Effective-field approximations for disordered magnets

Abstract

Various effective-field approximation schemes are presented for describing the effects of fluctuations due to random spatial disorder on magnetic spin systems. An S=1/2 Ising model Hamiltonian is used, for which the spins occupy sites on a regular lattice but the exchange bonds are taken to be independent random variables. Both ferromagnetic and spin-glass types of ordering are considered. The results of the various approximation schemes are compared and related to previous work on disordered magnets.