Magnetic correlations in ferromagnets with quenched random fields

The critical dynamics of the relaxational model for ferromagnets in quenched random fields is studied within the framework of the -expansion (=6–d). The shape functionf_x() is obtained exactly atT_c; it remains finite when the frequency vanishes. The static and dynamic properties of the model belowT_c are also considered. The equation of state and the static correlation function are related to those of the (d–2)-dimensional pure systems. The dynamic response functionG is obtained for zero momentum. The scaling form of the random correlation functionC^(s), which determines the spin-glass order parameter, is obtained. The coexistence curve singularities of ,G andC^(s) when the number of spin componentsn2, are studied.