Relaxation effects in spin glasses around the freezing temperature

Abstract

Measurements of the ac magnetic susceptibility in zero field for several insulating spin-glasses are reported. By resolving the frequency dependence of both the in-phase component X′ and the out-of-phase component X″, the dynamical behavior of these spin systems around their freezing temperatures Tf can be clearly characterized. For two insulating systems: (EuSr)S and cobalt aluminosilicate, the susceptibility behavior can be described in terms of a wide distribution of relaxation times for temperatures well above Tf and whose width increases dramatically as the temperature nears T f. Furthermore by employing a simple phenomenological relaxation model, a quantitative picture of the relaxation time distribution can be ascertained as it evolves. From these pictures for the insulating as well as metallic spin-glass system, the dynamic behavior near Tf is qualitatively different than that of a long-range magnetically ordered solid.