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Abstract: 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. [Copyright &y& Elsevier]

Abstract: We report on the structural and magnetic properties of epitaxial Mn5Ge3 films grown by molecular beam epitaxy (MBE) on Ge(111) substrates with film thicknesses ranging from 5 to ~185nm. It is shown that epitaxial Mn5Ge3 films with a thickness as large as 185nm can be obtained despite a misfit of ~3.7% between two materials. Measurements of the in-plane lattice parameter carried out by means of reflection high-energy electron diffraction (RHEED) revealed that Mn5Ge3 films were fully relieved of strain after deposition of the first monolayer. For film thicknesses smaller than 50nm, the easy axis of magnetization is found to lie in the hexagonal basal (001) plan, parallel to the interface and the hard axis is perpendicular to the layers. When the film thickness increases above 50nm, magnetization measurements with magnetic field applied in-plane of the samples reveal that the easy axis of magnetization progressively turns out of the hexagonal basal (001) plan of Mn5Ge3. Even for Mn5Ge3 films with a thickness larger than 185nm, the easy axis of magnetization never becomes perpendicular to the sample surface as being expected for bulk Mn5Ge3 materials. [Copyright &y& Elsevier]