In a publication in Nature Communications, researchers at the Max Planck Institute for the Structure and Dynamics of Matter laid the theoretical foundation for more efficient magnetic storage.
In many materials, macroscopic magnetic properties emerge when microscopically small magnets align in a fixed pattern throughout the whole solid. In a publication in Nature Communications, Johan Mentink, Karsten Balzer and Martin Eckstein from the University of Hamburg at the Center for Free-Electron Laser Science (CFEL) and the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) have predicted that the interactions causing this alignment can be changed almost instantaneously and reversibly under the influence of a laser pulse. In future, this effect may be used for the development of faster magnetic storage. Besides this, the finding implies the highly counter-intuitive consequence that the magnetic dynamics can effectively run backwards in time under the influence of a sufficiently strong time-periodic laser field.
The strongest interactions in magnetic materials are called exchange interactions since they are caused by the exchange of electrons between individual microscopic magnets, called spins. A spin can feel a force from its neighbor that is up to a hundred times larger than the magnetic fields available in the laboratory. Johan Mentink and collaborators have shown that the electric field of the laser can influence the electrons during this exchange process and thus modify the interaction. Owing to the strength of the exchange interactions, this holds the promise to achieve a control of magnetism on the fastest possible timescale, with high relevance for technological applications such as magnetic storage.
While it has been demonstrated before that exchange interactions can be modified very rapidly, the ultimate control of exchange interactions would be achieved when one can selectively strengthen or weaken the interactions when the electric field is turned on and off, for example. This has now been demonstrated by exposing the magnetic material to a time-periodic electric field that is deliberately tuned to avoid a direct excitation of the electrons. Interestingly, even for the model system considered, this protocol already displays a rich control: the exchange interaction can be enhanced, weakened, and even reverse sign, thus favoring parallel instead of anti-parallel alignment of neighboring spins.
Quite surprisingly, upon changing the sign of the exchange interaction by the periodic electric laser field, it was observed that the spin dynamics turns back time. Mentink: ‘This demonstration caused a lot of excitement during our studies. Intuitively, one expects that a sign change of the interaction causes a rapid change of the magnetic state, but we find instead that the spins evolve back to their original orientation without any signature of a different magnetic state’. As a result, our studies do not only have high relevance for technological applications, but also for fundamental studies on the time-reversibility of quantum systems.
Prof. Dr. Martin Eckstein
Max-Planck-Institut für Struktur und Dynamik der Materie
Luruper Chaussee 149
22761 Hamburg / Germany
Tel.:+49 (0)40 8998-6270
Dr. Johan Mentink
Institute for Molecules and Materials
6525 AJ Nijmegen / The Netherlands
Tel.: +31 (0)24 3652903
Johan. H. Mentink, Karsten Balzer, and Martin Eckstein, "Ultrafast and reversible control of the exchange interaction in Mott insulators”, Nature Communications, 2015, DOI: 10.1038/ncomms7708
http://dx.doi.org/10.1038/ncomms7708 Original publication
http://www.mpsd.mpg.de/en/research/cmd/theo Research group of Prof. Dr. Martin Eckstein
http://www.mpsd.mpg.de/en Max Planck Institute for the Structure and Dynamics of Matter
Dr. Joerg Harms | Max-Planck-Institut für Struktur und Dynamik der Materie
Further reports about: > Communications > Dynamics > Electrons > Max Planck Institute > Max-Planck-Institut > Nature Communications > electric field > insulators > interactions > magnetic fields > magnetic interactions > magnetic material > magnetic storage > microscopic > quantum systems > small magnets > technological applications
Sharpening the X-ray view of the nanocosm
23.03.2018 | Changchun Institute of Optics, Fine Mechanics and Physics
Drug or duplicate?
23.03.2018 | Fraunhofer-Institut für Angewandte Festkörperphysik IAF
Satellites in near-Earth orbit are at risk due to the steady increase in space debris. But their mission in the areas of telecommunications, navigation or weather forecasts is essential for society. Fraunhofer FHR therefore develops radar-based systems which allow the detection, tracking and cataloging of even the smallest particles of debris. Satellite operators who have access to our data are in a better position to plan evasive maneuvers and prevent destructive collisions. From April, 25-29 2018, Fraunhofer FHR and its partners will exhibit the complementary radar systems TIRA and GESTRA as well as the latest radar techniques for space observation across three stands at the ILA Berlin.
The "traffic situation" in space is very tense: the Earth is currently being orbited not only by countless satellites but also by a large volume of space...
An international team of researchers has discovered a new anti-cancer protein. The protein, called LHPP, prevents the uncontrolled proliferation of cancer cells in the liver. The researchers led by Prof. Michael N. Hall from the Biozentrum, University of Basel, report in “Nature” that LHPP can also serve as a biomarker for the diagnosis and prognosis of liver cancer.
The incidence of liver cancer, also known as hepatocellular carcinoma, is steadily increasing. In the last twenty years, the number of cases has almost doubled...
In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.
Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...
Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.
They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...
A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...
23.03.2018 | Event News
19.03.2018 | Event News
16.03.2018 | Event News
23.03.2018 | Materials Sciences
23.03.2018 | Agricultural and Forestry Science
23.03.2018 | Physics and Astronomy