X-ray and Neutron Scattering Studies of Magnetoelectric Multiferroics

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****NON-TECHNICAL ABSTRACT****Magnets are widely used in modern technology, from heavy industrial applications to information storage. Ferroelectrics are similar to magnets, but the role of the magnetic field is played by an electric field (they possess "electric polarization"). They are also widely used in applications, such as actuators and certain types of memory chips. Multiferroics are materials combining magnetism and ferroelectricity. They are of interest to scientists, and hold potential for future applications in electronics and solar energy utilization. In this project, two different classes of multiferroics, one based on Mn and Co, and the other on Bi and Fe, will be studied. Determination of the structural and magnetic properties of the first class of these materials will help understand how to make multiferroics with enhanced functional properties. Studies of the second class of materials will also be useful for that purpose, but in addition are expected to establish design principles for novel prototype electronic devices. As an example, a model diode (a common electronic circuit component) with properties controllable by applied voltage will be designed and investigated. Graduate students and young scientists will drive this project, and high-school students will be involved via a pilot nanotechnology program. This project is expected to show ways towards materials with enhanced properties for future electronic and solar energy devices, and to educate young scientists for this important field.****TECHNICAL ABSTRACT****Multiferroics are materials combining magnetism and ferroelectricity. In addition to their scientific interest, they hold potential for applications in electronics, spintronics, and as photovoltaic devices. This project is devoted to two classes of multiferroics; (1) Ca(3)MM'O(6), where M, M? are 3d metals, are novel multiferroics driven by exchange striction. This mechanism is predicted to give rise to giant coupling between magnetism and ferroelctricity. X-ray and neutron scattering will be used to study structural and magnetic properties of these materials with the goal to determine the microscopic mechanism of multiferroicity, and to elucidate the strategy for synthesis of materials with enhanced functional properties. (2) BiFeO(3) is so far the only multiferroic material utilized in model room-temperature devices. Single crystals of BiFeO(3) have only recently become available. Structural and magnetic properties of these crystals will be studied, and the mechanism of the magnetoelectric coupling investigated. Young specialists in neutron scattering techniques (graduate students and a postdoc) will be trained, helping to meet an important need at the new national neutron scattering facilities. This project is expected to show ways towards materials with enhanced properties for future electronic and solar energy devices, and to educate young scientists for this important field.