Development of magnetism in Fe-doped magnetic semiconductors: Resonant photoemission and x-ray magnetic circular dichroism studies of (Ga,Fe)As

Fe-doped III-V ferromagnetic semiconductors (FMSs) such as (In,Fe)As, (Ga,Fe)Sb, (In,Fe)Sb, and (Al,Fe)Sb are promising materials for spintronic device applications because of the availability of both n- and p-type materials and the high Curie temperatures. On the other hand, (Ga,Fe)As, which has the same zinc-blende crystal structure as the Fe-doped III-V FMSs, shows paramagnetism. The origin of the different magnetic properties in the Fe-doped III-V semiconductors remains to be elucidated. To address this issue, we use resonant photoemission spectroscopy (RPES) and x-ray magnetic circular dichroism (XMCD) to investigate the electronic and magnetic properties of the Fe ions in a paramagnetic (Ga0.95,Fe0.05)As thin film. The observed Fe 2p-3d RPES spectra show that the Fe 3d states are similar to those of ferromagnetic (Ga,Fe)Sb. The estimated Fermi level is located in the middle of the band gap in (Ga,Fe)As. The Fe L2,3 XMCD spectra of (Ga0.95,Fe0.05)As show preedge structures, which are not observed in the Fe-doped FMSs, indicating that the minority-spin (???) e??? states are vacant in (Ga0.95,Fe0.05)As. The XMCD results suggest that the carrier-induced ferromagnetic interaction in (Ga0.95,Fe0.05)As is short ranged and weaker than that in the Fe-doped FMSs. The experimental findings suggest that the electron occupancy of the e??? states contributes to the appearance of ferromagnetism in the Fe-doped III-V semiconductors, for p-type as well as n-type compounds.