Driving a spin-vortex “skyrmion” by minute electric current Towards magnetic storage using 1/100,000 current density of current media
A magnetic memory storing digital information in electron spin has attracted much attention because of its potential for high-speed processing and non-volatility. Recently, many studies have focused on the control of magnetic information by electric current, instead of using magnetic fields. If a current is passed through a ferromagnet, it is possible to move the magnetic domain walls, the boundaries between domains where magnetization is upward- or downward-orientated (at domain walls, the direction of magnetic spin gradually changes). In this way information can be written by reversing magnetization. However, a large current density of about 105 A/cm2 is required for moving domain walls, which results in a huge energy consumption. For this reason, realization of the low current-density electric control of magnetic information is highly sought after.
A schematic illustration of a skyrmion driven by an electric current (the current of the conduction electrons). © Yoshinori Tokura and Naoya Kanazawa
The arrows indicate the magnetic moments, whose directions are opposite to those of the spins. The vortex-like spin order “skyrmion” is driven by the flow of the conduction electrons (yellow particles in the figure) through interactions between the magnetic moments of the skyrmion and the conduction electrons.
Prof. Yoshinori Tokura, leading a FIRST program “Quantum Science on Strong Correlation” at the University of Tokyo, Dr. Xiuzhen Yu at RIKEN, and their colleagues investigated spin texture in a microelement made from a helical magnet FeGe. They discovered that a nanoscale spin vortex or “skyrmion” can be driven by electric current near room temperature. The required current density for moving skyrmions is about five orders of magnitude smaller than that for moving ferromagnetic domains. This discovery paves the way to a low cost, high efficiency skyrmion magnetic memory. Skyrmions are expected to find many applications in the field of “spintronics,” the next generation of electronics.
Department release/press release (Japanese)Paper
X. Z. Yu, N. Kanazawa, W. Z. Zhang, T. Nagai, T. Hara, K. Kimoto, Y. Matsui, Y. Onose, Y. Tokura,
“Skyrmion flow near room temperature in an ultralow current density”
Nature Communications 3 (2012): 988, doi:10.1038/ncomms1990
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