Nuclear quadrupole coupling and EPR parameters of Mn2+ in Na2ZnCl4 · 3H2O and in various other host lattices

Abstract

AbstractFrom the “forbidden” (Δm1 ≠ 0) transitions in the EPR spectrum of Mn2+ in Na2ZnCl4 · 3H2O the quadrupole coupling constant P = 3e2qQ/(4 I(2I‐1)) is deduced by solving the complete energy matrix of Mn2+ (S = 5/2, I = 5/2) as well as by perturbation theory up to terms in fourth order; P = (1.0 ± 0.5) MHz is found. The positions of the “forbidden” transitions within the EPR spectrum are mainly due to terms involving the hyperfine constant A and the crystal field splitting constant D. The center of the transitions Ms = −1/2, m1 = ± 1/2 → M's = ∓1/2, m'1 = ‡1/2 is shifted as a function of D. For |D| > 150 Oe g‐values of Mn2+, deduced from the center of these hyperfine transitions, are not correct. The contribution of the fourth order perturbation terms of ASI to the positions of the “forbidden” transitions within the spectrum is not essential. Correlations between P and D, and between P and the anisotropic part (A∥‐A⊥)/|A‖| of the hyperfine coupling constant, respectively, are discussed. It is shown that P and (A∥‐A⊥/|A∥|of Mn2+ depend linearly on the axial component of the crystal fie.d the axial crystal field parameter D is found to be due to the axial crystal field and to the covalence of the Mn2+ bond.