Paramagnetic anisotropies in RTaO4 (R = Nd, Ho and Er) crystals

RTaO4 (R = Nd to Er) crystals are expected to be ferroelastics with pseudoelasticity below room temperature and to be antiferromagnetics below 4.2 K, as found in RNbO4 (R = La to Lu) crystals. Single crystals of NdTaO4, HoTaO4 and ErTaO4 were grown by the floating zone method, and magnetization measurements were made by a vibrating sample magnetometer. 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 ErTaO4 crystal shows, however, an anisotropic behaviour different from the NdTaO4 and HoTaO4 crystals: (1) the relative magnitudes of the magnetic 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. (orig.)