Antiferro-quadrupole ordering of Ce [formula omitted]La [formula omitted]B [formula omitted] under high magnetic fields

Abstract

We have investigated the magnetic phase diagrams for antiferro-quadrupole (AFQ) phase II in Ce x La 1 - x B 6 by ultrasonic measurements under high magnetic fields up to 30 T by using the hybrid-magnet (Gama) at National Institute for Materials Science in Tsukuba. Ce 0.50 La 0.50 B 6 reveals that the AFQ phase boundary in applied magnetic fields along the [0 0 1] direction closes at about 29 T and the boundaries in fields along the [1 1 0] and [1 1 1] directions are still open even at 30 T. The AFQ phase transition temperature in Ce 0.75 La 0.25 B 6 shows maximum at about 25 T in H ∥ [ 0 0 1 ] . These experimental results support the idea that the multipole RKKY-type inter-site interaction of the quadrupoles O yz , O zx , O xy and the field-induced octupole T xyz play an important role in the highly anisotropic magnetic phase diagram of phase II of Ce x La 1 - x B 6 in high magnetic fields.