We report a change in the structural and magnetic properties of epitaxial Mn5Ge3 on a Ge-on-Si (111) substrate by applying strain engineering through ms-range flash lamp annealing (FLA). X-ray diffraction results demonstrate that during FLA for 20 ms, the formation of nonmagnetic MnxGey secondary phases is suppressed, while the in-plane expansion of the lattice increases with increasing annealing temperature. Temperature-dependent magnetization results indicate that the Curie temperature of Mn5Ge3 rises from 287 K in the as-prepared sample to above 400 K after FLA, making Mn5Ge3 an attractive material for spintronics. Experimental results together with theoretical Monte Carlo simulations allow us to conclude that the expansion of the in-plane lattice causes the increase of the Curie temperature due to enhancement of the ferromagnetic interaction between Mn atoms.
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