A comparative study of the temperature-dependent magnetic susceptibilities of CuInX2(X=S, Se, Te)

Abstract

The absolute magnetic susceptibilities chi of polycrystalline CuInSe2 (n-type) and CuInTe2 (p-type) are reported from liquid helium temperatures to 300K. The temperature dependence of chi in the two compounds can be fitted to the equation chi (10-6 cm3 mol-1)=- chi 0+C(1-exp(-E/2T))/(T+ theta ) in the whole temperature range. A physical basis for this equation is given which leads to the determination of carrier concentration (from C), the donor/acceptor activation energy E and the Curie-Weiss temperature theta . From the fit, the obtained parameters for CuInS2 CuInSe2 and CuInTe2 are respectively: chi 0=83.7, 97.9, 119.0;C=185.0, 128.6, 164.7; E(K)=200, 240, 140; and theta (K)=3.0, 2.9, 1.7. The presence of shallow donor/acceptor levels in CuInX2 is established and the values for the obtained activation energies (E) are comparable with the estimates reported from other studies. The positive constant theta suggests antiferromagnetic exchange interactions between localised charge carriers. However, no magnetic ordering is observed down to 4.2K in CuInS2 and CuInSe2 and down to 1.4K in CuInTe2.