Crystal growth and characterization of the non-centrosymmetric antiferromagnet Ba2CuGe2O7

It is well known that non-centrosymmetric tetragonal antiferromagnets can host a number of interesting properties, including multiferroicity as well as magnetic skyrmions and Ba2CuGe2O7 is one notable example. The study of all these complex phenomena requires the availability of good crystals. We have carried out the single crystal growth of the helimagnet Ba2CuGe2O7 by the floating zone technique, using different gas atmospheres and pressures and report the optimal growth conditions allowing the synthesis of large crystals. X-ray Laue back reflection has been used to determine the orientations of the as-grown crystals. The morphology and chemical composition of the crystals have been investigated by scanning electron microscopy (SEM) with wavelength dispersive spectrometry (WDS). By using powder X-ray diffraction and energy dispersive spectroscopy (EDS) maps, the composition of the starting polycrystalline rods was checked. Powder X-ray diffraction has been also used to check the composition of the grown single crystals. Furthermore, the excellent quality of the Ba2CuGe2O7 crystals was confirmed by rocking curve measurements, giving a FWHM of ~0.012°. The crystal growth parameters reported in this work allow the synthesis of high quality single crystals suitable for detailed investigations of the complex magnetic phase diagram of this non-centrosymmetric compound.