Evolution of transport and low-energy spin fluctuations in YbXCu₄ (X = Au and Pd) with the application of magnetic field

We have investigated evolution of transport and low-energy spin fluctuation properties of heavy Fermi liquid compounds YbAuCu₄ and YbPdCu₄ with the application of magnetic field. YbAuCu₄ is found to be driven from the originally antiferromagnetically (AFM) ordered ground state (T_N ∼ 0.8 K) to a nonmagnetic Fermi liquid (FL) one through the field-tuned quantum critical point (QCP) at H_cr ≃ 13 kOe (T_N → 0). In the vicinity of H_cr, the electrical resistivity measurement provides evidence for the increase in the inelastic scattering of heavy electrons, and the ⁶³ Cu spin-lattice relaxation rate measurement exhibits the occurrence of AFM spin order instability. Whilst, YbPdCu₄ transforms from the originally ferromagnetically (FM) ordered ground state (T_C ∼ 0.6 K) into the nonmagnetic FL state, without any intermediate NFL phenomena. This result indicates that the competition of the field-stabilized FM correlation and field-destabilized AFM correlation plays an important role on the field-driven quantum critical phenomena.