THERMOREMANENT MAGNETIZATION AS A PROBE OF THE FIELD-QUENCHED STATES IN SPIN-GLASSES

The aging process for spin glasses has been characterized by barrier h opping between states of similar magnetization, with the maximum barri er height surmounted proportional to the logarithm of the waiting time t(w). We investigate the microscopic nature of the decay of the irrev ersible component of the magnetization upon a change in magnetic field . In particular, we examine transitions between states with magnetizat ions associated with the initial and final values of the magnetic fiel d, and their related barrier heights. We employ a field cycling protoc ol during the waiting time to determine which states (barriers) are oc cupied upon a change of magnetic field. We find that the rapid compone nt of magnetization change is associated with transitions between stat es of low barrier heights (we surmise of energy less than the change i n overall Zeeman energy), and the slow component of magnetization chan ge [decay of the thermoremanent magnetization (TRM)] is associated wit h diffusion from states at larger barrier heights to the ''sink'' asso ciated with the (rapid) small barrier height transitions. The transiti ons between states of differing magnetization are limited to transitio ns between states of similar (small) barrier heights. We believe these observations account for the microscopics of spin-glass dynamics duri ng the time decay of the TRM.