title: THz-Driven Ultrafast Spin-Lattice Scattering in Amorphous Metallic Ferromagnets.
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 (∼30  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.
authors: Department of Physics, Stockholm University, Stockholm 10691, Sweden.
authors: S
authors: S
authors: Bonetti
authors: Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA.
authors: M C
authors: MC
authors: Hoffmann
authors: Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA.|Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA.
authors: M-J
authors: MJ
authors: Sher
authors: Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA.|Department of Physics, Stanford University, Stanford, California 94305, USA.
authors: Z
authors: Z
authors: Chen
authors: IBM Almaden Research Center, San Jose, California 95120, USA.
authors: S-H
authors: SH
authors: Yang
authors: IBM Almaden Research Center, San Jose, California 95120, USA.
authors: M G
authors: MG
authors: Samant
authors: IBM Almaden Research Center, San Jose, California 95120, USA.|Max-Planck Institut für Mikrostrukturphysik, Weinberg 2, Halle 06120, Germany.
authors: S S P
authors: SS
authors: Parkin
authors: Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA.
authors: H A
authors: HA
authors: Dürr