Der effektive Spin als Modell zur Beschreibung von ESR- Hyperfeinspektren polykristalliner Systeme / The Effective Spin as a Model to describe ESR-Hyperfine Spectra of poly cry stalline Samples

Abstract

Abstract Paramagnetic ions with hyperfine interaction generally have an involved ESR-spectrum. For host lattices of cubic symmetry it will be shown that while going from single crystals to powdered systems the true spin quantum number S can be substituted by an effective spin quantum number S' = ½. Using an isotropic spin Hamilton operator the energy-levels and their eigenfunctions as well as the transition probabilities are calculated explitely. The model is then applied to the ESR-spectrum of manganese-doped polycrystalline CaO. The theoretical spectrum fits the experimental up to 2·10-5 and is in every respect comparable to results of the 3rd order perturbation theory. Above all the model reproduces the true values for the g-factor and the hyperfine coupling constant A as known from single crystal investigations. This is also verified for Mn2+ -ions on cubic sites of MgO and BaO.