Dresden 2014 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 42: Magnetic Materials III

MA 42.5: Vortrag

Donnerstag, 3. April 2014, 16:00–16:15, HSZ 04

Long range incommensurable spin ordering in a swedenborgite compound — •Johannes Reim¹, Martin Valldor², and Werner Schweika¹ — ¹Jülich Centre for Neutron Science JCNS-2 and Peter Grünberg Institut PGI-4, Forschungszentrum Jülich, Jülich, Germany — ²II. Max-Planck-Institut für Chemische Physik fester Stoffe, Dresden, Germany

The new swedenborgite compound family (P6₃mc) displays similarly to the pyrochlores a highly frustrated network of tetrahedral coordinated magnetic ions. However, its broken inversion symmetry raises further the complexity of ordering due to non-vanashing DM interactions. Recently investigated materials of this family show various signs for unusual geometric frustration. In compounds with magnetic Co and Fe ions, where single crystals are available like CaBaCo₂Fe₂O₇, we observed an antiferromagnetic ordering below T_N≈160 K, which, however, turned out to be rather complex. Diffuse neutron scattering at DNS (FRM II) has revealed a magnetic order in a three times larger supercell. A particular intriguing result was the chiral interference observed apparently as an asymmetry of the magnetic Bragg intensities.
Further powder diffraction experiments at POWGEN (SNS) with higher resolution evidenced additional satellite peaks close to the main magnetic peaks, with a propagation vector τ=0.016 Å⁻¹ corresponding to a long periodicity of about 400 Å.