Investigation of magnetic, thermal and hyperfine properties of Tb3+ in the single crystal of terbium trifluoromethanesulfonate nonahydrate

Abstract

The single crystals of terbium trifluoromethanesulfonate nonahydrates Tb(CF3SO3)3·9H2O (TbTFMS) were grown and the principal magnetic susceptibilities measured from 300K down to 13K, for external field orientations both parallel and perpendicular to the c-axis which is the symmetry axis of this hexagonal crystal. The non-Kramers ion Tb3+ occupies a site of C3h symmetry in this uniaxial crystal. The principal magnetic susceptibilities, observed by us and the Friedberg group, over the range of temperature, 300 down to ∼1.0K, are explained very well by the theoretical expressions of susceptibility obtained from the crystal field perturbed J-mixed eigenvectors with due consideration of the intermediate coupling effects. No noticeable ordering effects were observed down to ∼13K; this indicates the interionic interactions to be weak, being predominantly of the dipolar type, which is consistent with the detection of a ferromagnetic transition at T∼0.24K by the Friedberg group. The g-values derived from other sources are also reasonably accounted for. The crystal field energy level structure predicts a Schottky anomaly in the heat capacity at around 0.23K, which agrees well with that observed by Friedberg et al.; another Schottky peak appears at around 48K. One interesting aspect of the present analysis is that almost all the principal features of the magnetic, thermal and optical properties of TbTFMS at high temperatures as well as liquid helium temperatures could be explained quite satisfactorily with a single CF alone. Present analysis also suggests that two singlets lie lowest whose separation is 0.37cm−1; this profoundly influences the magnetic and thermal properties. The interaction of the nuclear spin with the electric field gradient and the hyperfine magnetic field has also been discussed.