Bulletin of the American Physical Society
2011 Annual Meeting of the Four Corners Section of the APS
Volume 56, Number 11
Friday–Saturday, October 21–22, 2011; Tuscon, Arizona
Session D2: Magentic Thin Films |
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Chair: Kristen Buchanan, Colorado State University Room: UA Student Union Ventana |
Friday, October 21, 2011 2:00PM - 2:12PM |
D2.00001: Intrinsic damping due to electron-magnon interactions in ferromagnetic metals Shulei Zhang, Shufeng Zhang Magnetic relaxation in ferromagnetic metals is usually ascribed to the interaction between conduction electrons and spin waves (or magnons). This interaction involves two types of physical processes. First, an electron absorbs or emits a magnon in a spin-flip electron-magnon scattering. At low temperature, this process is operative only for disordered ferromagnet; otherwise it is prohibited by energy and momentum conservation. The other process is that electrons are scattered by magnons without changing their spins, also known as spin-conversing electron-magnon scattering. We show that this latter process exists even at zero temperature without disorders. We calculated the damping parameters for both processes and found that the intrinsic damping in general has the same order of magnitude as extrinsic damping at low temperatures. We further apply our results to thin magnetic films with magnetization parallel and perpendicular to film planes respectively. The intrinsic damping parameter scales as square of temperature. A more interesting result is thickness dependence of the damping parameter. For an in-plane magnetized layer, the damping is inversely proportional to thickness whereas for the perpendicularly magnetized layer, it increases with thickness. [Preview Abstract] |
Friday, October 21, 2011 2:12PM - 2:24PM |
D2.00002: Evolution of Magnetic Domain Morphology in Co/Pt Thin Films Andrew Westover, Karine Chesnel, Yanping Cai, Olav Hellwig Co/Pt thin films are important materials due to their property of exerting perpendicular magnetic anisotropy. On a microscopic scale Co/Pt thin films form into magnetic domains, with magnetic moments directed perpendicularly into or out of the films. Using In-Situ Magnetic Force Microscopy we observed that as a uniform magnetic field of increasing intensity is applied to the sample, the initial labyrinthine domain pattern slowly shrinks, eventually forming a bubble state and finally completely saturating. As the magnetic field is released domains begin to nucleate, and then spread out from the nucleation sites, eventually returning to a labyrinthine state. In addition we observed that if the external magnetic field is released before saturation is achieved, that the remnant domain pattern changes according to the domain morphology of the sample before the magnetic field was released. [Preview Abstract] |
Friday, October 21, 2011 2:24PM - 2:36PM |
D2.00003: Growth of High-Quality Yttrium Iron Garnet Thin Films on Metallic Electrodes Yiyan Sun, Young-Yeal Song, Mingzhong Wu Yttrium iron garnet (YIG) is a magnetic garnet and shows extremely low loss at microwave frequencies. One typically grows YIG on single-crystal gadolinium gallium garnet (GGG) substrates. For some monolithic on-chip device applications, however, one needs to grow YIG films on metallic electrodes. This is challenging due to problems with the oxidation, diffusion, and breakup of metallic electrodes during the deposition of YIG films at high temperatures. This presentation reports on the development of new sandwich-type bottom electrodes and the growth of low-loss YIG thin films on such electrodes. The new electrodes consist of a thick metallic layer sandwiched between two thin cladding layers. The thick layer is a high-conductivity metal. The thin cladding layers are materials with high oxidation resistance and good thermal stability. The electrodes were deposited at room temperature by magnetron sputtering, while the YIG films were deposited at 650 \r{ }C by pulsed laser deposition. Scanning electron microscopy, x-ray diffraction, and energy dispersive spectroscopy measurements confirmed the structure of the YIG films Static magnetic measurements indicated a saturation induction of about 1471 G, which was 16{\%} smaller than that for a YIG bulk. Ferromagnetic resonance measurements yielded a peak-to-peak linewidth of about 0.8 Oe at 9.45 GHz. [Preview Abstract] |
Friday, October 21, 2011 2:36PM - 2:48PM |
D2.00004: Control of Ferromagnetic Relaxation in Magnetic Thin Films through Spin Seebeck Effects Lei Lu, Yiyan Sun, Michael Jantz, Mingzhong Wu Since its discovery in 2008, the spin Seebeck effect has been demonstrated in thin film strips of ferromagnetic metals, semiconductors, and magnetic garnets. This presentation reports for the first time the tuning of ferromagnetic relaxation in magnetic thin films through the spin Seebeck effect. The experiments used a 4.6 $\mu $m-thick yttrium iron garnet (YIG) film capped by a 20 nm- thick platinum (Pt) layer. A temperature gradient was established across the YIG film thickness. This temperature gradient induces a spin accumulation at the YIG/Pt interface through the spin Seebeck effect. This spin accumulation in turn results in a spin current across the thickness of the Pt layer. The net effect is a torque on the magnetic moments in the YIG film. This torque can either enhance or mitigate the relaxation rate of the magnetic moments in the YIG film. The effects were demonstrated through a change in the ferromagnetic resonance linewidth of the YIG film with the temperature gradient and were confirmed by the use of different temperature gradients and samples. [Preview Abstract] |
Friday, October 21, 2011 2:48PM - 3:00PM |
D2.00005: Magnetic Memory in Field Cooled Exchange Biased Thin Films Matthew Rytting, Karine Chesnel, Brian Wilcken, Joseph Nelson, Andrew Westover, Eric Fullerton, Steve Kevan, David Vine, Ian McNulty We have fabricated samples of alternating ferromagnetic multilayers of Co/Pd, with antiferromagnetic layers of an IrMn alloy. This system exhibits exchange bias, i.e. the magnetization loop is shifted - or ``biased''- toward a preferred direction. This effect occurs when the sample has been cooled in the presence of a magnetic field. It has been found that such samples exhibit a high degree of magnetic domain memory when cooled below the blocking temperature in absence of a magnetic field (Zero Field Cooled state). We are interested in studying the behavior of memory when cooling the sample in the presence of a magnetic field (Field Cooled state). To quantify the amount of memory, we collect X-ray Resonant Magnetic Scattering (XRMS) images at synchrotron facilities. Using a cross- correlation technique, we can determine the degree of memory exhibited by the sample. We are also complementing the XRMS study with MFM images measured with an in-situ magnetic field. [Preview Abstract] |
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