https://uvadoc.uva.es/handle/10324/31951 Materiales Magnéticos Sun, 05 Apr 2026 15:32:14 GMT 2026-04-05T15:32:14Z https://uvadoc.uva.es/handle/10324/70142 M-type hexagonal ferrites have been getting considerable attention owing to their promising application in electronic fields. Though, the growth of nanosized M-type hexagonal ferrites is still a big challenge. Herein the fabrication of M-type hexaferrite with nominal composition Ca1-xBixFe12-xCoxO19 (x=0.00, 0.05, 0.10, 0.15, 0.20) with high quality is reported by the sol-gel auto combustion route. The objective of the study is to improve the structural, spectral, dielectric, and magnetic characteristics of M-type hexagonal ferrite which was achieved through the variation of concentration of Cobalt and Bismuth. X-ray diffraction (XRD) patterns confirmed the single-phase M-type hexagonal structure. The crystallite size of all samples was found to be in the range of 42–49 nm. Other parameters such as lattice parameters a & c, unit cell volume, crystallite size, X-ray density, Bulk density, and porosity were also calculated. The doping contents were found to decrease the bulk and X-ray densities while increasing the porosity. Fourier-transform infrared (FTIR) spectra showed the formation of metaloxygen stretching vibrations that confirmed the formation of hexagonal ferrites. The scanning electron microscopy (SEM) images revealed a regular platelet hexagonal structure and homogeneously distributed grains were examined. The dielectric constant was high at low frequency and then decreased with increasing frequency, while the dielectric loss was decreased appreciably with doping. The saturation magnetization ranged from 15.51 to 38.27 emu/g, coercivity increased from 207.93 to 1359.69 Oe, and the squareness ratio was found to be in the range of 0.19–0.78. The dielectric and magnetic properties of Ca1- BixFe12-xCoxO19 (x=0.00, 0.05, 0.10, 0.15, 0.20) with the variation of Co and Bi revealed that these materials are good candidates for modern devices Mon, 01 Jan 2024 00:00:00 GMT https://uvadoc.uva.es/handle/10324/70142 2024-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/70067 The Y-type hexaferrite and its nanocomposite with carbon dots have been made by using a hydrothermal approach, whereas BaSrZn2-xMnxFe12-2ySiyNiyO22 (x = 0.0, 0.25, 0.5, 0.75, and 1.0) was made using a conventional microemulsion process. A variety of approaches are used to explore the structural features, Surface area, and morphology of the materials. As indicated by on-site substitutions and super-exchange interaction, saturation magnetization (Ms) and magnetic remanence (Mr) rise from 18 to 6 to 47.4 emu g- 1 and 6.7–18.3 emu g- 1, respectively with x,y = 0.75, although coercivity (Hc) declines from 1.4 to 0.39 kOe. The ferrite material’s electrical resistivity enhanced from 25.85 × 106 to 49.13 × 106 Ω-cm. The increased saturation magnetization (Ms), magnetic remanence (Mr), and electrical resistance of ferrite material make it suitable for both high-density recording and microwave devices. The photocatalyst (composite) for the degradation of Rhodamine B in the presence of visible light was made from SrBaZn1.25Mn0.75Fe10.5Si0.75Ni0.75O22/CDs with different ratios. Photocatalysts with a modest CDs concentration (2.5 wt%) successfully degraded Rhodamine B (RhB) up to 94%. After eight rounds, the composite showed excellent structural stability and good reusability. The trapping experiments confirmed that OH radical species are the major contributor in the degradation process. The composite material could be used to catch visible light and purify the environment from various pollutants in the future. Sun, 01 Jan 2023 00:00:00 GMT https://uvadoc.uva.es/handle/10324/70067 2023-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/70065 A major issue is the production of green and sustainable energy while the development of an effective, affordable, readily available with a higher rate of oxygen and hydrogen evolution reactions is need of the time. Here in present work, we fabricated CuScS2, CoO, and CuScS2/CoO to replace the extremely expensive Pt/C and IrO2 that are employed as the benchmark materials for water electrolysis. We have also investigated their electrochemical performance in an alkaline environment for the oxygen evolution reaction (OER). The CuScS2/CoO nanocomposite is more effective electrode material than CuScS2 and CoO. The composite material shows smaller overpotential (179 mV) and reduced Tafel slope (46 mV dec−1) value than individual materials to attain a current density of 10 mA cm−2. The better efficiency of the composite material is due to well-distinct good shape with greater BET surface area, and relatively small resistance to charge transfer. Furthermore, the CuScS2/CoO exhibits remarkable electrocatalytic as well as photocatalytic performance in comparison to CuScS2 and CoO. This research provides a valuable guide for developing an OER electrocatalyst in an alkaline medium and shows better electrochemical as well as photocatalytic performance of CuScS2/CoO nanomaterials. Mon, 01 Jan 2024 00:00:00 GMT https://uvadoc.uva.es/handle/10324/70065 2024-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/40723 Noncollinear spin systems with magnetically induced ferroelectricity from changes in spiral magnetic ordering have attracted significant interest in recent research due to their remarkable magnetoelectric effects