μ+knight shifts and trapping in diluteSbSn alloys

Abstract

Giant μ+ Knight shifts Kμ have been studied previously in Sb andSbBi alloys. Here we report μ+SR measurements on Sb with dilute heterovalent Sn impurities. A dramatic concentration dependence is observed: Kμ is increased slightly (relative to the value in pure Sb) by Sn concentrations of 60K. The amplitude of the low Kμ signal grows with increasing T at the expense of the amplitude of the high-Kμ, low-T signal, suggesting that the μ+ migrates through the host lattice to trap sites. A simple trapping model correctly describes the observed T-dependence of the amplitudes, phases and relaxation rates of the two signals. We conclude that the low-T Knight shift is truly characteristic of the host band structure while the much lower Kμ value of the high-T site is characteristic of a specific trap site, presumably adjacent to a Sn impurity.