Determination of The Spin Contributed Knight Shift in $N{a}_{0.35}Co{O}_2\cdot 1.3H_{2}O$

Abstract

The spin contributed Knight shift ${}^{59}{K}_s$ of ${}^{59}\mathrm{Co}$ in the triangular lattice superconductor, $\mathrm{N}{\mathrm{a}}_{0.35}\mathrm{Co}{\mathrm{O}}_2\cdot 1.3{\mathrm{H}}_2\mathrm{O}$, has been estimated by NMR experiments in an oriented 2-dimensional powder sample. The Knight shift in the paramagnetic state was estimated by $\hat{I}´\hat{I}½/({\hat{I}}^3{}_{\mathrm{N}}{H}_i)$ vs. $({\hat{I}}^3{}_{\mathrm{N}}{H}_i{)}^{-2}$ plot at various temperatures. A Knight shift vs. magnetic susceptibility diagram revealed that at least 0.3 % for $K_x$ and 0.1 % for $K_y$ are attributed to the spin contribution. Below $T{}_{\mathrm{c}}$, $\hat{I}´\hat{I}½/({\hat{I}}^3{}_{\mathrm{N}}{H}_i)$ vs. $({\hat{I}}^3{}_{\mathrm{N}}{H}_i{)}^{-2}$ plot does not give unique Knight shift because of the diamagnetic effect and/or the other ones. We concluded that the invariant behavior at about 7 T (between $H{}_{c1}$ and $H{}_{c2}$) below $T{}_{\mathrm{c}}$ possibly indicates the nature of the spin-triplet superconductivity.