Magnetic properties of tetragonal Ce_1-xLu_xB ₂C₂ (0 ≤ x ≤ 0.31) compounds

Specific heat, dc- and ac-magnetic susceptibility and magnetization measurements were performed on rare earth intermetallic compounds Ce _1-xLu_xB₂C₂ (0 ≤ x ≤ 0.31) in order to elucidate the magnetic interaction in CeB₂C₂. In the process of the substitution of Ce by Lu in CeB₂C₂, the characteristics of magnetic transition change from a first-order transition to a second-order one. Furthermore, the spin-glass phase appears at Lu concentration x = 0.31. We suppose that the ferromagnetic (FM) and antiferromagnetic (AFM) interactions compete and nearly cancel out each other in CeB₂C₂, and hence that a biquadratic interaction might cause the first-order magnetic transition at T_N. The Lu substitution breaks the competition between AFM and FM interactions and brings forth randomness in interactions acting on each Ce moment. The typical spin-glass behavior of x = 0.31 originates in this random distribution of magnetic interactions.