The influence of mild thermal annealing and nickel addition on the magnetic properties of Co–CoO multilayers is investigated. Co–CoO and CoNi–CoNiO multilayers were fabricated by radio-frequency magnetron sputtering and natural oxidation. Their magnetic properties have been studied via the magneto-optical Kerr effect and a vector network analyzer ferromagnetic resonance setup. The Co–CoO multilayers were annealed up to 90[Formula: see text]min at [Formula: see text]C and they were found to be always in-plane magnetized. The value of Gilbert damping was evaluated. The multilayers after annealing or Ni addition show a small increase in coercivity without considerable changes in their anisotropy. The phenomenon of inverted hysteresis with negative remanence, with the field being applied perpendicular to the film plane, has been recorded. It was modeled with two coexisting magnetic moments with in-plane and perpendicular anisotropies, respectively.

Ultrathin Ag and Ni/NiO films are sequentially produced on Corning glass and silicon substrates by means of magnetron sputtering. Post annealing treatment in a furnace with air at [Formula: see text]C and [Formula: see text]C may lead to the formation of Ag nanostructures in NiO environment. Some of these samples present local surface plasmon resonances (SPRs). The sequence in which each layer is deposited, as well as, the state of the structure on which the layer is deposited, appears to play a pivotal role in the optical properties of these nanostructures, which are attributed to the growth properties of the nanocomposite thin films. Ultimately, rigorous theoretical calculations have been made for comparison and discussion with the experimental results.

In this work, a phononic metamaterial that could be applied for both acoustic and elastic wave attenuation is numerically examined. The hollow yablonovite structure with the addition of hollow spheres on a face-centered cubic arrangement is examined numerically, and wide bandgaps are found for the propagation of acoustic and elastic waves. The calculations were performed by using the finite element method. The research includes an investigation of all the geometric parameters of the structure and how the bandgaps are being affected from the values of each parameter. The proposed structure is found to have wide bandgaps for both elastic and acoustic waves. These findings strongly indicate that the proposed acoustoelastic metamaterial is a powerful candidate for several applications such as sound and vibrations attenuation, noise reduction, and acoustic filtering.

Ultrathin films of Ni0.9Co0.1 were grown by radio frequency magnetron sputtering. By means of a periodic natural oxidation procedure they were transformed into Ni0.9Co0.1/NiCoO multilayers. Room temperature hysteresis loops recorded via the magneto-optic Kerr effect have revealed over all in-plane magnetic anisotropy due to magnetostatic anisotropy. Mild thermal annealing at 250 °C enhanced a tendency for perpendicular magnetic anisotropy, mainly due to an increase of the uniaxial volume anisotropy term. Spin reorientation transition, exchange bias larger than 700 Oe, and strong coercivity enhancement were observed via a superconducting quantum interference device at low temperatures after field cooling.

No abstract