Regensburg 2010 – scientific programme

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MA: Fachverband Magnetismus

MA 33: Poster II

MA 33.47: Poster

Friday, March 26, 2010, 11:00–14:00, Poster B1

Conical magnetic structure in the kagome-related Swedenborgite CaBaFe4O7 — •Navid Qureshi, Martin Valldor, and Markus Braden — II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln

Recently, a new type of metal oxides with magnetic kagome sub-structure was discovered, being closely related to the Swedenborgite mineral. Valldor et al. were able to synthesise the structural homologue YBaCo4O7 [1] and the spin-spin correlation proved to be strong and antiferromagnetic, which immediately raised the question about geometrical frustration in the magnetic Co substructure. Late last year, a new Swedenborgite homologue only containing Fe has been discovered: CaBaFe4O7 [2]. Macroscopic measurements showed that this compound undergoes a magnetic transition at 270 K into a ferrimagnetic state and a spin reorientation at 200 K into a multi-k structure, which could be confirmed by our neutron single crystal diffraction experiment. The temperature dependent investigation of the magnetic reflections (h k 0), (0 0 l) and (h+d k l) yielded first conclusions concerning the magnetic structures. At Tc the Fe magnetic moments order along the c axis with a small component within the a-b plane which does not break translation symmetry. Rietveld analysis shows that the c-component of the moments alternate between the Fe layers. Below 200 K the a-b component becomes modulated by k=(1/3 0 0) resulting in an interesting conical magnetic structure.

[1] Valldor et al., Solid State Sci. 2002, 4, 923 [2] Raveau et al., Chem. Mater. 2008, 20, 6295