We have measured 101Ru Knight shift (101K) in the spin triplet superconductor Sr2 RuO4 in various magnetic fields applied parallel and perpendicular to the RuO2 plane to determine the spin direction of the Cooper pair. We measured temperature dependence of 101K in 0.15 and 0.055 T parallel to the RuO2 plane using nuclear-quadrupole-resonance (NQR) technique. We found that 101K is invariant with temperature in both fields on passing through the superconducting (SC) transition temperature. These results indicate that the spin susceptibility parallel to the RuO2 plane does not change in the field greater than 0.055 T, suggesting that the SC d-vector is along the c-axis when the magnetic field greater than 0.055 T is applied along to the RuO2 plane. The possible spin state in magnetic fields is discussed on the basis of the Knight-shift measurements so far.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics