College of Liberal Arts and Sciences at Iowa State University

Superconductive

Iowa State physics team follows up on a discovery made in Japan.

A group of Iowa State physicists have been studying intermetallic and metal oxide materials for years.

Of particular interest are materials that exhibit local moment magnetism coexisting with superconductivity, and metal-to-insulator transitions. The researchers place specific emphasis on the design, discovery, growth, and characterization of new exotic materials, usually in single crystal form.

Despite all that background, the lives of the Iowa State researchers have been turned upside down by a discovery in Japan. And all this has happened since the first of the year.

Physicists involved with the research include Paul Canfield, associate professor of physics; Serguei Bud'ko, associate scientist; Doug Finnemore, Distinguished Professor of physics; Vladimir Antropov, associate scientist; and Ferdinando Borsa, professor of physics.

The Japanese research team announced in early January that the compound, magnesium boride, was a superconductor and remained a superconductor at temperatures to below 40 K (Kelvin which is approximately minus 387 degrees Fahrenheit). That's about 29 degrees higher than any other simple metallic compound. A superconductor is a material that has no electrical resistance so that energy can be transported more efficiently.

"This is a fantastic discovery," Canfield said. "We immediately thought, 'wow, what can we do with that.'"

What Canfield and his colleagues have done may be almost as fantastic as the original discovery. While they didn't hear about the Japanese discovery until a week after it was announced, they soon made up for lost time.

In the subsequent three weeks, the Iowa State physicists wrote, submitted and had three papers accepted for publication. Ironically, their first paper was actually published prior to the Japanese paper discussing the discovery made it to print.

The group worked almost nonstop conducting experiments on magnesium boride, working seven days a week and up to 16 hours a day.

It's an environment that the researchers have truly loved.

"We were sprinting there for a month and it has been an absolute blast," Canfield said. "For a month now we have been leaders of the pack."

The Iowa State research has attracted national and international attention from the New York Times, Washington Post, the Associated Press, Science Magazine, as well as newspapers in Europe and Asia.

The experiments suggest that the compound works like traditional superconductors and not like high-temperature superconductors. Specifically, they found that electron-ion interactions cause the superconductivity and that supercurrents pass through barriers more easily than in the high-temperature, oxide superconductors.

Magnesium diboride is less dense and has higher normal state conductivity than other, traditional superconductors. In addition, magnesium and boron are also available in much greater abundance and are cheaper, raising hopes that it might eventually find applications in magnetic resonance imaging (MRI) machines among other items.

The group has also produced superconducting wires by exposing commercially available fibers of boron to magnesium vapors.

Cooperation with other areas on campus is what has made it possible for the Iowa State researchers to come so far, so quickly with magnesium boride.

"We were able to move very efficiently because we have a nucleus of people here at Iowa State and Ames Laboratory that are interested in making and understanding novel materials," Canfield said. "The fact that we could do it so fast was because of the resources and people that we have on campus."