Evolution of 4f heavy fermion state from 5f heavy fermion state in U_1-xCe_xPd₂Al₃ system

Abstract

We report the effect of Ce substitution for U in the heavy-electron antiferromagnetic superconductor UPd₂Al₃. CePd₂Al₃ is an established non-superconducting heavy-electron system which undergoes antiferromagnetic ordering below 2.8 K. Thus studies on U_1-xCe_xPd₂Al₃ system provide a unique opportunity to observe the evolution from a 4f heavy-electron state to a 5f heavy-electron state. We have measured the resistivity and magnetic susceptibility from 1.5 to 300 K and the heat capacity from 2 to 20 K for several U_1-xCe_xPd₂Al₃ samples. Our studies show that the antiferromagnetic (AF) ordering temperature (T_N) of U_1-xCe_xPd₂Al₃ does not decrease monotonically from T_N = 14 K for UPd₂Al₃ to T_N = 2.8 K for CePd₂Al₃ but rather shows a local maximum of 5 K near x = 0.4.