Driving an electron spin vortex "Skyrmion" with a microcurrent

Aug 27, 2012
Fig. :Magnetic structure observed by Lorentz transmission electron microscopy. (a) Helical stripe structure in the zero magnetic field. Dotted lines show the crystal grain boundary. (b) Skymrion crystal formed by applying a 150mT magnetic field perpendicular to the device. (c) Enlarged diagram of the skyrmion crystal. (d) Distribution of magnetization in a single skyrmion. Colors and arrows show the direction of electron spin in the skyrmion.

RIKEN and the National Institute for Materials Science (NIMS) have succeeded in forming a skyrmion crystal in which electron spin is aligned in a vortex shape in a microdevice using the helimagnet FeGe. The skyrmion crystal is driven with an ultra-low current density less than 1/100,000 that of the current necessary to drive magnetic domain walls in ferromagnets. This research lays the groudwork for technology that manipulates the states of magnetic information media with extremely low power consumption.

Magnetic memory devices that use the direction of —the source of magnetism—as digital information have attracted attention because of their high speed and non-volatility, etc. In recent years, numerous attempts have been made to manipulate that magnetic information electrically without utilizing a magnetic field. If a current is passed through a , it is possible to move the magnetic domain walls. These walls are the boundaries between those domains with upward-oriented magnetization and those with downward orientation (at domain walls, the direction of magnetic spin gradually changes). Therefore, reversal of magnetization becomes possible and information can be written. However, in order to drive the domain walls in this manner, a large of at least approximately 105 A/cm2 was necessary. Because this causes large —in other words, large —a method of manipulating magnetic information media with a smaller current density is advantageous.

The research team investigated various functional , and in 2010, succeeded in forming and observing a skyrmion crystal by applying a weak magnetic field of less than 200 millitesla (mT) to a thin slice of the helimagnet FeGe at near room temperature. In the present research, the team fabricated microdevices with a length of 165μm, width of 100μm, and thicknesses of 100nm to 30μm using the same FeGe. When a magnetic field of approximately 150mT at temperatures from -23°C to near-room temperature (-3°C) was applied, skymrion crystals in which a stable skyrmion with a diameter of about 70nm was aligned in a triangular lattice shape were observed. The team succeeded in driving the skymrion crystal with an ultra-low current density (the minimum density is approximately 5A/cm2), which is less than 1/100,000th that required to drive magnetic domain walls in conventional ferromagnets. The fact that the skymrion can be driven with this extremely low current density represents the first step toward the development of low magnetic memory devices using skymrions as an information medium. Various applications can also be expected in the field of spintronics, which is currently an area of active research as a next-generation electronic technology.

Explore further: Pseudoparticles travel through photoactive material

More information: This research was published in the online edition of the British science journal Nature Communications on August 7 (August 8 Japan time).

Related Stories

Manipulating the texture of magnetism

Feb 03, 2012

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 ...

Vortices get organized

Feb 25, 2011

Exotic entities that arrange into a crystalline structure at near room-temperature could lead to a new approach to electronic memory.

Recommended for you

Pseudoparticles travel through photoactive material

Apr 23, 2015

Researchers of Karlsruhe Institute of Technology (KIT) have unveiled an important step in the conversion of light into storable energy: Together with scientists of the Fritz Haber Institute in Berlin and ...

From metal to insulator and back again

Apr 22, 2015

New work from Carnegie's Russell Hemley and Ivan Naumov hones in on the physics underlying the recently discovered fact that some metals stop being metallic under pressure. Their work is published in Physical Re ...

Electron spin brings order to high entropy alloys

Apr 22, 2015

Researchers from North Carolina State University have discovered that electron spin brings a previously unknown degree of order to the high entropy alloy nickel iron chromium cobalt (NiFeCrCo) - and may play ...

Expanding the reach of metallic glass

Apr 22, 2015

Metallic glass, a class of materials that offers both pliability and strength, is poised for a friendly takeover of the chemical landscape.

Electrons move like light in three-dimensional solid

Apr 22, 2015

Electrons were observed to travel in a solid at an unusually high velocity, which remained the same independent of the electron energy. This anomalous light-like behavior is found in special two-dimensional ...

Quantum model helps solve mysteries of water

Apr 20, 2015

Water is one of the most common and extensively studied substances on earth. It is vital for all known forms of life but its unique behaviour has yet to be explained in terms of the properties of individual ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.