Magnetotransport and magnetic properties of sulfospinels Zn_xFe_1−xCr₂S₄

Abstract

Cr-based chalcogenide spinels, which do not have heterovalency and distortioninduced ions such as manganese oxides with perovskite structure, have demonstrated the existence of colossal magnetoresistance. In order to investigate the magnetotransport phenomena and magnetic properties of sulfospinels Zn _x Fe_1−x Cr₂S₄, polycrystalline Zn _x Fe_1−x Cr₂S₄ samples were synthesized in the 0≥x≤0.2 range by a solid reaction method. The crystal structure for x=0.05, 0.1, and 0.2 turned out to be cubic at room temperature by X-ray diffraction measurement. In magnetoresistance measurement, Zn _x Fe_1−x Cr₂S₄ samples indicate that this system is semiconducting below about 150 K. The temperature of maximum magnetoresistance is almost consistent with Curie temperature. The isomer shift and the electric quadrupole shift of Zn _x Fe_1−x Cr₂S₄ samples by Mössbauer experiment show that Fe²⁺ ions occupy the tetrahedral site in the spinel structure. As the Zn ions are substituted for Feions, the Jahn-Teller relaxation slows down and the electric quadrupole shift increases. The magnetotransport phenomena of Zn _x Fe_1−x Cr₂S₄ is related to Jahn-Teller effect and half-metallic electronic structure, which are different from the double exchange interactions of the manganite La-Ca-Mn-O system or the triple exchange interactions of sulfospinel Cu _x Fe_1−x Cr₂S₄.