Magnetoresistance in Chalcogenide Spinels

Abstract

The consequences of a simple type of exchange interaction between charge carriers in a broad energy band and localized magnetic moments will be discussed for a ferromagnetic semiconductor. The interaction causes (1) a splitting of the energy band into two bands for the different spin directions, (2) spin disorder scattering of the charge carriers. The calculated temperature and field dependence of the magnetoresistance are compared with experimental data of CdCr2Se4. The magnetoresistance of compounds MeCr2S4, Me=Fe, Co, Cd was measured. For n-type CdCr2S4 and for p-type FeCr2S4 and p-type CoCr2S4, the magnetoresistance −Δρ/ρ0 was found to be 0.78, 0.05, and 0.05, respectively, at 12 kOe near Tc, whereas n-type FeCr2S4 and CoCr2S4 show no effect. The magnetoresistance of the system Fe1−xCdxCr2S4 was also measured. The temperature dependence of the polar magneto-optical Kerr effect of CdCr2Se4 is discussed in connection with the described model for the energy bands.