MAGNETORESISTANCE OF THE SEMICONDUCTING SPINELIDE CU0.625GA0.375CR2SE4 HAVING A LOW-TEMPERATURE LONG-RANGE MAGNETIC ORDER SPIN-GLASS TRANSITION

A study is reported of the dependence of magnetoresistance Delta rho/r ho on the square of magnetization sigma(2) of the semiconducting spine lide Cu0.625Ga0.375Cr2Se4, which exhibits a low-temperature transition from long-range magnetic order (LRMO) to the spin glass (SG) state in strong magnetic fields. It is shown that at the freezing temperature T-f the Delta rho/rho(sigma(2)) relations change their slope, and that below T-f this slope is about one half that for T>T-f This finding, t ogether with the earlier observation that the freezing temperature doe s not depend on the frequency of the ac magnetic field in which it was measured, suggests that the spin-glass phase consists of spins of ind ividual Cr3+ ions, and that the SG-LRMO crossover is a phase transitio n. (C) 1998 American Institute of Physics.