Superhyperfine structure in the EPR spectra of Gd 3+ ions in PbTe

Abstract

X-band EPR measurements have been made from 4.2K up to 300K on single crystals of PbTe doped with a nominal Gd content of 0.04 and 0.1 at.%. A multi-fold splitting of the ( − 1 2 , 1 2 ) fine structure transition was recorded along the [100] and [111] crystallographic directions. The splitting is shown to arise from a superhyperfine interaction between gadolinium ions and the lead isotope 207Pb. The superhyperfine coupling constant is temperature independent within experimental error. At 24K we obtain a Pb = 2.026±0.006G or (1.883 ± 0.005). 10 −4 cm −1. The superhyperfine lines broaden with increasing temperature due to a localized spin-free carrier interaction and cannot be resolved above 80K. These results show that the interactions of the 4f electrons, while somewhat smaller than those of Mn 3d electrons, are not negligible. The superhyperfine structure shows that the Gd ions occupy cation sites. No evidence of interstitial sites was seen.