A systematic study of the angular and temperature dependencies of the ferromagnetic resonance (FMR) of manganese germanide Mn 5 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

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... ny temperature. It is also shown that the Callen-Callen law cannot be used to describe the temperature dependence of the perpendicular anisotropy in Mn 5 Ge 3 . Such temperature dependence of the magnetocrystalline anisotropy shows the invalidity of the single-ion anisotropy model for Mn 5 Ge 3 .