Investigations of Spin Precession in Perpendicular Magnetic Materials Enabled by Time-Resolved Magneto-Optical Kerr Effect

Invited

Abstract

Time-Resolved Magneto-Optical Kerr Effect (TR-MOKE) is an all-optical method based on the ultrafast pump-probe technique that can be used to study the magnetization dynamics of materials, in addition to thermal and mechanical characterization. With optical excitation and the capability of reaching large magnetic fields, TR-MOKE can probe spin precession at high resonance frequencies (up to a few hundreds of GHz), beyond those achievable by conventional Ferromagnetic Resonance (FMR) methods. In this talk, we demonstrate the use of TR-MOKE to study the spin precession of two model material systems with large perpendicular magnetic anisotropy (PMA). The first model system is a series of tungsten (W) -seeded CoFeB thin films, capable of sustaining good PMA after post-annealling at temperatures of up to 400 °C. We measure the Gilbert damping (α) of W-seeded CoFeB films, and attribute the dependence of α on the annealing temperature to two competing effects: the enhanced crystallization of CoFeB and the dead-layer growth occurring at the CoFeB interfaces. The second model system of interest is composed of perpendicular ferromagnetic [Co/Pd]n multilayers with varying anisotropy. We use ultrafast-laser heating to launch acoustic strain waves and capture their coupling with the spin precession in these [Co/Pd]n multilayers. Understandings on such a strain-spin coupling may shed light on manipulating the precession and switching the magnetization in magnetoacoustic devices.

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Presenters

  • Xiaojia Wang

    Mechanical Engineering, University of Minnesota Twin Cities, University of Minnesota, Twin Cities, Department of Mechanical Engineering, University of Minnesota

Authors

  • Xiaojia Wang

    Mechanical Engineering, University of Minnesota Twin Cities, University of Minnesota, Twin Cities, Department of Mechanical Engineering, University of Minnesota

  • Dustin Lattery

    Mechanical Engineering, University of Minnesota Twin Cities, University of Minnesota, Twin Cities

  • Jie Zhu

    Mechanical Engineering, University of Minnesota Twin Cities, University of Minnesota, Twin Cities, Department of Mechanical Engineering, University of Minnesota

  • Delin Zhang

    Electrical and Computer Engineering, University of Minnesota Twin Cities, University of Minnesota, Twin Cities

  • Tao Qu

    Electrical Engineering, University of Minnesota, University of Minnesota, Twin Cities, University of Minnesota

  • R. Victora

    Electrical Engineering, University of Minnesota, University of Minnesota, Twin Cities

  • Jianping Wang

    Electrical and Computer Engineering, University of Minnesota Twin Cities, University of Minnesota, Twin Cities, Electrical and Computer Engineering, University of Minnesota