Magnetic circular dichroism and absorption spectra of f-f transitions I-5(8) -> F-5(2) and F-5(3) in the HoFe3(BO3)(4) single crystal

Magnetic circular dichroism (MCD) and absorption spectra of multiferroic HoFe₃(BO₃)₄ of ⁵I₈ → ⁵F₂ and ⁵F₃ f–f transitions are measured at T = 90 K. The absorption spectra are expanded into Lorentzian components, and the transition intensities are obtained. The Zeeman splitting of some transitions is determined using the MCD and absorption spectra. The MCD spectra and Zeeman splitting are theoretically analyzed in the free-atom |J, ±M_J〉 wave function approximation by using the concept of a crystalline quantum number. An inconsistency is revealed when this concept is applied to ions with an integer moment, and a modification of the concept is proposed. Anomalously intense vibronic repetitions of electronic transitions from excited sublevels of the ground multiplet are found