Rare-earth hexaboride HoB6 shows a ferroquadrupole ordering of Oyz, Ozx and Oxy with ΓQ symmetry at TQ = 6.1 K accompanied by a structural change from cubic to trigonal. In order to examine the order parameter in HoB6, we have performed ultrasonic and thermal expansion measurements. The lattice length along  expands ΔL/L = 2.5 × 10-4 just below TQ, while the length along  shrinks appreciably ΔL/L = -4.5 × 10-3. This result confirms the cubic-trigonal distortion observed by neutron scattering experiments.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Electrical and Electronic Engineering