非双交换作用巨磁电阻材料Fe1+xCr2-xS4的磁性

Spinel compounds Fel +x.Cr2 - xS4 (x = 0 1 0. 1 ) with CMR effects hut without JahnTaller ions are researched. Mossbauer spectra identify that, in FeCr2S4, Fe ions occupy tetrahedral sites in Fe2+ valence state forming Fe sub-lattice, Cr ions occupy octahedral sites in + 3 valence forming Cr sub-lattice; in Fel.1Crl.9S4, the excessive Fe ions substitute for Cr ions in + 3 valence. ESR measurements show that only one ESR signal with g-factor near 2 appears at temperatures above Tcthe PM state) for each sample; at T < T1 (T1 corresponding to the minimum resistivity in o-T curve below Tc ), the original PM peak in ESR spectra splits into high field ESR peak and lower field ESR peak simultaneously. Therefore the micro-magnetism in this system can be illustrated as below: for FeCr2S4, the spins of Fe and Cr sub-lattices enter ferromagnetic states respectively, at the same time, the magnetic moments of these two sub-lattices are anti-parallel to each other; for Fel. ICrl .9S4, the spins of these excessive Fe ions are anti-parallel to that o f Cr ions, which weakens not only the internal field of Cr sub-lattice hut also the coupling between these two sub-lattices. Whereby the abnormal transport behavior reveled by o-T curves for Fel +x.Cr2-x.S4 can be well explained.