New Design for Infinitesimal Rings

Photo: A magnet

A team of researchers at The Johns Hopkins University has come up with a possible design: tiny, irregularly shaped cobalt or nickel rings that can serve as memory cells. These "nanorings" can store a great quantity of information. They also are immune to the problem of "stray" magnetic fields, which are fields that "leak" from other kinds of magnets and can thus interfere with magnets next to them.

"It's the asymmetrical design that's the breakthrough, but we are also very excited about the fast, efficient and inexpensive method we came up with for making them," said Frank Q. Zhu, a doctoral candidate at Krieger School of Arts and Sciences at Johns Hopkins.

The asymmetrical design allows more of the nanorings to end up in a so-called "vortex state," meaning they have no stray field at all. With no stray field to contend with, Zhu's team's nanorings act like quiet neighbours who don't bother each other and, thus, can be packed together extremely densely. As a result, the amount of information that can be stored in a given area is greatly increased.

Fabrication of the nanorings is a multistep procedure involving self-assembly, thin film deposition and dry etching. The key to creating the irregular rings, Zhu said, is to - while etching the rings with an argon ion beam at the end of the process - tilt the substrate on which the rings are formed.

"In our previous study, we found that 100 nanometer symmetric nanorings have only about a 40 percent chance to get vortex state," Zhu said. "But the asymmetric nanorings have between a 40 percent and 100 percent chance to get vortex state. This chance can be controlled on-demand by utilizing the direction of magnetic field."; Source: Johns Hopkins University