Micromagnetic simulations of the transition between vortex and single-domain magnetization states in sub-100 nm nanodots

ORAL

Abstract

The magnetic vortex state in nanodots has demonstrated unique properties, which may improve magnetic data storage technologies. To utilize these properties, we must understand magnetic switching to and from the vortex state. We used a ``rigid-vortex approximation'' to calculate the total magnetic energy of a nanodot for various magnetic configurations. This was done for 20 nm-thick iron nanodots with different diameters (30, 40, 65, and 80 nm) as a function of applied magnetic field. By analyzing the energy landscape for different magnetic configurations, we calculated the energy barrier for switching from the vortex to the single-domain state (vortex annihilation) and the converse (vortex nucleation). The applied fields required to overcome these two barriers are compared to those obtained from the simulations directly and to the experimental values.\footnote{R. K. Dumas, C.-P. Li, I. V. Roshchin, I. K. Schuller and K. Liu, Appl. Phys. Lett. \textbf{91}, 202501 (2007). } The role of the thermal fluctuations in the temperature dependence of these critical fields will be discussed by comparison of the energy barriers with the thermal energy, kT.

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Authors

  • Andrew T. King

  • Allan Headley

    Texas A\&M, Sam Houston State University, Southern Methodist University, Dept of Physics, Texas Tech University, Depts of Cell Physiology and Molecular Biophysics, Texas Tech University HSC, Texas Tech University, Lee College, Texas A\&M University, Texas A\&M Univ.-Commerce, University of North Texas, Texas A\&M University and Princeton University, Princeton University, The University of North Texas, University of Texas at Austin, Center for High Energy Density Science, University of Texas at Austin, Institute for Fusion Studies, University of Texas at Austin, UT Arlington, Stephen F. Austin State University, Texas A&M University--Commerce, University of Texas at Dallas, University of Texas at El Paso, Department of Physics, The University of Texas at Dallas, Department of Physics and Astronomy, Francis Marion University, University of Texas at Brownsville, Texas State University--San Marcos, UTSA, Northwestern University, Rice University, Abilene Christian University, Texas Southern University, Department of Physics, Southern Methodist University, Dallas, Texas A\&M University Cyclotron Institute, Sciprint.org, University of Texas MD Anderson Cancer Center, University of Texas at San Antonio, Paschal High School, Fort Worth, TX, Department d'Enginyeria Electronica, Universitat Autonoma de Barcelona, Department of Physics, Texas State University at San Marcos, Texas State University at San Marcos, Angelo State University, Texas State University-San Marcos, Department of Surgery, The University of Texas Southwestern Medical Center, Dallas, TX 75390, Department of Medicine, Baylor College of Medicine, Department of Bioengineering, Rice University, Department of Physics and Astronomy, Rice University, Department of Surgery, University of Texas Southwestern Medical Center, University of Texas at Dallas, Physics, Viginia State University, Jefferson Laboratory, Trinity University, LIGO, UTB-TSC, Mount Holyoke College, Texas A&M University, Electrical and Computer Engineering, TAMU, American Institute of Physics, University of Texas at Arlington, Texas Christian University, Fort Worth, TX, University of Pennsylvania, Philadelphia, PA, University of Missouri-Columbia, Columbia, MO, Paine College, Augusta, GA, Univ. of Edinburgh, INFN-LNS, INFN LNS CATANIA ITALY, Arkansas Technical University, AR, USA, Cyclotron Institute Texas A\&M University College Station Usa, and Heather Galloway, Texas State University--San Marcos