Critical behavior of the random uniaxial anisotropy model

The critical behav or of an isotropic ferromagnet with random uniaxial anisotropy is studied to the first order in ε=6-d. Even though the fourth-order coefficients are irrelevant for d>4, and the exponents are all given by their mean-field values, the longitudinal susceptibility for T<Tc is found to diverge on the coexistence curve for d<~6. Thus the upper critical dimension is dc=6 for this nodel. © 1978 The American Physical Society.