Evidence of a perpendicular magnetocrystalline anisotropy in a Mn5 Ge3 epitaxial thin film revealed by ferromagnetic resonance

A systematic study of the angular and temperature dependencies of the ferromagnetic resonance (FMR) of manganese germanide ${\mathrm{Mn}}_{5}{\mathrm{Ge}}_{3}$ grown on Ge(111) by solid phase epitaxy is reported. The FMR measurements performed in the out-of-plane geometry show that an out-of-plane anisotropy contribution exists in this material, and it increases with decreasing temperatures. However, the perpendicular magnetization curves imply that the shape anisotropy determines the orientation of the magnetization at any temperature. It is also shown that the Callen-Callen law cannot be used to describe the temperature dependence of the perpendicular anisotropy in ${\mathrm{Mn}}_{5}{\mathrm{Ge}}_{3}$. Such temperature dependence of the magnetocrystalline anisotropy shows the invalidity of the single-ion anisotropy model for ${\mathrm{Mn}}_{5}{\mathrm{Ge}}_{3}$.