XANES Investigations on Electronic Structure and Magnetic Properties of GaFeO3 Nanocrystals

Nanocrystals of GaFeO3 were prepared using co-precipitation followed by thermal annealing at 800 °C for 6 h. The lattice parameters and crystallite size were studied using x-ray diffraction (XRD). Transmission electron microscopy (TEM) measurements were performed to study the size and morphology and revealed the formation of 40–70 nm sized nanoparticles. X-ray absorption near-edge structure measurement was performed to probe the valence state of constituent elements in the GaFeO3 nanocrystals. It has been observed that Fe is present in solely the +3 valence state (i.e., Fe3+). The Ga3+ ions are found with vivid distribution at tetrahedral and octahedral sites and the occupancy of Ga3+ ions is quantitatively evaluated using Ga K-edge XANES spectra. The low-temperature (50 K) M-H loop measurement conveys a ferrimagnetic character of GaFeO3 compound. The paramagnetic behavior is seen at 300 K. The observed magnetic moments per formula unit (~ 1.6 μB) are close to the magnetic moment of Fe3+ ions with a low spin state (t2g5). The abundant Ga3+ ions at the tetrahedral site, as confirmed by Ga K-edge XANES analysis, lead to weak anisotropy in the compound and favor the regular hysteresis loop rather the pinched-like hysteresis loop at 50 K.