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MA: Fachverband Magnetismus

MA 2: Ultrafast Magnetization I

MA 2.9: Vortrag

Montag, 16. März 2020, 11:45–12:00, HSZ 101

Spin Relaxation and Domain Wall Dynamics in Optically Excited Ferromagnetic [Co/Pt]3 Multilayers — •Fangzhou Wang¹, Roman Adam¹, Daniel E. Bürgler¹, Derang Cao^1,2, Umut Parlak¹, Sarah Heidtfeld¹, Christian Greb¹, and Claus M. Schneider¹ — ¹Peter Grünberg Institute, Research Centre Jülich, 52425 Jülich, Germany — ²College of Physics, Qingdao University, 266071 Qingdao, China

Earlier, we demonstrated [1] that the area of the laser-modified magnetization decreases with the reduced repetition rate at room temperature, but remains constant at low temperature. The strong temperature dependence indicates that thermally activated domain wall motion (TA-DWM) plays an important role in the spin dynamics triggered by a fs laser pulse. In this work, we investigate in detail the relaxation processes following the femtosecond excitation in out-of-plane (OOP) magnetized [Co(0.4 nm)/Pt(0.7 nm)]3 multilayers by performing time-resolved MOKE measurements at varying magnetic field and laser power. We determine the time scales relevant for intrinsic and extrinsic magnetization relaxation processes. Based on the recorded magnetization dynamics transients and assuming TA-DWM as an additional relaxation mechanism, we estimate a time-dependent domain wall velocity for magnetization relaxation. Our analysis contributes to an understanding of spin relaxation processes in OOP magnetized multilayers on the picosecond time scale. [1]U. Parlak, R. Adam, D. E. Bürgler, S. Gang, and C. M. Schneider, Physical Review B 98, 214443 (2018).