Helical scattering signatures of strain and electronic textures in   YbFe2O4 from three-dimensional reciprocal space imaging
  The insulating ternary oxide YbFe$_2$O$_4$ displays an unusual frustration-driven incommensurate charge-ordering (CO) transition, linked to possible ferroelectricity. Based on high-resolution synchrotron data, we report a detailed structural model showing that the CO phase is an incommensurate charge-density wave and cannot be ferroelectric, since the electrical dipole moments are also incommensurately modulated. The change between continuous and "spotty" helices of scattering at the CO transition is attributed to three-dimensional fluctuations of the direction of the ordering wavevector. 
Alexander J. Hearmon, Dharmalingam Prabhakaran, Harriott Nowell,   Federica Fabrizi, Matthias J. Gutmann, Paolo G. Radaelli
cond-mat.str-el