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We numerically and experimentally investigated dual-band absorption of sandwich-structure metamaterials which include periodic metal coupled rings at the front separated from the metal plane at the back by a dielectric layer. The properties are demonstrated in both GHz and mid-IR regimes of electromagnetic (EM) wave. The dual-band perfect absorber with polarization independence is observed under normal incidence. In order to understand the EM properties of dual-band perfect absorber, the plasmonic excitation was clarified for both peaks. Finally, by connecting the rings, the perfect-absorption peaks can be controlled with the polarization angle of incident EM wave.

Cobalt (Co) antidot arrays with different lattice geometries, square and rhomboid structures were fabricated and their magnetic reversal properties were studied by scanning-electron microscopy (SEM), magneto-optic Kerr effect, and magnetic force microscopy (MFM). Different lattice symmetries induced the corresponding anisotropies with changing easy and hard axes. The nearest-neighbor rule is not applicable in case of the rhomboid antidot lattice, while the inclusion theory is. These results are different from those of the previous investigations. The differences are due to different sizes and spacing’s between the antidots. The MFM images in the remanent state showed well-defined domain structures, periodic in nature according to the lattice geometry.

The microstructural and the magnetotransport properties of La 0.7 Ca 0.3 MnO 3 and La 0.7 Sr 0.3 MnO 3 films, deposited on a BaTiO 3 layer ͑LCMO/BTO and LSMO/BTO, respectively͒, and on LaAlO 3 and SrTiO 3 ͑001͒ single crystals ͑LCMO/LAO, LSMO/LAO and LSMO/STO͒ by rf-magnetron sputtering using the "soft" ͑or powder͒ targets, have been investigated. The films grown on BTO demonstrate biaxial tensile in-plane and compressive out-of-plane strains, while those grown on LAO show the opposite trend, i.e., compressive in-plane and tensile out-of-plane strains. The films with a biaxial tensile in-plane strain undergo the magnetic transition at a higher temperature than those with a biaxial compressive one. This implies that the variation of Mn-O-Mn bond angle, controlled by the lattice strain, plays a more important role in the formation of spin ordering in the manganite film than the modification in the Mn-O bond length does. It was shown that the magnetic inhomogeneity, observed through the difference between field-cooled and zero-field-cooled temperature-dependent magnetization, is not greatly relevant to the electronic nature, but is controlled by the lattice distortion and the microstructural defects. The observed enhancement of magnetoresistance for the LSMO/BTO bilayer at room temperature makes this material system promising in the development of new hybrid ferromagnetic/ferroelectric devices.

In general metamaterial perfect absorber, the single meta-pattern makes the single absorption band. Therefore, the multi-absorption bands need the corresponding kinds of meta-patterns. Here, we introduce the triple-band metamaterial perfect absorber utilizing only single kind of pattern. We also demonstrate the absorption mechanism of the triple perfect absorption. The first and the second absorption bands were induced by the fundamental magnetic resonance of the major and the minor axes, respectively, of cut-wire bar. The third peak was caused by the third-harmonic magnetic resonance of the major axis. Additionally, the unexpected third band was formed, which was the overlapping of the third absorption peak with another absorption peak, which was made by pairs of antiparallel currents parallel or antiparallel to the incident electromagnetic wave.