THz-driven ultrafast spin-lattice scattering in amorphous metallic   ferromagnets
  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 structure: 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 modelling 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 that 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. 
S. Bonetti, M.C. Hoffmann, M.-J. Sher, Z. Chen, S.-H. Yang, M. Samant,   S.S.P. Parkin, H.A. D\"urr
cond-mat.mtrl-sci cond-mat.other