MAGNETORESISTANCE IN CHALCOGENIDE SPINELS

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 MeCr 2S4, Me=Fe, Co, Cd was measured. For n-type CdCr 2S4 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 CoCr 2S4 show no effect. The magnetoresistance of the system Fe1-xCdxCr2S4 was also measured. The temperature dependence of the polar magneto-optical Kerr effect of CdCr 2Se4 is discussed in connection with the described model for the energy bands. © 1969 The American Institute of Physics.