The 2007 physics Nobel Prize awarded achievements in the field of magnetism. When they started their fundamental research, the laureates Albert Fert and Peter Grünberg did certainly not foresee in how little time their results would be used for everyday applications in computer hard disks’ drives.
Dr. Karsten Küpper and Dr. Jürgen Fassbender from the Forschungszentrum Dresden-Rossendorf (FZD) tackle similar fundamental questions concerning the physics of magnetism whose potential applications are unpredictable today. More precisely, they study magnetic vortices, which are like magnetic swirls on the nanoscale (one nanometer is the billionth part of a meter). These magnetic cores, located in the center of the magnetic swirl, have a size of only about 10 nanometers and a very stable magnetization. Hence, experts consider them as potential candidates for future non volatile magnetic memories.
Today researchers study the basic physical phenomena of magnetic vortices, observed experimentally for the first time only a few years ago. A vortex can be described as a round, thin ferromagnetic disc with a diameter of only a few micrometers showing a circular magnetization, to some extent similar to the wind in a tornado. In the center of the disk a very small core of about 20 atoms only exhibits a perpendicular magnetization (like the eye of a tornado storm points towards the earth). Applying a magnetic field to a magnetic vortex pushes the vortex away from the center of the disk towards the frame. If one then turns the field off abruptly, the vortex moves either clockwise or counter clockwise on a spiral like trajectory back into its initial position in the center of the disk. This special movement is called gyration. In principal, the perpendicular magnetization of the vortex core can point either upwards or downwards, and four different kinds of movement can be found: right- and left rotating magnetic swirls, combined either with an up- or downward directed perpendicular core magnetization.
Analogous to any other physical particle or particle like property one can find an anti-particle, i.e. an antivortex in the present case. The physicists of the FZD could now tackle the dynamic magnetic properties of two vortices and an antivortex, i.e. the movement of the three cores in response to a short magnetic field pulse. Usually a vortex and an antivortex annihilate immediately under emission of energy. However, two vortices located around an antivortex can built up a pretty stable micromagnetic unit, a so called single cross-tie wall. The experiments concerning the magnetization dynamics and the subsequent core movements were performed at the Swiss Light Source of the Paul Scherrer Institute in Switzerland. Fundamental questions were the driving force for these investigations: How do the two vortices and the antivortex influence the dynamic properties of the overall structure and the movement of the cores themselves? Do antivortex and vortices attract or repel each other in this specific arrangement? Are the subsequent spiral motions of the cores amplified or damped? Are other components of the overall cross-tie like the domain walls important for the overall dynamics?
Dr. Jürgen Fassbender sums up the outcome: “We could study some intriguing effects, in particular the gyrating movement of an antivortex has not been investigated experimentally so far. Due to comparison with complementary simulations we now understand details of the dynamic interaction between the three cores. Furthermore we could unravel the orientation of the three cores via analyzing their movements, although the lateral resolution of the used microscope is not high enough to extract the core orientation directly.”
What’s next? Dr. Jürgen Fassbender’s nanomagnetism team is now ready for its new challenge: to create a single antivortex and to experimentally investigate the magnetization dynamics of it for the first time. All this will certainly help in understanding the magnetization dynamics of even more complex micromagnetic structures, which might lay the basis for unforseen technological advances in the future.
Christine Bohnet | alfa
Magnetic nano-imaging on a table top
20.04.2018 | Georg-August-Universität Göttingen
New record on squeezing light to one atom: Atomic Lego guides light below one nanometer
20.04.2018 | ICFO-The Institute of Photonic Sciences
University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.
Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.
Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.
Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...
Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.
The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...
Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.
Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...
In the fight against cancer, scientists are developing new drugs to hit tumor cells at so far unused weak points. Such a “sore spot” is the protein complex...
13.04.2018 | Event News
12.04.2018 | Event News
09.04.2018 | Event News
20.04.2018 | Physics and Astronomy
20.04.2018 | Interdisciplinary Research
20.04.2018 | Physics and Astronomy