Ferromagnetism induced by hybridization of Fe 3d orbitals with ligand InSb bands in the n -type ferromagnetic semiconductor (In,Fe)Sb

The Fe-doped III-V ferromagnetic semiconductor (FMS) (In,Fe)Sb is a promising material for spintronic device applications because of the $n$-type carrier conduction and the ferromagnetism with high Curie temperature $({T}_{\mathrm{C}}>300\phantom{\rule{0.16em}{0ex}}\mathrm{K})$. To clarify the mechanism of the $\text{high}\text{\ensuremath{-}}{T}_{\mathrm{C}}$ ferromagnetism, we have investigated the electronic structure and magnetic properties of an $({\mathrm{In}}_0.94,{\mathrm{Fe}}_0.06)\mathrm{Sb}$ thin film by performing x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) measurements at the Fe ${L}_2,3$ edges. The magnetic-field $({\ensuremath{\mu}}₀H)$ dependence of the XMCD spectra reveals that there are ferromagneticlike Fe and paramagneticlike Fe components in the (In,Fe)Sb thin film. The XAS and XMCD spectra of the ferromagneticlike and paramagneticlike Fe components resemble those of other Fe-doped FMSs and extrinsic oxides, respectively. The finite value of the ratio between the orbital and spin magnetic moments estimated by applying the XMCD sum rules indicates that the valence state of the Fe ions substituting for the In sites in (In,Fe)Sb is not purely ionic ${\mathrm{Fe}}³⁺$, but intermediate between ${\mathrm{Fe}}³⁺$ and ${\mathrm{Fe}}²⁺$. The qualitative correspondence between the ${\ensuremath{\mu}}₀H$ dependence of the visible-light magnetic circular dichroism intensity and that of the XMCD intensity demonstrates that the Zeeman splitting of the InSb band is proportional to the net magnetization of the doped Fe. These results suggest that the ferromagnetism of (In,Fe)Sb originates from the Fe $3d$ orbitals hybridized with the host InSb bands.