Rotational alignment of magnetic microdisks in composites for high frequency applications

In this work, we present an experimental and theoretical investigation of the alignment dynamics of disk-shaped magnetic particles in a Newtonian fluid under the influence of a rotating magnetic field. This work is motivated by the need for developing soft magnetic composite materials, with aligned particles, for high frequency inductor and antenna applications. Composite materials, consisting of soft magnetic particles embedded in a non-magnetic insulating matrix, have great potential for such high frequency applications: the dielectric and magnetic properties can be tailored by the choice of matrix as well as particle composition, size and concentration. Further, magnetic anisotropy in the composite can be engineered by controlling orientation of anisotropic particles within the matrix [1, 2]. In previous work, we have shown that the alignment of disk-shaped particles in a composite results in planar anisotropy, increasing both the ferromagnetic resonance frequency and in-plane permeability as desirable for high frequency applications [3].