Quadrupolar Response from the Crystal Electric Field Level Scheme Consisting of Only Kramers Doublets in DyNiAl

Abstract

The rare earth compound DyNiAl shows ferromagnetic and antiferromagnetic phase transitions at T C = 30 K and T 1 = 15 K, respectively. Elastic properties of DyNiAl have been investigated by means of ultrasonic spectroscopy. The transverse elastic modulus C 44 shows an elastic softening below 60 K and exhibits a bend at T C. The softening continues down to T 1 and an elastic hardening is observed below T 1. The softening above T C is well reproduced by Curie-Weiss-type equation including a quadrupole interaction. A quadrupole-quadrupole coupling constant obtained from C 44 is negative, suggesting an antiferroquadrupolar-type interaction between quadrupoles O yz or O zx .