First-principles investigation of magnetocrystalline anisotropy oscillations in Co2FeAl/Ta heterostructures

Abstract

We report first-principles investigations of magnetocrystalline anisotropy energy (MCAE) oscillations as a function of capping layer thickness in Heusler alloy Co2FeAl/Ta heterostructures. Substantial oscillation is observed in FeAl-interface structure. According to k-space and band-decomposed charge density analyses, this oscillation is mainly attributed to the Fermi-energy-vicinal quantum well states (QWS) which are confined between Co2FeAl/Ta interface and Ta/vacuum surface. The smaller oscillation magnitude in the Co-interface structure can be explained by the smooth potential transition at the interface. These findings clarify that MCAE in Co2FeAl/Ta is not a local property of the interface and that the quantum well effect plays a dominant role in MCAE oscillations of the heterostructures. This work presents the possibility of tuning MCAE by QWS in capping layers, and paves the way for artificially controlling magnetic anisotropy energy in magnetic tunnel junctions.

Phase stability and the effect of lattice distortions on electronic properties and half-metallic ferromagnetism of Co2FeAl Heusler alloy: an ab initio study

“…We have carefully chosen the ranges of distortions to see the trends of the density of states and their effect on half-metallicity, as these properties are highly sensitive to the distortions applied. Numerous reports on band structures are available on unstrained (i.e., cubic) cases based on the Co 2 FeAl alloy [43,51,[54][55][56][57][58][59][60]. However, some of our calculation results must be addressed in predicting the device compatibility under uniform-strain and tetragonal distortions.…”

Efficient technique for ab-initio calculation of magnetocrystalline anisotropy energy

“…Another merit of FT is that by Equ. ( 14) some k-space resolved analyses can be performed, such as the contribution of the quantum well states to the oscillation of MCAE [10].…”

“…Usually, the MCAE is on the order of meV at surfaces and interfaces [4,5,6], about 3 orders of magnitude larger than that of bulk crystals [7,1]. Apart from the interest in fundamental science, the practical applications have also stimulated lots of research into the understanding and optimization of MCAE [8,9,10,11,12,13]. One of the applications is the magnetic tunnel junction (MTJ), which is the core structure of magnetic random access memory (MRAM) [14,15].…”

Effect of L21 and XA ordering on phase stability, half-metallicity and magnetism of Co2FeAl Heusler alloy: GGA and GGA + U approach

“…We studied Fe2CoAl Heusler alloy and found that XA ordered structure was much more stable than the regular L21 structure [26,27]. The comprehensive theoretical reports are available on L21 ordered Co2FeAl Heusler alloy [28][29][30][31][32][33][34]. However, a proper understanding of the site preferences of 3d atoms in their respective structures (L21 and XA) is yet to be explored.…”