Researchers now make use of local electric fields for writing and deleting individual nanoscale magnetic skyrmions
Physicists of the University of Hamburg in Germany have demonstrated for the first time the controlled writing and deleting of individual nanoscale magnetic knots – so called skyrmions – by applying local electric fields to an ultrathin film of iron as data storage medium.
Fig. 1: Controlled deleting (left) and writing (right) of individual nanoscale magnetic skyrmions by local electric fields. Between the individual images the tip of a scanning tunneling microscope was properly positioned and the local electric field was raised for a short time up to +3 V/nm (left) or -3V/nm (right). A single atomic vacancy in the ultrathin iron film (dark contrast) indicates the extremely small scale of the written and deleted skyrmions (bright contrast).
Fig. 2: Nanoscale skyrmions ligned up along linear tracks in ultrathin iron films being three atomic layers thick only. The magnetization direction rotates within atomic-scale distances within the skyrmions (bright contrast features), while it is constantly pointing perpendicular to the film plane in the ferromagnetic regions (dark blue regions). The image was recorded with a spin-polarized scanning tunneling microscope, which is the only technique that can reveal magnetization distributions with atomic-scale accuracy.
These tiny knots in the magnetization of ultrathin metallic films exhibit an exceptional stability and are highly promising candidates for future ultra-high density magnetic recording. So far, they could be manipulated by local spin-currents and magnetic fields only.
Now the research group at the University of Hamburg, headed by Roland Wiesendanger, report on the first electric-field controlled manipulation of nanoscale magnetic skyrmions in the journal Nature Nanotechnology (online issue of November 7, 2016). This work paves the way towards a new energy-efficient data storage technology in which electric fields can switch between two distinct magnetic states encoding the bits of information.
Magnetic skyrmions are highly complex three-dimensional spin textures, where the individual magnetic moments rotate in a unique sense by 360° from one side to the other. These objects have particle-like character and a non-trivial topology in contrast to the commonly known ferromagnetic state for which all magnetic moments are aligned in the same direction. Accordingly, skyrmions carry a topological charge „1“, whereas the ferromagnetic state has a topological charge of „0“.
In conventional magnetic data storage devices, the magnetic bits still consist of a rather large number of magnetic atoms with parallel aligned magnetic moments in two opposite directions, thereby encoding the „1“ and „0“ as bits of information. These two different magnetic states of conventional magnetic data storage systems can only be transformed into one another by magnetic fields or by spin currents, but not by electric fields because they are symmetry-related.
This is different in the case of skyrmions: they are topologically distinguishable from the ferromagnetic state and these two states can therefore be transformed into one another by local electric fields. The research group of Roland Wiesendanger could indeed show that tiny magnetic skyrmions can be switched by the local electric field present between the sharp tip of a scanning tunneling microscope and a sample consisting of a three atomic-layer thick iron film on an iridium substrate, and that the direction of the local electric field determines whether skyrmions can be created or deleted (see figure 1). Amazingly, the individual skyrmions in that three atomic layer thick iron film have a size of only 2.2 nm x 3.5 nm and can be aligned along linear tracks as shown in figure 2.
Conventional magnetic bits would never be stable in that size regime, whereas magnetic skyrmions pave the way towards ultra-dense data storage devices. Moreover, the demonstration of controlled electric-field induced writing and deleting of individual magnetic skyrmions can lead to an unprecedented energy-efficient way to store information since spin currents are no longer needed to switch between the two different bit states.
The research work leading to this fascinating discovery was partially supported by the Hamburgische Stiftung für Wissenschaften, Entwicklung und Kultur Helmut und Hannelore Greve in the framework of the “Hamburg Science Prize” for Roland Wiesendanger and his group.
Electric-field-driven switching of individual magnetic Skyrmions,
Pin-Jui Hsu, André Kubetzka, Aurore Finco, Niklas Romming, Kirsten von Bergmann, and Roland Wiesendanger,
Nature Nanotechnology (2016).
Prof. Dr. Roland Wiesendanger
Heiko Fuchs | idw - Informationsdienst Wissenschaft
Meteoritic stardust unlocks timing of supernova dust formation
19.01.2018 | Carnegie Institution for Science
Artificial agent designs quantum experiments
19.01.2018 | Universität Innsbruck
On the way to an intelligent laboratory, physicists from Innsbruck and Vienna present an artificial agent that autonomously designs quantum experiments. In initial experiments, the system has independently (re)discovered experimental techniques that are nowadays standard in modern quantum optical laboratories. This shows how machines could play a more creative role in research in the future.
We carry smartphones in our pockets, the streets are dotted with semi-autonomous cars, but in the research laboratory experiments are still being designed by...
What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...
For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.
Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...
At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.
No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...
Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.
Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...
08.01.2018 | Event News
11.12.2017 | Event News
08.12.2017 | Event News
19.01.2018 | Materials Sciences
19.01.2018 | Health and Medicine
19.01.2018 | Physics and Astronomy