Giant Magnetoresistance in Spinel CuCr1.6Sb0.4S4

Abstract

A giant magnetoresistance (MR) is found in the CuCr 1.6 Sb 0.4 S 4 semiconductor spinel, consisting of a solid solution of the CuCr 1.5 Sb 0.5 S 4 antiferromagnet (AF) and the CuCr 2 S 4 ferromagnet. This MR is negative and isotropic. Its value is equal to 74% at temperature T ¼ 3 K (magnetic field H ¼ 38 T) and decreases with decreasing T. Magnetization isotherms are the superposition of a linear part, as for AF, and a small spontaneous magnetization. Therefore we assume that the sample is an AF in which droplets with spontaneous magnetization are disposed. Nagaev showed that giant MR in doped AF semiconductors is explained by similar magnetic two-phase state, in which all the electrons are concentrated in droplets because of the energy gain in s-d exchange.In this work, a giant magnetoresistance (MR) was found in the CuCr 1.6 Sb 0.4 S 4 compound semiconductor consisting of a solid solution of two compounds with the normal spinel structure: Cu 1þ Cr 1.5 3þ Sb 0.5 S 4 antiferromagnet (AF) with conduction of the semiconductor type [1] and CuCr 2 3þ S 4 2--ferromagnet (F) with conduction of the metallic type [2]. This is surprising because no MR was observed within the experimental error (0.01%) in either CuCr 1.5 Sb 0.5 S 4 or CuCr 2 S 4 . The magnetoresistance Dr/r ¼ (r H --r H¼ 0 )/r H¼ 0 , the resistivity r, and the magnetization M of the polycrystalline CuCr 1.6 Sb 0.4 S 4 sample were investigated. The magnetization in a constant magnetic field H 14 T was measured by the induction method, and the resistivity was measured by the four probe method. Both a stationary magnetic field H 10 T and a pulsed magnetic field H 38 T were used for measuring MR.The dependence of r on the temperature T is of the semiconductor type. The dependence of (Dr/r) on T at H ¼ 10 and 38 T is shown in Fig. 1. This MR is negative and isotropic. It is apparent in Fig. 1 that the MR value at low temperature is very large (Dr/r ¼ 74% at T ¼ 3 K and H ¼ 38 T) and decreases with decreasing temperature, becoming close to zero at 35 K T 39 K. (The Neel temperature of this compound is T N ¼ 42.8 K [3]).

Sb Doping of Metallic CuCr2S4 as a Route to Highly Improved Thermoelectric Properties

“…However, to the best of our knowledge, thermoelectric properties were not investigated for Sb-doped CuCr 2 S 4 . On the basis of these previous reports, − we assume that replacing some Cr by Sb can cause a significant influence on thermoelectric properties. Although CuCr 2 S 4 is reported to be metallic, − a detailed literature survey did not show any report related to the effect of Sb addition on the thermoelectric properties except that CuCr 1.5 Sb 0.5 S 4 is a semiconductor …”

“…18 Moreover, giant magnetoresistance has been reported for CuCr 1.6 Sb 0.4 S 4 . 19 However, to the best of our knowledge, thermoelectric properties were not investigated for Sb-doped CuCr 2 S 4 . On the basis of these previous reports, 17 −19 we assume that replacing some Cr by Sb can cause a significant influence on thermoelectric properties.…”

“…Sb-doped CuCr 2 S 4 has been investigated regarding its interesting magnetic properties: CuCr 1.5 Sb 0.5 S 4 is reported to be antiferromagnetic, while CuCr 2 S 4 is described as ferromagnetic . Moreover, giant magnetoresistance has been reported for CuCr 1.6 Sb 0.4 S 4 . However, to the best of our knowledge, thermoelectric properties were not investigated for Sb-doped CuCr 2 S 4 .…”