Electron paramagnetic resonance study of a new Fe3⁺centre in KiTiOPO₄

Abstract

An EPR experiment of Fe3+ in an iron-doped single-crystal of KiTiOPO4 was carried out at the Q-band frequency. The angular dependences of the spectra were studied in the three crystallographic planes. The zero-field splitting of Fe3+ is of the same order of magnitude as the quantum hv; so many Delta Ms=+or-2 transitions were observed together with all the Delta Ms=+or-1 transitions between spin states. All spin-Hamiltonian parameters were calculated using Delta Ms=+or-1 or +or-2 transitions for 36 and 18 different orientations, respectively. They use, on the one hand, of the pseudo-symmetries of the fourth-order constants of the spin Hamiltonian and, on the other hand, of the structure data and a fourth-order crystal-field calculation for the Ti(2) octahedron allowed the authors to locate Fe3+ in the Ti(2) site. Indeed the octahedron environment of Fe3+ does not differ much in orientation from Ti4+ and the lattice relaxation is very weak when Fe3+ substitutes for Ti4+.