Magnetic, Kondo and non-Fermi-liquid behaviour of U1-xThxPd2Al3

Abstract

Electrical resistivity (T), magnetoresistance MR, magnetization M(T,B) and magnetic susceptibility (T,B) measurements at temperatures down to 25 mK and applied magnetic fields up to 14 T are presented for Th-diluted U1-xThxPd2Al3 alloys. For U-rich alloys, antiferromagnetic order is observed and TN varies slowly with the Th concentration in the region 0 x0.2. From (T) data we calculate a value of the energy gap = 12 K in the spin-wave spectrum. In the U-rich concentration region a coherent Kondo description applies, but for alloys with 0.4 x0.93 a non-Fermi-liquid (NFL) phase prevails. An approximately linear temperature dependence of (T) is observed at low temperatures for about a decade in temperature, but deviation from this dependence occurs at the lowest temperatures. We show that the MR of the NFL alloys may be described in terms of the Coqblin-Schrieffer Hamiltonian, from which values of the single-ion characteristic Kondo temperature TK40 K are calculated. An applied magnetic field is shown to recover Fermi-liquid dynamics in both (T) and (T). We give a description of the low-temperature magnetization M(T,B) in terms of a two-channel Kondo model.