Hall effect and resistivity measurements on a series of reduced strontium titanate crystals

Abstract

Results of A.C. Hall mobility measurements on three crystals of strontium titanate in different stages of reduction are reported for the temperature range 190°K-500°K. A significant dependence of the magnitude of the mobility on the density of charge carriers was found with the mobility increasing with an increase in the degree of reduction of the crystals. The carrier concentrations were found to be 2.4x10¹�, 4.5x10¹�, and 10¹� carriers/cm³ at the room temperature with increasing degree of reduction. The sample with the lightest reduction has more than two orders of magnitude fewer carriers than any sample on which Hall mobility measurements have previously been reports. The scattering is attributed to polar interactions with the two highest longitudinal optical modes. A plausibility argument is given to show that the mobility variations from sample-to-sample are due to a screening effect in the heavily reduced samples.