Tuning of magnetic properties and Kondo effect by Cu concentration in Ce(Pd_1-xCu_x)₂Al₃

The electrical resistivity, magnetic susceptibility and specific heat measurements were performed on Ce(Pd_1-xCu_x) ₂Al₃ (x = 0.0-0.7) system to investigate the effects induced by Cu substitution in the heavy fermion compound CePd₂Al ₃. A dramatic evolution of the magnetic properties was observed with the substitution of Pd by Cu: (1) a small amount of Cu (x < 0.1) in CePd ₂Al₃ leads to a rapid decrease of the antiferromagnetic transition temperature T_N; (2) passing through a crossover region without a long-range magnetic order, a ferromagnetic-like state, which reveals an enhanced magnetic susceptibility and a distinct peak in the specific heat curve at low temperatures, occurs around x = 0.1-0.4; (3) by furthering the substitution through a second crossover region, however, the antiferromagnetic ordering is recovered close to x = 0.5-0.7. A decrease tendency of the Kondo temperature T_K with increasing x is derived from the analysis on the specific heat results. It is suggested that the change of the conduction-electron concentration rather than the chemical pressure dominates the evolution of the physical properties in this system.