Spectroscopic Properties of TbAsO₄

Abstract

Abstract Absorption spectra of Tb 3+ in TbAsO 4 , indicate that this material undergoes a Jahn‐Teller induced phase transition from tetragonal to a lower, probably orthorhombic, symmetry at T D = (25.5 ± 2.5) K. Zeeman spectra with the magnetic field in the basal plane taken below T D , show a large anisotropy which is caused not only by the g ‐factor but also by large internal fields. The g ‐tensor of the isolated two lowest singlets, which are separated less than 0.6 cm −1 at 1.74 K, is uniaxial with g 110 = 17.0 ± 1.0 in the [110] direction. Measurements down to 0.77 K show a magnetic phase transition at T N , = (1.48 ± 0.04) K to an antiferromagnetically ordered state which increases the splitting of the two lowest lying singlets up to (2.62 ± 0.06) cm −1 at 0.77 K.