REMANENT MAGNETIZATION IN SPIN-GLASSES

A spin-glass model consisting of a kinetic Ising model with random nearest-neighbor interactions is studied by Monte Carlo methods. As in real experiments the system is cooled, and a magnetic field is applied and then switched off. Below a freezing temperature Tf both an irreversible and a reversible magnetic susceptibility are observed. A remanent magnetization M occurs which decays very slowly with time t with a power law M∼t-a to the equilibrium value M=0. For different cooling procedures different remanent magnetizations are discussed as a function of temperature and previously applied field. A characteristic difference between field cooled (TRM) and isothermal (IRM) remanent magnetization is observed in the field dependence of the exponent a. Many of the predictions resemble experimental results. In the second part an exactly solvable spin-glass model incorporating a symmetric distribution of random interactions and frustration is introduced. Since the range of the interactions is infinite there exist no local clusters in this model. A phase transition with a cusp in the susceptibility, a remanent magnetization, and a ferromagnet-spin-glass transition are found. © 1979 The American Physical Society.