Mossbauer studies of /sup 57/Fe-doped anatase TiO/sub 2/

Ti/sub 1-x//sup 57/Fe/sub x/O/sub 2/ compounds were fabricated using the chemical solution method, and the crystal structure and ferromagnetic properties were investigated as a function of doped /sup 57/Fe concentration. X-ray diffraction patterns showed a pure anatase single phase, without any segregation of Fe into particulates within the instrumental resolution limit. Magnetic properties were characterized by vibrating sample magnetometer and Mossbauer spectroscopy with a /sup 57/Co(Rh) source. With varying /sup 57/Fe concentration, we could observe unusual magnetic phenomena in these materials. Doping /sup 57/Fe into the TiO/sub 2/ nonmagnetic semiconductor formed magnetic properties, but the gradual increase of /sup 57/Fe concentration decreased rapidly the ferromagnetic properties rather than enhanced the ferromagnetic properties. This result reveals an interesting feature, there is a critical limit of /sup 57/Fe concentration to get ferromagnetic properties at room temperature.