencies appeared in the multilayer film due to the difference in exchange couple energies at their interfaces. A multilayer thin film with varying thickness of Permalloy layers was also fabricated with the properties of a wide-band absorber. Its range of 1-4 GHz (the absorption width where the reflection loss is less than 10 dB) appears promising for future applications.

  6. 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.

  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. Organic Multilayer Films Studied by Scanning Tunneling Microscopy.

    PubMed

    He, Yang; Kröger, Jörg; Wang, Yongfeng

    2017-03-03

    This Minireview focuses exclusively on work with scanning tunneling microscopy to study the self-assembled multilayer films (SAMTs) of organic molecules. The π-conjugated organic molecules form different structures within different monolayers on various substrates. The interplay between molecule-substrate and intermolecular interactions plays a key role in determining the stacking mode of organic multilayer films. Different substrates strongly influence the organic-film growth and electronic properties of the organic molecules. Geometric and electronic structures of SAMTs are important factors that may determine device performance. In addition to the inorganic interface, this Minireview addresses the organic-organic interface. Homo- and hetero-SAMTs of organic molecules are also considered. The subtle interplay between structural and electronic characteristics, on one hand, and functionality and reactivity, on the other hand, are highlighted.

  9. 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.

  10. He ion irradiation damage in Al/Nb multilayers

    SciTech Connect

    Li Nan; Anderoglu, O.; Zhang, X.; Martin, M. S.; Shao, L.; Misra, A.; Wang, H.

    2009-06-15

    We investigate the evolution of microstructure and mechanical properties of sputter-deposited Al/Nb multilayers with miscible fcc/bcc type interface and individual layer thickness, h, of 1-200 nm, subjected to helium ion irradiations: 100 keV He{sup +} ions and a fluence of 6x10{sup 16}/cm{sup 2}. Helium bubbles, 1-2 nm in diameter, are 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 phase 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.

  11. 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.

  12. Effect of diffusive scattering on giant magnetoresistance in magnetic multilayers

    NASA Astrophysics Data System (ADS)

    Stewart, Derek Alan

    2001-07-01

    Dramatic changes in resistance due to external magnetic fields or giant magnetoresistance (GMR) have provided revolutionary advances in disciplines ranging from computer memory to land mine detection. This thesis explores the crucial role of interfaces in producing GMR in systems such as magnetic multilayers and spin valves where magnetic layers (Co or Fe) are separated by simple metal layers of Cu or Cr. A semi-classical Boltzmann transport model is used to model GMR in Co|Cu magnetic multilayers. Parameters required to fit experimental results indicate minority carriers in Co have a very small mean free path and experience enhanced diffusive scattering at layer interfaces. Parameters fitted for magnetic multilayers (>100 layers) are used to calculate the GMR in corresponding spin valve systems. The model provides GMR and resistivity values in good agreement with current experimental results for spin valves. Scattering at a single interface is examined using two techniques to provide a better theoretical basis for treatment of interfaces in semi-classical calculations. An analytical Green's function approach is developed that treats the interface as a sheet of randomly placed point scatterers. This formalism provides closed forms for interface specularity parameters that depend on electron momentum and interface roughness. The specularity parameters for transmission and reflection differ in functional form, a fact neglected in current Boltzmann models. The layered Korringa Kohn Rostoker method (LKKR) is also used to examine transport across free electron and Co|Cu interfaces. The interdiffused region is treated as an alloy layer under the Coherent Potential Approximation (CPA). Specularity parameters found using this technique for free electrons agree well with analytical Green's function results. The LKKR also provides the first energy dependent specularity parameters for a real material interface. The electronic properties of FeCr alloys are examined using the

  13. MSAT: a New Matlab Toolbox for the Analysis and Modelling of Seismic Anisotropy

    NASA Astrophysics Data System (ADS)

    Walker, A. M.; Wookey, J.

