New findings from scientists at the Berkeley Lab (US) indicate that the road to magnetic vortex RAM might be more difficult to navigate than previously supposed, but there might be unexpected rewards as well. In an experiment made possible by the unique X-ray beams at Berkeley Lab’s Advanced Light Source (ALS), a team of researchers led by Peter Fischer and Mi-Young Im of the Center for X-Ray Optics (CXRO), in collaboration with scientists in Japan, discovered that contrary to what was previously believed, the formation of magnetic vortices in ferromagnetic nanodisks is an asymmetric phenomenon. It is possible that this breaking of symmetry would lead to failure in a data storage device during its initialization process.

"Our experimental demonstration that the vortex state in a single magnetic nanodisk experiences symmetry breaking during formation means that for data storage purposes, there would probably need to be a lengthy verification process to correct for errors," Im says. "On the plus side, non-symmetric behavior creates a biasing effect that could be applied to a sensor or a logic device."

"Our study is also a nice example of mesoscale science, which brings the nanoscience of the last decade to the next level," Fischer says. "Mesoscale phenomena encompass complexity and functionality over various length scales."

Mi-Young Im, Peter Fischer, Keisuke Yamada, Tomonori Sato, Shinya Kasai, Yoshinobu Nakatani, Teruo Ono: Symmetry breaking in the formation of magnetic vortex states in a permalloy nanodisk, In: Nature Communications, Vol. 3, July 31, 2012, Article number 983, DOI:10.1038/ncomms1978 http://dx.doi.org/10.1038/ncomms1978

Image left: MTXM images of in-plane (a) and out-of-plane (b) magnetic components in an array of permalloy nanodisks. In-plane magnetic rotation is shown by white arrow (a). Core polarization is marked by black (up) and white (down) spots. Image (c) shows the complete vortex configuration of each nanodisk in the array. © Im and Fischer