Regensburg 2025 – scientific programme

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MA: Fachverband Magnetismus

MA 31: Poster II

MA 31.2: Poster

Wednesday, March 19, 2025, 17:00–19:30, P1

Polarized inelastic neutron scattering studies on magnetic excitations in the SDW ordered state of qasi 2D Sr_1.5Ca_0.5RuO₄ — •Felix Wirth¹, Yvan Sidis², Paul Steffens³, and Markus Braden¹ — ¹II. Physic. Inst., Univ. Cologne, Germany — ²LLB, CEA Saclay, France — ³ILL, Grenoble, France

Superconductivity in the layered ruthenate Sr₂RuO₄ emerges near competing magnetic fluctuations. The different d orbitals of Ru⁴⁺ give rise to the multi-band structure causing spin fluctuations with incommensurate (IC) propagation vector due to fermi-surface nesting. These antiferromagnetic fluctuations are anisotropic and condensate to static spin density wave (SDW) order with moments oriented along c when Sr is replaced by 25 % of isovalent Ca. Only a few realizations of SDW in metals have been studied concerning their magnetic excitations. Cr exhibits strong anisotropy as well as new excitations like the Fincher-Buke mode, while the spin-orbit coupling (SOC) is much smaller than in Sr_1.5Ca_0.5RuO₄. This renders it an ideal material for studying SDW state in the presence of SOC. Our contribution presents inelastic polarized neutron scattering measurements on the IC SDW signal. With scattering vector within the layer, we discriminated between transversal and longitudinal excitations. We see longitudinal or c-polarized spectral weight enhancement at low energy. At the same time, the transversal or in-plane response is suppressed over a broad temperature range and exhibits single-relaxor behavior like in the pure compound. SOC induces strong anisotropy in the magnetic fluctuations in Sr_1.5Ca_0.5RuO₄.

Keywords: Spin Density Wave; Spin-Obit Coupling; Polarized Neutron Scattering; Ruthenates