THz-Driven Ultrafast Spin-Lattice Scattering in Amorphous Metallic Ferromagnets

ORAL

Abstract

We use single-cycle THz fields and the femtosecond magneto-optical Kerr effect to, respectively, excite and probe the magnetization dynamics in two thin-film ferromagnets with different lattice structures: crystalline Fe and amorphous CoFeB. We observe Landau-Lifshitz-torque magnetization dynamics of comparable magnitude in both systems, but only the amorphous sample shows ultrafast demagnetization caused by the spin-lattice depolarization of the THz-induced ultrafast spin current. Quantitative modeling shows that such spin-lattice scattering events occur on similar time scales than the conventional spin conserving electronic scattering ($\sim30$ fs). This is significantly faster than optical laser-induced demagnetization. THz conductivity measurements point towards the influence of lattice disorder in amorphous CoFeB as the driving force for enhanced spin-lattice scattering.

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Authors

  • Stefano Bonetti

    • Stockholm University

  • Matthias Hoffmann

    • SLAC National Accelerator Laboratory

  • Meng-Ju Sher

    • Stanford University

  • Zhao Chen

    • Stanford University

  • See-hun Yang

    • IBM Almaden Research Center

  • Mahesh Samant

    • IBM Almaden Research Center

  • Stuart Parkin

    • Max-Planck Institut für Mikrostrukturphysik

  • Hermann Dürr

    • SLAC
    • SLAC National Accelerator Laboratory