Submillimeter ESR spectra of Fe²⁺ ions in synthetic and natural beryl crystals

Abstract

© 2017, Pleiades Publishing, Ltd. Electron spin resonance spectra of non-Kramers bivalent iron (Fe 2+ ) ions have been detected in synthetic and natural beryl crystals with an iron impurity. The observed ESR spectra have been attributed to resonance transitions of Fe 2+ ions from the ground (singlet) state to excited (doublet) levels with the splitting Δ = 12.7 cm –1 between the levels. The experimental angular and frequency dependences of the resonance field of the ESR signal have been described by the spin Hamiltonian with the effective spin S = 1. The analysis of the ESR data and optical absorption spectra indicates that the Fe 2+ ions are situated in tetrahedral positions and substitute Be 2+ cations in the beryl structure.