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Photonic metamaterials consisting of artificial opal with magnetic inclusions were considered, used in controllable microwave electronic devices. The analyzed structures consist of matrices of SiO2 nanospheres (diameter 200 - 400 nm) with included clusters of ferrite spinels (MnxCo0.6-xZn0.4Fe2O4, NixCo0.6-xZn0.4Fe2O4, LaxCo0.6-xZn0.4Fe2O4, NdxCo0.6-xZn0.4Fe2O4) in interspherical nanospacing (4 ÷ 7% concentration). The ellipsoidal clusters are polycrystalline, with spatial dimensions of 20 – 30 nm and grains of 5 – 12 nm. A controlled wave absorption was obtained in these high inductivity structures. Evolution of the wave attenuation coefficient, α[dB/m], in function of the applied magnetic field and particle inclusion size, for different content of the magnetic ions in the ferrite inclusion, have been determined at frequencies around the samples ferromagnetic resonance, by structural simulation. The test configuration was: sample inside the rectangular waveguide, mode TE10, in the frequency range 24 ÷ 40 GHz. The polarizing magnetic field for the ferrites was tested in the range of 0 ÷ 20 kOe and minimized by modifying the structure. The metamaterial design optimization was realized, controllable by different parameters at structure level. The ferromagnetic resonance influence on the control process was pointed out and also the particular results and effects which can be induced by the resonant behavior.

The inverse opal structures present very good mechanical and optical properties, like high mechanical strength and Young modulus, important photoluminescence and stimulated Brillouin scattering. Enhancement of the optical properties of the metamaterials based on different types of inverse opal can be obtained by controlling the stopband of the 3D periodic structure. SiO2, TiO2 and CeO2 photonic crystals with inverse opal structures have been studied, presenting voids of 100 – 280 nm. The stopband dependence on the physical and geometrical parameters of the matrix has been analyzed (ions nature, voids diameter, photoelastic constant). The study was performed by structural simulation methods, using the HFSS program. The test configuration was set for the visible light domain. The effective refraction index n and the stimulated Brillouin scattering coefficient gP have been determined and represented on parametrical graphs. Results were compared with the theoretic calculated values. By varying different structural parameters and the stopband control, superior values of the optical parameters have been obtained, in comparison with the data given in literature. We report an increasing of the photoluminescence with about 7%, respectively and enhancement of the stimulated Brillouin scattering coefficient of 11 % when parameters are correlated.

Read heads performances have been analyzed by simulation (HFSS) in the case of the devices designed with a category of spin valve structures with nano-oxide-layer insertion, based on Co alloys. Different structures of the stack of layers in the spin valve were considered in order to increase the magnetic resistance due to contribution of the insertion layer. A parametrical evolution of the resistance-area product variation ΔRA, and of the areal storage density have been obtained using the simulation and theoretical data. Results indicate areal densities up to 780 Gbit/in2 for the system manufactured in practice, when the variation of the resistance-area product was greater than 7.4…9 mΩ•μm2, strongly dependent on the nanooxide insertion layer. These performances can be overlapped by parameters correlation, indicated by simulation. Consequently, our simulations offer solutions for improving the recording performances by controlling the spin valve structure.

Some peculiar spin valve structures with increased magneticresistance (MR), based on Co alloys, have been analyzed in this paper by simulation methods (with help of the HFSS 13.0 program) and their performances were determined for applications at digital sensors. Structures involve specular nano-oxide-layer spin valves (NOL-SV) presenting a NOL insertion inside the pinned layer. A controlled structure has been obtained, simulations indicating the parameters correlation in order to obtain the MR maxima. Values of around 5.8…16% for the MR ratio have been obtained, respectively a variation of the resistance-area product of 0.7…9 mΩ•μm2, for an individual layer thickness of around 2ߝ3.2 nm, in an applied field of about 0.4…2.7 kOe. Our results illustrate better performances of the NOL spin valves in comparison with the results previously reported in literature.