Manipulating the texture of magnetism
Derivation of equations that describe the dynamics of complex magnetic quasi-particles may aid the design of novel electronic devices
Knowing how to control the combined magnetic properties of interacting electrons will provide the basis to develop an important tool for advancing spintronics: a technology that aims to harness these properties for computation and communication. As a crucial first step, Naoto Nagaosa from the RIKEN Advanced Science Institute, Wako, and his colleagues have derived the equations that govern the motion of these magnetic quasi-particles1.
The magnetic behavior of a material is a result of a phenomenon known as spin. This can be thought of as the rotation of electrons and is usually visualized as an arrow pointing along the rotation axis. In some crystalline solids, neighboring electron spins can interact with each other such that the arrows form vortex-like patterns (Fig. 1). This spin ‘texture’ is robust and remains intact despite outside influences; it can also move through the material crystal, even though the atoms themselves remain stationary. Because of these properties, physicists often think of such spin vortices as particles in their own right; they call them skyrmions. The work of Nagaosa, with researchers from China, the Netherlands and Korea, provides a theoretical framework that describes skyrmion dynamics.
Skyrmions, and the ability to control them, have the potential to increase the packing density of magnetic recording media; as such, skyrmion-based devices are likely to be more efficient than conventional memories. “Skyrmions can be moved with a current density as much as a million times smaller than those needed to control magnetic structures, thus far,” explains Nagaosa.
The researchers theoretically investigated skyrmion crystals—ordered arrays of many skyrmions—that are supported by thin metallic films. Nagaosa and his collaborators2 had suggested previously that skyrmion crystals are more stable in thin films than they are in thicker ‘bulk’ materials, making films more amenable to practical applications. The equations of motion derived by Nagaosa and colleagues also showed: how the electrons are influenced by skyrmions; that skyrmions can become pinned to impurities in the film; and that the skyrmion trajectory bends away from the direction of an electrical current. The researchers called this phenomenon the skyrmion Hall effect because of its similarity to the sideways force that is exerted on an electron as it moves through a conductor in a magnetic field, which was discovered by Edwin Hall in 1879.
“Next we intend to study the effect of thermal fluctuations of the skyrmion structure and the optical manipulation of skyrmions,” says Nagaosa. “These are the important issues on the road towards applications.”
The corresponding author for this highlight is based at the Theoretical Design Team, RIKEN Advanced Science Institute
gro-pr | Research asia research news
The most recent press releases about innovation >>>
Die letzten 5 Focus-News des innovations-reports im Überblick:
The Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope (LBT) in Arizona released its first image of the surface magnetic field of another star. In a paper in the European journal Astronomy & Astrophysics, the PEPSI team presents a Zeeman- Doppler-Image of the surface of the magnetically active star II Pegasi.
A special technique allows astronomers to resolve the surfaces of faraway stars. Those are otherwise only seen as point sources, even in the largest telescopes...
Researchers at Chalmers University of Technology and the University of Gothenburg, Sweden, have proposed a way to create a completely new source of radiation. Ultra-intense light pulses consist of the motion of a single wave and can be described as a tsunami of light. The strong wave can be used to study interactions between matter and light in a unique way. Their research is now published in the scientific journal Physical Review Letters.
"This source of radiation lets us look at reality through a new angle - it is like twisting a mirror and discovering something completely different," says...
New research group at the University of Jena combines theory and experiment to demonstrate for the first time certain physical processes in a quantum vacuum
For most people, a vacuum is an empty space. Quantum physics, on the other hand, assumes that even in this lowest-energy state, particles and antiparticles...
Physicists in the EPic Lab at University of Sussex make crucial development in global race to develop a portable atomic clock
Scientists in the Emergent Photonics Lab (EPic Lab) at the University of Sussex have made a breakthrough to a crucial element of an atomic clock - devices...
A new way to sense earthquakes could help improve early warning systems
Every year earthquakes worldwide claim hundreds or even thousands of lives. Forewarning allows people to head for safety and a matter of seconds could spell...