Quantum spin system in f-electron compounds -YbAl₃C₃ and its related compounds-

A quantum spin system is seldom observed in f-electron compounds, probably because their magnetic ground states are represented by the total angular momentum J which is usually much larger than 1/2. One of exceptional cases is Yb₄As₃, which behaves as a one-dimensional S=1/2 Heisenberg antiferromagnet. Recently, a new candidate of the quantum spin system YbAl₃C₃ with the ScAl₃C₃ type crystal structure has been found, where a magnetic dimer ground state is realized at low temperatures. To investigate the mechanism of the magnetic dimer formation in YbAl₃C₃, we have prepared several rare earth compounds RAl₃C₃with the ScAl₃C₃ type crystal structure and compared their physical properties with those of YbAl₃C₃.