SPECTRUM OF RELAXATION-TIMES FOR ISING SPIN CLUSTERS IN RANDOM-FIELDS

Exact results on the single-spin-flip Glauber dynamics of six-coupled random field Ising spins with the coordination number of four are pres ented. Two distributions of random fields (RF), binary (BD) and Gaussi an (GD) ones, are investigated. The effects of the static magnetic fie ld are discussed. In the zero-magnetic-field case, the number of diver ging relaxation times is equal to the number of energy minima minus on e. This rule breaks in the presence of a magnetic field. The longest r elaxation times in the absence of the field verify the Arrhenius law w ith the energy barrier determined by the energy needed to invert the g round-state spin configuration. At low temperature, according to the A rrhenius law, the spectrum of relaxation times shows a two-peaked dist ribution on a logarithmic scale. In the GD case of RF, the energy barr ier distribution is continuous, while it is quasi-discrete in the BD c ase.