Researchers generate electron spin vortex state "skyrmion molecules"

Feb 25, 2014
Fig. 1: The arrows indicate the directions of the electron spins. The electron spins in a skyrmion head toward the center, while spinning in a vortex shape. The spin directions at the center and at the outermost periphery are vertically opposite. b: Schematic diagram of a skyrmion molecule c: Skyrmion molecule observed within a ferromagnetic thin film in an experiment The plus and minus signs respectively indicate clockwise and counterclockwise spin direction.

RIKEN, the University of Tokyo, and the National Institute for Materials Science (NIMS; President: Sukekatsu Ushioda) succeeded for the first time in generating and visualizing electron spin vortex state "skyrmion molecules" with topological charge 2 within a thin film of "La1+2xSr2-2xMn2O7," a layered manganese oxide which is a ferromagnetic material with uniaxial anisotropy. While the current density required for driving domain walls within a ferromagnetic system is about 1 billion amperes per square meter, they managed to drive those skyrmion molecules with one-thousandth that density .

This result was achieved by a joint research group led by Dr. Xiuzhen Yu, Senior Research Scientist, and Dr. Yoshinori Tokura, Group Director (Professor at the School of Engineering, the University of Tokyo) of the Strong Correlation Physics Research Group, RIKEN Center for Emergent Matter Science (Center Director: Dr. Yoshinori Tokura), and Dr. Koji Kimoto, Unit Director of the Surface Physics and Structure Unit, Advanced Key Technologies Division (Division Director: Dr. Daisuke Fujita), NIMS.

Magnetic , which use the direction of electron spins within materials as magnetic information, are considered to be promising next-generation devices with high-speed and non-volatile properties. In recent years, that manipulate domain walls within ferromagnetic nanowires by using spin polarized electric current have been intensively studied. However, moving domain walls requires a large of at least about 1 billion amperes per square meter, and the large power consumption presented a problem. Therefore, a way to drive them under smaller current density had been sought.

In this respect, attention has been paid to "skyrmions," which are magnetic topological textures in which electron spins are aligned in a vortex shape. Unlike ferromagnetic domain walls, skyrmions have no intrinsic pinning sites and can avoid obstacles in the device. Thus, they can be driven under smaller current density than ferromagnetic domain walls. A single skyrmion has topological charge 1, which is equivalent to 1 bit of information. Skyrmions with higher topological charge had been predicted theoretically, but they had never been actually observed. The joint research group succeeded for the first time in generating skyrmion molecules with topological charge 2 in layered manganese oxide La1+2xSr2-2xMn2O7 while controlling the uniaxial anisotropy and the externally-applied magnetic field, and in driving them with one-thousandth the current density conventionally required for driving ferromagnetic . Such findings will bring about great development in designing novel magnetic memory devices with high-density and low power consumption with use of skyrmions. The research result has been published in the online edition of the British science journal Nature Communications on January 25

Explore further: Team invents microscopic sonic screwdriver

Related Stories

Controlling magnetism with an electric field

Feb 18, 2014

There is a big effort in industry to produce electrical devices with more and faster memory and logic. Magnetic memory elements, such as in a hard drive, and in the future in what is called MRAM (magnetic random access memory), ...

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.

Controlling skyrmions for better electronics

Aug 08, 2013

Physicists at the University of Hamburg managed for the first time to individually write and delete single skyrmions, a knot-like magnetic entity. Such vortex-shaped magnetic structures exhibit unique properties ...

Recommended for you

Researchers prove magnetism can control heat, sound

7 hours ago

Phonons—the elemental particles that transmit both heat and sound—have magnetic properties, according to a landmark study supported by Ohio Supercomputer Center (OSC) services and recently published by ...

How researchers listen for gravitational waves

16 hours ago

A century ago, Albert Einstein postulated the existence of gravitational waves in his General Theory of Relativity. But until now, these distortions of space-time have remained stubbornly hidden from direct ...

What's fair?: New theory on income inequality

May 27, 2015

The increasing inequality in income and wealth in recent years, together with excessive pay packages of CEOs in the U.S. and abroad, is of growing concern, especially to policy makers. Income inequality was ...

Scientists one step closer to mimicking gamma-ray bursts

May 27, 2015

Using ever more energetic lasers, Lawrence Livermore researchers have produced a record high number of electron-positron pairs, opening exciting opportunities to study extreme astrophysical processes, such ...

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.