Spin Resonance of Transition Metal Ions in Corundum

Abstract

The results of electron spin resonance experiments on a series of transition metal ions in single crystals of corundum are reviewed and interpreted in terms of crystal field theory emphasizing three topics: (1) The strength of the cubic crystal field, (2) the axial field as an indicator of position of the impurity ion, and (3) Jahn-Teller effects in the ground state. The 4d and 5d ions which were examined, i.e., Ru3+, Rh3+, and Ir3+ are found to be strong crystal field cases. In addition, the increased charge of Ni3+(3d7) is shown to be sufficient to drive it to a strong crystal field case (t26e) with S = ½ compared to Co2+ (3d7) which is t25e3 with S = 32. The parameter v which measures the trigonal field potential, was found to be +850 cm−1 in Ru3+ in good agreement with other ions such as Co2+ and V3+ whose cubic field ground states are also orbitally degenerate. In contrast, the determination of v from ESR data on ions with singlet ground states such as Cu3+ and Ni2+ is regarded as less reliable. The Jahn-Teller effect was observed for Pt+ (or Pt3+), Ni3+, and Cu2+.

Theoretical studies of the spin Hamiltonian parameters for the tetragonal Co4+ and Ir4+ centers in SrTiO3

“…λ pσ /S σ ≈ λ s /S s within the same σ component. Obviously, when taking S γ = λ γ = 0 and A = 0, the above formulas return to those in the absence of the ligand contributions [13,14]. ).…”

“…By considering the contributions to the spin Hamiltonian parameters from the orbital reduction (or covalency effect) and spin-orbit coupling interactions, the formulas of the anisotropic g factors and the hyperfine structure constants for the low-spin (S = 1/2) d 5 systems were obtained [13,14]. Later on, improved studies were carried out for trigonally distorted Ru 3+ clusters in garnets [15], by considering the contributions from the anisotropies of the orbital reduction effect (i.e.…”

Orbit–Lattice Interaction Hamiltonian for Iron‐Group Ions in Non‐Cubic Sites

“…The A1,03 structure has been described by Geschwind and Remeika [9]. It exhibits a threefold rotation symmetry about an axis perpendicular to the planes of the oxygen ions.…”

“…The other three ions give a similar contribution but with different values for the angle v, and the bond length b as the triangles are of unequal areas. From the information given in [9] we obt,ain the following set of parameters: cp, = 64.37", bl= 1.84 A, and v, = 46.70°, b, = 1.98 A.…”

“…The first three components of (9) arise from the ions situated on the Z-axis and can of course be obtained from (3)…”