Due to the issues associated with rare-earth elements, there arises a strong need for magnets with properties between those of ferrites and rare-earth magnets that could substitute the latter in selected applications. Here, we produce a high remanent magnetization composite bonded magnet by mixing FeCo nanowire powders with hexaferrite particles. In the first step, metallic nanowires with diameters between 30 and 100 nm and length of at least 2 μm are fabricated by electrodeposition. The oriented as-synthesized nanowires show remanence ratios above 0.76 and coercivities above 199 kA/m and resist core oxidation up to 300 °C due to the existence of a >8 nm thin oxide passivating shell. In the second step, a composite powder is fabricated by mixing the nanowires with hexaferrite particles. After the optimal nanowire diameter and composite composition are selected, a bonded magnet is produced. The resulting magnet presents a 20% increase in remanence and an enhancement of the energy product of 48% with respect to a pure hexaferrite (strontium ferrite) magnet. These results put nanowire–ferrite composites at the forefront as candidate materials for alternative magnets for substitution of rare earths in applications that operate with moderate magnet performance.

We here present a simple model of a vibrating sample magnetometer (VSM). The system allows recording magnetization curves at room temperature with a resolution of the order of 0.01 emu and is appropriated for macroscopic samples. The setup can be mounted with different configurations depending on the requirements of the sample to be measured (mass, saturation magnetization, saturation field, etc.). We also include here examples of curves obtained with our setup and comparison curves measured with a standard commercial VSM that confirms the reliability of our device.

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Strontium hexaferrite nanocrystalline powders are synthesized using a citrate combustion method and subsequently subjected to a post-synthesis processing aiming at tuning the micro-nanostructure for improving the magnetic properties. First, the synthesis thermal treatments are optimized in order to minimize the formation of secondary phases, mainly hematite. Second, the as-synthesized powders are conditioned by a two-step process: ball milling in wet medium (ethanol) and high-speed mixing. The final processed powders exhibit a saturation magnetization of 74 emu/g and a coercivity of 6450 Oe. Following a low-temperature combustion synthesis, the coercivity is one of the largest values reported for strontium ferrites.The combination of the two-step conditioning procedure results in a useful methodology to obtain SrFe12O19 nanocrystalline powders with competitive properties. The morphological, structural and magnetic properties of the processed material make it a promising candidate for hard-soft ferrite-based composite magnets, where large coercivity values are highly desirable.

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SrFe12O19 (SFO) films grown on Si (100) substrates by radio-frequency magnetron sputtering have been characterized in terms of composition, structural and magnetic properties by a combination of microscopy, diffraction and spectroscopy techniques. Mössbauer spectroscopy was used to determine the orientation of the films magnetization, which was found to be controlled by both the sputtering power and the thickness of the films. Additionally, the coupling between the SFO films and a deposited cobalt overlayer was studied by means of synchrotron-based spectromicroscopy techniques. A structural coupling at the SFO/Co interface is suggested to account for the expetimental observations. Micromagnetic simulations were performed in order to reproduce the experimental behaviour of the system.

The use of metallic nanowires is mostly reduced to scientific areas where a small quantity of nanostructures are needed. In order to broaden the applicability of these nanomaterials, it is necessary to establish novel synthesis protocols that provide a larger amount of nanowires than the conventional laboratory fabrication processes at a more competitive cost. In this work, we propose several modifications to the conventional electrochemical synthesis of nanowires in order to increase the production with considerably reduced production time and cost. To that end, we use a soft anodization procedure of recycled aluminum at room temperature to produce the alumina templates, followed by galvanostatic growth of CoFe nanowires. We studied their morphology, composition and magnetic configuration, and found that their properties are very similar to those obtained by conventional methods.