Bulletin of the American Physical Society
Annual Meeting of the Four Corners Section of the APS
Volume 58, Number 12
Friday–Saturday, October 18–19, 2013; Denver, Colorado
Session D3: Condensed Matter II: Magnetics |
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Chair: Markus Raschke, University of Colorado - Boulder Room: 281 |
Friday, October 18, 2013 2:00PM - 2:24PM |
D3.00001: Theory and simulations linking molecular features to morphology in polymer nanocomposites Invited Speaker: Arthi Jayaraman To engineer polymer nanocomposites for target macroscopic properties, it is important to find ways to control the spatial arrangement of nanoscale additives within the polymer matrix. In this talk, I will present our recent theory and simulation work focused on linking molecular features of the additives and polymers to the morphology of the composite. Two specific studies will be discussed. First, I will show how polydispersity in homopolymers grafted on the nanoadditives stabilizes dispersed morphology of the additives in the nanocomposite. Second, I will show how polymer architecture and additve-polymer miscibility affect morpholgical features, such as interfacial area and domain shapes, in conjugated polymer based composites. [Preview Abstract] |
Friday, October 18, 2013 2:24PM - 2:36PM |
D3.00002: Damping in Nanometer-Thick Yttrium Iron Garnet Films Capped by Platinum Houchen Chang, Yiyan Sun, Michael Kabatek, Young-Yeal Song, Zihui Wang, Michael Jantz, William Schneider, Mingzhong Wu, Eric Montoya, Bartek Kardasz, Bret Heinrich, Suzanne te Velthuis, Helmut Schultheiss, Axel Hoffmann Damping in magnetic materials can be realized through energy redistribution within the magnetic subsystem, energy transfer to non-magnetic subsystems and to external systems via spin pumping. This presentation reports on experimental evidences for a new damping. In samples of nm-thick ferromagnetic yttrium iron garnet (YIG) films capped by Pt films, the 3 nm or thicker Pt layer produces an extra damping much larger than the expected damping from spin pumping and with a shift in the ferromagnetic resonance (FMR) field. This damping can be switched off by a Cu spacer The damping may originate from the FM ordering in the Pt atomic layers by magnetic proximity effect near the YIG/Pt interface and the dynamic exchange coupling between the ordered Pt spins and the YIG spins. The YIG-Pt coupling allows for transfer of the damping of the FM Pt to the YIG film. The presence of the FM Pt causes spin pumping from FM Pt into paramagnetic Pt instead of conventional spin pumping from YIG to Pt. [Preview Abstract] |
Friday, October 18, 2013 2:36PM - 2:48PM |
D3.00003: Computational Analysis of Exchange Bias XRMS Data Alex Safsten Magnetic thin films possess a domain structure which is easily affected by the influence of external magnetic fields. Under proper conditions, however, the film will exhibit the property of ``magnetic memory,'' in which the film shows a preference for reforming in a domain structure similar to the original if possible. Previous work has shown the extent of magnetic memory in films whose preferred domain structure yields zero net magnetization on the sample. We show computational results for films under ``exchange bias'' conditions, in which the preferred state of the film has a nonzero net magnetization. [Preview Abstract] |
Friday, October 18, 2013 2:48PM - 3:00PM |
D3.00004: Spin Pumping due to Traveling Spin Waves in Yttrium Iron Garnet Thin Films Pasdunkorale Janantha, Yiyan Sun, Houchen Chang, Mingzhong Wu Yttrium iron garnet (YIG) has a very small magnetic damping and thereby represents a good candidate material for the generation of spin currents. Previous work has demonstrated the use of ferromagnetic resonance (FMR) and standing spin waves in YIG thin films to produce spin currents. In a contrast, this presentation will report on spin pumping from traveling spin waves. Experiments used a micron-thick YIG strip capped by a nanometer-thick Pt layer. The YIG film was biased by an in-plane magnetic field. The spin waves pumped spin currents into the Pt layer, and the latter produced electrical voltages across the width of the Pt strip through the inverse spin Hall effect (ISHE). Two distinct modes were observed, one at a lower frequency and another at a higher frequency, which were due to the spin pumping from the traveling spin waves and FMR modes, respectively. The spin-wave pumping shows several important features. For example, it yields stronger ISHE signals and is broad-band, in comparison with the FMR pumping. [Preview Abstract] |
Friday, October 18, 2013 3:00PM - 3:12PM |
D3.00005: Properties of protein-based ferrihydrite nanoparticles Stephen Erickson, John Colton, Trevor Smith, Richard Watt Absorption spectroscopy was used to optically measure the band gaps of ferrihydrite nanoparticles within ferritin protein shells. These band gaps were measured accurately to within .01 eV and the nanoparticles were shown to be indirect gap semiconductors. The effects of anions in solution, nanoparticle size, and aging were examined. Orderly variations in band gap due to these conditions show the potential for selectively tuning that gap. Band gaps increased with time as the ferritin worked to crystallize the ferrihydrite, with stronger trends for larger nanoparticles. Nanoparticle size was shown to be inversely proportional to band gap. Evidence of a second indirect absorption edge suggests the possibility of a second local minimum in the conduction band. [Preview Abstract] |
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