Magnetic anisotropy of the antiferroquadrupole phase in Ce _0.50La_0.50B₆

The magnetic anisotropy of antiferroquadrupole (AFQ) phase II and antiferromagnetic (AFM) phase III in Ce_0.50La_0.50B ₆ with a T₈ ground state was investigated by ultrasonic measurements. Gama was employed for measurements up to 30 T and a ³He∓⁴He 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 closed at H _I∓II ∼ 29 t, while under fields along the [110] and [111] directions even up to 30 T , the boundary was still open. The AFM phase III reduced in the fields turning from the [001] to [110] and [111] directions.