15 research outputs found
Interfacial exchange interactions and magnetism of Ni2MnAl/Fe bilayers
Based on a multi-scale calculations, combining ab-initio methods with spin
dynamics simulations, we perform a detailed study of the magnetic behavior of
Ni2MnAl/Fe bilayers. Our simulations show that such a bilayer exhibits a small
exchange bias effect when the Ni2MnAl Heusler alloy is in a disordered B2
phase. Additionally, we present an effective way to control the magnetic
structure of the Ni2MnAl antiferromagnet, in the pseudo-ordered B2-I as well as
the disordered B2 phases, via a spin-flop coupling to the Fe layer.Comment: 7 pages, 6 figure
Imaging Spin Reorientation Transitions in Consecutive Atomic Co layers
By means of spin-polarized low-energy electron microscopy (SPLEEM) we show
that the magnetic easy-axis of one to three atomic-layer thick cobalt films on
ruthenium crystals changes its orientation twice during deposition:
one-monolayer and three-monolayer thick films are magnetized in-plane, while
two-monolayer films are magnetized out-of-plane, with a Curie temperature well
above room temperature. Fully-relativistic calculations based on the Screened
Korringa-Kohn-Rostoker (SKKR) method demonstrate that only for two-monolayer
cobalt films the interplay between strain, surface and interface effects leads
to perpendicular magnetization.Comment: 5 pages, 4 figures. Presented at the 2005 ECOSS conference in Berlin,
and at the 2005 Fall meeting of the MRS. Accepted for publication at Phys.
Rev. Lett., after minor change
Modeling ultrafast all-optical switching in synthetic ferrimagnets
Based on numerical simulations, we demonstrate thermally induced magnetic
switching in synthetic ferrimagnets composed of multilayers of rare-earth and
transition metals. Our findings show that deterministic magnetization reversal
occurs above a certain threshold temperature if the ratio of transition metal
atoms to rare-earth atoms is sufficiently large. Surprisingly, the total
thickness of the multilayer system has little effect on the occurence of
switching. We further provide a simple argument to explain the temperature
dependence of the reversal process.Comment: 6 pages, 5 figure
A route towards finding large magnetic anisotropy in nano-composites: application to a WRe/Fe multilayer
We suggest here a novel nano-laminate, 5[Fe]/2[WRe] (x=0.6-0.8),
with enhanced magnetic hardness in combination with a large saturation moment.
The calculated magnetic anisotropy of this material reaches values of 5.3-7.0
MJ/m, depending on alloying conditions. We also propose a recipe in how to
identify other novel magnetic materials, such as nano-laminates and
multilayers, with large magnetic anisotropy in combination with a high
saturation moment
Coinage-metal capping effects on the spin-reorientations of Co/Ru(0001)
Thin films of Co/Ru(0001) are known to exhibit an unusual spin reorientation
transition (SRT) coupled to the completion of Co atomic layers for Co
thicknesses under 4 layers. By means of spin-polarized low-energy electron
microscopy, we follow in real space the magnetization orientation during the
growth of atomically thick capping layers on Co/Ru(0001). Capping with
coinage-metal (Cu, Ag, Au) elements modifies the SRT depending on the Co and
overlayer thickness and on the overlayer material, resulting in an expanded
range of structures with high perpendicular magnetic anisotropy. The origin of
the SRT can be explained in terms of ab-initio calculations of the
layer-resolved contributions to the magnetic anisotropy energy. Besides the
changes in the SRT introduced by the capping, a quantitative enhancement of the
magnetic anisotropy is identified. A detailed analysis of the interplay between
strain and purely electronic effects allows us to identify the conditions that
lead to a high perpendicular magnetic anisotropy in thin hcp Co films.Comment: 25 pages, 10 figures. Corrected several typos, added a reference. The
experimental and theory discussion has been rewritten in places for improved
readability. The experimental observations are summarized in a table instead
of a figur
Development of Antiferromagnetic Heusler Alloys for the Replacement of Iridium as a Critically Raw Material
As a platinum group metal, iridium (Ir) is the scarcest element on the earth but it has been widely used as an antiferromagnetic layer in magnetic recording, crucibles and spark plugs due to its high melting point. In magnetic recording, antiferromagnetic layers have been used to pin its neighbouring ferromagnetic layer in a spin-valve read head in a hard disk drive for example. Recently, antiferromagnetic layers have also been found to induce a spin-polarised electrical current. In these devices, the most commonly used antiferromagnet is an Ir-Mn alloy because of its corrosion resistance and the reliable magnetic pinning of adjacent ferromagnetic layers. It is therefore crucial to explore new antiferromagnetic materials without critical raw materials. In this review, recent research on new antiferromagnetic Heusler compounds and their exchange interactions along the plane normal is discussed. These new antiferromagnets are characterised by very sensitive magnetic and electrical measurement techniques recently developed to determine their characteristic temperatures together with atomic structural analysis. Mn-based alloys are found to be most promising based on their robustness against atomic disordering and large pinning strength up to 1.4 kOe, which is comparable with that for Ir-Mn. The search for new antiferromagnetic films and their characterisation are useful for further miniaturisation and development of spintronic devices in a sustainable manner
Electron Scattering in Solid Matter: A Theoretical and Computational Treatise
Addressing graduate students and researchers, this book gives a very detailed theoretical and computational description of multiple scattering in solid matter. Particular emphasis is placed on solids with reduced dimensions, on full potential approaches and on relativistic treatments. For the first time approaches such as the Screened Korringa-Kohn-Rostoker method that have emerged during the last 5 â 10 years are reviewed, considering all formal steps such as single-site scattering, structure constants and screening transformations, and also the numerical point of view. Furthermore, a very general approach is presented for solving the Poisson equation, needed within density functional theory in order to achieve self-consistency. Going beyond ordered matter and translationally invariant systems, special chapters are devoted to the Coherent Potential Approximation and to the Embedded Cluster Method, used, for example, for describing nanostructured matter in real space. In a final chapter, physical properties related to the (single-particle) Greenâs function, such as magnetic anisotropies, interlayer exchange coupling, electric and magneto-optical transport and spin-waves, serve to illustrate the usefulness of the methods described