The effect of manganese ions in a MnCr1.9857Fe0.02O4 by Mössbauer spectroscopy

Abstract

Polycrystalline MnCr1.9857Fe0.02O4 compound was prepared by a wet-chemical process. The crystal structure was found to be a cubic spinel with a space group of Fd3m. The lattice constant a0 and the internal structural parameter x of the oxygen were determined to be 8.444Å and 0.263, respectively. Mössbauer spectra of MnCr1.9857Fe0.02O4 were taken from 4.2to295K. The absorption spectra slow well-developed two sextets, superposed with small difference in hyperfine fields of 482 and 472kOe below the Néel temperature of 50K, and a paramagnetic doublet above the Néel temperature. We have observed a sudden change in sextet around 22K, which corresponds to the spin structure transition temperature. Even though the values of the magnetic hyperfine fields of MnCr1.9857Fe0.02O4 on B sites are close to those of CoCr1.9857Fe0.02O4, there is a noticeable difference in the Néel temperature between them, which is due to the A-B superexchange interaction with spin-orbit coupling attributable to ionic bond lengths.