Local environment of Gd3+ in MgF2

The electron paramagnetic resonance (EPR) of Gd3+ in MgF2 reveals that Gd3+ has two different environments in the lattice. One of them has D2h symmetry, the EPR spectrum is characterized by a large zero field splitting [B2 0= 968.10-4 cm-1; B2 2= 357.10-4 cm-1] and the fourth order term of the spin Hamiltonian is axial; it is assumed that one Gd3+ substitutes two Mg2+. The other Gd3+ center has only monoclinic symmetry. From the analysis of the fourth order term of the spin Hamiltonian of the corresponding spectrum it is seen that one Gd3+ substitutes one Mg2+ and that this substitution produces a large local distortion of the lattice. © 1990 Springer-Verlag