To exhibit electromagnetic wave absorption power with practically allowable thickness by dispersing soft magnetic fine metal powder having grain size of specified value or below into a matrix of rubber or synthetic resin.
A soft magnetic fine metal powder preferably includes fine powder of Fe, Ni, Co, Fe-Si-Al and permalloy. Fine powder finer than 4 micron is available easily through reductive decomposition of a metal oxide, e.g. carbonyl iron. Carbonyl iron powder thus produced is spherical and can be mixed easily with a matrix material. Chlorinated polyethylene rubber is optimally employed as the matrix material. Permittivity ' decreases and permeabilities μ', μ" increase as the grain size decreases. The μ' increases abruptly when the grain size decreases below 4 micron and prevents the peak of return loss from being shifted to the low frequency side through interaction with decrease of '. When the grain size of soft magnetic metal powder decreases, return loss increases to enhance electromagnetic wave absorption power.
SAITO AKIHIKO
ENDO HIROSHI
TSUTSUI KAZUHISA
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