Moldable, "Tunable" Magnets Make Their Debut

In the February 25 issue of the journal, Science, a first step toward tunable, ceramic magnets is reported by a group of researchers from Canada's University of Toronto (UT). Lead Science author Mark J. MacLachlan and colleagues tweaked iron-and-polymer molecules, transforming them into a magnetic ceramic material, which was molded into various shapes.

Key to the process is a technique for opening the rings in polymers. The group begins with monomers of silaferrocenophane (SFP). Subjecting the SFP to gentle heat produces poly(ferrocenylsilane), or PFS. Poured into molds of various shapes and subjected to more low heat, the molecules in this precursor material transform into a cross-linked network, which is loaded with trapped iron.

High doses of heat in a pyrolysis chamber sets the encapsulated iron free to seek other iron and form nanoclusters. Because larger clusters are more strongly magnetic, or ferromagnetic, the researchers can tune the material's magnetism, by adjusting the temperature inside the pyrolysis chamber. Around 500 degrees Celsius (932 degrees Fahrenheit), "The structure transforms, and iron starts coming together," Manners explains. "You get bigger and bigger clusters as you go to higher and higher temperatures."

Practical applications are still "far down the road," Manners emphasizes, but the possibilities seem limitless.

"We have created a new class of magnetically tunable, shaped ceramics, which you could potentially form as powders, wires, films, or tapes, for example," says Science coauthor Geoffrey A. Ozin. The UT team focused on basic scientific problems, Ozin notes. "We have characterized these materials to the point where you can now sit down and decide, what would be the utility of these materials?"

Along with MacLachlan, Ozin and Manners, coauthors on the Science paper were UT colleagues Madlen Ginzburg, Neil Coombs, Thomas W. Coyle, and Nandyala P. Raju, as well as John E. Greedan of the Institute for Materials Research at McMaster University.