Demagnetization of spin systems at low temperature
نویسندگان
چکیده
We report on analytical and numerical results for the time evolution of a ~lattice! model of ferromagnetic particles after field inversion. Relaxation from the metastable phase occurs by superposition of two independent spin-flip processes: with probability 12p , the flip obeys the Metropolis rule at finite temperature, T , while the flip is performed at random, as for T→` , with probability p . For small p , the latter process mimics quantum tunneling or any other sort of impurity that would induce both additional randomness and a nonequilibrium steady-state condition asymptotically. Critical avalanches and constant magnetic viscosity at low T ensue as two key features of the relaxation for any pÞ0. This has some implications for experiments on demagnetization and mesoscopic quantum coherence. @S0163-1829~97!08437-3#
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