Effect of Co-Fe substitution on room-temperature spin polarization in Co3-xFexSi Heusler-compound films

Using low-temperature molecular beam epitaxy, we experimentally examine the substitutions of Fe atoms for Co ones in Co3-xFexSi (1.0 <= x <= 3.0) Heusler-compound films grown on Si and Ge. The Co-Fe atomic substitution at A and C sites can be confirmed by the conversion electron Mossbauer spectroscopy measurements. The magnetic moment and the magnitude of spin signals in nonlocal spin-valve measurements are systematically changed with increasing x in Co3-xFexSi. By assuming proper spin diffusion length for Co3-xFexSi on the basis of our previous work [Phys. Rev. B 85, 100404(R) (2012)], we experimentally verify that the Co-Fe substitution in Co3-xFexSi can directly affect the room-temperature spin polarization.