Letter | Published:

Light-wave dynamic control of magnetism

Abstract

The enigmatic interplay between electronic and magnetic phenomena observed in many early experiments and outlined in Maxwell’s equations propelled the development of modern electromagnetism1. Today, the fully controlled evolution of the electric field of ultrashort laser pulses enables the direct and ultrafast tuning of the electronic properties of matter, which is the cornerstone of light-wave electronics2,3,4,5,6,7. By contrast, owing to the lack of first-order interaction between light and spin, the magnetic properties of matter can only be affected indirectly and on much longer timescales, through a sequence of optical excitations and subsequent rearrangement of the spin structure8,9,10,11,12,13,14,15,16. Here we introduce the regime of ultrafast coherent magnetism and show how the magnetic properties of a ferromagnetic layer stack can be manipulated directly by the electric-field oscillations of light, reducing the magnetic response time to an external stimulus by two orders of magnitude. To track the unfolding dynamics in real time, we develop an attosecond time-resolved magnetic circular dichroism detection scheme, revealing optically induced spin and orbital momentum transfer in synchrony with light-field-driven coherent charge relocation17. In tandem with ab initio quantum dynamical modelling, we show how this mechanism enables the simultaneous control of electronic and magnetic properties that are essential for spintronic functionality. Our study unveils light-field coherent control of spin dynamics and macroscopic magnetic moments in the initial non-dissipative temporal regime and establishes optical frequencies as the speed limit of future coherent spintronic applications, spin transistors and data storage media.

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Data availability

The data that support the findings of this study are available from the corresponding author upon request.

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Acknowledgements

We acknowledge infrastructural support by F. Krausz. This work was supported by the Max Planck Society, the Deutsche Forschungsgemeinschaft Cluster of Excellence: Munich Centre for Advanced Photonics (http://www.munich-photonics.de), the Deutsche Forschungsgemeinschaft CRC/Transregio 227 (Project A04) and the US Air Force Office of Scientific Research under award number FA9550-16-1-0073.

Reviewer information

Nature thanks Marie Barthelemy, Ilias Perakis and the other anonymous reviewer(s) for their contribution to the peer review of this work.

Author information

M.S., S.S. and M.M. designed and initiated the study. Experiments were performed by F.S., J.A.G., M.O., M.C.S., Y.-P.C. and M.S. Sample design and preparation were carried out by C.D., U.M., J.W. and M.M. Theoretical investigations were conducted by S.S. and J.K.D. Design and manufacturing of XUV optics were carried out by A.G., Y.C., M.S. and U.K. The manuscript was written by M.M., M.S. and S.S.; all authors discussed the results and contributed to the manuscript.

Correspondence to Martin Schultze.

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Extended data figures and tables

Extended Data Fig. 1 Hysteresis of the longitudinal magneto-optical Kerr effect for nickel and Ni/Pt multilayers.

The Kerr rotation angle, θk, is shown as a function of the applied external magnetic field, µ0H (µ0, magnetic constant). Both samples (blue, Ni; red, Ni/Pt multilayer) exhibit soft magnetic hysteresis and low saturation fields, which are needed to orient the macroscopic magnetization in the sample plane.

Extended Data Fig. 2 Fidelity of attosecond MCD.

Results are shown for an integration time of 300 s (green dots, individual data points; green line, moving average from 7 data points) and 20 s (red dots, individual data points; red line, moving average from 7 data points).

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Fig. 1: Attosecond MCD for the study of ultrafast magnetism.
Fig. 2: Attosecond MCD measurements of light-field-induced coherent spin transfer.
Fig. 3: Optically induced spin-transfer, post-excitation spin dynamics and quantum dynamical modelling.
Extended Data Fig. 1: Hysteresis of the longitudinal magneto-optical Kerr effect for nickel and Ni/Pt multilayers.
Extended Data Fig. 2: Fidelity of attosecond MCD.

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