High-field ultrasonic study on PrPtBi with non-Kramers doublet ground state

Abstract

We have measured the elastic constants of PrPtBi single crystal with the cubic MgAgAs-type structure as functions of temperatures and magnetic fields. A remarkable softening of 10% in ( c 11− c 12)/2 was observed below 20 K with decreasing temperatures, while c 44 shows a monotonous increase. These behaviors are attributed to the crystal-field ground state non-Kramers doublet Γ 3. The enormous softening in ( c 11− c 12)/2 prefers a ferro-quadrupolar order of O 2 0 or O 2 2, which brings about a structural phase transition of cubic–tetragonal or cubic-orthorhombic. The magnetic field dependences of c 11 and ( c 11− c 12)/2 up to 25 T were explained qualitatively in terms of a quadrupolar susceptibility assuming the crystal-field level proposed by inelastic neutron scattering. Above 1.8 K the field dependence shows no clear indication of phase transition, which mean paramagnetic phase is stable above 1.8 K up to 25 T .