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Regensburg 2019 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 17: Poster Session: Correlated Electrons 1

TT 17.37: Poster

Monday, April 1, 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 Braden11II. Physikalisches Institut, Universität zu Köln, Deutschland — 2Laboratoire Léon Brillouin, CEA, Saclay

The Ruthenate system Ca2−xSrxRuO4 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 dxy orbital and an occupation of the dxz,yz orbitals by the remaining two electrons. However, this orbital occupation only roughly corresponds to the measured ordered moment of 1.3 µB. 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 Ca1.5Sr0.5RuO4 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 TN = 110 K indicating a 3D correlation of the magnetic order.

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