Temperature dependence of carrier-nucleus interactions in semimetallic antimony

Previous Sb-121 relaxation measurements in pure antimony metal show a typic al metallic (Korringa) temperature dependence of the nuclear spin-lattice r elaxation rate at low temperatures, followed by a quadratic temperature dep endence above the Debye temperature. This deviation was previously ascribed to the onset of significant phonon-induced relaxation. In this paper, nucl ear spin-lattice relaxation of both Sb-121 and Sb-123 has been investigated over the temperature range 4-435K using pulsed NQR. These two-isotope data allow for a decisive investigation of the importance of quadrupolar relaxa tion mechanisms over a wide temperature range. Our results show that the ra tio of quadrupole to magnetic transition rates changes from a fraction of a percent to order 1% as the temperature is increased through the Debye temp erature, but this change cannot account for the observed deviation from Kor ringa behaviour. The relaxation data, therefore, suggest a significant temp erature dependence of the carrier properties of antimony. Possible explanat ions for the high-temperature behaviour are discussed in terms of the elect ronic structure of antimony. (C) 2000 Elsevier Science B.V. All rights rese rved.