Scaling and critical slowing down in random-field Ising systems

A simple scaling description of the ordering transition in random-field Ising systems is developed and supported by renormalization-group arguments in terms of a zero-temperature critical fixed point. The main prediction is that the characteristic relaxation time {τ} will diverge extremely rapidly as the critical point is approached: {τ}{~}exp(ξᵗʰᵉᵗᵃ) with {ξ} the correlation length and theta the ``violation of hyperscaling'' exponent (d-theta){ν}=2-{α}. Recent experiments which exhibit onset of hysteresis in a very narrow temperature range are discussed.