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We explore a simple and optimized approach for obtaining magnetic nanoparticle-carbon composites by a novel one-pot sol-gel method. In them, various metal cations ratios of Fe3+ and Co2+ are evaluated. The ratio of Fe:Co is a critical parameter that governs the presence of different crystalline phases with tailored magnetic properties. Interestingly, the smallest introduction of Co into the synthesis (19Fe:1Co) provides an abrupt emergence of the body-centered cubic (bcc) Fe-Co alloy, instead of the orthorhombic Pnma structure characteristic of the Fe3C intermetallic compound (1Fe:0Co). Advanced structural and electronic characterizations reveal the formation of Fe-Co/Co-ferrite core/shell nanoparticle structures embedded in a carbon matrix. The sphere-like nanoparticles range from 10 to 45 nm and the shells show a spinel structure with a thickness of 2–3 nm. In addition, X-ray absorption spectroscopy unveils that the oxidation state of Fe and Co cations is close to zero, demonstrating their predominant metallic character. The magnetic properties can be modulated by a precise control of the alloy composition varying the Co content, displaying saturation magnetization values close to ∼137 emu/g. The nanoparticles are mainly single magnetic domain with a considerable coercive field (∼450 Oe), higher than those reported in the literature for Fe-Co nanoparticles. This semi-hard character is due to a notable spring exchange effect emerged by passivating the surface of Fe-Co-bcc cores with a thin Co-ferrite-like shell.

El sputtering o pulverización catódica es una técnica ampliamente utilizada en la industria, sobre todo en la producción de películas delgadas. Es una técnica muy versátil que permite también la creación de estructuras nanocolumnares de distintos materiales. Estas nanocolumnas se obtienen inclinando el sustrato durante la deposición de los átomos, confiriéndoles potenciales aplicaciones en campos muy diversos. Por ejemplo, las nanocolumnas de titanio han demostrado ser una opción prometedora al utilizarse como recubrimiento antibacteriano en implantes biomédicos [1], y las de óxido de titanio como capa nanoestructurada para células solares de perovskita [2]. Las nanocolumnas de plata, por otro lado, han sido utilizadas como recubrimientos antimultipactor para la industria espacial [3]. En este trabajo, diferentes morfologías de nanoestructuras de Au se han fabricado sobre sustratos de silicio: i) película delgada, ii) película de nanocolumnas verticales y iii) película con nanocolumnas inclinadas. Las muestras se han caracterizado morfológicamente mediante microscopía de fuerzas atómicas (AFM) y microscopía electrónica de barrido (SEM). Su estructura cristalina y estructura electrónica se han caracterizado mediante difracción de rayos X (XRD) y espectroscopía de absorción de rayos X (XAS) en el borde L3 del Au (11919 eV) en el European Synchrotron Radiation Facility (ESRF) en Grenoble, Francia.

Sputtering is a technique widely used in industry, mainly in the production of highly homogeneous thin films. The versatility of this technique also enables the growth of nanocolumnar structures to be made of a variety of materials. These nanocolumn arrays, obtained by tilting the substrate during sputtering deposition, have potential applications in biology and medicine. The materials include, for example, titanium, which has been used as a coating for implants [1]. Materials such as gold or iron oxides, both of which are biocompatible, are potential candidates for a wide range of biomedical applications [2-4].

