2010 Highlights

Surface plasmons are light-energy propagating electromagnetic modes trapped at the interface between certain metals (notably gold and silver) and a dielectric. They are also of interest for optical processes enhanced by strong local electric fields.

We studied the plasmonic properties of silver nanowire gratings with varying widths whose center-to-center spacings equaled twice their width. We excite the plasmons by using light at 514 nm wavelength. As the emission intensity of a fluorophore is proportional to the intensity of the local electric field, we experimentally determined the local field intensity by measuring fluorescence from a molecular layer 8 nm above the metal’s surface. We compared the experimental results with numerical calculations.

Micron-sized non-volatile magnetoresistance devices are being pursued using ferroelectric/magnetostrictive multilayers. Previously, we have demonstrated reversible ferroelastic domains in PZT ferroelctric bilyaers (Adv. Materials 21, 3497 (2009)). In such bilayers, different elastic states can be achieved through reversible twin boundary motions induced by small voltage pulses. The elastic states are used to tune magnetic anisotropy in FeGa layer.

Magnetism is typically associated with “transition metal” elements such as nickel or iron, from the middle of the periodic table.  These elements contain d electrons which are localized on the atoms, and have a “spin” or magnetic moment.  Carbon contains no d electrons and is not normally magnetic.

Ordered double perovskites, such as Sr₂FeMoO₆, are among the very few materials that allow electrons of one spin direction to move through them as though they were passing through a normal metal, while blocking electrons of the opposite spin.  Materials that behave this way at room temperature are even more exotic.