Higher-Order Multipolar Effects on Elastic Properties of PrNi₅

Abstract

We have measured the elastic constants of PrNi₅, which has a singlet ground state, Γ₄, as a function of the temperature. The characteristic anomalies have been observed around 23 K in longitudinal C₁₁ and C₃₃. The minimum temperature of C₁₁ and C₃₃ are higher than calculated results only with quadrupolar interactions. Therefore, we have used a magnetoelastic Hamiltonian with coupling of strains and higher-order multipoles in analysis. In C₁₁ and C₃₃, the anomalies can be explained by the strain susceptibilities, which include the multipolar operators O₆⁰ and O_xy⁴.