Permeability enhancement of soft magnetic films through metamaterial structures

The present article proposes a structure consisting of a single magnetic film enclosed in a metamaterial. This planar structure can be manufactured using conventional deposition and patterning techniques commonly utilized in the silicon industry. One example of such a structure was manufactured, and its permeability was measured in a wide frequency range and compared to the permeability of its core. Theoretical investigations of this structure were performed in order to establish its permeability as a function of the frequency, and an excellent agreement between the predicted and measured values was observed. Parametrical studies revealed that the metafilm exhibited two resonances; one below the gyromagnetic resonance frequency of the magnetic core, and one at a much higher frequency. Metafilms are attractive negative permeability materials since they exhibit large negative permeability levels within a wide frequency range, and since they are readily adjustable. In this respect, they combine the advantages of metamaterials and of their magnetic cores.It has been previously established that the quantity ∫0Fμ″(f)fdf is a good figure of merit for microwave magnetic materials. It is bounded in conventional magnetic materials by a quantity directly related to the saturation magnetization. The bounds associated with metafilms were derived, and it was shown that the ultimate limitations of metafilms with regard to this figure of merit were equivalent to those for conventional magnetic materials in the case of low-frequency operations.