Interfacial spin-glass-like state in Mn5Ge3 single crystalline films grown on germanium substrates

Thermal irreversibility of the magnetization in Mn5Ge3 epitaxial thin films on Ge(111) is reported. The frequency dependence of the ac susceptibility demonstrates a spin-glass-like behavior, despite the fact that the thin film is a single crystal. Such glassy behavior is attributed to the presence of a "ferromagnetically dead" layer with spin-glass-like properties at the Mn5Ge3/Ge interface, which results in frustrated interactions with the ferromagnetic Mn5Ge3. Moreover, it is shown that the magnetic phase diagram in the H-T plane of the glassy state is very sensitive to the growth conditions. Variation in the growth temperature and film thickness changes the spin-glass-like properties and the Curie temperature. The sensitivity of the glassy state to the growth conditions is related to the variation in the properties of the interfacial layer.