A micromachined thermal platform being wirebonded on a custom sample mount

1. Can Heat Generate Pure Spin Currents in Ferromagnetic Metal Thin Films?Barry Zink, University of Denver, DMR 0847796 In recent years, many researchers have begun to explore if the coupling between the charge and spin of electrons with heat could provide new ways to store information or generate energy. One important question is if heating a ferromagnet can generate a flow of angular momentum, or a pure spin current. Initial reports of this effect, called the spin Seebeck effect (SSE) generated excitement, but have yet to be repeated. Our major result this year (under consideration at PRL) is to probe this physics using a novel micromachined sample structure that removes artifacts introduced by a bulk substrate. Our results show the symmetry of a previously little-known thermoelectric effect, the planar Nernst effect (PNE), and show no sign of thermal generation of spin currents. We expect this to stimulate debate and new measurements to better understand and use thermal effects in nanomagnetic systems. SEM micrograph and Schematic of the micromachined thermal isolation platform with a thin film FM sample and thin film Si-N substrate Example data for a Ni thin film shows that the signal has the sin(2q) symmetry of PNE, not the expected cos(q) symmetry of the SSE

2. Can Heat Generate Pure Spin Currents in Ferromagnetic Metal Thin Films?Barry Zink, University of Denver, DMR 0847796 GRAs Rubina Sultan (now at Intel) and Dain Bassett work with Undergrad Di Wei (who recently entered the Harvard SEAS PhD program) work on our UHV chamber . The Broader Impacts of our work during the past year include the development of the novel micromachined thermal isolation platform required to probe thermal generation of spin currents in suspended thin films, support of graduate and undergraduate research students from underrepresented groups (GRA Azure Avery, URAs DiDi Wei and Gail Cotteril), outreach via public talks on “Nanoscience and Nanotechnology, What’s so big about small” at DU’s alumni symposium, and the continued integration of Peer Instruction techniques in upper division Quantum Mechanics classes at DU. PhD student Azure Avery poses with her award-winning poster A micromachined thermal platform being wirebonded on a custom sample mount