Evolution of normal-state magnetic fluctuations by Ca and Ti substitutions in Sr2RuO4:: 87Sr-NMR study -: art. no. 214412

We report magnetic properties of (Sr2-xCax)RuO4 and Sr-2(Ru1-yTiy)O-4 investigated by Sr-87 nuclear magnetic resonance NMR to shed light on the effect of multibands on the magnetic character in the spin-triplet superconductor Sr2RuO4. In (Sr2-xCax)RuO4, the Knight shift (K-87) at 1.4 K increases progressively up to x=1.5. The Korringa relation between K and the nuclear-spin-lattice-relaxation rate 1/T-1 divided by temperature (1/T1T) reveals that ferromagnetic (FM) fluctuations develop with the increasing Ca content. In Sr-2(Ru1-yTiy)O-4, in contrast, it is found that anisotropic incommensurate (IC) antiferromagnetic (AFM) fluctuations present in the y=0 material are enhanced by a small amount of Ti substitution: 1/T1T is enhanced with the magnetic field parallel to the RuO2 plane, whereas it is unchanged for the field along the c axis in 3% Ti-doped Sr2RuO4. We demonstrate that Ca substitution affects the two-dimensional (2D) gamma band by enhancing the FM fluctuations, and that the Ti-substitution affects the 1D alpha and beta bands by enhancing the IC-AFM fluctuations. The unique substitution effects would relate with the multiband character in Sr2RuO4.