Electrical Resistivity ofPdFeAlloys

Abstract

The electrical resistivity $\ensuremath{\rho}$ of a series of ferromagnetic $\mathrm{Pd}\mathrm{Fe}$ alloys varying in composition from 1 to 12 at.% Fe was measured from 4.2 to 300 \ifmmode^\circ\else\textdegree\fi{}K. The data were analyzed by subtracting from the measured $\ensuremath{\rho}$ values, the value of the electrical resistivity of a sample of 99. 999+%-purity Pd at each temperature. From these values of the incremental resistivity $\ensuremath{\Delta}\ensuremath{\rho}$ we have obtained the temperature-dependent part by subtracting its limiting low temperature value (at 4.2-\ifmmode^\circ\else\textdegree\fi{}K). The reuslting temperature- and concentration-dependent resistivity ${\ensuremath{\rho}}_{m}$ has the following properties: For alloys of Fe concentration $c\ensuremath{\gtrsim}2$ at.%, ${\ensuremath{\rho}}_{m}\ensuremath{\propto}A{T}^{2}$ up to about 40 \ifmmode^\circ\else\textdegree\fi{}K in all but the highest-concentration alloys studied. Above this temperature we find a ${T}^{\frac{3}{2}}$ law up to the ferromagnetic ordering temperature ${T}_{C}$ except in alloys with $c\ensuremath{\gtrsim}6$ at.%, where the temperature dependence is faster above $\ensuremath{\approx}0.7{T}_{C}$. A 1 at.% alloy sample had a low-temperature behavior intermediate between the ${T}^{2}$ behavior of the higher-concentration alloys and the ${T}^{\frac{3}{2}}$ behavior observed in alloys with Fe concentration less than 1 at.%. The coefficient $A$ of the low-temperature ${T}^{2}$ dependence of ${\ensuremath{\rho}}_{m}$ increases approximately linearly with Fe concentration, and at 2 at.% is about seven times as large as the value found in pure Pd. These results suggest that electron-magnon scattering is the dominant scattering mechanism determining ${\ensuremath{\rho}}_{m}$. Our data, above 2 at.% Fe, are best interpreted in terms of a model in which the $\mathrm{Pd}\mathrm{Fe}$ alloys are considered to be approximately magnetically homogeneous with an effective, concentration-dependent "$s\ensuremath{-}d$" exchange interaction. In terms of this model, the expected correlation between the coefficient $A$ and the spin-wave excitation spectrum, at low temperatures, is shown to exist.