Loss of anisotropy in strained ultrathin epitaxial L1_0 Mn-Ga films

摘要

We have investigated the magnetization and loss of anisotropy in ultrathin strained and unstrained Mn-Ga films at room temperature. Two Mn-Ga compositions, one of which is doped with Co, were grown on Cr buffered MgO (001) substrates. Films with a thickness below 10 nm are highly strained and the ratio c/a vs. thickness is depending on composition. The perpendicular magnetic anisotropy is shown to be drastically reduced with decreasing thickness and increasing strain. These findings should be considered when generalizing and downscaling results obtained from films ＞ 20 nm. The strain can effectively be reduced by introducing an additional Pt buffer and thus maintaining a high perpendicular magnetic anisotropy for a thickness as low as 6 nm.