Towards equilibrium in spin glasses (invited)

Abstract

New nonequilibrium features of the magnetic susceptibility of spin glasses are reviewed. Experimental observations on the time variation of the zero-field-cooled (ZFC) and field-cooled (FC) susceptibilities indicate that the same equilibrium value is obtained after the same characteristic time teq(T). ZFC and ac susceptibility measurements on metallic spin glasses unambiguously reveal the existence of aging of the zero-field spin-glass state. The possibility to probe the aging process from these measurements is outlined. The aging of the zero-field state ends at the characteristic time teq(T), where a spin-glass state at dynamic equilibrium is retained.