Measurement of the 101Ru-Knight shift of superconducting Sr2RuO4 in a parallel magnetic field -: art. no. 167004

Ru-101-Knight shift (K-101) in the spin-triplet superconductor Sr2RuO4 was measured under magnetic fields parallel to the c axis (perpendicular to the RuO2 plane), which is the promising superconducting (SC) d-vector direction in a zero field. We succeeded in measuring K-c in the field range from 200 to 1200 Oe and at temperatures down to 80 mK, using nuclear-quadrupole-resonance spectra. We found that K-101(c) is invariant with respect to the field and temperature on passing through H-c2 and T-c above 200 Oe. This indicates that the spin susceptibility along the c axis does not change in the SC state, at least, in the field greater than 200 Oe. The results imply that the SC d vector is in the RuO2 plane when the magnetic field is applied to the c axis.