    2011-12-01

    Studies of seismic anisotropy rarely end with measurements of shear-wave splitting - instead an explanation of the physical origin of the anisotropy is sought in order to yield useful geological or geophysical information. We describe a new Matlab toolbox designed to aid the modelling needed for this interpretative step of the analysis of seismic anisotropy. Provision of key building blocks for modelling in this modern integrated development environment allows the rapid development and prototyping of explanations for measured anisotropy. The Matlab graphical environment also permits plotting of key anisotropic parameters. Furthermore, this work complements the SplitLab toolbox used for measuring shear wave splitting and the MTEX toolbox used for the analysis of textures in rocks. MSAT (the Matlab Seismic Anisotropy Toolbox) includes a wide range of functions which can be used to rapidly build models of seismic anisotropy. Available functions include: the determination of phase velocities as a function of wave propagation direction, the analysis of multi-layer splitting, a novel interpolation scheme for elastic constants tensors, the estimation of the anisotropy caused by the presence of aligned inclusions and the measurement of the degree of anisotropy exhibited by an elastic material. We include a database of elastic properties of rocks and minerals and functions to plot seismic anisotropy as a function of wave propagation direction in the form of pole figures or as three-dimensional plots. The toolbox includes extensive documentation and example applications which integrate with the Matlab documentation system alongside automated test cases for all functions. All code is open source and available freely to all. We encourage users to feed back any changes they may need to make. Key examples of the use of this software include: (1) Calculation of the pattern of backazimuthal variation of shear wave splitting caused by the interaction of two dipping layers of

  14. 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.

  15. Element Specific Magnetic Anisotropy Energy of Alternately Layered FeNi Thin Films

    NASA Astrophysics Data System (ADS)

    Sakamaki, Masako; Amemiya, Kenta

    2011-07-01

    The element specific magnetic anisotropy energy (MAE) of alternately layered FeNi thin films grown on Ni (4-20 MLs)/Cu(001) is investigated by means of the X-ray magnetic circular dichroism (XMCD) and magneto-optic Kerr effect (MOKE). Although surface Fe is known to show strong perpendicular magnetic anisotropy, the Ni-sandwiched Fe layer has a tiny MAE of 10+/-40 µeV. On the other hand, the Fe-sandwiched Ni layer has a positive MAE of 60+/-30 µeV. The total MAE simulated from the XMCD analysis shows good agreement with the MOKE result. We demonstrate that in-situ analysis of the element specific MAE gives a possible strategy for manipulating the magnetic anisotropy of multilayers.

  16. Electric field modulation of magnetic anisotropy in perpendicularly magnetized Pt/Co structure with a Pd top layer

    NASA Astrophysics Data System (ADS)

    Hibino, Yuki; Koyama, Tomohiro; Obinata, Aya; Miwa, Kazumoto; Ono, Shimpei; Chiba, Daichi

    2015-11-01

    We investigated the electric field effect on magnetic anisotropy in a perpendicularly magnetized Pt/Co system with a top ultrathin layer of nonmagnetic Pd. By applying an electric field to the surface of the ferromagnetic Pd layer, we observed a clear modulation of the perpendicular magnetic anisotropy of the system. This result shows that the magnetic anisotropy can be modulated by an electric field even when nonmagnetic Pd is inserted at the interface formed by the magnetic layer and insulator. The electric field effect of the proximity-induced moment in Pd might contribute to the anisotropy modulation.

  17. Density gradient multilayer polymerization for creating complex tissue.

    PubMed

    Karpiak, Jerome V; Ner, Yogesh; Almutairi, Adah

    2012-03-15

    An adaptable density gradient multilayer polymerization (DGMP) method facilitates simple fabrication of complex multicompartment scaffolds with structurally continuous interfaces. Solvent density liquid-liquid phase segregation compartmentalizes varied mechanical and chemical cues independently. Bulk photopolymerization produces stratified three-dimensional and two-dimensional matrices. Cells attach to patterned adhesion peptides on biomimetic 2D substrates. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Realizing topological stability of magnetic helices in exchange-coupled multilayers for all-spin-based system

    NASA Astrophysics Data System (ADS)

    Fust, Sergej; Mukherjee, Saumya; Paul, Neelima; Stahn, Jochen; Kreuzpaintner, Wolfgang; Böni, Peter; Paul, Amitesh

