Spin-Hamiltonian parameters and off-center displacements for Rh⁴⁺and Ir⁴⁺ions in rhombohedral BaTiO₃

Abstract

By means of the formulae based on the first-order theory of resonance for a low-spin 2 T 2 term in trigonal symmetry, the spin-Hamiltonian parameters (g factors g // , g ⊥ and hyperfine structure constants A // , A ⊥ ) for Rh 4+ (4d 5 ) and Ir 4+ (5d 5 ) ions in the low-temperature rhombohedral phase of BaTiO 3 are calculated. The calculated results are in reasonable agreement with the experimental values. From the calculations, the off-center displacements of Rh 4+ and Ir 4+ in the oxygen octahedra of BaTiO 3 crystal are acquired. These impurity displacements are much smaller than that of the replaced host ion Ti 4+ . This point is analogous to the displacements of 3d n impurities Fe 3+ and Co 2+ in rhombohedral BaTiO 3 obtained by analyzing their spin-Hamiltonian parameters.

Investigations of the spin-Hamiltonian parameters and tetragonal distortions due to Jahn–Teller effect for the monovalent d9 (Ni+, Pd+, Pt+) impurity centers in AgCl crystals

“…From a number of studies for the hyperfine structure constants A i of md n ions in the same crystal, a trend that the core polarization constant Ä increases with the increase of m is found [33,34,37,40]. The values of Ä for md 9 ions in AgCl crystals obtained from the above calculations are in keeping with the trend and can be regarded as reasonable.…”