Positron annihilation in Al single crystals from 85 mK to 300K

Abstract

Doppler-broadening and positron lifetime data have been taken for well annealed ultra-pure Al(110) crystals from 85 mK to 300K. The Doppler-broadening data are independent of specimen temperature from 85 mK to 77K, while they show an increase between 77K and 300K consistent with the linear slope observed previously by Hood and Schultz (1979). Over the whole temperature range studied, the Doppler data scale to the static thermal expansion coefficient. The lifetime data also show no obvious dependence on temperature over the entire range studied, although they were statistically limited by the cryostat geometry. These results, which represent the lowest temperatures studied by any positron annihilation technique, provide no evidence for positron localisation at low temperatures in very well annealed single crystals.