Anomalous Mossbauer lineshapes in the magnetically ordered Ga₂O₃-Fe₂O₃ System

Abstract

Mossbauer measurements show that an incomplete annealing of the magnetically ordered Ga₂O₃-Fe₂O₃ system gives rise to anomalous Mossbauer spectra which are characterised by an enhancement in the intensity (or percentage absorption) of their central portions as compared to the intensity of outer absorption peaks. Measurements carried out in an external magnetic field confirm that the observed anomalous Mossbauer lineshapes are due to ionic spin fluctuations (either due to the motion of individual spins, i.e. electronic relaxation effects, or due to the collective motion of large number of spins in a small region of material, i.e. superparamagnetic effects) and are not a result of any distribution of hyperfine field or the presence of critical superparamagnetism in the incompletely annealed solid solutions.