The ground state of the ferrous ion in alumina and calculation of spin-lattice relaxation

Abstract

The spin-lattice relaxation time by the direct process of the ground state of the ferrous ion in ruby is estimated using a crystal-field treatment and a method which does not use normal coordinates for the ion and its immediate neighbours. For a regular octahedron the transition probability is shown to be identical with that using the normal mode approach of Van Vleck. In contrast with the corresponding situation in MgO the relaxation time is found to be long, which suggests that the ion is not a strong candidate for the role of a fast-relaxing impurity in ruby. Since, in addition, magnetic dipole transitions are forbidden for a non-Kramers doublet, the problem of detecting ferrous ions in Al₂O₃ is discussed.