Posted in | Nanomagnetics

Electron Pulses Used to Manipulate Nanomagnets and Store Information

Magnets and magnetic occurrences underpin the huge majority of advanced data storage, and the measurement scales for research dedicated on magnetic behaviors continue to shrink with the rest of digital technology.

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Skyrmions, for instance, are a kind of nanomagnet, made up of a spin-correlated collection of electrons serving as a topological magnet on specific microscopic surfaces. The precise properties, like spin orientation, of such nanomagnets can accumulate information. But how does one go about moving or controlling these nanomagnets at will to store the data that is needed?

New research from a German-U.S. partnership currently shows such read/write ability using bursts of electrons, encoding topological energy structures strongly enough for promising data storage applications. As the team reports this week in Applied Physics Letters, from AIP Publishing, the magnetization of these collective excitations, or quasiparticles, is regulated by tweaking the profile of the electron pulses, differing either their width in space or the total number of electrons.

The work shows how magnetization of nanoscale magnets can be steered by intense ultrashort electron pulses. Experiments at SLAC already demonstrated the ultimate speed limit of magnetic switching with this scheme. Here we show that tailored electron pulses can swiftly write, erase or switch topologically protected magnetic textures such as skyrmions.

Alexander Schäffer, a Doctoral Student, Martin-Luther-Universität Halle-Wittenberg in Halle, Germany, and Lead Author of the paper

Up to now, Schäffer says there are just a few recognized applications of these skyrmions, which are comparatively new to the forefront of solid state physics, but their properties and the existing research capabilities make them suitable for next generation technologies.

In the tradition of the field of spin dynamics in nanostructures, I still appreciate the idea of non-volatile (long-term) memory devices, as the community of spintronics is also pursuing. The nice interplay between the mathematical concept of topological energy barriers and the physical transport properties of skyrmions, which are highly mobile, are the outstanding aspects for me.

Alexander Schäffer, a Doctoral Student, Martin-Luther-Universität Halle-Wittenberg in Halle, Germany, and Lead Author of the paper

Not only are these magnetic excitations manageable, but the team's results verify a number of the dynamic understandings provided by concept. Furthermore, their results show potential for accomplishing similar topological charge transcription through laser pulses, whose lower and mass-free energy provide many practical benefits.

"These quasiparticles are robust against external perturbations, and hence are usually difficult to manipulate, and have a high potential for applications in data storage and computing," Schäffer said. "I was positively surprised about the nice accordance between experiment, analytics and numerical results, which gave me a good feeling in continuing this path. A second point was the finding that textures can be written with much lower beam intensity using tightly focused electron pulses. This brings their technological exploitation within reach as the required high-energy ultrafast electron microscopy setup is currently being developed at SLAC and other places worldwide."

This major step lends itself to many more in the development from this generation's pioneering research to next generation's hard drives. As they carry on furthering their research, Schäffer and his partners are aiming at broader applicability in several ways.

Further development in the setups is required to be able to write skyrmionic structures on extended films, where we can't make any profit of geometric confinements like in the nanodisks. The next steps are manifold. Of course, an experimental realization is what we strive for with our experimental colleagues, especially the question of how good the switching-behavior between different topological states can be covered by our calculations. A complete simulation of laser-irradiated TEM of magnetic samples is one of our big goals at the moments.

Alexander Schäffer, a Doctoral Student, Martin-Luther-Universität Halle-Wittenberg in Halle, Germany, and Lead Author of the paper

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