Slight Y-doping induced ferromagnetism in YbCuAs₂

Single crystals of Yb_1-xY_xCuAs₂ (0.0 ≤ x ≤ 1.0), that crystallize into the tetragonal HfCuSi₂-type structure, have been grown by a high-temperature ternary melt technique. Physical properties were investigated by measuring magnetization, electrical resistivity, and specific heat. For x = 0, magnetic susceptibility measurement shows an antiferromagnetic (AFM) ordering below 3.7 K and electrical resistivity measurement reveals a typical Kondo lattice behavior. A small Y substitution for Yb in YbCuAs₂ lowers the AFM ordering temperature. Interestingly, a ferromagnetic (FM) state is induced between x = 0.2 and 0.6. At further elevated Y concentrations (0.8 ≤ x ≤ 1.0) a paramagnetic state is realized. In this talk, we will present the evolution of the magnetic ground state under various Y concentrations. We suggest that the transition from AFM to FM state arises from the formation of a ferromagnetic cluster in conjunction with crystallographic disorder accompanied by Y substitution.