High-frequency EPR of Tb3+-doped KPb2Cl5 crystal

Abstract

High-frequency electron paramagnetic resonance (EPR) spectra of the KPb2Cl5:Tb3+ crystal have been investigated. Three types of spectra were observed in the frequency range of 74-200 GHz. The most intensive spectrum with the resolved hyperfine structure corresponded to transitions between sublevels of the 159Tb3+ ground quasi-doublet with the zero-field splitting (ZFS) close to 48 GHz. Experimental results were analyzed by the exchange charge model of the crystal field affecting terbium ions in low-symmetry Pb2+ positions with the chlorine sevenfold coordination and the charge compensating vacancy in the nearest potassium site. The calculated values of g-factors and ZFS were in agreement with the experimental data. The nature of a broad EPR line with ZFS of about 180 GHz and of additional weak EPR lines observed as satellites of the main Tb3+ lines was discussed.