with promising applications. Single phase multiferroics are of great interest for these new multifunctional devices, being Y-type hexaferrites good candidates, and among them the ZnY compounds due to their ordered magnetic behaviour over room temperature. Polycrystalline Y type hexaferrites with composition Ba0.5Sr1.5Zn2Fe2O22 (BSZFO) were sintered in 1050 °C–1250 °C temperature range. Transverse susceptibility measurements carried out on these BSZFO samples in the temperature range 80–350 K with DC fields up to ± 5000 Oe reveal different behaviour depending on the sintering temperature. Sample sintered at 1250 °C is qualitatively different, suggesting a mixed Y and Z phase like CoY hexaferrites. Sintering at lower temperatures produce single phase Y-type, but the transverse susceptibility behaviour of the sample sintered at 1150 °C is shifted at temperatures 15 K higher. Regarding the DC field sweeps the observed behaviour is a peak that shifts to lower values with increasing temperature, and the samples corresponding to single Y phase exhibit several maxima and minima in the 250 K–330 K range at low DC applied field as a result of the magnetic field induced spin transitions in this compound. Wed, 01 Jan 2020 00:00:00 GMT https://uvadoc.uva.es/handle/10324/40723 2020-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/37265 Single phase multiferroics in which ordered magnetism and ferroelectricity coexist, are of great interest for new multifunctional devices, and among them Y-type hexaferrites are good candidates. Transverse susceptibility measurements, which have been proved to be a versatile tool to study singular properties of bulk and nanoparticle magnetic systems, have been carried out with a broadband system on polycrystalline Y type hexaferrites with composition Ba0.5Sr1.5Co2Fe2O22, optimal to exhibit multiferroic properties. In the temperature range 80–350 K transverse susceptibility measurements with DC fields up to ±5000 Oe reveal different behaviour depending on the sintering temperature. The thermal evolution of the anisotropy field peak exhibits four regions with different slopes: positive in 80–130 K, negative in 130–200 K, constant in 200–280 K and negative in 280–350 K, which can be considered a signature of spin transitions in this compound. Tue, 01 Jan 2019 00:00:00 GMT https://uvadoc.uva.es/handle/10324/37265 2019-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/37264 Lithium ferrites are well known materials due to their numerous technological applications especially in microwave devices. Mn-doped lithium ferrite nanoparticles were prepared by sol-gel technique by means of Pechini method, and then annealed at different temperatures in 250–1000 °C range. XRD confirms spinel formation with particle size in the 15–200 nm range, with increased size with annealing temperature. Microwave magnetoabsorption data of annealed lithium ferrite nanoparticles, obtained with a broadband system based on a network analyzer operating up to 8.5 GHz are presented. At fields up to 200 m T we can observe a broad absorption peak that shifts to higher frequencies with magnetic field according to ferromagnetic resonance theory. The amplitude of absorption, up to 85%, together with the frequency width of about 4.5 GHz makes this material suitable as wave absorber. Samples annealed at higher temperatures show a behaviour similar to polycrystalline samples, thus suggesting their multidomain character. Tue, 01 Jan 2019 00:00:00 GMT https://uvadoc.uva.es/handle/10324/37264 2019-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/37263 Lithium ferrites are well known materials due to its numerous technological applications especially in microwave devices. Lithium ferrite nanoparticles were prepared by sol-gel technique by means of Pechini method, and then annealed at different temperatures in 250–1000 °C range. XRD confirms spinel formation with particles sizes in 15–700 nm range, with increased size with annealing temperature, whereas FTIR and Raman measurement confirm that single phase lithium ferrite with ordered cationic structure is obtained. Microwave magnetoabsorption data of the annealed lithium ferrite nanoparticles were obtained with a broadband system based on a network analyzer that operates up to 8.5 GHz. At fields up to 200 mT we can observe a broad absorption peak that shifts to higher frequencies with magnetic field according to ferromagnetic resonance theory. The amplitude of absorption, up to 85%, together with the frequency width of about 5.5 GHz makes this material suitable as wave absorber. FMR parameters like resonance field, linewidth and broadening are analyzed in order to obtain the characteristic parameters and analyze the microwave behaviour. Mon, 01 Jan 2018 00:00:00 GMT https://uvadoc.uva.es/handle/10324/37263 2018-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/37262 Magnetic after-effects in ferrite nanoparticles have been measured with magnetic disaccommodation technique. For higher annealing temperature multidomain formation is detected with low temperature relaxation process similar to single crystal and polycrystalline NiFe2O4. As expected, no room temperature processes are observed due to low vacancy content. On the other hand, logarithmic relaxations are observed at lower annealing temperatures, revealing monodomain character. Mon, 01 Jan 2018 00:00:00 GMT https://uvadoc.uva.es/handle/10324/37262 2018-01-01T00:00:00Z