|
Modeling
of spins at zero and finite temperatures. |
Not long ago, techniques for modeling
and evaluating magnetic materials
were too simplistic to reproduce accurately
all the data obtained in experiments.
But in 1995, researchers at Ames Laboratory,
led by Bruce Harmon, developed a "spin
dynamics" computational technique
that can be used to accurately represent
and evaluate the fluctuations of atomic
moments (magnetic orientations) in
solid magnetic materials at different
temperatures. Among its benefits,
the method can be used to make calculations
of realistic-sized systems at temperatures
of practical and scientific interest.
Using this technique, scientists for
the first time theoretically determined
the magnetic moments in iron and nickel
at high temperatures, even above a
key temperature at which the magnetic
moments vary in magnitude and point
in random directions. Current studies
focus on how and why specific defects
in permanent magnets are crucial in
determining desirable magnetic properties.
Oak Ridge National Laboratory and
collaborators used the technique in
a record-setting supercomputer calculation.
Scientific Impact:
The spin dynamics approach is a significant
contribution to the foundations of
a new theory of the dynamics of magnetic
moments at finite temperature and
in response to external applied fields.
It enables scientists to model material
properties at room temperature, at
which magnets typically are used.
Social Impact: Metallic
magnetism is key to many technologies,
including magnetic data storage and
electric power generation devices.
Accurate modeling of computer bit
switching is essential for the design
of future high-density computer disks,
and the capability to optimize high-temperature
magnetic materials will lead to more
energy efficient motors and transformers.
Reference: Phys.
Rev. Lett., 75,729 (1995).
URL:
http://cyclops.ameslab.gov/
Technical Contact:
Daniel A Hitchcock, Mathematical,
Information, & Computational Sciences
Division, Office of Advanced Scientific
Computing Research, 301-903-6767
Press Contact: Jeff
Sherwood, DOE Office of Public Affairs,
202-586-5806
SC-Funding Office:
Office of Advanced Scientific Computing
Research |