Magnetic field induced local structural transformations in the optically excited states F-5(2) and F-5(3) of HoFe3(BO3)(4) single crystal

We measured absorption spectra of transitions ⁵I₈ → ⁵F₂, ⁵F₃ in Ho³⁺ ion in the HoFe₃(BO₃)₄ single crystal at temperature 2 K as a function of magnetic field 0–65 kOe directed along a and c axes. The spectra were decomposed to the Lorentz shape components and magnetic field dependences of their parameters: position, intensity and line width, were obtained. Substantial difference between dependences of the energy and intensity of the transitions on magnetic field was revealed. So, the abrupt changes of the electron transition energies were mainly observed at the reorientation magnetic phase transitions in the crystal. A number of singularities in the magnetic field dependences of the electron transition intensities were revealed both at the reorientation transitions and outside of them. The singularities in the average intensities of transitions into multiplets at the reorientation magnetic transitions are due to the changes of the odd part of the crystal field, responsible for the allowance of f-f transitions, and also are due to the changes of the magnetic state. The singularities in behavior of intensity of each separate transition are due to the local even distortions in the excited states, which mix the electron states.