Non-collinear magnetic structures in the Swedenborgite CaBaFe4O7 derived by powder and single-crystal neutron diffraction

We have investigated the magnetic structures of the Swedenborgite compound CaBaFe4O7 using magnetic susceptibility and neutron diffraction experiments on powder (FRM-II, Garching) and single-crystal samples (ILL, Grenoble). Below TN1 = 274 K the system orders in a ferrimagnetic structure with spins along the c axis and an additional antiferromagnetic component within the kagome plane which obviously cannot satisfy all exchange interactions. Competing single-ion anisotropy and exchange interactions lead to a transition into a multi-q conical structure at TN2 = 202 K.