    2016-09-01

    Topologically stabilized spin configurations like helices in the form of planar domain walls (DWs) or vortex-like structures with magnetic functionalities are more often a theoretical prediction rather than experimental realization. In this paper we report on the exchange coupling and helical phase characteristics within Dy-Fe multilayers. The magnetic hysteresis loops with temperature show an exchange bias field of around 1.0 kOe at 10 K. Polarized neutron reflectivity reveal (i) ferrimagnetic alignment of the layers at low fields forming twisted magnetic helices and a more complicated but stable continuous helical arrangement at higher fields (ii) direct evidence of helices in the form of planar 2π-DWs within both layers of Fe and Dy. The helices within the Fe layers are topologically stabilized by the reasonably strong induced in-plane magnetocrystalline anisotropy of Dy and the exchange coupling at the Fe-Dy interfaces. The helices in Dy are plausibly reminiscent of the helical ordering at higher temperatures induced by the field history and interfacial strain. Stability of the helical order even at large fields have resulted in an effective modulation of the periodicity of the spin-density like waves and subsequent increase in storage energy. This opens broad perspectives for future scientific and technological applications in increasing the energy density for systems in the field of all-spin-based engineering which has the potential for energy-storing elements on nanometer length scales.

  19. Realizing topological stability of magnetic helices in exchange-coupled multilayers for all-spin-based system.

    PubMed

    Fust, Sergej; Mukherjee, Saumya; Paul, Neelima; Stahn, Jochen; Kreuzpaintner, Wolfgang; Böni, Peter; Paul, Amitesh

    2016-09-28

    Topologically stabilized spin configurations like helices in the form of planar domain walls (DWs) or vortex-like structures with magnetic functionalities are more often a theoretical prediction rather than experimental realization. In this paper we report on the exchange coupling and helical phase characteristics within Dy-Fe multilayers. The magnetic hysteresis loops with temperature show an exchange bias field of around 1.0 kOe at 10 K. Polarized neutron reflectivity reveal (i) ferrimagnetic alignment of the layers at low fields forming twisted magnetic helices and a more complicated but stable continuous helical arrangement at higher fields (ii) direct evidence of helices in the form of planar 2π-DWs within both layers of Fe and Dy. The helices within the Fe layers are topologically stabilized by the reasonably strong induced in-plane magnetocrystalline anisotropy of Dy and the exchange coupling at the Fe-Dy interfaces. The helices in Dy are plausibly reminiscent of the helical ordering at higher temperatures induced by the field history and interfacial strain. Stability of the helical order even at large fields have resulted in an effective modulation of the periodicity of the spin-density like waves and subsequent increase in storage energy. This opens broad perspectives for future scientific and technological applications in increasing the energy density for systems in the field of all-spin-based engineering which has the potential for energy-storing elements on nanometer length scales.

  20. Realizing topological stability of magnetic helices in exchange-coupled multilayers for all-spin-based system

    PubMed Central

    Fust, Sergej; Mukherjee, Saumya; Paul, Neelima; Stahn, Jochen; Kreuzpaintner, Wolfgang; Böni, Peter; Paul, Amitesh

    2016-01-01

    Topologically stabilized spin configurations like helices in the form of planar domain walls (DWs) or vortex-like structures with magnetic functionalities are more often a theoretical prediction rather than experimental realization. In this paper we report on the exchange coupling and helical phase characteristics within Dy-Fe multilayers. The magnetic hysteresis loops with temperature show an exchange bias field of around 1.0 kOe at 10 K. Polarized neutron reflectivity reveal (i) ferrimagnetic alignment of the layers at low fields forming twisted magnetic helices and a more complicated but stable continuous helical arrangement at higher fields (ii) direct evidence of helices in the form of planar 2π-DWs within both layers of Fe and Dy. The helices within the Fe layers are topologically stabilized by the reasonably strong induced in-plane magnetocrystalline anisotropy of Dy and the exchange coupling at the Fe-Dy interfaces. The helices in Dy are plausibly reminiscent of the helical ordering at higher temperatures induced by the field history and interfacial strain. Stability of the helical order even at large fields have resulted in an effective modulation of the periodicity of the spin-density like waves and subsequent increase in storage energy. This opens broad perspectives for future scientific and technological applications in increasing the energy density for systems in the field of all-spin-based engineering which has the potential for energy-storing elements on nanometer length scales. PMID:27677227