DMREF: Search for Magneto-electronic Behavior in Complex Fluoride-based Interfaces

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NON-TECHNICAL SUMMARYThere is significant interest in multifunctional materials, such as multiferroics, which combine simultaneous responses to electric, magnetic, and strain fields. Potential applications include new power efficient electronics and ultra-fast information processing devices. To date, most of the multiferroics that have been studied are complex oxide materials. Despite the exciting fundamental discoveries emanating from research on these materials, their multiferroic performance is not yet adequate for use in practical applications. In this project, the investigators propose to systematically study complex fluoride materials as alternatives to complex oxides because the different physical origins of the multiferroic effects in fluorides can potentially enhance the multiferroic response. The research will consist of a synergistic collaboration between computational and experimental researchers. The computational effort will predict the most likely materials to have desired multiferroic properties, and the experimental portion will synthesize and characterize the suggested materials. In turn, the experimental results will be used to improve the accuracy of the calculations, which ultimately will lead to an efficient optimization of the design of the new materials.TECHNICAL SUMMARYThe goal of this project is to search for and understand the properties of fluoride-based magnetoelectric multiferroic materials. Recent theoretical work suggests that in ABF3 compounds, ferroelectricity results from the A-site ionic displacement, and not from the magnetic B-site, which should enhance the magnetic response. This is in contrast to many complex oxides, where it is the magnetic ion site that undergoes the displacement, which at the same time tends to weaken the magnetic properties. Moreover, the fluorine ions can lead to large canting in antiferromagnetic structures, again enhancing the magnetoelectric response. There are also indications that interfaces between complex fluorides and other fluorides or oxides should have large and novel magnetoelectric responses. In this project, the properties of complex fluoride compounds and heterostructures will be studied using ab-initio computational techniques, and the most promising materials will be synthesized via molecular beam epitaxy and characterized using scanning probe and optical techniques. The experimental results will be used to improve the approximations used in the computational models. This joint theoretical-experimental effort will efficiently identify the most likely interfaces and materials which have desirable magnetoelectric properties, thus significantly reducing the time necessary for evaluating the vast number of possible material candidates.