Synthesis of Mn₃Ge and other Mn-Ge phases by molecular beam epitaxy

Binary Mn-Ge alloys are thought to support a wide range of interesting electronic and magnetic phenomena, such as novel spin-orbit-torques, Berry-curvature driven anomalous Hall effect, and magnetovolume effects, which play an important role in the realization of spintronic devices. Here we report the molecular beam epitaxy growth, on insulating oxide substrates, of numerous stable phases in this system: D0₂₂-Mn₃Ge, D0₁₉-Mn_3+xGe, Mn₅Ge₂, and an epitaxially stabilized Mn_5+yGe phase that has not been reported before. Rutherford backscattering spectrometry confirmed the film compositions, while variable temperature resistivity measurements revealed metallicity for all phases. The observed ferrimagnetism in D0₂₂-Mn₃Ge and Mn₅Ge₂ adheres closely to bulk behavior, while much smaller magnetizations are observed in D0₁₉-Mn₃Ge and Mn_5+yGe films, consistent with antiferromagnetic ordering.