The coexistence of magnetic ordering and ferroelectricity,known as multiferroics,has drawn a lot of research effort.Depending on the origin of ferroelectricity,multiferroic materials can be classified into different groups.In this paper,we review recent progress in the field of multiferroics induced by different forms of charge ordering.In addition to a general description of charge order and electronic ferroelectricity,we focus on two specific systems:(1) charge order with frustration in RFe2O4(R=Lu,Yb) system;(2) charge ordered perovskite manganites of the type(R1xCax)MnO 3(R=La,Pr).The charge ordering can be tuned by external electric fields,which results in pronounced magnetoelectric effects and strong dielectric tunability.Other materials and possible candidates with charge order induced multiferroics are also briefly summarized.
