Spin-glass-like ordering in giant magnetoresistive CuCo

The magnetic dynamics in melt-spun CoxCu100-x measured by ac-susceptibiliti es and magnetic relaxation reveal interaction affects for low Co contents ( x = 2, 10). The frequency dependence of the ac-susceptibility curves vs. te mperature described by Neel-Arrhenius relaxation over a distribution of ene rgy barriers yield unphysically small prefactors for the microscopic timesc ale. The dependence of the peak temperatures on frequency can be described by critical functions with exponents similar to those of conventional spin- glasses. Magnetic relaxation is slow on a logarithmic timescale. The result s indicate magnetic interactions resulting in glassy dynamics. Samples of C o10Cu90 with high magnetoresistance ratio show magnetic aging effects in re laxation experiments, which are observed by waiting-time dependences in the time evolution of the magnetization or resistivity after zero-field-coolin g, These results are unequivocal evidence for magnetic ordering similar to that in spin-glasses.