Mossbauer studies of 57Fe-doped anatase TiO2

Ti_1-x⁵⁷Fe_xO₂ compounds were fabricated using the chemical solution method, and the crystal structure and ferromagnetic properties were investigated as a function of doped ⁵⁷Fe 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 ⁵⁷Co(Rh) source. With varying ⁵⁷Fe concentration, we could observe unusual magnetic phenomena in these materials. Doping ⁵⁷Fe into the TiO₂ nonmagnetic semiconductor formed magnetic properties, but the gradual increase of ⁵⁷Fe concentration decreased rapidly the ferromagnetic properties rather than enhanced the ferromagnetic properties. This result reveals an interesting feature, there is a critical limit of ⁵⁷Fe concentration to get ferromagnetic properties at room temperature.