Origin of perpendicular magnetic anisotropy in Fe_0.6Al_0.4/Cr_0.8Al_0.2 metallic superlattice

Abstract

In this study, we investigated a perpendicular magnetic anisotropy (PMA) in a ferromagnet/antiferromagnetic stacking structure without using heavy metal elements. The Fe0.6Al0.4/Cr0.8Al0.2/Fe0.6Al0.4 stacked films exhibited perpendicular magnetization. We discussed the origin of the PMA based on the Cr0.8Al0.2 thickness, t Cr–Al (=0.6–3.0 nm) dependences of the uniaxial anisotropy energy density K u, elastic strain ε 1 – ε 3, and unit cell volume V of the Fe0.6Al0.4 and Cr0.8Al0.2 layers. The K u value was approximately 25 kJ m−3, independent of t Cr–Al. The positive ε 1 – ε 3, i.e., the tensile strain in the Cr0.8Al0.2 layer can promote the PMA. The possible degradation of PMA due to the lattice relaxation with increasing t Cr–Al could be compensated by recovering the Cr magnetic moment. Our analysis suggests that PMA is caused by interfacial exchange coupling between ferromagnetic Fe0.6Al0.4 and antiferromagnetic Cr0.8Al0.2.