Crossover scaling function for exchange anisotropy: Heisenberg toXY-like crossover

The crossover behavior of the susceptibility ${\chi }^{\mathrm{xx}}$ of the classical Heisenberg model with $\mathrm{XY}$ -like anisotropic exchange coupling is studied following the methods of Pfeuty, Jasnow, and Fisher. The universal scaling function is obtained and, from it, the crossover of the effective susceptibility exponent ${\gamma }_{\mathrm{eff}}$ is found.