Investigation of Half-Metallic Magnetic Oxides Jinke Tang, University of Wyoming, DMR Polytetrafluoroethylene (C n F 2n+2 ), also known as Teflon, was used as the tunnel barrier in an Fe 3 O 4 intergranular tunneling experiment because Teflon has a relatively high melting point and thus potential for spintronic applications. Giant negative MR was observed at room temperature and the maximum MR ratio is about 16.6 % in an applied field of 5 T for the samples annealed at 320  C in hydrogen (upper figure). The enhancement is attributed to that Teflon can act as barrier material and, more importantly, prevent the oxidation of the surface of Fe 3 O 4. Our results suggest that there is high degree of spin polarization at room temperature for half metallic Fe 3 O 4 if its surface state can be preserved. High quality europium oxide films have been successfully prepared on Si(100) wafer via pulsed laser deposition (PLD) and their magnetic properties investigated. Stoichiometric and oxygen deficient films of EuO with and without the addition of Gd/Ce as a dopant exhibit changes in lattice constant, texture growth and T C. The increase in the T C (lower figure) may be attributed to the enhanced magnetic coupling by donor states and/or conduction electrons. Due to the exchange splitting of either the conductance band edge or the addition of a defect donor state impurity level, EuO 1-x is believed to have a high spin polarization but the states introduced by oxygen vacancies may not be identical to those introduced by the inclusion of a large local moment impurity like Gd/Ce. Magnetoresistance of an Fe 3 O 4 -polytetrafluoroethylene (Teflon) nanocomposite. Normalized magnetization as a function of temperature for stoichiometric EuO, oxygen deficient EuO and Ce-doped EuO.

Investigation of Half-Metallic Magnetic Oxides Jinke Tang, University of Wyoming, DMR Training The project supports one graduate student, Pan Liu, and partially supported an undergraduate student, Kyle Fox. Another graduate student, Corin Chepko, and two other undergraduate students, Teri Sones and Trent Mankowski, have also received training in materials physics research and benefitted from the award. They learned materials preparation methods such as solid state sintering, mechanical alloying, vacuum techniques, pulsed laser deposition, and annealing and experienced with the materials characterization equipment such as x- ray diffraction, SEM/TEM, magnetic measurement, Seebeck coefficient, electrical conductivity, and thermal conductivity measurement. Student Presentations Undergraduate student Kyle Fox is a co-author of our EuO paper that was published in IEEE Transactions on Magnetics in 2010 Undergraduate student Teri Sones presented her work on Teflon coated Fe 3 O 4 interface at the McNair Scholars Program Course Development My graduate students participate and continue to assist a graduate course on the experimental methods in physics by providing Quantum Design’s PPMS platform and their expertise. Outreach In addition to hosting visiting high school students and participating in Wyoming State Science Fair, we are now involved in a NSF fellowship grant that support PhD students who will conduct research activities on campus and go out to high schools to communicate to Wyoming students about their research.