Epitaxial growth of Mn5Ge3/Ge(111) heterostructures for spin injection

Epitaxial Mn5Ge3/Ge(111) heterostructures were grown by Solid Phase Epitaxy (SPE) method, which consists of a room temperature Mn deposition followed by thermal annealing. It is shown that upon annealing at a temperature of about ~ 430–450  °C, the Mn5Ge3 phase is formed and it is stable up to ~ 850  °C. This phase is the unique epitaxial phase observed on the Ge(111) substrate. Transmission electron diffraction (TED) patterns confirm that the hexagonal basal (001) plan of Mn5Ge3 is parallel to the (111) plan of the Ge substrate and cross-sectional transmission electronic microscopy (TEM) analyses reveal a relatively smooth interface at the atomic scale. Magnetic characterizations indicate that epitaxial Mn5Ge3 films present a strong ferromagnetism up to room temperature. However, in contrast to bulk Mn5Ge3 material which has uniaxial anisotropy along the c axis, epitaxial Mn5Ge3 films exhibit easy axis of magnetization lying in the hexagonal basal (001) plane, parallel to the interface between the Mn5Ge3 films and the substrate.