Spin susceptibility in superconductingYBa2Cu3O7fromCu63Knight shift

Abstract

The ${}_{}{}^{63}{}_{}{}^{}\mathrm{Cu}$ Knight shift in ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_7$ has been measured at both Cu(1) (chain) and Cu(2) (plane) sites, using a uniaxially aligned powder. The isotropic part of the spin Knight shift ($K_s$) was found to be positive for both sites, suggesting large transferred hyperfine fields from oxygen p states. The Knight shifts at both sites show significant change below $T_c$, indicating important roles of both the planes and chains in the superconductivity. Despite the uncertainty in the diamagnetic screening, the axial part of $K_s$ at Cu(2) sites is found to show linear-T behavior at low temperatures.