Electron-Spin Resonance Studies of Cr3+ in LiNbO3

Abstract

ESR studies were performed on a single crystal of ferroelectric LiNbO3 doped with chromium. For the main spectrum, attributed to Cr3+ at the Nb site, all transitions (including forbidden transitions) were identified. The experimental rotation pattern observed at X-band frequency was compared with that computed from the appropriate spin Hamiltonian {H = H̄·ḡ·s̄ + D[Sz2 − 13S(S + 1]} and the best fit ESR parameters obtained: D = 0.411 cm−1 and g = 1.969. In examining these parameters as a function of temperature, the g value was found to be temperature independent, and the variation of D with temperature was attributed to anisotropic lattice expansion. On the main central transition, two additional peaks were observed. EPR parameters (D = 0.21 ± 0.02 cm−1 and g = 1.97) are given for the peak on the high-field side. It is proposed that this peak arises from Cr3+ at the Li site. A discussion of the peak on the low-field side is also given.