Particle and crystallite size effects on the modulated structure of multiferroic CaMn7O12

A systematic study of the atomic position modulation in polycrystalline CaMn7O12 with different particle sizes (determined from scanning electron microscopy) and crystallite sizes (determined from X-ray diffraction) is reported. The morphology and phase composition are characterised by scanning electron microscopy, selected area electron diffraction and energy dispersive X-ray spectroscopy. The crystal structure and the atomic position modulation in polycrystalline CaMn7O12 samples are explored with high-resolution synchrotron radiation based powder X-ray diffraction. The modulation vector and the modulation amplitudes observed at T=10 K do not change as a function of particle size, crystallite size and microstrain fluctuations. In addition, we report and discuss the formation of the additional CaMn4O8 nanowire phase during high temperature annealing.

Graphical abstractThe particle size morphology of the multiferroic CaMn7O12 has a weak influence on the atomic position modulation length and the amplitude of the atomic position modulation below T=250 K.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Atomic position modulation occurs in CaMn7O12 with different particle sizes. ► The modulation length is the same for different CaMn7O12 particle sizes. ► Nanowire shaped crystals of CaMn4O8 can be synthesized.