HALL-EFFECT AND MAGNETORESISTANCE IN FE1-XCUXCR2S4

The Hall effect and the magnetoresistance effect are studied in Fe 1-xCuxCr2S4. FeCr2S 4 is a ferrimagnetic semiconductor and CuCr2S4 is a ferromagnetic metal. The number and the mobility of charge carriers are determined independently. The mobility decreases as the temperature increases toward the Curie temperature. This shows that the anomalous increase in the electrical resistivity around the Curie temperature is caused by the decrease in the mobility by the spin-disorder scattering. The temperature dependence of the number of charge carriers indicates that this system is still in a semiconductor state at x=0.65. The negative magnetoresistance effect is observed below the Curie temperature, and is discussed in terms of the spin-disorder scattering. The compositional dependences of the magnetoresistance effect and the Curie temperature suggest the semiconductive-to-metallic transition near x=0.85.