Critical Behavior of Anisotropic Cubic Systems

The critical behavior in zero field above T₂ of ferromagnets or ferroelectrics with a Hamiltonian of cubic symmetry is studied, to order ^2, by exact renormalization-group techniques in d=4- dimensions with n-component spins. For =1, n3, a crossover from isotropic (Heisenberg) to characteristic cubic behavior occurs, with the new value 2v^C=1+ (n-1) 3n+ (n-1) 324{n^3} (17n^2+290n-424) ^2+O (^3), and cubic symmetry appearing in the four-spin correlation function. Experiments on structural phase transitions are considered briefly.