Magnetic phase transitions in anisotropic Heisenberg antiferromagnets. II. CoCl2.6H2O

Differential magnetic susceptibility measurements have been used to examine the temperature dependence of the magnetic phase boundaries in antiferromagnetic Co${\mathrm{Cl}}_2$.6${\mathrm{H}}_2$O between 0.33 and 2.0 K. The spin-flop to paramagnetic phase boundary has a predominantly $T^{\frac{5}{2}}$ temperature dependence, similar to the case of Mn${\mathrm{Cl}}_2$.4${\mathrm{H}}_2$O reported in the preceding paper. No evidence is found for the predicted $T^{\frac{3}{2}}$ dependence. The values of the critical fields, extrapolated to $T=0\mathrm{}$, are consistent with a Heisenberg model with isotropic exchange and a single-ion-type anisotropy.