Trigonal and monoclinic Gd3+ centers with close initial splittings that had no analogs in crystals without Y were detected in the electron spin resonance spectrum of Y0.03Cd0.97F2.03:Gd3+ single crystals. The centers observed were attributed to Gd ions localized in tetrahedral Y and Y-Cd clusters. The values of the parameters of the second-rank spin Hamiltonian were explained (in order of magnitude) in terms of a superposition model that uses the tetrahedral-cluster structure obtained by minimizing the energy of a lattice with a rare-earth cluster.

Structure of Paramagnetic Defects in Cadmium Fluoride Doped with Yttrium and Gadolinium. V.A.Vazhenin, A.P.Potapov, A.D.Gorlov, V.A.Chernyshev, S.A.Kazanskiĭ, A.I.Ryskin: Physics of the Solid State, 2006, 48[4], 686-92