Ultrasonic investigation of a local-symmetry-sensitive electronic state and magnetic ordering in NdIr 2 Zn 20

Abstract We previously reported a local-symmetry-sensitive elastic softening, which is not explicable by a crystal field model, in the Kramers doublet system NdCo 2 Zn 20 . We conducted ultrasonic measurements on an isomorphic NdIr 2 Zn 20 compound to investigate whether a molecular-like many-body electronic state proposed in NdCo 2 Zn 20 exists. A magnetically robust elastic softening is detected in the transverse modulus ( C 11 − C 12 )/2, indicating that the softening is not attributed to a magnetic interaction. The softening cannot be reproduced by the crystal field model as well as NdCo 2 Zn 20 . We propose that the molecular-like many-body electronic state appears also in NdIr 2 Zn 20 .