New avenues for ultrafast magnetic memory, ultra-performance sensing and low-energy computing

Due to its multidisciplinary nature and a diversified collection of world-leading competences in experimental and theoretical ultrafast and nanoscale magnetism, nano-optics, and molecular magnetism, the project also enjoyed an exciting atmosphere of spin-off advances into other research fields. These include nanoscale sensing, molecular quantum technologies, and next-generation electronics.
Now, the leaders and partners of the project look back at the achievements they've made over the last three years, and try to foresee what the future holds.

What was the initial idea?

Alexandre Dmitriev, University of Gothenburg, project coordinator: We started with an idea of the possible building block for this potential technology - an antenna for light. That is, it would be a nanoscale object that can capture efficiently visible and near-infrared light and can shuttle into the spot only several nanometers in size. What’s more, the light we capture would be carrying a twist – that is, it would be circularly-polarized. The field of switching magnetism in thin magnetic films with such twisted light has been developing for some time. While very demanding because it requires extremely short (femtosecond) and intense light pulses, the technology is considered very promising for future light-operated (that is, extremely fast) magnetic memory. With Femtoterabyte, we wanted to do this at the extremely small spot making such potential memory not only fast and energy-efficient (as less light power would be needed for the process), but also potentially extremely dense.

How did you initially think to proceed with such a huge task?

A. Dmitriev: The key was to gather the experts in all the needed fields – we’re talking here everything from conventional and ultrafast magnetism to light nanoantennas and the eventual industry-relevant technical development. The nanoGUNE research center (San Sebastian, Spain) was taking care of designing with electromagnetic simulations nanoantennas with required advanced properties; University of Gothenburg (Gothenburg, Sweden) was producing them with the state-of-the-art nanofabrication; Uppsala University (Uppsala, Sweden) and University of York were theoretically and experimentally designing all the magnetic materials that would go into nanoantennas and were figuring out the fundamental principles that would make such hybrid nanoantenna-nanomagnet systems to function; University of Florence (Florence, Italy) and University of Pisa (Pisa, Italy) were adding the ultimately small magnetic units to such nanoantennas – that is, magnets that are just one molecule in size; and Radboud University (Nijmegen, The Netherlands) and Paul Scherrer Institute (Villigen, Switzerland) were ready to measure the resulting nanoantennas by pulsing them with ultrashort light and looking at the signal from the entire sample with millions of nanoantennas or at each nanoantenna individually. Finally, a small tech company NanOsc (Stockholm, Sweden) and a major multinational corporation Thales (Paris, France) were jointly looking at possible industrial exploitation for the emerging technology in the project.
Armin Kleibert, Paul Scherrer Institute / Swiss Light Source, Switzerland: Using x-rays we can visualize things extremely sensitively and also at the very small scale (the scale of the magnetic units we are after in this project). We also add the pulsed light to such measurements. Such very complex experiments require large scale experimental facilities such as the Swiss Light Source at Paul Scherrer Institut, one of the partners in this project.

What are the main results of such massive collaboration three years later, when the project is now finished?

A. Dmitriev: What we have achieved essentially confirms the main hypothesis at the origin of the project, i.e., that it’s possible to influence a magnetic state with pulsed light at the nanoscale in a highly controlled fashion. We have created sophisticated nanoantennas that could channel an extremely short pulse of light to the extremely small spot, and we managed to measure what happens to the magnetic material in such a small spot.

Roberta Sessoli, University of Florence, Italy: Unexpected spill-overs often originates from frontier research. Here, the combination of circularly polarized light and nanoantennas has lead to a significant amplification of the magnetic signal coming from a very tiny amount of magnetic molecules. This can make the use of our laboratory instrumentation competitive with more powerful light sources, such as synchrotrons. We also found that we can use light concentrated by nanoantennas as a very precise probe for local magnetic fields at the nanoscale.

Paolo Vavassori, nanoGUNE Research center, Spain: Reading the information recorded in very tiny magnetic bits was also an additional challenge we had to tackle in the design of the new ultrafast and ultrasmall memory. We created a design in which a new type of coupling between the small magnet and the optical antenna leads to a 10-fold boost of the signal coming from the reading of the recorded magnetic information. This means we can both read and write such magnetic memory just with light.

What’s next for the science and technology that the project developed?

Paolo Bortolotti, Thales: In the project we developed a collection of proof-of-concept technologies that we believe will make up a breakthrough magnetic memory in the near future. We also approached constructing a physical demonstrator that in the future could be used for testing these technologies in close-to-real settings. Moreover, we foresee using the Femtoterabyte platform for the development of novel low-energy approaches for the information processing, that is – beyond simple magnetic storage.

A. Dmitriev: Like always with this kind of scientific ventures, one produces much more new knowledge that we planned for or anticipated from the beginning. This is also true for the spin-off technologies. For example, while working on combining nanoantennas with complex magnetic films, we discovered that such nanoantennas are also extremely good sensors of the properties of such films, specifically – their atomic composition. The latter can be just measured by detecting the visible light reflection from the film. This is unprecedented, as currently only highly sophisticated and expensive methods exist for this task. So we’ve submitted a patent application for this unexpected technology and are looking now into commercialization.

More information

Contact Professor Alexandre Dmitriev, Department of Physics, University of Gothenburg: alexd@physics.gu.se
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