Osuna Ruiz, David

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https://academica-e.unavarra.es/handle/2454/51993

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Osuna Ruiz

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David

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Ingeniería Eléctrica, Electrónica y de Comunicación

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0000-0001-7474-1512

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751447

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812670

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    PublicationOpen Access
    Spin waves in ferrimagnets near the angular magnetization compensation temperature: a micromagnetic study
    (American Institute of Physics, 2024) Sánchez-Tejerina, Luis; Osuna Ruiz, David; Martínez, Eduardo; López-Díaz, Luis; Raposo Víctor; Alejos, Óscar; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza
    Spin wave propagation along a ferrimagnetic strip with out-of-plane magnetization is studied by means of micromagnetic simulations. The ferrimagnetic material is considered to be formed by two antiferromagnetically coupled sub-lattices. Two critical temperatures can be defined for such systems: that of magnetization compensation and that of angular momentum compensation, both different due to distinct Landé factors for each sub-lattice. Spin waves in the strip are excited by a spin current injected at one of its edges. The obtained dispersion diagrams show exchange-dominated forward volume spin waves. For a given excitation frequency, the Néel vector describes highly eccentric orbits, the eccentricity depending on temperature, whose semi-major axis is oriented differently at distinct locations on the FiM strip.
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    PublicationOpen Access
    Artificial intelligence-enhanced metamaterial bragg multilayers for radiative cooling
    (Wiley, 2024-10-08) Osuna Ruiz, David; Aznárez-Sanado, Maite; Herrera, Pilar; Beruete Díaz, Miguel; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute of Smart Cities - ISC; Gobierno de Navarra / Nafarroako Gobernua
    A full numerical study combining artificial intelligence (AI) methods and electromagnetic simulation software on a multilayered structure for radiative cooling (RC) is investigated. The original structure is made of SiO2/Si nanometer-thick layers that make a Bragg mirror for wavelengths in the solar irradiance window (0.3–4 μm). The structures are then optimized in terms of the calculated net cooling power and characterized via the reflected and absorbed incident light as a function of their structural parameters. This investigation provides with optimal designs of beyond-Bragg, all-dielectric, ultra-broadband mirrors that provide net cooling powers in the order of ≈100 W m−2, similar to the best-performing structures in literature. Furthermore, it explains AI's success in producing these structures and enables the analysis of resonant conditions in metal-free multilayers with unconventional layer thickness distributions, offering innovative tools for designing highly efficient structures in RC.
  • Thumbnail Image
    PublicationOpen Access
    Metal-free design of a multilayered metamaterial with chirped Bragg grating for enhanced radiative cooling
    (Optica, 2023) Osuna Ruiz, David; Lezaun Capdevila, Carlos; Torres García, Alicia E.; Beruete Díaz, Miguel; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
    A wideband, all-dielectric metamaterial structure for enhancing radiative cooling is investigated. The structure is optimized to reflect most of the solar irradiance window (between 0.3 µm–3 µm), which is one of the biggest challenges in highly efficient radiative cooling coatings. The design is based on the principles of Bragg gratings, which constitutes a simple synthesis procedure to make a broadband reflector of reduced dimensions, without metallic layers, while keeping a flat enough response in the entire bandwidth. Numerical results show that reflection of solar irradiation can be easily tailored and maximized using this method, as well as the net cooling power of the device, about ∼79 W/m2 at daytime (about double at night-time) and a temperature reduction of 23 K (assuming no heat exchange) and 7 K assuming a heat exchange coefficient of 10 W/m2/K, for a device and ambient temperatures of 300 K and 303 K, respectively. This occurs even in detriment of absorption in the atmospheric window (8 µm–13 µm). Results also show the importance of efficiently reflecting solar irradiance for such technologies and its relevance in synthesis and design without using metallic components.