Funded by the National Science Foundation
A number of materials change from an ordered magnetic state (e.g. ferromagnet) to exhibiting glassy behavior when structurally and/or chemically disordered. The glassy magnetic behavior can be attributed to disordered surface states that freeze like a spin glass, or the freezing of ferromagnetic grains with randomly oriented anisotropy.
We are studying the magnetic transitions that occur when systems change from crystalline to nanocrystalline. In elements, the primary effect is reduction of the grain size, which increases the fraction of the sample that is in between grains. In alloys, a combination of chemical disorder and grain size refinement must be considered. We consider complex systems that often undergo multiple transitions. Our goal is to understand how you can differentiate between different types of magnetic glassiness using the nanostructure of the system to control interactions between grains and order.
We use mechanical alloying and cluster assembly to fabricate samples. We are particularly interested in magnetically glassy behavior that arises in systems with very high concentrations of magnetic moments (i.e. GdAl2, SmCo5) This project is in collaboration with Prof. Paul Shand (University of Northern Iowa), Prof. Tom Pekarek (University of North Florida), Prof. Valeri Petkov (Central Michigan University) and Dr. Daniel Haskel at Argonne National Laboratory.
For more information, see: