A phenomenological theory of metastable states in disordered ising magnets

A mechanism of the formation of an exponentially large number of metastable states in magnetic phases of disordered Ising magnets as a result of conde nsation of fractal delocalized modes near the localization threshold is sug gested. The thermodynamic properties of metastable states are studied in th e effective-field approximation in the vicinity of transitions in magnets w ith zero uniform magnetization in the ground state such as dilute antiferro magnets, spin glasses, and dilute ferromagnets with dipole interaction. The se properties are shown to determine the parameters of nonequilibrium proce sses in the glassy phase, namely, the shape of the hysteresis loop, the the rmodynamic values in field-cooled and zero-field-cooled regimes, and the th ermoremanent and isothermal remanent magnetization values. (C) 2001 MAIK "N auka/ Interperiodica".