Influence of magnetic ordering on electronic structure of Tb3+ ion in TbFe3(BO3)4 crystal
L. V. Kirensky Institute of Physics, Siberian Branch of Russian Academy of Sciences, 660036 Krasnoyarsk, Russian Federation
2 B. Verkin Institute for Low Temperature Physics and Engineering, National Academy of Sciences of Ukraine, 61103 Kharkov, Ukraine
Corresponding author: a email@example.com
Revised: 8 December 2010
Published online: 1 March 2011
Optical absorption spectra of trigonal crystal TbFe3(BO3)4 have been studied in the region of 7F6 → 5D4 transition in Tb3+ ion depending on temperature (2–220 K) and on magnetic field (0–60 kOe). Splitting of the Tb3+ excited states, both under the influence of the external magnetic field and effective exchange field of the Fe-sublattice, have been determined. Landé factors of the excited states have been found. Stepwise splitting of one of the absorption lines has been discovered in the region of the Fe-sublattice magnetic ordering temperature. This is shown to be due to the abrupt change of equilibrium geometry of the local Tb3+ ion environment only in the excited state of the Tb3+ ion. In general, the magnetic ordering is accompanied by temperature variations of the Tb3+ local environment in the excited states. The crystal field splitting components have been identified. In particular, it has been shown that the ground state (in D3 symmetry approximation) consists of two close singlet states of A1 and A2 type, which are split and magnetized by effective exchange field of the Fe-sublattice. Orientations of magnetic moments of the excited electronic states relative to that of the ground state have been experimentally determined in the magnetically ordered state of the crystal. A pronounced shift of one of absorption lines has been observed in the vicinity of the TbFe3(BO3)4 structural phase transition. The temperature interval of coexistence of the phases is about 3 K.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2011