THz-driven ultrafast spin-lattice scattering in amorphous metallic ferromagnets

Authors :: Bonetti, S.
Hoffmann, M. C.
Sher, M. -J.
Chen, Z.
Yang, S. -H.
Samant, M.
Parkin, S. S. P.
Dürr, H. A.
Source :: Phys. Rev. Lett. 117, 087205 (2016)
Publication Year :: 2016
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 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.<br />Comment: 10 pages, 4 figures