Magnetic Anisotropy of the Antiferroquadrupole Phase inCe0.50La0.50B6

Abstract

Magnetic phase diagrams for antiferroquadrupole (AFQ) phase II and antiferromagnetic (AFM) phase III in ${\mathrm{C}\mathrm{e}}_{0.50}{\mathrm{L}\mathrm{a}}_{0.50}{\mathrm{B}}_6$ with a ${\Gamma }_8$ ground state have been investigated by ultrasonic measurements. The hybrid magnet (Gama) in the National Institute for Materials Science was employed for high-field measurements up to 30 T and a ${}^3\mathrm{H}\mathrm{e}\mathrm{\text{−}}{}^4\mathrm{H}\mathrm{e}$ dilution refrigerator was used for low-temperature experiments down to 20 mK. The phase boundary from paramagnetic phase I to AFQ phase II under [001] magnetic fields closes at $H_{\mathrm{I}\mathrm{\text{−}}\mathrm{I}\mathrm{I}}\sim 29\mathrm{T}$, while the boundary is still open under fields along the [110] and [111] directions even up to 30 T. This anisotropic character of phase II in fields is consistent with the theoretical calculation based on the $O_{xy}$-type AFQ ordering. We also found that AFM phase III reduces considerably in fields turning from the [001] to [110] and [111] directions.