We present the potential of ultrathin bilayer metallic nanofilms for use as broadband antireflection coatings in the terahertz frequency range. The metallic layers are modeled using a wave-impedance matching approach. The experimental and theoretical results are in good agreement. Further, a novel method using our broadband antireflection coatings is proposed to eliminate unwanted reflections that interfere with the important reflection from the sample in terahertz reflection measurement. The proposed method significantly improves the calculation of the optical properties of liquid and biological samples.

Single-phase La2(1−x)Co2xO3−δ polycrystalline samples with x=0%–8% were synthesized by the conventional ceramic method, and the effect of Co content on the magnetic behaviors has been systemically investigated. X-ray diffraction and x-ray photoelectron spectroscopy studies indicate no Co metal clusters or secondary magnetic phases in any samples in this study. It is found that the undoped or slightly doped samples show no ferromagnetic signal, while samples with x in the range of 0.5%–2% exhibit an exponential increase of saturation magnetization (Ms) as a function of Co concentration. When x increases beyond 2%, an inverse correlation between the magnetization and Co content was observed. We reported an Ms as large as 0.05emu∕g and a Curie temperature above RT in our samples, rendering Co:La2O3 a candidate diluted magnetic oxide for RT applications. Our results also strongly support the oxygen vacancy (F-center) mediated mechanism for RT ferromagnetism in transition-metal doped high-k oxides

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Diluted magnetically doped CeO2 films is an attractive dilute magnetic oxide which would facilitate the practical realization of spintronic devices and may also be used to explore novel magneto-optical applications. In this experiments, 3 at% cobalt-doped CeO2 films with the stoichiometry of Ce0.97Co0.03O2-δ (CCO) were deposited by magnetron sputtering methods on Al2O3 (0001) substrates. The structural, magnetic, and magneto-optical properties were investigated. The results indicate that CCO films with CeO2 (100) orientation can readily be obtained via magnetron sputtering on Al2O3 (0001) substrates. Films are ferromagnetic at room temperature, which is anisotropic with an out-of-plane magnetization easy axis. Magneto-optical measurements exhibit a giant Faraday rotation of about 4800 deg/cm at 650 nm wavelength in out-of-plane direction. The excellent room-temperature ferromagnetism and the giant Faraday rotation in CCO films show highly potential applications in novel magneto-optical devices as well as in spintronics.

M-type barium hexaferrite (BaM) is a promising gyromagnetic material for self-biased microwave\millimeter wave devices because of its large uniaxial magnetocrystalline anisotropy and low microwave loss in high frequency. Due to the limitation of growth conditions, it is difficult to deposit BaM films with enough thickness by PLD, MBE and Magnetron Sputtering for practical application. However, it is demonstrated in present experiment that large area polycrystalline BaM thick films (500μm) with self-biasing (high remanence) and low microwave loss can be successfully fabricated by tape casting. X-ray diffraction and Scanning electron microscopy results indicate that these BaM thick films have highly c-axis oriented crystallographic texture with hexagonal morphology. Magnetic hysteresis loops reveal that samples exhibit excellent properties with a saturate magnetization (4πMs) of 3606G, a high squareness ratio (Mr/Ms) of 0.82. In addition, ferromagnetic resonance (FMR) measurement shows that the FMR linewidth is as small as 431Oe at 48GHz. These parameters ensure these BaM thick films are potentially useful for self-biased microwave\millimeter wave devices such as circulator, phase shifter and filter.