Paramagnetic-Resonance Absorption of Ions with Spin 5/2: Mn++ in Calcite

Abstract

The theory of the paramagnetic‐resonance absorption of ions with S = S=52 in crystalline fields of trigonal symmetry is presented. The case of manganous ions in calcite (CaCO3) is taken as an example. It is shown that the splitting of the fine‐structure satellites into doublets first reported by Hurd, Sachs, and Hershberger [Phys. Rev. 93, 373 (1954)] can be accounted for by assuming that the manganous ions can occupy the two nonequivalent Ca++ sites at random. The maximum splitting was measured at X band and K band and found to be 19.3±0.5 gauss. The value computed from the theory, assuming an ionic model, is 23.8 gauss. In addition, five pairs of weak lines were found, each pair occurring midway between adjacent hyperfine groups. The origin of these lines is uncertain. The applicability of the present theory to Al2O3:Fe, a zero‐field maser material, and to the photosensitive Fe+++ center in CdS is pointed out