Mössbauer studies of dynamic Jahn-Teller relaxation on the Cu-substituted sulfur spinel

Abstract

Samples of Fe1−xCuxCr2S4 (x=0.0, 0.1, 0.3, and 0.5) have been studied with Mössbauer spectroscopy, x-ray diffraction, magnetization, and magnetoresistance. A cusp-like anomaly is observed for the sample x=0.1 in the both field-cooled and zero-field-cooled magnetization curves near 130 K under an applied field H=100 Oe. The charge state of iron ions are ferrous for the samples x=0.0 and x=0.1, whereas they are ferric for the samples x=0.3 and x=0.5. The Mössbauer spectra for the sample x=0.1 show asymmetric line broadening, and it is considered to be dynamic Jahn-Teller relaxation. The unusual reduction of magnetic hyperfine field below 110 K can be interpreted in terms of cancellation effect between the mutually opposite orbital current field HL and Fermi contact field HC.