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 Fe 0.6 Al 0.4 /Cr 0.8 Al 0.2 /Fe 0.6 Al 0.4 stacked films exhibited perpendicular magnetization. We discussed the origin of the PMA based on the Cr 0.8 Al 0.2 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 Fe 0.6 Al 0.4 and Cr 0.8 Al 0.2 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 Cr 0.8 Al 0.2 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 Fe 0.6 Al 0.4 and antiferromagnetic Cr 0.8 Al 0.2 .