Magneto-optical activity of f-f transitions and properties of 4f states in single-crystal DyFe3(BO3)4.

Magnetic circular dichroism and polarized optical absorption spectra of single-crystal DyFe3(BO3)4 were measured in the region of the crystal transparency from 8700 to 16 000 cm−1 in the temperature range from 90 K up to room temperature. Spectra of d-d and f-f transitions were separated, and f-f transitions 6H15/2 → 6(F9/2+H7/2), 6F7/2, 6F5/2, and 6F3/2 were studied. From these measurements, temperature dependences of the paramagnetic magneto-optical activity (MOA) of the electric dipole-forbidden f-f transitions were obtained. It was revealed that, in contrast to allowed transitions, temperature dependences of the MOA of some f-f transitions substantially deviate from the Curie-Weiss law. The theories of MOA of allowed and f-f transitions were considered and the experimental results obtained were accounted for. Circular polarizations in magnetic field and linear polarizations of absorption lines were determined. The Zeeman splitting of some absorption lines were found. Symmetries of the crystal field states were analyzed on the bases of the obtained results in D3 local symmetry approximation. A small splitting (≈16.5 cm−1) between the two lowest sublevels of the ground manifold was detected, and symmetries of these states were identified as E1/2 (M = ±13/2) and E3/2 (M = ±15/2), respectively. Deviation of the local symmetry of the Dy3+ ion from D3 is small, and it was revealed that polarizations of the majority of absorption lines can be accounted for in the D3 symmetry. This also testifies that in the process of some other electron transitions, the equilibrium configuration of the local environment deviates from D3 symmetry stronger than it does in the ground state. In addition, it has been shown that the distortions depend not only on the excited but also on the initial state. [ABSTRACT FROM AUTHOR]