Anisotropy in layered half-metallic Heusler alloy superlattices

Abstract

We show that when two Heusler alloys are layered in the [001], [110], or [111] directions for various thicknesses to form a superlattice, the Slater-Pauling rule may still be satisfied and the resulting superlattice is often half-metallic with gaps comparable to or larger than those of its constituents. In addition, uniaxial magnetocrystalline anisotropy is induced because of the differences in the electronic structure of the two Heuslers in the superlattice. Various full-full, full-half, and half-half Heusler superlattices are studied, and potential half-metallic superlattices with perpendicular magnetocrystalline anisotropy are identified.

Epitaxial Heusler superlattice Co2MnAl/Fe2MnAl with perpendicular magnetic anisotropy and termination-dependent half-metallicity

“…A separate sample series (not shown) grown only on MgO (001) substrates at 300 • C did not experience a spin reorientation transition below M S,crit , further supporting the conclusion that K ⊥ ef f is maximized for [CMA n /FMA n ] q with high aluminum excess grown on GaAs (001) at 150 • C with no subsequent anneal. This combines the advantages of the superlattice structure with compressive strain resulting in c/a > 1, both of which are expected to enhance K ⊥ M CA [8,17]. This factor is then allowed to dominate by increasing the aluminum content, thereby lowering the shape anisotropy contribution.…”

“…Recently, it was predicted that atomic superlattices of certain pairs of Heusler materials could be perpendicularly magnetized half-metals [8]. Heusler superlattices are distinct from other magnetic multilayers because they maintain the same crystal structure and, in many cases, several of the same atomic species in both constituent layers.…”

“…Heusler superlattices are distinct from other magnetic multilayers because they maintain the same crystal structure and, in many cases, several of the same atomic species in both constituent layers. The uniaxial anisotropy in the growth direction arises from changes in electronic structure between layers, and from lattice distortions produced by variations in lattice constant between parent bulk crystals [8]. Equivalently, symmetry breaking due to the layer structure results in tetragonal space group symmetry, which gives rise to tetragonal magnetic anisotropy with the unique axis aligned out-of-plane.…”

Robustness of the Half-Metallicity at the Interfaces in Co2MnSi -Based All-Full-Heusler-Alloy Spintronic Devices

“…The possible existence of a dead interface magnetic layer lowering the magnetoresistive performances was moreover reported in the case of Co 2 MnGe/Rh 2 CuSn SVs [34]. Other Heusler-alloy-based heterostructures have mostly been studied numerically from first principles [35][36][37][38][39][40][41]. Chadov et al, in particular, proposed to select the best all-Heusler-alloy MTJs among those which minimize the mismatch between the atomic and the band structures of the electrode and spacer materials: They first decided to select the half-metallic electrode material Co 2 MnAl and further proposed to use CoVMnAl as the nonmagnetic insulating spacer [37].…”

Site-Preference, Electronic, Magnetic, and Half-Metal Properties of Full-Heusler Sc2VGe and a Discussion on the Uniform Strain and Tetragonal Deformation Effects

“…It was also found that, in terms of lattice distortion, the HM properties of these alloys can be maintained in the range of −4.8% to 6.6% and −7.7% to 4.5%, respectively. The discovery of the presence of HM properties in HH alloys has led to the availability of more options for spintronics materials [26,27].…”