High perpendicular magnetic anisotropy in <i>D</i>22-Mn3+<i>x</i>Ge tetragonal Heusler alloy films

Abstract

We prepared D022-Mn3+xGe (−0.67 ≤ x ≤ 0.35) epitaxial thin films on MgO(001) substrates with Cr(001) buffer layers and systematically investigated the dependence of their perpendicular magnetic anisotropy constant, saturation magnetization, coercivity, and tetragonal axial ratio (c/a) on their composition and substrate temperature. Single-phase D022 crystal structures were formed in films with compositions of 0 ≤ x ≤ 0.35, prepared at 400 °C. The D022-Mn3Ge films exhibited perpendicular magnetization with a magnetic squareness close to unity. Performing magnetic torque measurements at an applied field of 140 kOe, we estimated a perpendicular magnetic anisotropy constant of 11.8 ± 0.5 Merg/cm3, the highest and the most reliable value yet reported.