Extensive studies on the low-temperature properties of TbPO4. I: Magnetic measurements

At low temperatures, TbPO4 shows two phases with antiferromagnetic ordering in immediate succession, the upper one with tetragonal and the lower one with monoclinic crystal symmetry. Magnetisation and magnetic susceptibility were measured in the region of these phases for different external field directions. One main aspect was to study the anisotropy of the susceptibility for a single-domain crystal in one of the low-symmetry phases. Unexpectedly, it turned out that the susceptibility is isotropic in the basal plane.