Ferromagnetic granules with the size range of a few tens of microns have been successfully used in integrated electronic devices as microwave absorbers in the form of high permeability sheets with thickness of about 100 microns where the granules are embedded in polymer(1). Their high production rate, high resistivity and high permeability performance in the GHz range are quite attractive if their thickness could be reduced to less than a few tens of microns. However, many factors such as eddy current, magnetic anisotropy, dipole-dipole interaction, and size distribution are involved in determination of their frequency characteristics and more basic study is needed to design thinner high performance materials. In this study particle assemblies composed of Fe particles and Fe3O4 nanoparticles are studied to obtain fundamental insight to the most appropriate approach to develop a new high permeability particle assembly.
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