A Chiral, Frustrated, Manganese Sulfate Robert J. Cava, Princeton University, DMR 0703095

1. A Chiral, Frustrated, Manganese SulfateRobert J. Cava, Princeton University, DMR 0703095 Inorganic materials with crystal structures that lack a center of inversion are rare, but can exhibit technologically important properties such as ferro-, piezo- and pyroelectricity. Such materials are used, for example, in motion detectors, to move the mirrors in large astronomical telescopes, and as capacitors in random access memory. This past year we found a new class of chiral manganese sulfates without inversion symmetry. The chirality results in a competition between nearest and next nearest neighbor magnetic interactions, and therefore to geometric frustration of the ordering of the magnetic moments at low temperatures. With the combination of chirality, no inversion symmetry and magnetic frustration, PbMn(SO4)2 could be the first of a class of new multiferroic materials with unexpected properties. Competition between nearest and next nearest neighbor (nn and nnn) interactions results in magnetic frustration (shown as “?”) in PbMn(SO4)2, a new inorganic material in the chiral piezoelectric crystal class 422.

2. Magnetism at a Middle School Science Expo Robert J. Cava, Princeton University, DMR 0703095 The middle school years are a time when many students who are at first interested in science lose interest because strong social forces act to push them in more conventional directions, and also because they don’t get to see how interesting a career in science can really be. To help address this issue, the PI and other science and engineering researchers at Princeton hold a “Science Expo” for middle school students every year. In these photos, the PI is seen demonstrating magnetism and superconducting levitation to middle school students at this year’s Expo. The levitation demo (above) surprises them every time.