Crystal field effects on thermal expansion and magnetostriction of TmSb

Abstract

The Schottky‐anomaly of the low temperature specific heat cp is a well known crystal field effect. Recently it has been shown that the splitting of crstal field levels also leads to anomalies in the elastic constants.1) According to the Gruneisen‐relation, the linear thermal expansion coefficient α should show similar anomalies as well. We have measured the thermal expansion along the [100]‐axis of a TmSb single crystal between 1.5 K and 20 K and we observe a negative Schottky‐type anomaly of the order of 2×10−6 which corresponds nicely with the anomaly in cp1). The Gruneisen‐constant γ= (3αΩ/κcp) is a measure of the volume dependence of the crystal field energy level splitting. From our measurements below 10 K we deduce a reduction of the splitting of the lowest energy levels with decreasing volume, being in contrast to point charge model predictions. We obtain (with Ω=33.89 cm3, κ=15×10−13 cgs) γ=−1.4. Above 10 K the measured thermal expansion strongly deviates from the Schottky‐type anomaly, indicating...