Ultrafast optically induced Spin Transfer (OISTR) in Ferromagnetic Alloys INVITED

Author / Creator

MMM 2020 (2020)

Conferences

MMM 2020 G3: Magnetization Dynamics and Damping II: Ultrafast Demagnetization and Magneto-optics (2020)

Available as

Online

Summary

A thorough understanding of femtosecond magnetism will address the important questions of how fast the magnetization can be reoriented in a material and what physical processes present fundamental ...

A thorough understanding of femtosecond magnetism will address the important questions of how fast the magnetization can be reoriented in a material and what physical processes present fundamental limits to this speed. Ultimately, light represents the fastest means to alter the state of a material since laser pulses can now be generated with extremely short temporal duration down to a few tens of attoseconds. One particularly interesting and novel scheme for the ultrafast manipulation of spins using light takes advantage of the optically-induced spin transfer (OISTR), which was recently introduced by Dewhurst et al. [1]. This microscopic mechanism is driven by a spin-selective direct optical excitation from one magnetic sublattice to another. Guided by time dependent density functional theory calculations, we are able to monitor the optically induced transient changes in the model systems FeNi in real time by time-resolved magneto-optical Kerr spectroscopy using high-harmonic generation (HHG TMOKE) [2]. Exploiting the spectral sensitivity of this measurement technique we are able to follow the ultrafast spin transfer from Fe to Ni during the optical excitation. OISTR, therefore, opens up a new avenue towards manipulating solids on timescales only limited by the duration of the exciting light pulse, which forecasts a control of the spin dynamics on the attosecond time scale. How far this spin manipulation via OISTR is a general phenomenon or restricted to a subset of materials with specific properties is an open experimental and theoretical question. In order to opens up a systematic path for coherent manipulation of spin dynamics by direct light-matter interaction we started to investigate OISTR in a variety of different compounds with higher complexity [3]. We reveal for example that the half-Heusler materials NiMnSb and CoMnSb exhibit strong signatures of OISTR, whereas this is less pronounced in the full-Heusler compounds Co2MnSi, Co2FeSi, and Co2FeAl in agreement with ab initio calculations [4].References: [1] J.K. Dewhurst et al, Nano Lett. 18 1842 (2018) [2] M. Hofherr et al. Sci. Adv. 6 eaay8717 (2020) [3] P. Tengdin et al , Sci. Adv. 6 eaaz1100 (2020) [4] D. Steil et al, Phys. Rev. Research 2, 023199 (2020)

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