Electron holography reveals the startling beauty of nanoscale magnetic vortices

May 30, 2014
Figure 1: High-resolution, three-dimensional analysis of skyrmions reveals a remarkably detailed magnetic structure. Credit: H. S. Park et al.

Nanoscale magnetic swirls known as skyrmions can form in certain materials such as thin magnetic films. These tiny vortices pack into dense lattices that are more stable than conventional magnetic domains and can be transported and manipulated with minimal electrical power—features that hold great promise for future information storage applications. To exploit skyrmions in such memory technologies, however, scientists need a deeper understanding of their fundamental properties.

Hyun Soon Park, Toshiaki Tanigaki and colleagues from the RIKEN Center for Emergent Matter Science, in partnership with industrial and academic researchers from across Japan, have now made major progress in this area by conducting the first three-dimensional analysis of skyrmion lattices using an electron holography microscope.

The RIKEN-led team has pioneered techniques to view skyrmions in two dimensions using techniques that include Lorentz transmission electron microscopy. However, the of skyrmions—defined by the orientation of electron spins—is not flat, and instead involves a three-dimensional distribution of spin orientations to form a true vortex. Analyzing this structure in quantitative detail is difficult because the features are beyond the resolution limit of Lorentz microscopy and can be obscured by the inherent roughness of the film's surface.

Electron holography, a technique for generating three-dimensional visualizations from interfering , can be used to resolve magnetic structures with unprecedented detail. Through collaboration with the group of the late Akira Tonomura—a forefather of electron holography—at Hitachi, Ltd, the researchers constructed a high-voltage electron holography microscope with sufficient power to resolve the skyrmion structure.

Using their holographic microscope, the researchers imaged the magnetic structure of a thin iron–cobalt–silicon film while applying a magnetic field. As the magnetic field intensity was increased, they observed a change in the electron spin arrangement from a helical structure to the swirling skyrmion structure. The three-dimensional images revealed that the skyrmions adopt a distinct cylindrical shape with an eerily beautiful interior pattern (Fig. 1). Intriguingly, this magnetic vortex switches from right- to left-handed as the direction of the applied is changed.

Park notes that skyrmions with cylindrical spin configurations can be expected to provide more effective spin transfer torque—a critical factor in transporting skyrmions for data storage applications. He is also confident that high-voltage electron holography has enormous potential to resolve many of the uncertainties associated with spintronic devices. "Seeing complex magnetic structures with high precision or in three dimensions is key to understanding these systems," he notes.

Explore further: Harnessing skyrmions for electronics and spintronics applications

More information: Park, H. S., Yu, X., Aizawa, S., Tanigaki, T., Akashi, T., Takahashi, Y., Matsuda, T., Kanazawa, N., Onose, Y., Shindo, D. et al. "Observation of the magnetic flux and three-dimensional structure of skyrmion lattices by electron holography." Nature Nanotechnology 9, 337–342 (2014). DOI: 10.1038/nnano.2014.52

add to favorites email to friend print save as pdf

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 ...

Recommended for you

Relaxing DNA strands by using nano-channels

14 hours ago

A simple and effective way of unravelling the often tangled mass of DNA is to 'thread' the strand into a nano-channel. A study carried out with the participation of the International School for Advanced Studies ...

Сalculations with nanoscale smart particles

Aug 19, 2014

Researchers from the Institute of General Physics of the Russian Academy of Sciences, the Institute of Bioorganic Chemistry of the Russian Academy of Sciences and MIPT have made an important step towards ...

Nanostructure enlightening dendrite-free metal anode

Aug 19, 2014

Graphite anodes have been widely used for lithium ion batteries (LIBs) during the past two decades. The replacement of metallic lithium with graphite enables safe and highly efficient operation of LIBs, however, ...

Bacterial nanowires: Not what we thought they were

Aug 18, 2014

For the past 10 years, scientists have been fascinated by a type of "electric bacteria" that shoots out long tendrils like electric wires, using them to power themselves and transfer electricity to a variety ...

User comments : 0