EPR of Се3+ in the Rb2NaYF6 single crystal

The EPR spectrum of the Ce3+ ion in the crystal of the elpasolite type Rb2NaYF6 has been observed and studied at low temperatures (Т = 4.2 - 80 K). It was established that the paramagnetic center Ce3+ has tetragonal symmetry confirming the experimental fact we reported recently that at low temperatures the Rb2NaYF6 crystal exists in the tetragonal phase, into which it transferred from the cubic phase as a result of the structural phase transition (PT). Parameters of the spin Hamiltonian of the tetragonal EPR spectrum were determined. A scheme of 4f energy levels of the Ce3+ ion in Rb2NaYF6 before and after PT was proposed from the theoretical interpretation of the observed g-factors and parameters of the crystal fields acting on it were determined.