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Magnetostriction of Field-Structured Composites

Published online by Cambridge University Press:  01 February 2011

James E. Martin ,
Robert A. Anderson  and
Gerald Gulley
James E. Martin
Affiliation:
Sandia National Laboratories Albuquerque, New Mexico 87185, U.S.A.
Robert A. Anderson
Affiliation:
Sandia National Laboratories Albuquerque, New Mexico 87185, U.S.A.
Gerald Gulley
Affiliation:
Dominican University, River Forest, IL 60305, U.S.A.
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Abstract

Field-structured magnetic particle composites are an important new class of materials that have great potential as both sensors and actuators. These materials are synthesized by suspending magnetic particles in a polymeric resin and subjecting these to magnetic fields while the resin polymerizes. If a simple uniaxial magnetic field is used, the particles will form chains, yielding composites whose magnetic susceptibility is enhanced along a single direction. A biaxial magnetic field, comprised of two orthogonal ac fields, forms particle sheets, yielding composites whose magnetic susceptibility is enhanced along two principal directions. A balanced triaxial magnetic field can be used to enhance the susceptibility in all directions, and biased heterodyned triaxial magnetic fields are especially effective for producing composites with a greatly enhanced susceptibility along a single axis. Magnetostriction is quadratic in the susceptibility, so increasing the composite susceptibility is important to developing actuators that function well at modest fields. To investigate magnetostriction in these field-structured composites we have constructed a sensitive, constant-stress apparatus capable of 1 ppm strain resolution. The sample geometry is designed to minimize demagnetizing field effects. We have demonstrated field-structured composites with nearly 10,000 ppm strain, and have shown that at large magnetic fields a structural phase transition occurs within the composite. These experimental results are compared to microscopic, self-consistent field simulations of magnetostriction in these complex, disordered materials.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 785: Symposium D – Materials and Devices for Smart Systems , 2003 , D12.5
Copyright
Copyright © Materials Research Society 2004

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References

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