Bulletin of the American Physical Society
Annual Meeting of the Four Corners Section of the APS
Volume 57, Number 11
Friday–Saturday, October 26–27, 2012; Socorro, New Mexico
Session J3: Condensed Matter III |
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Chair: Nicolai Kalugin, New Mexico Institute of Mining and Technology Room: Macey Center Auditorium |
Saturday, October 27, 2012 1:30PM - 1:42PM |
J3.00001: Characterization of NiPt, FePt, and NiFePt nanoparticles Greg Sutherland, Darren Wood, Amy Jackson, Andrew Warren, Kevin Coffey, Richard Vanfleet Many metal alloys can form in chemically ordered structures, often resulting in significant changes in properties. The ordered structures are preferred at low temperatures and will go through an order-disorder phase transition at a critical temperature. The formation and stability of these ordered structures in alloy nanoparticles is not well understood but may give insight into the role size plays in phase transitions. To this end we are studying FePt, NiPt, and FeNiPt alloy nanoparticles. We will focus this presentation on the characterization of these nanoparticles in a Transmission Electron Microscope (TEM) for composition, size, and structure. These nanoparticles are made by co-sputtering the constituents and annealing at different temperatures in various gas mixtures. The nanoparticle samples are prepared for TEM viewing by wedge polishing. We find FePt to be ``well behaved'' meaning this alloy forms particles, retains the as deposited composition, and chemically orders as expected. However, the order-disorder temperature is too high for the desired further studies. NiPt, which has a lower order-disorder temperature, is not ``well behaved'' in that the nanoparticle compositions are not good matches to the as deposited conditions and no chemical ordering has been achieved even under conditions that should be sufficient based on bulk processing. We will discuss these results and possible implications. [Preview Abstract] |
Saturday, October 27, 2012 1:42PM - 1:54PM |
J3.00002: Structural and magnetic behavior of Fe$_3$O$_4$ nanoparticles Karine Chesnel, Matea Trevino, Yanping Cai, Betsy Olsen, Stacey Smith, Roger Harrison The study of magnetic nanoparticles grows rapidly because of its wide range applications: ultrahigh density recording media, quantum information devices, biomedicine etc. When their size is down to few nanometers, magnetic particles exhibit interesting superparamagnetic behaviors, where each particle carries a single macrospin. We investigated various chemical routes to synthesize our Fe$_3$O$_4$ ferrimagnetic nanoparticles, and characterized their structural properties by XRD and magnetic properties with VSM magnetometry. We were able to identify the structure and size of nanoparticles, ranging from 5 to 50nm. We also studied their bulk magnetic behavior under field cooling and zero field cooling measurements to identify a superparamagnetic phase transition. Finally, we have deposited the particles onto membranes to let them self-assemble and form a thin layer, and have studied the structure of the self assmblies by TEM imaging. [Preview Abstract] |
Saturday, October 27, 2012 1:54PM - 2:06PM |
J3.00003: Magnetic order of Fe$_3$O$_4$ Nanoparticles Yanping Cai, Karine Chesnel, Matea Trevino, Andrew Westover, Alex Safsten, Roger Harrison, Andreas Scherz Magnetite (Fe$_3$O$_4$) nanoparticles tend to self-assemble when they are deposited on a substrate and form a film. Our goal is to understand the magnetic order and magnetic interactions between the particles, when they are self-assembled. After bulk structural and magnetic characterizations previously presented, we have been studying our Fe$_3$O$_4$ nanoparticles by using soft X-ray Resonant Magnetic Scattering (XRMS) at synchrotron radiation facilities. This technique utilizes the interaction between magnetic spins and polarized light. [1] The resulting scattering patterns contain information about the magnetic order and magnetic fluctuations in the nanoparticles assembly. By studying the profile of the XRMS patterns, we try to extract the magnetic signal from the charge signal, and learn about the magnetic order between the nanoparticles. We also utilize the coherence of the X-ray light and apply a correlation spectroscopy technique to learn about magnetic fluctuations. [Preview Abstract] |
Saturday, October 27, 2012 2:06PM - 2:30PM |
J3.00004: Science at 100 Tesla Invited Speaker: Neil Harrison Within the last year, Los Alamos National Labs produced magnetic fields of 100 tesla strength non-destructively for the first time. Fields of such a strength open up many new possibilities for condensed matter research. I will present some recent examples of condensed matter physics experiments performed in magnetic fields reaching 100 tesla, which includes recent work on high temperature superconductivity, magnetism and low dimensional materials. [Preview Abstract] |
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