Comparison of the resistivity ofPdCr with canonical spin-glass systems

Abstract

The electrical resistivity of several PdCr alloys, with between 11- and 18-at.% Cr, has been investigated between 1.4 and 300 K, and found to resemble that of canonical spin glasses (CSG). At low temperatures $\ensuremath{\Delta}\ensuremath{\rho}(T)\ensuremath{\propto}A{T}^{\frac{3}{2}}$, with $A\ensuremath{\propto}\ensuremath{-}logc$ over the concentration range investigated; the range of validity of this ${T}^{\frac{3}{2}}$ variation ($T<{T}_{1}$) is small in PdCr (where $A$ is comparatively large) as in AgMn. At higher temperatures $\ensuremath{\Delta}\ensuremath{\rho}(T)$ passes through an inflection point (at ${T}_{m}$) reaching a maximum (at ${T}_{\ensuremath{\mu}}$) above which it decreases with increasing temperature. The ratio $\frac{{T}_{m}}{{T}_{1}}$ is found to be roughly constant, as predicted by recent spin-glass theories, but as in CSG its magnitude is smaller than predicted. There are, however, several quantitative differences between PdCr and CSG; specifically both ${T}_{\ensuremath{\mu}}$ and $\ensuremath{\Delta}\ensuremath{\rho}({T}_{\ensuremath{\mu}})\ensuremath{-}\ensuremath{\Delta}\ensuremath{\rho}(0)$ are typically an order of magnitude smaller than in CSG of comparable concentration, whereas the slope of $\ensuremath{\Delta}\ensuremath{\rho}(T)$ above ${T}_{\ensuremath{\mu}}$ is about an order of magnitude larger than in CSG. This latter point in particular lends support to the assertion that such differences may arise from the fact that CSG are good moment systems (${T}_{K} or {T}_{S}\ensuremath{\ll}{T}_{m}$), but PdCr is not (${T}_{S}\ensuremath{\sim}{T}_{m}$).