Transformation of the HoFe3(BO3)(4) absorption spectra at reorientation magnetic transitions and local properties in the excited F-5(5) states of the Ho3+ ion

Malakhovskii, AV; Gnatchenko, SL; Kachur, IS; Piryatinskaya, VG; Gudim, IA PHYSICAL REVIEW B, 96 (22):10.1103/PhysRevB.96.224430 DEC 27 2017

Polarized absorption spectra of the 5I85F5 transition of the Ho3+ ion in the HoFe3(BO3)4 single crystal were measured at T=2K as a function of magnetic field 0–60 kOe directed along the a, b, and c axes of the crystal. The spin-reorientation transitions were observed in the field Hc at 5.35 kOe, in the field Ha at 10.25 kOe, and in the field Hb at 9.1 kOe. We also observed a small hysteresis of the transitions. We found that the optical properties of the crystal change as a function of the magnetic field orientation in the basal plane in spite of the nominally axial symmetry of the crystal. We found a number of specific local properties in the Ho3+ excited states. Nonequivalent positions of the Ho3+ ion appear in some excited states. It was shown that during one of the electron transitions the local symmetry changes not only in the excited state but in the ground state as well. We observed local metamagnetic transitions in some Ho3+ excited states. In some excited states, the Ho3+ ion is in the easy-plane state while the total crystal is in the easy-axis state and vice versa. This means that the magnetic moments of the Fe3+ and Ho3+ ions in these excited states of the Ho3+ ions are mutually perpendicular. Such phenomenon testifies to the existence of the antisymmetric Fe-Ho exchange interaction in the Ho3+ excited states.