High-Permeability Magnetic Polymer Additives for Lightweight Electromagnetic Shielding

Report No. ARL-TR-7372
Authors: Kristen S Williams; B Christopher Rinderspacher
Date/Pages: August 2015; 44 pages
Abstract: This report describes fundamental research on the magnetic properties of organometallic complexes and their performance as potential dopants in polymeric electromagnetic (EM) shielding materials. The research hypothesis was that ferromagnetic polymers can be realized via doping with magnetic organometallic complexes, and that the magnetic spin state of the dopant determines the bulk magnetic response. To test this hypothesis, the magnetic properties of several organometallic complexes were investigated using spin-polarized quantum chemistry calculations. It was found that organometallic complexes can have high spin states with large magnetic stabilization energies. The key chemical design principles for achieving high-spin dopants were identified, and the best performance was found in organometallic complexes containing Cr2+, Mn2+, and Fe2+ bound to aromatic rings. A FORTRAN code to simulate the 3-dimensional Ising model was developed, and it revealed that ferromagnetic ordering in doped polymers is highly dependent on dopant distance and not possible for cases when complexes are widely dispersed. Nevertheless, polymeric matrices doped with high-spin complexes still exhibit a paramagnetic response to an external magnetic field and could enable the development of lightweight EM shielding materials. To guide future materials selection, this report concludes with a table of recommended complexes that have the best magnetic performance.
Distribution: Approved for public release
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Last Update / Reviewed: August 1, 2015