S. Kunkemoller1, A. A. Nugroho2, Y. Sidis3 and M. Braden1
1II. Physikalisches Institut, Universitat zu K ¨ oln, Z ¨ ulpicher Straße 77, D-50937 K ¨ oln, Germany ¨
2Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jalan Ganesha 10, 40132 Bandung, Indonesia
3Laboratoire Leon Brillouin, CEA/CNRS, F-91191 Gif-sur-Yvette Cedex, France ´ (Received 6 December 2013; published 14 January 2014)
Physical Review B 89, 045119 (2014)
The spin-density-wave ordering in Ca0.5Sr1.5RuO4 was studied by polarized and unpolarized neutron diffraction experiments. Below about 20 K Ca0.5Sr1.5RuO4 exhibits quasistatic correlations at exactly the incommensurate wave vector at which pure Sr2RuO4 shows strong inelastic fluctuations driven by Fermi-surface nesting. The magnetic character of the signal and the orientation of the ordered moments along the c direction can be ascertained by neutron polarization analysis. The magnetic ordering at low temperature is very similar to that found upon minor Ti substitution of Sr2RuO4, underlining that this incommensurate spin density wave is the dominant magnetic instability of the unconventional superconductor Sr2RuO4.