Spin fluctuations in the ruthenium oxides RuO2, SrRuO3, CaRuO3, and Sr2RuO4 probed by Ru NMR

作     者：H. Mukuda K. Ishida Y. Kitaoka K. Asayama R. Kanno M. Takano 

作者机构：Core Research for Evolutional Science and Technology (CREST) of the Japan Science and Technology Corporation (JST) Kawaguchi Saitama 332-0012 Japan 

出 版 物：《Physical Review B》 (物理学评论B辑：凝聚态物质与材料物理学)

年 卷 期：1999年第60卷第17期

页      面：12279-12279页

核心收录：

学科分类：07[理学] 0702[理学-物理学] 

摘      要：By means of Ru NMR, magnetic properties in three-dimensional (3D) perovskites SrRuO3 (ferromagnet) and CaRuO3 (exchange enhanced paramagnet) were investigated and compared with those in the two-dimensional (2D) layered perovskite Sr2RuO4 (superconductor), RuO2, and Ru metal (Pauli paramagnet). We found that 4d-spin contributions in the Knight shift and 101(1/T1) of Ru are predominant in SrRuO3, CaRuO3, and Sr2RuO4, but not in nonmagnetic RuO2 and Ru metal. The experimental results that a Stoner factor for CaRuO3 is close to 1 and that a correlation factor estimated from modified-Korringa behavior of Ru−T1 is much less than 1 indicate that CaRuO3 is a nearly ferromagnetic (FM) metal dominated by low-frequency and long-wavelength components of the spin fluctuations (SF). Even though the Stoner factor for Sr2RuO4 also indicates the closeness to the ferromagnetism, the SF in Sr2RuO4 are different from those in CaRuO3. The results combined with the previous 17O NMR study in Sr2RuO4 indicate that the in-plane low-frequency components of SF are exchange enhanced without any significant q dependence due to 2D electronic character (2D nearly FM), while the out-of-plane low-frequency component of SF shows the existence of antiferromagnetic (AFM) SF between layers at low temperature. We propose that this evolution from 3D to 2D nearly FM SF is relevant to the onset of spin-triplet superconductivity in Sr2RuO4. The 2D nearly FM SF in the in-plane 4dxy−pπ band may play a significant role for the stabilization of parallel spin pairing state within the basal plane among various representations of spin-triplet order parameter in Sr2RuO4.