Quadrupolar Response and Rotational Invariance of Singlet Ground State System; HoVO₄

Abstract

Elastic properties of holmium vanadate, HoVO 4 , have been investigated by means of an ultrasonic method. The elastic constants C 11 , ( C 11 - C 12 )/2 and C 66 exhibited remarkable softenings possessing minimum points around 13.5 K, which are characterized by the quadrupolar responses for the singlet ground state system. Appling magnetic fields along the tetragonal c -axis, the elastic anomalies of ( C 11 - C 12 )/2 and C 66 associated with the level crossing of the singlet ground state at about 10.6 T have been found. The rotational invariance effect has been revealed in the C 44 mode under magnetic fields along c -axis.