Impurity‐related magnetism in the diluted magnetic semiconductors Pb_1−xSn_xTe:Yb

Abstract

The effect of ytterbium impurity on the magnetic and galvanomagnetic properties of new diluted magnetic semiconductors Pb 1-x Sn x Te : Yb was investigated. Impurity-related Curie-Weiss paramagnetism was revealed. The concentration of magnetic centers and the ytterbium impurity-band occupancy as a function of impurity content were determined. The results are discussed assuming the formation of a ytterbiuminduced level under the valence-band top and a variation of the magnetic centers concentration due to changing of the mutual arrangement of the valence band, impurity level and Fermi-level position.

XAFS studies of ytterbium doped lead-telluride

“…The impurity levels of In and Ga are narrow, but that of Yb is rather broad [6]. Further, while the position of pinned E F is independent of In and Ga concentration, it does depend on Yb concentration [7,8]. The most intriguing observation related to all impurities in question is their mixed-valence behaviour in PbTe and related alloys.…”

“…These effects are ascribed to formation of deep defect states in energy spectrum of semiconductor, and are common for group III impurities (In and Ga, in particular). Appearance of impurity states that stabilize E F has been observed also in Yb doped PbTe-based alloys [6][7][8], although it is believed that the mechanism itself is substantially different. Ytterbium modifies electronic spectrum of PbTe in a different way than In and Ga, and its introduction leads to increase of the band gap [9].…”

“…Induced by hybridization between localized 4f and conduction electrons, such a ground state is believed to be responsible for the valence instabilities phenomena observed in many rare-earth based compounds [22]. Another explanation could be the self-compensation effect, proposed in [7,8], which assumes the formation of native acceptors to compensate for the donor effect of doping. Detailed band structure calculations, necessary to resolve these doubts, are in progress.…”

“…It enters the Pb sub-lattice in PbTe by replacing Pb 2+ ion and hence a non-magnetic Yb 2+ state is expected. However, impurity-induced magnetic response related to the presence of magnetically active Yb 3+ ions is observed in a number of PbTe-based alloys [7,8]. This change of the Yb valence state is ascribed to change of the f-shell occupancy, from 14 electrons in Yb 2+ to 13 electrons in Yb 3+ state (4f 13 5d 1 6s 2 ), and is accompanied with charge redistribution in the local surrounding of the impurity atom.…”

Vanadium deep impurity level in diluted magnetic semiconductors Pb1 − x − y Sn x V y Te

“…At present, this DMS group is rather numerous and, in addition to well known conventional Mn containing semiconductors, it includes new representatives of this class, namely, alloys doped with impurities with a variable valence (transition and rare earth elements) [5][6][7][8][9][10][11][12][13]. In con trast to Mn, these impurities are electrically active and, being at metal sublattice sites, they can be in two different charged states (2+ or 3+).…”