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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 8: Multiferroics and Magnetoelectric Coupling I (joint session MA/KFM)

KFM 8.6: Vortrag

Mittwoch, 18. März 2020, 11:00–11:15, HSZ 401

Revealing the antiferromagnetic spin density in multiferroic Ba₂CoGe₂O₇ — •Henrik Thoma¹, Vladimir Hutanu², Manuel Angst³, Georg Roth⁴, and Thomas Brückel³ — ¹Jülich Centre for Neutron Science JCNS at MLZ, 85747 Garching, Germany — ²Institute of Crystallography, RWTH Aachen and Jülich Centre for Neutron Science JCNS at MLZ, 85747 Garching, Germany — ³Jülich Centre for Neutron Science JCNS and Peter Grünberg Institute PGI, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany — ⁴Institute of Crystallography, RWTH Aachen, 52056 Aachen, Germany

Polarized neutron diffraction (PND) is a powerful method which provides direct access to the scattering contribution from nuclear-magnetic interference and thus reveals the phase difference between the nuclear and magnetic structure. Generally limited to the case of centrosymmetric structures in the paramagnetic state, this information can be used to construct spin density maps and local susceptibility tensors in order to study the anisotropy between magnetic interactions. Introducing an advanced approach in the maximum-entropy method for a model-free reconstruction of spin densities, these limitations were overcome. PND was applied to study the magnetic anisotropy in the non-centrosymmetric unconventional multiferroic Ba₂CoGe₂O₇. Using the new approach, a detailed 3D spin density distribution in the unit cell was obtained for the first time both in the paramagnetic and antiferromagnetic ground state. The obtained results clearly show the 2D character of the magnetic interactions in the title compound and are compared to the results of regular magnetic structure refinement.