EPR study of the Jahn-Teller effect of [Cu.sup.2+] ions in Zn[Ga.sub.2][O.sub.4]

The Jahn-Teller effect in the Zn[Ga.sub.2][O.sub.4] spinel single crystal has been investigated using electron paramagnetic resonance of [Cu.sup.2+] ions in the temperature range 110-560 K. It has been shown that copper ions occupy octahedral sites 16d in the Zn[Ga.sub.2][O.sub.4] crystal with cubic symmetry [O.sup.7.sub.h] (Fd-3m). At T < 560 K, the octahedra undergo tetragonal distortions (predominantly tension) and rotation around the fourfold axes by the angle θ ≅ 2.6°. The parameters of the spin Hamiltonian, which characterize the prolate ([g.sub.∥] = 2.355, [g.sub.[perpendicular to]] = 2.077, [A.sub.∥] = 116 Oe, [A.sub.[perpendicular to]] = 12 Oe) and oblate ([g.sub.∥] = 2.018, [g.sub.[perpendicular to]] = 2.246, [A.sub.∥] = 75 Oe, [A.sub.[perpendicular to]] = 44 Oe) octahedra, have been determined. At temperatures above 560 K, the static Jahn-Teller effect transforms into the dynamic effect and the spectrum of the magnetic resonance becomes isotropic with g = 2.116 (the experimental frequency corresponds to the X band).