Ultrasonic study on PrNi5 in high magnetic fields

We measured the elastic constants of PrNi5 by ultrasonic measurements up to 30T with the hybrid magnet. The magnetic field dependence of C-66 shows a softening at the energy level crossing held between the crystal-field groun d state and the first excited one. The minimum of C-66 in magnetic field de pendence is well reproduced qualitatively in terms of the quadrupolar susce ptibility based on the CEF level scheme taking into account the quadrupolar interaction. (C) 2001 Elsevier Science B.V. All rights reserved.