The magnetic phase transition in titanium oxide induced by proton irradiation

We have studied the magnetic properties of 57Fe-doped TiO2 compounds irradiated by proton with 0, 5 and 10pC/μm2. We have observed the enhancement of the magnetic moment, measured by superconducting quantum interference device magnetometer, with increasing proton irradiation ranging from 0 to 10pC/μm2. Mössbauer spectra of proton irradiated Ti0.9957Fe0.01O2 samples were taken at room temperature. Two sites of the wing (sextet) and the central (doublet) are shown in the spectra, which suggest the magnetically ordered phase and the paramagnetic phase, respectively. With increasing proton irradiation, the part of Fe3+ ions was converted to Fe2+ ions by compensation charge. This clearly suggests that the enhancement of magnetic moment after proton irradiation is contributed to the moment by the spin-orbit coupling of Fe2+ ions.