Ultrasound studies of single crystal thulium in an applied magnetic field

Abstract

The paper reports the first measurements of the single crystal elastic constants of the heavy rare earth metal thulium as a function of temperature and magnetic field. The constants were obtained from ultrasonic velocity measurements over a temperature range of 4.2-296K and in applied magnetic fields of up to 5T. The elastic constants; C11, C33, C44 and C66=(C11-C12)/2 were determined from the ultrasonic velocities. Anomalies in the elastic constants were observed at 58K from the c-axis propagated shear wave measurements and at 55K from the c-axis propagated longitudinal wave measurements. Significant softening of the elastic constants C33 and C44 was observed close to TN. Application of a magnetic field (>2T) along the c-axis direction induced further softening of the material. Electromagnetic acoustic transducers (EMATs) were also employed in addition to conventional piezoelectric quartz transducers. A marked increase in the EMATs acoustic coupling efficiency (generation and detection efficiency) occurred close to TN. © 2001 Elsevier Science B.V. All rights reserved.