Nonreciprocal electromagnetic properties of nanocomposites at microwave frequencies -: art. no. 092401

We report on the effects of composition and external magnetic field on the microwave permeability tensor of Ni/gamma-Fe2O3 nanocomposites. When compared to the zero-field case, the field measurements of the permeability tensor (mu) over bar exhibit nonzero off-diagonal components giving evidence of the nonreciprocity of wave propagation in these nanostructures. We observe that the diagonal and off-diagonal elements of (mu) over left right arrow of these nanocomposites depend sensitively on their Ni content and of the applied static magnetic field. These experimental results are analyzed within a recently developed multiscale modeling [S. Mallegol , Phys. Rev. B 68, 174422 (2003)] and can be understood as arising from magnetostatic intergranular interactions via a mean-field approximation. The application of these heterogeneous nanomaterials open possibilities for the design of field-controlled nonreciprocal components used in microwave integrated circuit technology.