Today’s society relies on the processing and storage of large amounts of data. The urgent need to increase data storage capacity and the burgeoning power consumption of data centers necessitate the optimization and innovation of magnetic data storage devices, in which data is stored in the orientation of tiny magnetic domains. Specifically, the goal is to reduce power consumption and enable higher data read and write speeds.
For his doctorate. research, Maarten Beens discovered that the use of very short laser pulses is a promising candidate for the development of faster magnetic memory devices.
Femtomagnetism
The area of research that focuses on controlling magnetic order with ultrashort (femtosecond) laser pulses is called femtomagnetism. The field emerged in the late 1990s when it was discovered that upon laser pulse excitation, the magnetization of a magnetic thin film changes surprisingly rapidly and turns off within a trillion of a second.
Later, it was shown that laser pulses can be used to change the direction of magnetization in specific types of magnetic alloys, a phenomenon called all-optical switching (AOS). Since it provides a means to direct the magnetic order from a “0” state to a “1” state, the discovery of AOS proved that femtomagnetism could lead to the development of innovative data-writing technologies.
More recent studies show that controlling magnetism with laser pulses goes beyond local level influence and can be used to generate “spin currents” that allow manipulation of magnetization over a finite distance. Here, “spin” refers to the basic magnetic property of an electron. The listed processes create various opportunities to create a robust and reliable data writing scheme.
Building on the past
In order to achieve the full potential of implementing femtomagnetism in future memory devices, it is necessary to understand the phenomena mentioned above at a microscopic level. In his doctorate. research, Maarten Beens and his collaborators build on the theoretical foundations that have been developed over the past decades and present new insights into the mechanisms underlying ultrafast magnetism.
For example, the mathematical models developed by Beens and his colleagues allow us to better understand the link between the local extinction of the magnetization and the generation of spin currents. In agreement with recent experimental studies, it turned out that the two processes seem to have the same physical origin. Here, the essential ingredients are the heating induced by the laser pulse and the subsequent wave-like magnetic excitations which are generated inside the magnet.
In addition, Beens has developed a theoretical model that allows comparison of the different magnetic material systems allowing all-optical switching. A bilayer consisting of a cobalt layer and a gadolinium layer proved to be an ideal candidate with regard to the robustness and reliability of the switching process. The layered structure allows relatively easy tuning of the magnetic characteristics of the complete system, so that material properties that are critical for the AOS process can be optimized.
Additionally, the clever engineering of the magnetic stacks allows the generated spin currents to play a role in assisting the switching process. Results Been’s simulations highlight that the use of femtosecond laser pulses remains a promising data writing tool for future magnetic memory devices. Nevertheless, the underlying physics is still not completely understood and needs to be explored further in the coming years to determine its full potential.
In-depth tracking of ultra-fast magnetization dynamics
Theoretical methods for femtomagnetism and ultrafast spintronics. research.tue.nl/nl/publication … ltrafast-spintronics
Provided by Eindhoven University of Technology
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