Enhanced spin accumulation in Fe3O4 based spin injection devices below the Verwey transition

Abstract

Spin injection into GaAs and Si (both n and p-type) semiconductors using Fe3O4 is achieved with and without a tunnel barrier (MgO) via three-terminal electrical Hanle measurement. Interestingly, the magnitude of spin accumulation voltage (ΔV) in semiconductor is found to be associated with a drastic increment in ΔV in Fe3O4 based devices for temperature <120 K (TV, the Verwey transition). Such an enhancement of ΔV is absent in the devices with Fe as spin source. Further, the overall device resistance has no drastic difference at TV. This renders a direct proof that the observed ΔV is not influenced by the so-called metal-to-insulator transition of Fe3O4 at TV. Observations from our elaborate investigations show that spin polarization of Fe3O4 has an explicit influence on the enhanced spin injection. It is argued that the theoretical prediction of half-metallicity of Fe3O4 above and below TV has to be reinvestigated.