Elucidating the lack of magnetic order in the heavy-fermion CeCu2Mg

Magnetic, transport, and thermal properties of CeCu2Mg are investigated to elucidate the lack of magnetic order in this heavy-fermion compound with a specific heat value, Cmag/T|T->0?1.2 J/mol K2 and robust effective magnetic moments (?eff?2.46?B). The lack of magnetic order is attributed to magnetic frustration favored by the hexagonal configuration of the Ce sublattice. In fact, the effect of magnetic field on Cmag/T and residual resistivity ?0 does not correspond to that of a Fermi liquid (FL) because a broad anomaly appears at Tmax?1.2 K in Cmag(T)/T, without changing its position up to ?0H=7.5 T. However, the flattening of Cmag/T|T->0 and its magnetic susceptibility ?T->0, together with the T2 dependence of ?(T), reveal a FL behavior for T<=2 K which is also supported by Wilson and Kadowaki-Woods ratios. The unusual coexistence of FL and frustration phenomena can be understood by placing paramagnetic CeCu2Mg in an intermediate section of a frustration-Kondo model. The entropy, Smag, reaches 0.87Rln6 at T?100 K, with a tendency to approach the expected value Smag=Rln6 of the J=5/2 ground state of Ce3+.