PARAMAGNETIC ANISOTROPIES IN RTAO(4) (R=ND, HO AND ER) CRYSTALS

RTaO(4) (R = Nd to Er) crystals are expected to be ferroelastics with pseudoelasticity below room temperature and to be antiferromagnetics b elow 4.2 K, as found in RNbO(4) (R = La to Lu) crystals. Single crysta ls of NdTaO4, HoTaO4 and ErTaO4 were grown by the floating zone method , and magnetization measurements were made by a vibrating sample magne tometer. A similar type of anisotropic paramagnetism has been observed in NdTaO4 and HoTaO4 crystals, as expected for a similar 4f electron asphericity in the same crystal field, as in NdNbO4 and HoNbO4. The Er TaO4 crystal shows, however, an anisotropic behaviour different from t he NdTaO4 and HoTaO4 crystals: (1) the relative magnitudes of the magn etic susceptibilities along the a- and c-axes are reversed, and (2) a rotational change of the easy axes of magnetization exists not only in the b-plane but also in the c-plane.