About two years ago, researchers in Germany introduced a new alternative in the world of magnetic storage media: skyrmions. A short description of skyrmions is that they are tiny, swirling magnetic spin patterns in thin films. What makes them important is that they could change the face of data storage, hugely increasing the storage capacity over today’s hard disk drives.
Now, within a span of week, three separate research teams, one at the National Institute of Standards and Technology (NIST) in the United States, another at KTH The Royal Institute of Technology in Sweden and still another at the RIKEN Center for Emergent Matter Science in Japan have all announced breakthroughs that may bring these magnetic spin patterns one step closer to being the basis of real-world data storage applications.
In most magnetic materials, the magnetic force of each atom—known as the magnetic moment—lines up in the same direction as those of all the others. However, some magnetic materials such as manganese silicon (MnSi), when under extreme conditions, can develop areas where the magnetic moments curve and twist; these areas are known as magnetic skyrmions. Once skyrmions are formed, they are pretty resilient to outside influence, which makes them an ideal storage medium because they are not easily corrupted.
The extreme conditions are the key. To first form skyrmions, some of the researchers exposed the magnetic material to extremely low temperatures. But generally speaking, the conditions for forming skyrmions involve either magnetic, thermal, or electrical stimuli.
All three research teams published their findings in the journal Nature Communications. The NIST researchers demonstrated that they could produce skyrmions by patterning asymmetric magnetic nanodots in a controlled circle on top of a thin film made of cobalt and palladium. The NIST researchers were able to create their skyrmions not only at room temperature, but also without an external magnetic field.
The Riken team out of Japan demonstrated that a new stimuli could create skyrmions, namely a mechanical force. While this method still involves creating the skyrmions in extremely low temperatures, it does offer the potential of both creating and deleting skyrmions with a small push. This, they say, could lead to new, low-cost memory devices that consume very little energy.
The KTH researchers demonstrated not only a novel way to produce the swirling magnetic regions, but also presented a way to maintain their stability. The Swedish group formed its skyrmions under a nanocontact in which a spin-polarized current had been injected into the magnetic thin film. This provided a so-called spin torque to the film’s magnetic moments so that the skyrmions remains more stable.
Observed as a group, this latest flurry of research suggests that skyrmions will become a mainstay of spintronics research for data storage. However, we may have a bit of a wait before we see this become the basis for magnetic data storage in our devices.
Dexter Johnson is a contributing editor at IEEE Spectrum, with a focus on nanotechnology.