The First Step towards Fast and Energy-Efficient Processors
Researchers from among others Uppsala University have shown how new types of magnetic material structures may be developed for energy-efficient memories and processors for future calculations, within for example artificial intelligence and machine learning. It is with the help of extremely short laser pulses the researchers have been able to control ultrafast magnetization changes in nanometre-sized magnets.
Magnetic materials contain domains with uniform magnetization. In hard drives, these domains are used for storage of information which is encoded in the direction of their magnetization. The domains’ magnetization state can be changed by redirecting the magnetization with the help of external magnetic fields. But the magnetization state in a material can also be changed with the help of the interaction between light (electromagnetic radiation) and the material. The material is demagnetized ultrafast before the magnetization direction is changed.
When short and power-intensive laser pulses in the form of visible or infrared light, hits a layer of a magnetic material, the size and direction of the magnetization might change. The phenomenon takes place within a few picoseconds (10-12 s) and is more energy efficient than methods based on magnetic fields.
Cones made of gold and magnetic tips of a terbium-cobalt alloy have been patterned in a lattice. Laser light that hits the cones is focused on the tips and create an ultrafast demagnetization. Image: Vassilios Kapaklis.
Vassilios Kapaklis and his research group have, together with researchers from the University of Gothenburg and the University of Nijmegen in the Netherlands, developed a method which gives more control over the magnitude of the demagnetization in magnetic nanostructures. With the help of nano-lithography the researchers have been able to create a regular geometric lattice of magnetic particles with sizes of tens of nanometer (10-9 m). The lattice is used to control the intensity distribution of the light pulses and can thereby be used to control each particle’s magnetization.
“Through the shape of the lattice and the particles, we can concentrate the laser light and control the magnitude of the demagnetization effect. In the long term, this could lead to a new generation of processors that use light and magnetism, instead of electric charges. These do not require electric currents and are thereby also more energy-efficient,” says Vassilios Kapaklis, professor at the Department of Physics and Astronomy.
All materials and the lattice structures used in the project have been developed at the Division of Materials Physics at Uppsala University. The nanopatterning has been made at the national infrastructure of MyFab Uppsala (the clean room) in the Ångström laboratory.
Contact
Vassilios Kapaklis, professor at the Department of Physics and Astronomy, Materials Physics, vassilios.kapaklis@physics.uu.se. 018-471 35 22.
Article Reference
Kshiti Mishra, Richard M. Rowan-Robinson, Agne Ciuciulkaite, Carl S. Davies, Alexandre Dmitriev, Vassilios Kapaklis, Alexey V. Kimel, and Andrei Kirilyuk, “Ultrafast Demagnetization Control in Magnetophotonic Surface Crystals”, Nano Letters 2022, 22, 23, 9773–9780 (2022), DOI: 10.1021/acs.nanolett.2c00769
Camilla Thulin
English translation: Johan Wall