Glancing Angle Deposition (GLAD) with magnetron sputtering (MS) is an easy and versatile route to fabricate nanocolumnar films in large areas (several cm2 and above) in a single-step process, in clear contrast to other techniques in the nanoscale range such as e-beam lithography and ion-beam lithography. The morphology of the nanocolumns can be controlled depending on several parameters such as the gas pressure, the angle of inclination of the substrate and its possible rotation, the electromagnetic power, the deposition time, and the optional use of collimating masks [1-4]. Moreover, as GLAD with MS it is usually carried out at RT and does not involve chemical products (thus, without associated recycling issues), this technique is environmentally friendly. In this talk, I will start explaining the fundamentals of GLAD with MS and then I will present some recent examples of nanocolumnar films that are of interest in the field of energy and environment: Gold nanocolumnar templates for effective chemical sensing by surface-enhanced Raman scattering [5], Iron nanocolumnar films with tailored magnetic behavior [6], and Titanium oxide nanocolumnar films that exhibit photo‐induced self‐cleaning properties [7]. It will be finally shown that this latter effect can be enhanced when the nanocolumns are decorated with gold nanoparticles using a gas aggregation source that is also based on MS. References:[1] R. Alvarez et al., Nanotechnology 24, 045604 (2013). [2] R. Alvarez et al., J. Phys. D: Appl. Phys. 49, 045303 (2016). [3] A. Vitrey et al., Beilstein J. Nanotechnol. 8, 434 (2017).[4] G. Troncoso et al., Appl. Surf. Sci. 526, 146699 (2020).[5] G. Barbillon et al., Nanomaterials 12, 4157 (2022).[6] E. Navarro et al., Nanomaterials 12, 1186 (2022).[7] F. Fresno et al., Adv. Sustainable Syst. 5, 2100071 (2021).

Antiferromagnets are magnetically ordered, but neighboring magnetic moments point in opposite directions, which results in zero net magnetization. This property makes them promising for future spintronic applications, since antiferromagnets produce no stray fields and are insensitive to external magnetic field perturbations. In addition, they show intrinsic dynamics in the terahertz range and exhibit considerable spin-orbit and magneto-transport effects. The above could allow the creation of high-density memories with no inter-bit dipole interactions and fast write times, as well as the development of compact room-temperature terahertz sources and detectors1,2. In this work, we will present the investigation of L10 MnPt antiferromagnetic thin films. The films consist of Pt/Mn multilayers, sputter-deposited onto commercial oxidized Si wafers. X-ray diffraction (XRD) characterization shows the emergence of the chemically-ordered L10 MnPt crystal structure after annealing the samples at temperatures 400oC or higher (see figure 1). Secondary ion mass spectroscopy (SIMS) shows the layered structure of the as-deposited stack, which thereafter transforms into an alloy film after annealing (see figure 2). Our initial findings are promising and static magnetic characterization by means of magnetometry and magnetic force microscopy will be also presented

Defective few-layered graphene mesostructures (DFLGMs) are produced from graphite flakes by high-energy milling processes. We obtain an accurate control of the generated mesostructures, as well as of the amount and classification of the structural defects formed, providing a functional material for microwave absorption purposes. Working under far-field conditions, competitive values of minimum reflection loss coefficient (RLmin) = ¿21.76 dB and EAB = 4.77 dB are achieved when DFLGMs are immersed in paints at a low volume fraction (1.95%). One step forward is developed by combining them with the excellent absorption behavior that offers amorphous Fe73.5Si13.5B9Cu1Nb microwires (MWs), varying their filling contents, which are below 3%. We obtain a RLmin improvement of 47% (¿53.08 dB) and an EAB enhancement of 137% (4 dB) compared to those obtained by MW-based paints. Furthermore, a fmin tunability is demonstrated, maintaining similar RLmin and EAB values, irrespective of an ideal matching thickness. In this scenario, the Maxwell-Garnet standard model is valid, and dielectric losses mainly come from multiple reflections, interfacial and dielectric polarizations, which greatly boost the microwave attenuation of MWs. The present concept can remarkably enhance not only the MW attenuation but can also apply to other microwave absorption architectures of technological interest by adding low quantities of DFLGMs.

The present invention relates to a chemiresistive sensor with a low limit for detecting NO2 at ambient temperature, an active layer of said sensor comprising a few-layer graphene material. The response of the sensor is not altered by relative humidity, and the sensor also demonstrates very low interference with ammonia, allowing this interference to be disregarded in the measurements.