Neutron diffraction determination of the magnetic phases of FeCl2·2H2O

The metamagnetic behaviour of FeCl₂·2H₂O has been determined. At T = 4.2 K the reflections of the antiferromagnetic zero-field-phase dissapear, when a magnetic field of H₁ = 39 kG is applied along the direction of sublattice magnetization. There is evidence for a ferrimagnetic phase with a unit cell in which the a axis is tripled. At H₂ = 46 kG this phase vanishes, and the magnetically saturated configuration is reached. As the temperature is increased, the three phases meet at a triple point at T_T = 11.7K and H_T = 42.0 kG.