Resistance maximum in spin glasses

The temperature Tₘ of the resistance maximum in spin-glass magnetic alloys is calculated as a function of the Kondo temperature TK for the single impurities and the average Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction strength Δc between different impurities. In addition Tₘ is shown to be independent of several other less relevant system parameters. The temperature dependence of the resistivity is obtained in the parquet approximation in the "noise model," where, besides the usual exchange scattering between conduction electrons and impurity spins, there is a transition rate Δc for spin-flip processes due to the RKKY interactions. The result is shown to be valid when ΔcTK, and applies to the low-TK spin-glass systems like AuMn, AgMn, CuMn, AuCr, and AuFe. For example, it permits the recently observed pressure variations of Tₘ to be understood in terms of simpler behaviors of the more fundamental system parameters Δc and TK. Asymptotically for ΔcTK one has Tₘ~Δcln(ΔcTK), which is bigger than the spin-glass freezing temperature T₀~Δc identified by the cusp in the magnetic susceptibility.