The magnon dispersion in Ca_{2}RuO_{4} has been determined by inelastic neutron scattering on single crytals containing 1% of Ti. The dispersion is well described by a conventional Heisenberg model suggesting a local moment model with nearest neighbor interaction of J=8  meV. Nearest and next-nearest neighbor interaction as well as interlayer coupling parameters are required to properly describe the entire dispersion. Spin-orbit coupling induces a very large anisotropy gap in the magnetic excitations in apparent contrast with a simple planar magnetic model. Orbital ordering breaking tetragonal symmetry, and strong spin-orbit coupling can thus be identified as important factors in this system.

The magnon dispersion of Ca2RuO4 has been studied by polarized and unpolarized neutron scattering experiments on crystals containing 0, 1 and 10 % of Ti. The entire dispersion of transverse magnons can be well described by a conventional spin-wave model with interaction and anisotropy parameters that agree with density functional theory calculations. Spin-orbit coupling strongly influences the magnetic excitations, which is most visible in large energies of the magnetic zonecenter modes arising from magnetic anisotropy. We find evidence for a low-lying additional mode that exhibits strongest scattering intensity near the antiferromagnetic zone center. This extra signal can be explained by a sizable magnetic moment of 0.11 Bohr magnetons on the apical oxygens parallel to the Ru moment, which is found in the density functional theory calculations. The energy and the signal strength of the additional branch are well described by taking into account this oxygen moment with weak ferromagnetic coupling between Ru and O moments. arXiv:1703.10017v1 [cond-mat.str-el]

SrRuO 3 is a highly interesting material due to its anomalous-metal properties related with ferromagnetism and its relevance as conductive perovskite layer or substrate in heterostructure devices. We have used optical floating zone technique in an infrared image furnace to grow large single crystals of SrRuO 3 with volumes attaining several hundred mm 3 . Crystals obtained for optimized growth parameters exhibit a high ferromagnetic Curie temperature of 165 K and a low-temperature magnetization of 1.6 μ B at a magnetic field of 6 T. The high quality of the crystals is further documented by large residual resistance ratios of 75 and by crystal structure and chemical analyzes. With these crystals the magnetic anisotropy could be determined.

The magnon dispersion of ferromagnetic SrRuO3 was studied by inelastic neutron scattering experiments on single crystals as function of temperature. Even at low temperature the magnon modes exhibit substantial broadening pointing to strong interaction with charge carriers. We find an anomalous temperature dependence of both the magnon gap and the magnon stiffness, which soften upon cooling in the ferromagnetic phase. Both effects trace the temperature dependence of the anomalous Hall effect. We argue that these results show that Weyl points and the anomalous Hall effect can directly influence the spin dynamics in metallic ferromagnets.

Inelastic neutron scattering experiments on Sr2RuO4 determine the spectral weight of the nesting induced magnetic fluctuations across the superconducting transition. There is no observable change at the superconducting transition down to an energy of ∼0.35 meV, which is well below the 2∆ values reported in several tunneling experiments. At this and higher energies magnetic fluctuations clearly persist in the superconducting state. Only at energies below ∼0.3 meV evidence for partial suppression of spectral weight in the superconducting state can be observed. This strongly suggests that the one-dimensional bands with the associated nesting fluctuations do not form the active, highly gapped bands in the superconducting pairing in Sr2RuO4.Sr 2 RuO 4 is one of the best studied unconventional superconductors [1-5] but its pairing symmetry and mechanism still remain a subject of very active debate. There is newly added evidence in favor of the most advocated symmetry of the superconducting order, namely the spintriplet chiral p-wave symmetry, such as the increase in the Knight shift expected in the equal-spin-pairing (ESP) triplet state [6], observation of the surface density of states consistent with the chiral edge state [7], and the magnetization steps corresponding to the half-quantum fluxoids [8]. On the other hand, there are results challenging the p-wave pairing scenario, such as the strong limiting of the in-plane upper critical fields [9], the firstorder superconducting transition [10,11], and the absence of the chiral edge current [12]. At present, there seems no symmetry model which can explain all the experimental facts available. If the most advocated symmetry of the superconducting order is correct, Sr 2 RuO 4 would be a topological superconductor proposed as a promising candidate for quantum computing [13,14].Another prominent feature of Sr 2 RuO 4 is that its normal state is quantitatively well characterized as a quasitwo-dimensional (Q2D) Fermi liquid [2,3]. The Fermi surface consists of three cylindrical sheets [2]: two originate from the d xz and d yz orbitals, called the α and β bands, and retain a quasi-one-dimensional (Q1D) character as well; the other one from the d xy , called the γ band, shows a Q2D character. All three bands disperse weakly along the interlayer c direction [15]. In such a multiband system with distinct orbital symmetries, superconductivity may be strongly orbital dependent [16]. The strong nesting between the Q1D bands results in strongly enhanced spin-density wave (SDW) fluctuations [17][18][19][20][21][22] and even minor chemical substitution leads to static ordering of this SDW instability with the moment along the c direction. Only 2.5% of Ti induce this SDW phase [23,24], and recent muSR experiments and neutron scattering studies show that the same magnetic order occurs upon replacing Sr with isovalent Ca [25,26]. Such spin fluctuations originating from the nesting of the Q1D Fermi surface sheets cannot easily lead to the most likely chiral superconducting state [2]. The...