Anisotropy in the incommensurate spin fluctuations of Sr2RuO4

It has been proposed that Sr2RuO4 exhibits spin-triplet superconductivity mediated by ferromagnetic fluctuations. So far neutron-scattering experiments have failed to detect any clear evidence of ferromagnetic spin fluctuations but, instead, this type of experiments has been successful in confirming the existence of incommensurate spin fluctuations near q=(1/3 1/3 0). For this reason there have been many efforts to associate the contributions of such incommensurate fluctuations to the mechanism of its superconductivity. Our unpolarized inelastic neutron-scattering measurements revealed that these incommensurate spin fluctuations possess c-axis anisotropy with an anisotropic factor chi(c)"/chi(a,b)" of similar to2.8. This result is consistent with theoretical ideas that the incommensurate spin fluctuations with a c-axis anisotropy may be the origin of p-wave superconductivity of this material.