Spin Polarization and Electonic Structure of Room-Curie Ferromagnetic Mn5Ge3 Epilayers

Germanium-based alloys hold great promise for future spintronics applications, due to their potential for integration with conventional Si-based electronics. Mn5Ge3 exhibits strong ferromagnetism up to the Curie temperature Tc~295K. We use Point Contact Andreev Reflection (PCAR) spectroscopy to measure the spin polarization of Mn5Ge3 epilayers grown by solid phase epitaxy on Ge(111). In addition, we calculate the spin polarization of bulk Mn5Ge3 in the diffusive and ballistic regimes using density-functional theory. The measured spin polarization, Pc=43+/-5% is compared to our theoretical estimates, PDFT=10+/-5% and 35+/-5% in the ballistic and diffusive limits respectively.