CRITICALITY AND CROSSOVER SCENARIOS IN UNIAXIAL DIPOLAR FERROMAGNETS

The critical behavior of a ferromagnet with dominant exchange interaction, dipolar interaction, and uniaxial anisotropy is studied to one-loop order of renormalized field theory. The analytical calculation of the effective exponent gamma(eff) for the susceptibility makes it possible to characterize quantitatively the crossover phenomena for arbitrary magnitudes of the competing effects. A type of logarithmic correction to the asymptotic gamma depending on the ratio of dipolar versus anisotropy strength is presented. Recent experiments on Gd are discussed in view of the obtained results.