Elastic Constants in the Antiferro-Quadrupole Ordered State

Abstract

The elastic constants C_Γ in the antiferro-quadrupole (AFQ) ordered state with two sublattices were studied by a mean field approximation. The temperature dependence of C_Γ below the AFQ ordering temperature T_Q in the zero magnetic field depends on the type of the AFQ order parameter and the applied strain. They are in principle the same as those of the parallel and perpendicular magnetic susceptibilities in the antiferromagnetic state. The magnetic field dependences of C_Γ also show the characteristic behaviors depending on the type of the AFQ ordering and the applied strain. We discuss C_Γ of CeB₆ which shows the AFQ ordering at T_Q=3.3, K by comparing the calculated results.