NMR shift behavior of the planar Cu(1) site in the underdoped superconductor Hg0.8Re0.2Ba2Ca2Cu3O8+y
63Cu hyperfine shift (Knight-shift) measurements have been carried out on the trilayered superconductor Hg0.8Re0.2Ba2Ca2Cu3O8.3 (Tc=130 K). The temperature dependence of the in-plane Cu(1) Knight shift, for the fourfold oxygen coordinated Cu-O plane, clearly exhibits non-Fermi-liquid behavior. Our data has been placed in the context of the magnetic phase diagram of the nonlinear σ model, which highlights the various regions of magnetic scaling. In this way, evidence is obtained for the presence of a spin pseudogap in this Hg-based compound. This work also supports the suggestion of a nearly antiferromagnetic (AFM) Fermi liquid that dominates the magnetic shift and relaxation behaviors of the 63Cu spins through an isotropic transferred coupling. To test the effects of the AFM enhancements on the Cu(1) spin-lattice relaxation rate, the ratio of the dynamical and static spin susceptibilities derived from relaxation and Knight-shift data is compared to that expected for materials having a transferred coupling of the Cu spins. There is a significant increase in the departure of this ratio from the expected value of 0.53, for an unperturbed transferred coupling scenario, with a drop in temperature below 300 K, suggesting an enhancement in the AFM fluctuations in this temperature region.