Magnetic field effect on the susceptibility of a Heisenberg ferromagnet CuK2Cl4.2H2O near the critical point

The results on the investigation of the susceptibility for the Heisenberg ferromagnet CuK₂Cl₄.2H₂O in the magnetic field are reported. The susceptibility divergence at the critical temperature in the magnetic field is shown to transform into susceptibility anomalies of two types, their shifts being approximated by the power functions with indices ω = 2.6 and ? = 0.58. The experimental data support the assumption about the complex critical temperature. The regions for the existence of phases with uniform and non-uniform magnetizations are determined.