Spontaneous magnetizaton of the Heisenberg ferromagnetic CuK2Cl4·2H2O under pressure

The results are reported of a study concerning the magnetization of the Heisenberg ferromagnet CuK2Cl4·2H2O(S = 1/2, Tc = 0.88° K) under hydrostatic compression. The spontaneous magnetization was determined from the magnetization isotherms for various pressures. Measurements were made on single crystals under hydrostatic pressures up to 10 kbar below 1°K in two mutually perpendicular directions: along the C4-axis and in the aa-plane. The direction of spontaneous magnetizations has been found to be perpendicular to the crystallographic C4-axis. As the pressure is raised, the magnetization of CuK2C14·2H2O decreases. The anisotropy field intensity along the C4-axis is 38 Oe at P = 0 and T = 0.45°K, increases by 8.0 kOe under the pressure of 10 kbar, but decreases to approximately 16.0 Oe at the phase transition temperature. Neither a residual magnetization nor a hysteresis was revealed in this experiment. This decrease in the spontaneous magnetization of CuK2C14·2H2O under pressure is explained here by a change in the ligand environment of the magnetic Cu2+ ion under pressure.

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