4f Shell of Gd²⁺and Gd³⁺Ions in Sn_1-xGd_xTe - Resonant Photoemission Study

Abstract

Introduction Like many other diluted magnetic semiconductors (DMSs), Sn 1-xGdxTe attracts persistent interest because of its magnetic, optical and electric properties. It is well known tlat the basic properties of DMSs are determined by interaction between magnetic ions and band electrons of the host crystal. Thus, the energy distribution of the d states of a transition metal or the f states of a rare-earth (RE) element with respect to the band structure of the crystal is an important factor which influences its properties.However, the properties of Sn1-xGdxΤe differ markedly from those of many other DMSs. The recently proposed model [1,2] predicts that the f-f coupling proceeds via f -d intra-ion and d-d inter-ion interaction. So, the energy positions of the 4f and 5d shells as well as the number of bound electrons are the crucial elements which characterize the system. For Sn1-x Gdx Te, it is exceptionally difficult to give an experimental 'answer whether the Gd 5d shell is occupied or empty. This is because in Sn1-xGdxTe the high optical absorption on free carriers obscures results of optical experiments.In this paper we present the resonant photoemission spectra which were obtained for the Sn 1 -x GdxΤe crystals with different Gd content (x = 0.02 and 0.08).