Prof. Visscher has worked in a number of fields of condensed
matter physics, most recently on the dynamics of magnetic
nanostructures. With Dmytro Apalkov, he worked out a
Fokker-Planck approach to the calculation of switching rates in spin-torque systems.
This type of switching has been known for only a few years and is being
intensively studied as a possible new information-storage technology --
a spin-torque switched magnetic random-access memory (MRAM) would
combine the speed of DRAM with the nonvolatility of flash
memory.
A unifying theme of Prof. Visscher's work is the use
of hierarchical and recursive methods to describe interacting systems.
He has applied renormalization-group methods to hydrodynamics and the
glass
transition, and most recently to magnetization dynamics in magnetic
materials
(the Landau-Lifshitz equation). The dynamics of high-speed switching of
magnetic materials is of interest to the UA's Center for Materials for
Information Technology (MINT) and to the computer industry. As one of
the
principal investigators of the University of Alabama's National Science
Foundation Materials
Research
Science and Engineering Center (MRSEC), Prof. Visscher has
developed
methods for computer
simulation
of colloidal suspensions of magnetic particles that are used to
manufacture
magnetic tapes and disks.
His group has made the first applications of hierarchical
fast-multipole
methods (first used in astrophysical simulations) to systems of
magnetic
nanoparticles. These simulations predict a fractal-like gel structure
for
magnetic colloids, and allow the calculation of their magnetic
susceptibility
-- susceptibility measurement has been used for some time in the
information-storage
industry to assay the quality of magnetic inks, and can now be directly
related to microstructural models.
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