Magneto-optical activity and luminescence of f-f transitions in trigonal crystal TmAl3(BO3)4

Absorption and magnetic circular dichroism (MCD) spectra in the region of the 3H6 → 3H4, 3H6 → 3F3, 3F2, 3H6 → 1G4, 3H6 → 1D2 electron transitions and also luminescence spectrum of the 1D2 → 3F4 transition in Tm3+ ion in the TmAl3(BO3)4 single crystal were measured in the temperature range 95-290 K. Temperature dependences of magneto-optical activity (MOA) of the absorption bands (ratio of the zero moments of MCD and absorption bands) were determined. Mechanisms responsible for MOA of f-f transitions and its temperature dependence in ions with the integer total magnetic moment are analyzed. It is shown that in TmAl3(BO3)4 crystal the temperature-independent paramagnetic effect due to mixing of the electronic states by the magnetic field (so-called B-term) gives the prevailing contribution into MOA of the studied f-f transitions. In contrast to the absorption, luminescence spectrum demonstrates no MOA.