The electron paramagnetic resonance spectra of Ni3+ ions which were created by room-temperature irradiation were measured at 15K. It was found that they could be described by an isotropic Zeeman term (S = ½, g = 4.183) and a super-hyperfine structure which corresponded to interaction with the 6 nearest-neighbor F ions. The values of the super-hyperfine parameters were A|| = 0.0141/cm and A = 0.0018/cm. The distance between the central ion and the ligands was estimated from the isotropic part of these super-hyperfine parameters.

R.Alcalá, B.Villacampa: Solid State Communications, 1994, 90[1], 13-6