For release: Dec. 7, 2007

Contacts:
Matthew Vannette, Condensed Matter Physics
   (515) 294-5440, vannette@iastate.edu
Ruslan Prozorov, Condensed Matter Physics
   (515) 294-9901, prozorov@ameslab.gov
Saren Johnston, Public Affairs
   (515) 294-3474, sarenj@ameslab.gov

AMES LABORATORY GRADUATE STUDENT
GIVES WINNING PRESENTATION

Matthew Vannette’s Talk Best at Conference on Magnetism and Magnetic Materials

AMES, Iowa – Matthew Vannette, a graduate student working in the Condensed Matter Physics program at the
U. S. Department of Energy’s Ames Laboratory on the Iowa State University campus, won the Best Student Presentation award at the 2007 Conference on Magnetism and Magnetic Materials, Nov. 5-9 in Tampa, Fla. The award recognizes and encourages excellence in graduate studies in the field of magnetism and consists of a one-year fellowship of $1,000.

Vannette’s award-winning presentation, “Distinguishing Local Moment vs. Itinerant Ferromagnets: Dynamic Magnetic Susceptibility,” was selected from an international field of approximately 1,000 graduate students. His work represents new physics using a unique device called a tunnel diode resonator, or TDR, an extremely stable self-resonating circuit. Vannette’s work has shown that TDR measurements offer a means of determining whether a ferromagnetic system is local moment or nonlocal (itinerant) in its behavior. The discovery is significant because both forms of magnetism can exist in metals, and it’s extremely difficult to determine experimentally the difference between the two. However, models of magnetism depend on whether a system is local or itinerant.

Matthew Vannette poses with conference officials after being selected as the winner of the Best Student Presentation Award at the 2007 Conference on Magnetism and Magnetic Materials.  (left to right)  Kai Liu, program co-chair; Kaizhong Gao, awards coordinator; Vannette; Jan-Ulrich Thiele, program co-chair; and Dieter Weller, conference chairman.

The difference between local moment magnets and itinerant magnets is where the electrons that carry the magnetism reside in the solid material. In local moment magnets, the magnetic electrons live near the ions that make up the solid. However, in itinerant magnets, the magnetic electrons live in what is called the conduction band, where they are free to move and transfer a charge. Itinerant magnets, such as nickel, are conductors, while local moment magnets, such as gadolinium, can be insulators.

“When I first started putting different materials into the tunnel diode resonator, I noticed that local moment magnets showed one very easily understood behavior, but itinerant magnets showed a very different behavior,” said Vannette. “The data we collect using this technique allows us to discriminate between the two for whatever reason, and we’re on the verge of learning how to interpret the data to understand what that reason might be.”

Ruslan Prozorov, an Ames Laboratory physicist and Vannette’s major professor, said, “The TDR has been used traditionally mostly for studying superconductors. Matt is the first to apply the TDR to the study of magnetic materials. It’s totally his work and a completely new development in experimental physics. Until now, it was difficult and often ambiguous to determine if a system was local or itinerant. We’ve just scratched the surface with this work; it has to be developed and understood in detail,” Prozorov added.

The ability to distinguish between local and itinerant ferromagnetic systems using the tunnel diode resonator is a tremendous scientific advancement, but Vannette has an additional reason to be pleased. “It’s not just the local/itinerant discovery, but also using the tunnel diode resonator to its fullest extent,” he said. “In the magnetic system, there are so many effects going on that we need to understand.” A professional journal article about Vannette’s work in which he is listed as the first author has been accepted for publication in the April 2008 Journal of Applied Physics.

The DOE Office of Science, Basic Energy Sciences Office funded the above work on local and itinerant magnet systems and the tunnel diode resonator. Ames Laboratory, celebrating its 60th anniversary in 2007, is operated for the Department of Energy by Iowa State University. The Lab conducts research into various areas of national concern, including the synthesis and study of new materials, energy resources, high-speed computer design, and environmental cleanup and restoration.

###

Note to editors: For a high resolution copy of the image above, please contact Kerry Gibson, 515-294-1405.

Return to 2007 Press Releases