NEWS=20 RELEASE
Office of Public Affairs
111 = TASF
Ames, IA=20 50011-3020
http://www.external.ameslab.gov

For=20 release:=20 Dec. 7, 2007

Contacts:
Matthew=20 Vannette, Condensed Matter Physics
   (515) = 294-5440,=20 vannette@iastate.edu
Ruslan=20 Prozorov, Condensed Matter Physics
   (515) = 294-9901,=20 prozorov@ameslab.gov
Saren=20 Johnston, Public Affairs
   (515) 294-3474, sarenj@ameslab.gov

AMES LABORATORY = GRADUATE=20 STUDENT
GIVES = WINNING=20 PRESENTATION

Matthew = Vannette=92s Talk Best at=20 Conference on Magnetism and Magnetic = Materials

AMES, Iowa =96 Matthew Vannette, a graduate student = working in=20 the Condensed Matter Physics program at the
U. S. = Department of=20 Energy=92s Ames Laboratory on the Iowa State University = campus, won=20 the Best Student Presentation award at the 2007 Conference = on=20 Magnetism and Magnetic Materials, Nov. 5-9 in Tampa, Fla. = The award=20 recognizes and encourages excellence in graduate studies in = the=20 field of magnetism and consists of a one-year fellowship of = $1,000.=20

Vannette=92s award-winning presentation, = =93Distinguishing=20 Local Moment vs. Itinerant Ferromagnets: Dynamic = Magnetic=20 Susceptibility,=94 was selected from an international = field of=20 approximately 1,000 graduate students. His work = represents new=20 physics using a unique device called a tunnel diode = resonator,=20 or TDR, an extremely stable self-resonating circuit.=20 Vannette=92s work has shown that TDR measurements = offer a means=20 of determining whether a ferromagnetic system is local = moment=20 or nonlocal (itinerant) in its behavior.

The discovery is significant because both forms of=20 magnetism can exist in metals, and it=92s extremely = difficult to=20 determine experimentally the difference between the = two.=20 However, models of magnetism depend on whether a = system is=20 local or itinerant.

Matthew Vannette poses with conference = officials after=20 being selected as the winner of the Best Student = Presentation=20 Award at the 2007 Conference on Magnetism and Magnetic = Materials. (left to right) Kai Liu, = program=20 co-chair; Kaizhong Gao, awards coordinator; Vannette;=20 Jan-Ulrich Thiele, program co-chair; and Dieter = Weller,=20 conference = chairman.

The difference between local moment magnets and itinerant = magnets=20 is where the electrons that carry the magnetism reside in = the solid=20 material. In local moment magnets, the magnetic electrons = live near=20 the ions that make up the solid. However, in itinerant = magnets, the=20 magnetic electrons live in what is called the conduction = band, where=20 they are free to move and transfer a charge. Itinerant = magnets, such=20 as nickel, are conductors, while local moment magnets, such = as=20 gadolinium, can be insulators.

=93When I first started putting different materials into = the tunnel=20 diode resonator, I noticed that local moment magnets showed = one very=20 easily understood behavior, but itinerant magnets showed a = very=20 different behavior,=94 said Vannette. =93The data we collect = using this=20 technique allows us to discriminate between the two for = whatever=20 reason, and we=92re on the verge of learning how to = interpret the data=20 to understand what that reason might be.=94

Ruslan Prozorov, an Ames Laboratory physicist and = Vannette=92s=20 major professor, said, =93The TDR has been used = traditionally mostly=20 for studying superconductors. Matt is the first to apply the = TDR to=20 the study of magnetic materials. It=92s totally his work and = a=20 completely new development in experimental physics. Until = now, it=20 was difficult and often ambiguous to determine if a system = was local=20 or itinerant. We=92ve just scratched the surface with this = work; it=20 has to be developed and understood in detail,=94 Prozorov = added.

The ability to distinguish between local and itinerant=20 ferromagnetic systems using the tunnel diode resonator is a=20 tremendous scientific advancement, but Vannette has an = additional=20 reason to be pleased. =93It=92s not just the local/itinerant = discovery,=20 but also using the tunnel diode resonator to its fullest = extent,=94 he=20 said. =93In the magnetic system, there are so many effects = going on=20 that we need to understand.=94 A professional journal = article about=20 Vannette=92s work in which he is listed as the first author = has been=20 accepted for publication in the April 2008 Journal of = Applied=20 Physics.

The DOE Office of Science, Basic Energy Sciences Office = funded=20 the above work on local and itinerant magnet systems and the = tunnel=20 diode resonator. Ames=20 Laboratory, celebrating its 60th anniversary in 2007, is = operated for the Department = of=20 Energy by Iowa State = University. The Lab conducts research into various areas = of=20 national concern, including the synthesis and study of new=20 materials, energy resources, high-speed computer design, and = environmental cleanup and restoration.

###

Note to editors: For a high resolution copy of the image = above,=20 please contact Kerry=20 Gibson, 515-294-1405.

Return=20 to 2007 Press Releases