Low-temperature magnetic properties of RE2Ni21B6 (RE = Er, Tm, Yb and Lu)

Highlights: ► We have investigated the low-temperature magnetic properties of RE2Ni21B6 (RE = Er, Tm, Yb and Lu) crystallizing into a cubic C6Cr23-type structure by measuring magnetic susceptibility, electrical resistivity and specific heat. ► An off-stoichiometric Er compound with a single phase undergoes antiferromagnetic ordering at 0.61 K. ► Tm and Yb compounds have no magnetic ordering down to 50 mK. ► Tm2Ni21B6 shows a quadrupolar glass state, which is novel phenomenon in quadrupolar interaction system. -- Abstract: The low-temperature magnetic properties of RE2Ni21B6 (RE = Er, Tm, Yb and Lu) crystallizing into a cubic C6Cr23-type structure were investigated by measuring magnetic susceptibility, electrical resistivity and specific heat. An off-stoichiometric Er compound with a single phase undergoes antiferromagnetic ordering at 0.61 K. Tm and Yb compounds have no magnetic ordering down to 50 mK. The 4f-electron ground state under a cubic crystalline electric field was deduced by the analysis of the specific heat for each magnetic compound. Tm2Ni21B6 is considered to have the non-Kramers Γ3-doublet ground state with a quadrupolar moment. The quadrupolar moment does not show a long-range order, but probably enters into a glass state owing to the presence of atomic disorder. Our study suggests that atomic disorder degrades the long-range nature of quadrupolar interactions