Elastic Properties and Magnetic Phase Diagrams of Dense Kondo Compound Ce0.75La0.25B6

TL;DR

This study investigates the elastic and magnetic phase behavior of the dense Kondo compound Ce0.75La0.25B6, revealing an isotropic ordered phase IV with ferro-quadrupole characteristics and detailed phase diagrams under various magnetic field directions.

Contribution

It provides new ultrasonic measurements and phase diagrams for Ce0.75La0.25B6, highlighting the nature of phase IV and its ferro-quadrupole ordering, which was not previously characterized.

Findings

Identification of phase IV with elastic softening c44

Isotropic nature of phase IV across field directions

Ferro-quadrupole moment induced by octupole ordering

Abstract

We have investigated the elastic properties of the cubic dense Kondo compound Ce0.75La0.25B6 by means of ultrasonic measurements. We have obtained magnetic fields vs temperatures (H-T) phase diagrams under magnetic fields along the crystallographic [001], [110] and [111] axes. An ordered phase IV showing the elastic softening of c44 locates in low temperature region between 1.6 and 1.1 K below 0.7 T in all field directions. The phase IV shows an isotropic nature with regard to the field directions, while the antiferro-magnetic phase III shows an anisotropic character. A remarkable softening of c44 and a spontaneous trigonal distortion εyz+εzx+εxy recently reported by Akatsu et al. [J. Phys. Soc. Jpn. 72 (2003) 205] in the phase IV favor a ferro-quadrupole (FQ) moment of Oyz+Ozx+Oxy induced by an octupole ordering.