Extensive studies on the low-temperature properties of TbPO4. III. Birefringence measurements and mean-field calculations

Abstract

For pt.II see ibid., vol.5, p.945 (1993). Measurements of the linear optical birefringence were used to determine the phase diagram of TbPO4 at temperatures down to 1.4 K. At least one new structural and magnetic phase transition was found that is not detectable in magnetic investigations. Calculations using an appropriate mean-field Hamiltonian, including crystal distortions of monoclinic symmetry, allowed the authors not only to reproduce the experimental phase diagram very satisfactorily but also to give further insight into the magnetic structures and the distortions of the crystal in the various phases.