High-Field Magnetization of CeRU2Al10

Magnetization measurements of Ce x La 1- x Ru 2 Al 10 ( x = 1, 0.75) under high magnetic fields were performed in order to obtain information on the long-range order (LRO) in CeRu 2 Al 10 . We successfully obtained the magnetic phase diagram of these two compounds for the applied magnetic field along the a -axis, which is the magnetization easy axis, and found that the LRO for x = 1 disappears at ∼50 T, which is the critical field for the paramagnetic phase. For x = 0.75, the critical magnetic field decreases to ∼37 T upon La substitution. The magnetic phase diagram and magnetization curve are qualitatively consistent with Hanzawa's recent mean field calculation results obtained by assuming the dimer of Ce ions, whose crystalline electric-field ground state has a large magnetic anisotropy. These results support the singlet pair formation scenario recently proposed by Tanida et al. [J. Phys. Soc. Jpn. 79 (2010) 043708] We also pointed out the possibility of the appearance of a field-induced magnetic phase ...