ABSTRACT
Contents 3.1 Introduction................................................................................................... 68 3.2 What Does Charge Order Mean? ............................................................... 69
3.2.1 Transition-Metal Oxides ................................................................ 69 3.2.2 What Are the Implications of is CO Picture for
Ferroelectric Polarization? ............................................................. 70 3.2.3 Molecular Compounds ................................................................... 71
3.3 Proposed Examples of Charge Order-Driven Multiferroicity .............. 71 3.3.1 Charge Order in Oxides and Fluorides ........................................ 71
3.3.1.1 Mixed-Valence Manganites ........................................... 72 3.3.1.2 LuFe2O4 ............................................................................. 73 3.3.1.3 Magnetite Fe3O4 ............................................................... 76 3.3.1.4 Fluorides ........................................................................... 81
3.3.2 Charge Order in Organics .............................................................. 81 3.3.2.1 (TMTTF)2X ...................................................................... 81 3.3.2.2 (BEDT-TTF)2X ................................................................. 83 3.3.2.3 Acid-Base Neutral-Ionic Materials ............................... 85
3.4 Conclusions and Outlook ............................................................................ 87 Acknowledgment ..................................................................................................... 89 References ................................................................................................................. 89
3.1 Introduction In this chapter, multiferroics with ferroelectricity originating from charge ordering are explored in depth. A er an examination of the basic concepts, the main focus is on the discussion of materials for which this mechanism has been proposed. I close this chapter with an outlook on considering application prospects of this class of multiferroics.
