Diamagnetic nuclear 119Sn probes in the copper chromites CuCr2X4 (X = O, S, Se) with a spinel structure

Abstract

The CuCr2X4 (X = O, S, Se) spinel system has been studied by the Mossbauer spectroscopy of the nuclear diamagnetic 119Sn probe at low temperatures in an external magnetic field. The hyperfine magnetic fields HSn induced by paramagnetic ions at tin nuclei in the CuCr2S4 and CuCr2Se4 chalcogenides have giant values and are somewhat higher than those detected in the CuCr2O4 oxide. This behavior is caused by the strong covalence of the chalcogenides, which is supported by the experimentally found isomer shifts. The HSn field is found to be mainly contributed by superexchange 90° interactions in the B-sublattice along the Cr[B]-X-Sn[B] bond chain, whose role increases in the series O-S-Se. In the oxygen CuCr2O4 spinel, the partial contributions to the HSn field induced by the Cu2+ and Cr3+ ions are estimated. The local magnetic structure of the CuCr2O4 spinel is refined, and its total magnetization is shown to be directed along the magnetic moment of copper in the A sublattice.