Dresden 2020 – scientific programme
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MA: Fachverband Magnetismus
MA 2: Ultrafast Magnetization I
MA 2.8: Talk
Monday, March 16, 2020, 11:30–11:45, HSZ 101
Optically-induced spin dynamics in NiFe/Pd multilayers investigated using soft X-rays and THz radiation — •Sarah Heidtfeld1, Roman Adam1, Daniel E. Bürgler1, Fangzhou Wang1, Christian Greb1, Derang Cao1,2, and Claus M. Schneider1 — 1Research Centre Jülich, Peter Grünberg Institute, 52425 Jülich, Germany — 2College of Physics, Qingdao University, 266071 Qingdao, China
In our earlier work we demonstrated that Pd in NiPd alloys exhibits a non-zero magnetic moment and shows transient demagnetization when excited with a train of femtosecond laser pulses [1]. Most importantly, we showed that ultrafast demagnetization depends on the Pd concentration and that the effect can be attributed to an increased spin-flip probability, which is proportional to the amount of Pd in the alloys. In our present work, we elucidate the role of super-diffusive spin currents in the process of optically inducing transient magnetization in metals close to the Stoner transition. We compare demagnetization times in NiPd alloys and NiFe/Pd multilayers by applying the time-resolved magneto-optical Kerr-effect (MOKE) using either visible or extreme ultraviolet (XUV) light. In addition, we analyze the generated spin currents flowing from the NiFe into the Pd layer by investigating THz radiation emitted from these ferromagnet (FM)/heavy metal (HM) double-layers due to the inverse spin Hall effect [2]. Our data provide further insight into the spin and charge dynamics in FM/HM multilayers. [1] S. Gang et al., Phys. Rev. B 97, 064412 (2018) [2] R. Adam et al., Appl. Phys. Lett. 114, 212405 (2019)