⁵⁹Co-NMR Knight Shift of Aligned Crystals and Polycrystalline Samples of Superconducting Na_0.3CoO₂·1.3H₂O

Magnetic Correlation of NaxCoO2and Successive Phase Transitions of Na0.5CoO2–NMR and Neutron Diffraction Studies–

“…However, it may not be realistic, because we have not observed a tendency of the ferromagnetic correlation in the T dependence of the Knight shift. 22) In any case, it seems to be important for the complete understanding of the superconductivity of Na 0.3 CoO 2 ⋅yH 2 O, to construct a consistent explanation of various kinds of experimental results. [12][13][14][15][16][17][18][19][20][21][22][23] …”

Search for Magnetic Excitation Spectra of NaxCoO2·yD2O –Neutron Scattering–

“…[2][3][4][5][6][7] Experimental studies have also been carried out intensively for both hydrated and non-hydrated systems. Among these studies, NMR measurements on polycrystalline and/or single-crystal samples have been applied to investigate the symmetry of the order parameter [8][9][10][11][12][13] and specific-heat (C) measurements have also been carried out. [14][15][16] Although the possibility of the triplet pairing has been proposed by many authors, the suppression of the spin component of the NMR Knight shift observed below T c by the present authors' group for both field directions within and perpendicular to the CoO 2 planes, indicates that the Cooper pairs are in the singlet state.…”

A critical assessment of the superconducting pairing symmetry in NaxCoO2·yH2O

“…Finally, we would like to comment on the (still controversial) Knight shift experiments [2][3][4][5] . The f -wave states that have emerged from our discussion correspond to Cooper pairs with spins in the xy plane and thus to a constant Knight shift.…”