The surface and the internal magnetic structure of bamboo-like cylindrical nanowires with tailored diameter modulations have been determined exploiting the direct photoemission and transmission contrasts using photoemission electron microscopy combined with X-ray magnetic circular dichroism, as well as complementary magnetic force microscopy and micromagnetic simulations. Bamboo-like cylindrical nanowires with diameters of 130 and 140 nm, and a modulation periodicity of 400 nm were electrochemically grown into the pores of alumina templates. FeCoCu and Co nanowires were selected to offer parallel and perpendicular magnetization easy axis, respectively. For FeCoCu nanowires, a main longitudinal magnetization configuration is found consistent with the predominant shape anisotropy. In addition, a weaker modulated contrast along the wires’ axis is observed that matches the position of each diameter modulation: vortex-like structures are observed at the ends of the wires and at the surface around the modulations. In Co nanowires, a multi-segmented vortex-like structure with alternating opposite chirality is found not matching the periodicity of the diameter modulations. Such a spin configuration is interpreted considering that Co nanowires exhibit hexagonal symmetry with c axis nearly perpendicular to the nanowires defining strong uniaxial transverse magnetocrystalline anisotropy.

Searching for high-performance permanent magnets components with no limitation in shape and dimensions is highly desired to overcome the present design and manufacturing restrictions, which affect the efficiency of the final devices in energy, automotive and aerospace sectors. Advanced 3D-printing of composite materials and related technologies is an incipient route to achieve functional structures avoiding the limitations of traditional manufacturing. Gas-atomized MnAlC particles combined with polymer have been used in this work for fabricating scalable rare earth-free permanent magnet composites and extruded flexible filaments with continuous length exceeding 10 m. Solution casting has been used to synthesize homogeneous composites with tuned particles content, made of a polyethylene (PE) matrix embedding quasi-spherical particles of the ferromagnetic τ-MnAlC phase. A maximum filling factor of 86.5 and 72.3% has been obtained for the composite and the filament after extrusion, respectively. The magnetic measurements reveal no deterioration of the properties of the MnAlC particles after the composite synthesis and filament extrusion. The produced MnAlC/PE materials will serve as precursors for an efficient and scalable design and fabrication of end-products by different processing techniques (polymerized cold-compacted magnets and 3D-printing, respectively) in view of technological applications (from micro electromechanical systems to energy and transport applications).

Advanced manufacturing techniques using composite materials made of magnetic particles and polymers are attracting much interest for new routes of fabrication of more efficient and functional devices with complex shapes. The 3D printing and bonding technologies of a broad range of materials, such as NdFeB, improved ferrites, and Mn-based alloys, show up as alternatives to traditional fabrication techniques for a large range of permanent magnets' (PMs) applications. This paper focuses on the fabrication of magnetic products based on strontium ferrite and NdFeB by extrusion of magnetic-polymer composite materials. The composites have been extruded using different nozzles and optimizing the extrusion temperature for each of them, obtaining strips and filaments with rectangular and circular cross section, respectively. The morphological characterization of the strips and filaments has revealed that the polymer covers homogeneously the particles, obtaining continuous strips and filaments with a high filling factor. A decrease in the filling factor has been observed for the NdFeB-based strip and filament ascribed to the larger particle size compared to the Sr-ferrite particles. This paper opens a new path for fabricating PMs' materials as final products and for their use in advanced 3D printing technologies of elements and devices with no-restriction in composition, size, and shape.

We present experimental evidence of transverse magnetic domains, previously observed only in nanostrips, in CoNi cylindrical nanowires with designed crystal symmetry and tailored magnetic anisotropy. The transverse domains are found together with more conventional vortex domains along the same cylindrical nanowire, denoting a bistable system with similar energies. The surface and the inner magnetization distribution in both types of domains are analyzed by photoemission electron microscopy with x-ray magnetic circular dichroism contrast, and hysteresis loop in individual nanowires are measured by magneto-optical Kerr effect. These experimental data are understood and compared with complementary micromagnetic simulations.

Control over the magnetization reversal process of nanowires is essential to current advances in modern spintronic media and magnetic data storage. Much effort has been devoted to permalloy nanostrips with rectangular cross section and vanishing crystalline anisotropy. Our aim was to unveil and control the reversal process in FeCoCu nanowires with significant anisotropy and circular cross section with tailored periodical modulations in diameter. Magneto-optical Kerr effect measurements and their angular dependence performed on individual nanowires together with their analysis allow us to conclude that the demagnetization process takes place due to the propagation of a single vortex domain wall which is eventually pinned at given modulations with slightly higher energy barrier. In addition these results create new expectations for further controlling of the propagation of single and multiple domain walls.