Theory of multiferroic materials and their heterostructures

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Materials with coupled electric, magnetic, and elastic properties are of great interest to science and technology, because they are able to connect effects that are usually independent of each other. Multiferroic materials are prime candidates for showing these couplings. They have coexisting ferroic (or antiferroic) orders such as ferromagnetism, ferroelectricity, and ferroelasticity. When these orders are coupled, an electric field is able to control magnetic and structural phases, and mechanical stress is able to affect magnetism and ferroelectricity. The "dream material" in multiferroic physics is a ferromagnet-ferroelectric at room temperature. Such a material does not yet exist, but its synthesis could enable the development of a new class of electronic devices, such as magnetic memories with electric-write and magnetic-read operations that have the speed and energy-efficiency required to integrate the hard drive with the processor in personal computers. This would revolutionize computer hardware with major impact in current technology. My research program is the first step towards transforming known materials into this "dream material". I am developing the theoretical tools to understand the coupling between different orders in multiferroic materials, and to determine their phase diagram as a function of strain and external electric and magnetic fields. My goal is to propose modifications to known materials and to combine different ones in heterostructures so that they are transformed into a state that is closer to the dream ferromagnet-ferroelectric at room temperature.