Magnetic localization and field-dependent variable-range hopping in disordered CuCr2S4

A study has been made of the magnetic and transport properties of CuCr2S4 powder compacts consisting of nanosized crystallites synthesized by mechanical alloying of the constituent elements at ambient temperature. It is found that the material is a typical spin glass with a spin freezing temperature of about 30 K, and that the temperature dependence of resistivity (rho) is well described by In(rho/rho (o))=(T-o/T)(1/4) in both the high-temperature (> 100 K) and low-temperature (<50 K) ranges with different values of T-o. The magnetoresistance, defined as {(0)- rho (50 kOe)}/rho (0). increases monotonically with decreasing temperature and reaches 0.3 at 5 K. It is shown that the temperature and field dependence of resistivity is consistently described in terms of spin-dependent variable-range hopping of the Cr t(2g) electrons localized by magnetic disorder.