The Specific Heat of Terbium Arsenate

Abstract

Abstract Specific heat measurements on TbAsO 4 were carried out in the temperature region between 0.8 and 30 K. They show that this compound undergoes two phase transitions; one at T D = (27.7 ± 0.5) K, which is caused by a crystallographic phase transition from tetragonal to orthorhombic symmetry and another, at T N = (1.50 ± 0.02) K, which has to be attributed to a magnetic phase transition from the paramagnetic to the anti ferromagnetic state. An effective exchange integral and critical parameters were determined and compared with theory. The contribution to the heat capacity associated with the crystallographic phase transition shows a typical molecular field behaviour; the experimental values and the data derived from a modified molecular field theory are in very good agreement.