Magnetic and thermal properties of terbium ethylsulfate

Abstract

A theoretical study of the magnetic and thermal properties of terbium ethylsulfate(TbES) has been made with a crystal field(CF) obtained by slightly modifying the one proposed by Hufner to get the best fit to the observed absorption spectra. The theoretical results have been compared with all the available experimental data on TbES. A good overall explanation to the observed nature of variation of χ∥ and χ⊥ is obtained. The agreement between the theoretical and experimental g values is excellent. A Schottky anomaly obtained at around 0.25 K agrees well with that observed by Hirvonen et al.; another Schottky peak is predicted at about 60 K. One interesting aspect of the present analysis is that almost all the principal features of the magnetic, thermal, and optical properties of TbES at high temperatures as well as at liquid helium temperatures could be explained moderately well with a single CF alone. An analysis of all the experimental data suggests that the separation between the ground singlets, Δ, which profoundly influences the magnetic and thermal properties only at very low tempeatures, is very close to 0.56 K. An experimental investigation of χ⊥ below 100 K and that of the Schottky heat capacity around 60 K is recommended for further confirmation of the CF used in the present work for which the parameters are, C20=110.6, C40=−75.0, C60 =−34.0, and C66=406.0, all in cm−1. The calculations have been carried out in the intermediate coupling scheme.