Anomalous magnetostriction in TbPO4 at low temperature

The longitudinal magnetostrictions parallel and perpendicular to the c axis of TbPO4 in fields up to 78.4 KOe were measured below 4.2 K by means of a capacitance dilatometer. Above Tsub(N), both longitudinal magnetostrictions parallel and perpendicular to the c axis show monotonic field dependence. Below Tsub(N), however, they show quite different field dependence with two conspicuous inflexion points, these depend strongly on temperature and show largely anisotropic character. These points can be understood as the critical fields of magnetic transitions from the canted antiferromagnetic state to the paramagnetic state via the spin-flip transition. From these results, the magnetic field temperature phase diagram of TbPO4 is obtained. (author)