Non-equilibrium behavior in a disordered magnetic system

Abstract

We have studied the non-equilibrium magnetic state of a thin film of cobalt ferrite with a nanocrystalline structure which shows a frozen disordered magnetic state with extended ferrimagnetic correlations at low temperature. The magnetization has been measured in a wide range of temperatures and magnetic fields, and the irreversible susceptibility and the relaxation rate of the magnetization along the hysteresis loop show a scaling behavior where the scaling field is a temperature-dependent magnetic field H0. The magnetic field H0 and the free energy barrier height in spin glasses show a similar temperature dependence. Our measurements, together with extensive studies of the spin glass phase, show that disordered magnetic systems share many common features. We have also observed that the relaxation of the magnetization that follows a magnetic field change has a behavior which is qualitatively similar to that observed in ageing experiments in spin glasses.