Bulletin of the American Physical Society
APS March Meeting 2013
Volume 58, Number 1
Monday–Friday, March 18–22, 2013; Baltimore, Maryland
Session R1: Invited Session: Controllng Magnetism Without Magnetic Fields |
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Sponsoring Units: DCMP GMAG Chair: Ramamoorty Ramesh, University of California at Berkeley Room: Ballroom I |
Wednesday, March 20, 2013 2:30PM - 3:06PM |
R1.00001: Electric Field Control of Magnetization Using Multiferroic BFO Invited Speaker: Sayeef Salahuddin |
Wednesday, March 20, 2013 3:06PM - 3:42PM |
R1.00002: Controlling Magnetism by light Invited Speaker: Theo Rasing From the discovery of sub-picosecond demagnetization over a decade ago to the recent demonstration of magnetization reversal by a single 40 femtosecond laser pulse, the manipulation of spins by ultra short laser pulses has become a fundamentally challenging topic with a potentially high impact for future spintronics, data storage and manipulation and quantum computation. In addition, when the time-scale of the perturbation approaches the characteristic time of the exchange interaction ($\sim$ 10-100 fs), the magnetization dynamics enters a novel, highly non-equilibrium, regime, which was recently demonstrated by both fs optical and X-ray experiments. Theoretically, this field is still in its infancy, using phenomenological descriptions of the none-equilibrium dynamics between electrons, spins and phonons via 2- or 3-temperature models and atomistic spin simulations. A proper description should include the time dependence of the exchange interaction and nucleation phenomena on the nanometer length scale. Such developments need to be supported by experimental investigations of magnetism at its fundamental time and length scales, i.e. with fs time and nanometer spatial resolution. Such studies require the excitation and probing of the spin and angular momentum contributions to the magnetic order at timescales of 10fs and below, a challenge that could be met by the future fs X-ray FEL's but in some cases also with purely optical techniques.\\[4pt] Recent references:\\[0pt] [1] A. Kirilyuk, et al, \textbf{Rev. Mod. Phys. 82}, 2731-2784 (2010)\\[0pt] [2] I. Radu et al, \textbf{Nature 472}, 205 (2011)\\[0pt] [3] J. Mentink et al, \textbf{Phys.Rev.Lett. 108, }057202 (2012)[0pt] [4] T. Ostler et al, \textbf{Nature Comm. 3}, 666 (2012)\\[0pt] [5] A.R. Khorsand et al, \textbf{Phys.Rev.Lett.108}, 127205 (2012) [Preview Abstract] |
Wednesday, March 20, 2013 3:42PM - 4:18PM |
R1.00003: Spin Mechanics in Ferromagnet/Ferroelectric Hybrid Structures Invited Speaker: Sebastian Goennenwein In most ferromagnets, magnetic and elastic degrees of freedom are coupled -- as evident, e.g., from the hum of a transformer. In the ``spin mechanics'' scheme, one intentionally exploits magneto-elastic coupling (inverse magneto-striction) to control the magnetization of ferromagnetic films. On the one hand, I will briefly review spin mechanics in the static limit, taking ferromagnetic nickel thin film/piezoelectric actuator hybrid structures as prototype examples [1]. In these hybrids, the application of an electric field to the actuator results in a uniaxial strain, which is transferred into the Ni film. Due to magneto-elastic coupling, the voltage-controlled strain modifies the magnetic anisotropy and thus induces a magnetization reorientation. This allows for a voltage-controlled, fully reversible magnetization orientation manipulation within a range of approximately 90 degrees at room temperature in these hybrids. On the other hand, I will show that the spin mechanics scheme also is operational at GHz frequencies. In the corresponding experiments, we use surface acoustic waves (SAWs) propagating in Ni/LiNbO$_{\mathrm{3}}$ hybrid devices for the all-elastic excitation and detection of ferromagnetic resonance (FMR). Our SAW magneto-transmission data are consistently described by a modified Landau-Lifshitz-Gilbert approach [2], in which the magnetization precession is not driven by a conventional, external microwave magnetic field, but rather by a purely virtual, internal tickle field stemming from radio-frequency magneto-elastic interactions. This causes a distinct magnetic field orientation dependence of elastically driven FMR, observed in both simulations and experiment. Last but not least, I will address perspectives for spin mechanics experiments, e.g., the study of magnon-phonon coupling, or acoustic spin pumping [3] in normal metal/ferromagnet hybrid structures. \\[4pt] [1] M. Weiler \textit{et al.}, New J. Phys. \textbf{11}, 013021 (2009).\\[0pt] [2] M. Weiler \textit{et al.}, Phys. Rev. Lett. \textbf{106}, 117601 (2011).\\[0pt] [3] M. Weiler \textit{et al.}, Phys. Rev. Lett. \textbf{108}, 176601 (2012). [Preview Abstract] |
Wednesday, March 20, 2013 4:18PM - 4:54PM |
R1.00004: Control of Magnetic Properties Across Metal to Insulator Transitions Invited Speaker: Jose de la Venta Controlling the magnetic properties of ferromagnetic (FM) thin films without magnetic fields is an on-going challenge in condensed matter physics with multiple technological implications. External stimuli and proximity effects are the most used methods to control the magnetic properties. An interesting possibility arises when ferromagnets are in proximity to materials that undergo a metal-insulator (MIT) and structural phase transition (SPT). The stress associated with the structural changes produces a magnetoelastic anisotropy in proximity coupled ferromagnetic films that allows controlling the magnetic properties without magnetic fields. Canonical examples of materials that undergo MIT and SPT are the vanadium oxides (VO$_{2}$ and V$_{2}$O$_{3})$. VO$_{2}$ undergoes a metal/rutile to an insulator/monoclinic phase transition at 340 K. In V$_{2}$O$_{\mathrm{3}}$ the transition at 160 K is from a metallic/rhombohedral to an insulating/ monoclinic phase. We have investigated the magnetic properties of different combinations of ferromagnetic (Ni, Co and Fe) and vanadium oxide thin films. The (0.32{\%}) volume expansion in VO$_{2}$ or the (1.4{\%}) volume decrease in V$_{2}$O$_{3}$ across the MIT produces an interfacial stress in the FM overlayer. We show that the coercivities and magnetizations of the ferromagnetic films grown on vanadium oxides are strongly affected by the phase transition. The changes in coercivity can be as large as 168{\%} and occur in a very narrow temperature interval. These effects can be controlled by the thickness and deposition conditions of the different ferromagnetic films. For VO$_{2}$/Ni bilayers the large change in the coercivity occurring above room temperature opens the possibilities for technological applications. [Preview Abstract] |
Wednesday, March 20, 2013 4:54PM - 5:30PM |
R1.00005: Controlling Magnetism with electric fields Invited Speaker: Leonid Rokhinson |
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