Electrical resistivity of noble-metal-host-3dsolute spin-glass alloys

Abstract

Measurements are presented of the electrical resistivity for a series of AuCr, AuMn, AgMn, and CuMn alloys in the temperature range 1.5-300 K and with magnetic impurity concentrations \ensuremath{\simeq} 0.5-10 at.%. Such alloys represent typical examples of spin-glass or mictomagnetic systems. We have found that for all four systems the "impurity" resistivity $\ensuremath{\Delta}\ensuremath{\rho}$ has an initial ${T}^{\frac{3}{2}}$ dependence, the coefficient of which decreases very slowly with increasing concentration. At higher temperatures around the freezing temperature ${T}_{0}$, $\ensuremath{\Delta}\ensuremath{\rho}$ increases roughly linearly with $T$, and this is followed at much higher temperatures by a resistance maximum. This paper is a sequel to an earlier resistivity study of the AuFe system. The similarities and differences between the four systems and also with AuFe are described. We interpret the initial ${T}^{\frac{3}{2}}$ temperature dependence in terms of a recent spin-diffusion theory due to Rivier and Adkins. The nature of the freezing process around ${T}_{0}$ and its effects on $\ensuremath{\Delta}\ensuremath{\rho}$ are discussed, as well as the formation of local magnetic clusters (short-range order) at $T\ensuremath{\gg}{T}_{0}$ which give rise to the resistance maximum. The temperature dependence of the derivative of the impurity resistivity $\frac{d[\ensuremath{\Delta}\ensuremath{\rho}(T)]}{\mathrm{dT}}$ has also been examined for the four systems, and it is found that $\frac{d(\ensuremath{\Delta}\ensuremath{\rho})}{\mathrm{dT}}$ has a well-defined maximum but, unlike AuFe, this does not correlate well with ${T}_{0}$.