Electrical resistivity ofAuFe alloys in the spin-glass, mictomagnetic, and ferromagnetic regimes

Measurements are presented of the electrical resistivity for a series of Au Fe alloys with concentrations between 0.5- and 22-at.% Fe, in the temperature range 0.5 - 300 K. We have called the concentration range between about 0.5- and 8-at.% Fe, the spin-glass regime. Here we find that the impurity resistivity Δρ has a T3/2 dependence down to the lowest temperatures of measurement, the coefficient of this dependence decreasing very slowly with concentration. At higher temperatures, around the "freezing" temperature T₀ the impurity resistivity is increasing linearly with temperature, and this is followed, at much larger temperatures, by a very broad resistance maximum. We have called the concentration range above {}10-at.% Fe, the mictomagnetic regime which is characterized by having large magnetic clusters and a sensitivity to thermal and magnetic history. Upon further increasing the concentration to the percolation limit c15 at.%, such that there is sufficient overlapping among these magnetic clusters, Au Fe gradually develops a long-range inhomogeneous ferromagnetic regime. Again we observe a T3/2 temperature dependence throughout both of these regimes at low temperatures, but at higher temperatures the deviation away from this dependence is much more complicated than in the spin-glass regime. Further, the onset of magnetic ordering is clearly seen in Δρ. We have also examined the temperature dependence of the derivative of the impurity resistivity d(Δρ)dT, and find that throughout our whole concentration range there is a well-defined maximum which correlates fairly well with T₀. The experimental and theoretical background of these measurements is fully discussed.