Low Symmetry Crystal Field Splitting of ⁴T₁ States of Co²⁺ in CuGaS₂

Abstract

The optical absorption spectra of CuGaS 2 :Co are observed at a room temperature and at 2 K in near infrared and visible regions, the low energy side of the absorption edge (20,000 cm -1 ) of the host crystal. The spectra show a broad band in the vicinity of 7,000 cm -1 and a fine structured band around 13,000 cm -1 . The fine structure of the upper band is analyzed by calculating the energy level scheme taking account of a low symmetry ( D 2 d ) crystal field and the spin-orbit coupling in addition to the cubic ( T d ) field. A reasonable choice of the parameters reproduces the observed spectra fairly well and give the g -shifts and zero field splitting constant which agree quite well with the observed values by Kaufmann et al. (Solid State Commun. 15 (1974) 1881).