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Optical control of magnetism thru strongly non-equilibrium phases
December 13, 2023 @ 10:45 - 11:15 CET
T. Rasing1*
1Radboud University, Institute for Molecules and Materials, Heijendaalseweg 135, 6525AJ Nijmegen, the Netherlands
The ability to switch magnets between two stable bit states is the main principle of digital data storage technologies since the early days of the computer. Since our demonstration of magnetization reversal by a single 40 femtosecond laser pulse, the manipulation of spins by ultra-short laser pulses has developed into an alternative and energy efficient approach to magnetic recording. Though originally thought to be due to an optically induced effective field, later studies demonstrated that the switching occurred via a strongly non-equilibrium state, exploiting the exchange interaction between the spins. Recent work also show how magnetic textures like skyrmions are generated via a non-equilibrium phase.
While for a long time, all-optical switching (AOS) was exclusively observed in ferrimagnetic alloys, more recent work demonstrated AOS in a broad range of ferromagnetic multilayer materials, albeit that in those examples a large number of pulses were required. By studying the dynamics of this switching process, we have discovered that this switching is a 2-step process, which led us to the subsequent demonstration that highly efficient AOS can be achieved by using pairs of femto/pico-second laser pulses. By combining optical laser excitation with in situ magnetic force microscopy we recently found that the nucleation and switching process evolves via a stochastic network of domains.
As new ICT technologies, such as Artificial Intelligence, is leading to a dramatic increase of the energy cost of computing, the development of radically new physical principles that combine energy-efficiency with high speeds and high densities is crucial for a sustainable future. One of those new principles is neuromorphic computing, that is inspired by the notion that our brain uses a million times less energy than a supercomputer while, at least for some tasks, it even outperforms the latter.
In this talk, I will discuss the state of the art in ultrafast manipulation of magnetic bits and present some first results and new ideas to implement brain-inspired computing concepts in magnetic materials.
Acknowledgement(s): Support from the Dutch Research Council (NWO) and the European Research Council ERC grant agreement no.856538 (3D-MAGiC) is acknowledged.
