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MA: Fachverband Magnetismus

MA 3: Complex Magnetic Oxides

MA 3.6: Vortrag

Montag, 9. März 2026, 10:45–11:00, POT/0112

Polarized Neutron Scattering Studies on SDW Order in Sr_1.5Ca_0.5RuO₄ and Sr₂Ru_0.95Co_0.05O₄ — •Felix Wirth¹, Yvan Sidis², Paul Steffens³, Kevin Jenni¹, Agustinus Agung Nugroho⁴, Karin Schmalzl⁵, Mechthild Enderle³, and Markus Braden¹ — ¹II. Physic. Inst., Univ. Cologne, Germany — ²LLB, CEA Saclay, France — ³ILL, Grenoble, France — ⁴Inst. Teknologi, Bandung, Indonesia — ⁵JCNS Outst. ILL, Grenoble, France

Superconductivity in Sr₂RuO₄ emerges close to magnetic instabilities from Fermi-surface nesting at incommensurate Q^αβ≈(0.3,0.3,L) and Q^γ≈(0.15,0.15,L)[1]. In Sr_1.5Ca_0.5RuO₄ the anisotropic fluctuations at Q^αβ condense into a c-axis polarized spin-density-wave[2]. Polarized inelastic neutron scattering reveals an unusual hierarchy of excitations with enhanced longitudinal modes. In contrast, transverse modes are suppressed, although their energy dependence remains similar to that of the parent compound. Above the SDW transition, longitudinal and transverse contributions show a split response, incompatible with tetragonal symmetry and suggestive of electronic nematicity. Ti⁴⁺ and Mn³⁺ substitution stabilise the same static order at Q^αβ[3]. By contrast, 5% Co doping does not yield the expected ferromagnetic cluster glass but a new magnetic order at Q≈(0.2,0.2,0) with intensity following the Ru⁴⁺ form factor that cannot be attributed to the known nesting vectors in this system. [1] Jenni, K. et al., Phys. Rev. B 103, 104511 (2021), [2] Kunkemöller, S. et al., Phys. Rev. B 89, 045119 (2014), [3] Braden, M. et al., Phys. Rev. Lett. 88, 197002 (2002)

Keywords: ruthenates; spin-orbit-coupling; spin-density-wave; unconventional SC; neutron scattering