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Strong Magnetoelectric Coupling in Multiferroic Bismuth Ferrite Venkatraman Gopalan, Pennsylvania State University, DMR 0512165.
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Strong Magnetoelectric Coupling in Multiferroic Bismuth FerriteVenkatraman Gopalan, Pennsylvania State University,DMR 0512165
Multiferroic materials that are both ferroelectric and magnetic are of keen interest because of the possibility of controlling magnetism with electric fields, which could revolutionize magnetic storage, and spintronics technologies. Bismuth ferrite (BiFeO3) is a highly studied multiferroic with a large room temperature ferroelectric polarization (~90 mC/cm2) and antiferromagnetism. While ferro-electricity is easy to probe, not many techniques other than neutron diffraction can probe the anti-ferromagnetism. We find a set of strong 2-phonon Raman peaks (top figure) that have not been reported before, which couple strongly to the anti-ferromagnetism. The 2E(LO8) mode in particular disappears above TN ~380 C (bottom figure). Further, an additional transition appears to be present around 150-200 C, which has also not been reported before. These results are also supported by optical second harmonic generation studies, and raise the possibility of a strong magnetoelectric coupling.
Raman shift (1/cm)
Women in Science and Engineering (WISE)E. Vlahos, L. Tian,V. Gopalan, Pennsylvania State University,DMR 0512165
The WISE program attracts bright young women from across the country who are interested in a science career to a summer camp at Penn State every year. Graduate students in PI group, L. Tian (top right, now a scientist at Corning Research Labs), and E. Vlahos (bottom right corner, NSF graduate fellow), conducted a workshop on the “Science and Technology of light” in August, 2006. They demonstrated how the Internet works by building an optical voice link over an optical fiber. Using the link, which is a transmitter and a receiver connected by an optical fiber, they could speak across the fiber. They also cut open laser diodes to see what is inside, and explored other properties of light, such as polarization, frequency, amplitude and phase.