Magnetic and structural properties of the chiral spin liquid system YBaCo3FeO7

We propose to study magnetic and structural properties of YBaCo3FeO7, which shows a novel chiral spin liquid ground state as recently reported. The compound is a layered Kagome system, in which the anti-ferromagnetic superexchange leads to highly frustrated spin correlations and the broken spatial inversion symmetry causes an antisymmetric exchange from which a chiral short-range order state emerges. There are important unresolved magnetic features in this system, needed for the understanding of the magnetic correlations. They are related to the precise crystal structure as well as to the full 3D diffuse scattering and the 3D spin correlations. In x-ray powder diffraction at RT, YBaCo3FeO7 appears to be hexagonal, in contrast to similar compounds, showing lower, e.g. orthorhombic or trigonal symmetry. The structure will be studied with neutron powder diffraction over a wide range of temperatures, being sensitive to the Co and Fe mixing on the magnetic sites. Upon lowering temperature, hyperfine fields, first on Kagome sites below 700 K, next on trigonal sites below 50 K, have been observed by Mössbauer spectroscopy. Accordingly, the spin correlations should change from 2D Kagome-type towards 1D quasi long-range order. The existing data are confined to only 2D planar cuts in reciprocal space and do not yet provide a complete picture of the actual 3D spin correlations.
We have large and high-quality samples available and ask for 2 days of beamtime at the instrument WISH.