Author
P. Weinberger
Bio: P. Weinberger is an academic researcher from New York University. The author has contributed to research in topics: Magnetoresistance & Spin valve. The author has an hindex of 2, co-authored 2 publications receiving 6 citations.
Papers
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TL;DR: In this paper, the authors investigated the switching properties of a spin valve and tunneling junction with a spin-polarized fully relativistic approach and showed that the existence of a stable and a metastable state, a necessary condition for a switching device, is essentially determined by the free energy contributions of the interfaces of that magnetic slab that is part of the spin valve as well as of the tunnel.
Abstract: The switching properties of a prototype system containing a spin valve as well as a tunneling junction are investigated by means of a spin-polarized fully relativistic approach. Shown are the changes in the free energy and in the magnetoresistance when the orientation of the magnetization in the magnetic slabs of such a system is changed individually. It is demonstrated that the existence of a stable and a metastable state, a necessary condition for a switching device, is essentially determined by the free energy contributions of the interfaces of that magnetic slab that is part of the spin valve as well as of the tunneling junction. Furthermore, in estimating individual switching times, it is found that most of the gain in magnetoresistance occurs within a time range of about 20 ps, the time to achieve complete switching, however, being about 1.5 ns, which is close to what is found in recent experimental results.
3 citations
TL;DR: In this article, a Taylor expansion is used to model the structural relaxation effects of free surfaces and magnetic tunneling junctions, for tunneling currents and for permittivities, which in turn determine Kerr angles.
Abstract: In viewing layer-resolved components of physical properties as a function of multiples of the interlayer spacing and by using a Taylor expansion structural relaxation effects can be described not only for the free-energy part of the magnetic anisotropy energy but directly also for electric and magneto-optical transport properties. Examples for such a procedure are shown for the anisotropy energy of free surfaces and magnetic tunneling junctions, for tunneling currents and for permittivities, which in turn determine Kerr angles. Considered as a test case, the already well-studied magnetic anisotropy energy of ${\text{Co}}_{2}/\text{Cu}(111)$ turns out to be in excellent agreement with very recent experiment data.
3 citations
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TL;DR: In this article, it was shown in terms of a fully relativistic spin-polarized ab initio-type approach that in Pt/Co/Pt trilayers two types of anisotropic magnetoresistance (AMR) have to be distinguished: an in-plane and an out-of-plane AMR.
Abstract: It is shown in terms of a fully relativistic spin-polarized ab initio-type approach that in Pt/Co/Pt trilayers two types of anisotropic magnetoresistance (AMR) have to be distinguished: an in-plane and an out-of-plane AMR. The obtained results, namely the magnetic field dependence as well as the thickness dependence of both AMR types are in very good agreement with a very recent experimental study, in which the in-plane as well as the out-of-plane AMR was reported for this system. The difference between the two types of AMR is visualized in terms of layer-resolved resistivities. In particular, it is confirmed that the anisotropic interface magnetoresistance (AIMR) introduced in the recent publication mainly originates in the vicinity of the Co/Pt interfaces.
9 citations
TL;DR: In this paper, the second-order strain contribution to the energy density of epitaxial monolayers is described as a second order contribution to energy density, and the importance of inhomogeneous strain and its relaxation for the magnetic anisotropy of nanostructures is discussed.
Abstract: Recent results of experimental studies on magnetoelastic coupling in epitaxial monolayers are compiled and discussed in view of theoretical work. The observation of non-bulk like magnetoelastic coupling in strained systems in experiment and theory is ascribed to an effective and strain-dependent magnetoelastic coupling. It is described as a second-order strain contribution to the energy density. We comment on the importance of inhomogeneous strain and of its relaxation for the magnetic anisotropy of nanostructures.
6 citations
Journal Article•
TL;DR: In this paper, the relationship between spin transfer and tunnel magnetoresistance (TMR) under finite bias was investigated, and it was shown that the spin torque per unit current exerted on the free layer decreases by < 10% over a bias range where the TMR decreases by > 40%.
Abstract: We employ the spin-torque response of magnetic tunnel junctions with ultrathin MgO tunnel barrier layers to investigate the relationship between spin transfer and tunnel magnetoresistance (TMR) under finite bias, and find that the spin torque per unit current exerted on the free layer decreases by < 10% over a bias range where the TMR decreases by > 40%. This is inconsistent with free-electron-like spin-polarized tunneling and reduced-surface-magnetism models of the TMR bias dependence, but is consistent with magnetic-state-dependent decay lengths in the tunnel barrier.
3 citations
TL;DR: In this article, it was shown that the spin-polarized (fully) relativistic screened Korringa-Kohn-Rostocker method and an equivalent Kubo equation can approximately overcome the difficulties with respect to a common Fermi level for the whole system in all those cases when the substrate (serving as lead) and the second lead are different materials.
Abstract: It is shown that by ‘stacking’ together a semi-infinite sample subsystem with a semi-infinite tip subsystem, difficulties with respect to a common Fermi level for the whole system can approximately be overcome in all those cases when the substrate (serving as lead) and the second lead are different materials. Based on this procedure by means of the spin-polarized (fully) relativistic screened Korringa–Kohn–Rostocker method and an equivalent Kubo equation, theoretical spin-polarized STM spectra for Pt(111)/Co n /Cr15 W22/Cu(111) with respect to an applied external magnetic field are evaluated in terms of difference conductivities as a function of the corresponding free energy. These spectra are interpreted using layer-resolved contributions to the difference conductivities in order to indicate which parts of the sample dominate changes in the tunneling current caused by changing the orientation of the magnetization. Also shown are estimates of the time-scales to switch from perpendicular to in-plane and vi...
2 citations
TL;DR: In this paper, an experimental study of the electric properties of Pt/Permalloy bilayers based on a simultaneous application of an in-plane microfrequency current and an external magnetic field is simulated on a fully relativistic ab initio level by considering the resistivity as an implicit function of the free energy.
Abstract: A recent experimental study of the electric properties of Pt/Permalloy bilayers based on a simultaneous application of an in-plane microfrequency current and an external magnetic field is simulated on a fully relativistic ab initio level by considering the resistivity as an implicit function of the free energy. It is found that the oscillations detected experimentally are caused by the different behavior of out-of-plane and in-plane resistivities in the vicinity of that value of the free energy that corresponds to the resonant field induced by the applied current. A necessary precondition for such oscillations is a sizeable perpendicular anisotropy, which is not the case in systems consisting only of Permalloy. It is shown that the observed phenomenon is essentially an interface effect.