Anisotropy in magnetic phase diagram of TbB₂C₂ with field-induced antiferroquadrupolar order

The field-direction dependence of the magnetic phase diagram was examined for the compound TbB₂C₂ with field-induced antiferroquadrupolar-ordering, in order to elucidate anisotropy in the magnetic phase diagrams for H ∥ [100] and H ∥ [110]. The field-induced phase for H ∥ [100] (phase III), which is a phase in which antiferromagnetic (AFM) and antiferroquadrupolar (AFQ) orders coexist, seems to change continuously into the other (AFQ + AFM) phase (phase II′) for H ∥ [110]. The result implies that both III and II′ phases have some similarity in their magnetic structures or they are possibly the same as each other.