Anisotropy of magnetoelastic properties in epitaxial Co2FexMn1−xSi Heusler alloy thin films

A strain modulated ferromagnetic resonance technique was applied to determine two cubic magnetoelastic constants of the epitaxially grown 30-nm-thick ${\mathrm{Co}}_{2}{\mathrm{Fe}}_{x}{\mathrm{Mn}}_{1\ensuremath{-}x}\mathrm{Si}$ magnetic layers with different Fe and Mn contents, which were deposited on a MgO substrate with a 20-nm-thick Cr buffer layer---MgO (001) $\ensuremath{\parallel}$ Cr(001) $\ensuremath{\parallel} {\mathrm{Co}}_{2}{\mathrm{Fe}}_{x}{\mathrm{Mn}}_{1\ensuremath{-}x}\mathrm{Si}$ (001). It was found that, for the samples with the Fe content $x=0.4$ or higher, the magnitudes of the two cubic magnetoelastic constants are clearly different, showing that the magnetoelastic properties of these samples are different than in the case of isotropic samples for which these two constants are expected to be equal. The magnitude of the cubic magnetocrystalline anisotropy constant reveals an evident maximum at the composition of $x=0.4$, which corresponds to the minimum of the minor spin density of states, and thus the correlation between the cubic magnetocrystalline anisotropy and the electronic band structure. For all the investigated samples, a large perpendicular component of the magnetocrystalline anisotropy was observed as well as inhomogeneous broadening of the ferromagnetic resonance linewidth.