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TT: Fachverband Tiefe Temperaturen

TT 17: Poster Session: Correlated Electrons 1

TT 17.37: Poster

Montag, 1. April 2019, 15:00–18:30, Poster D

The contribution of magnetic oxygen and magnetic correlations in the Mott insulator Ca₂RuO₄ — •Kevin Jenni¹, Stefan Kunkemöller¹, Yvan Sidis², and Markus Braden¹ — ¹II. Physikalisches Institut, Universität zu Köln, Deutschland — ²Laboratoire Léon Brillouin, CEA, Saclay

The Ruthenate system Ca_2−xSr_xRuO₄ exhibits a variety of interesting phenomena reaching from unconventional superconductivity in Sr₂RuO₄ to a Mott-insulating state in Ca₂RuO₄. Concerning the latter, the theoretical understanding of the Mott transition in this multi-band system with four electrons per Ru site is under debate to this day. There is consensus that the orbital ordering appearing in this strongly correlated material leads to an enhanced or fully occupation of the d_xy orbital and an occupation of the d_xz,yz orbitals by the remaining two electrons. However, this orbital occupation only roughly corresponds to the measured ordered moment of 1.3 µ_B. To yield better insight in the exact distribution of the ordered magnetic moment over the orbitals we analyzed the magnetic form factor in detail. Our elastic neutron scattering study of an untwinned single crystal in combination with polarization analysis exposes the contribution of the apical oxygen to the ordered magnetic moment, similar to the results in Ca_1.5Sr_0.5RuO₄ where the p-d hybridization causes a sizeable amount of magnetic moment residing on the oxygen. Additionally we present the analysis of magnetic correlations and their dimensionality. The magnetic Bragg peak intensity vanishes rather fast above T_N = 110 K indicating a 3D correlation of the magnetic order.