Use of finite size and applied magnetic field to characterize the interimpurity interaction in a spin glass.

Abstract

We report results of resistance measurements on Cu-Cr at several concentrations. We investigate the temperature ${\mathit{T}}_{\mathit{m}}$ of the resistance maximum of this spin glass as a function of sample size and applied magnetic field. From a fit of ${\mathit{T}}_{\mathit{m}}$ vs applied field, we obtain parameters that allow us to compare samples with different widths and thicknesses. We infer that the interimpurity interaction decreases with reduced sample size, and estimate the length scale for modifications of this interaction. We examine the magnetoresistance to gain further information about the effect of size. We also discuss the effect of concentration. The results are discussed within the context of previous observations of the reduction of the Kondo resistance contribution due to finite sample size. Our measurements span the regime where a resistance maximum is observed through the limit where the Kondo slope is the dominant contribution of the magnetic impurities to the resistivity. By adjusting the size of the samples to probe these regimes, we are able to illustrate the interplay between the spin glass and the Kondo resistivity contributions, deriving size effect information about both phenomena.