Search

The interplay between curvature and magnetization is a cornerstone in magnetism. Thus, in this work, we address the role of curvature on the propagation of magnetic skyrmions along a curved race track. Using a micromagnetic approach and simulations, we observed the creation of a curvature-induced force (CIF) that acts on the skyrmion while traveling along the track. We also show that curvature can stop the skyrmion if the current density is below a critical value. Above this limit, the skyrmion goes through the defect, a direct consequence of the CIF. Our results allow a better definition of the electric current needed for moving skyrmions along curved tracks.

A detailed analytical and numerical study of the spin wave modes of two nanopillar spin torque nano-oscillators coupled by magnetostatic interactions is presented under the macrospin approximation. Results show that the normal modes of the system oscillate with the magnetizations in-phase or anti-phase in both disks. The frequencies and critical current densities necessary to induce auto-oscillations of the spin wave modes of the coupled system depend on the relative position of the nanopillars and the applied magnetic field. If the oscillators are identical, these modes are degenerate at a certain relative position of the nanopillars, while if the oscillators are non-identical, such degeneracy is removed. Then, we can conclude that the magnetostatic coupling between two spin transfer torque nano-oscillators is a powerful mechanism to control the spin wave modes of these systems.

A detailed numerical analysis of the magnetization reversal processes in multisegmented nanowire arrays was developed. The nanowires have a long aspect ratio and are formed by magnetic and non-magnetic sections alternately arranged in such a way that the array resembles magnetic layers separated by non-magnetic layers. Attention has been focused on the influence of magnetostatic interaction in the magnetic pattern formation of these magnetic nanostructures. Results from a magnetic correlation function among layers show that three different reversal modes can be detected depending on the number and distance between the magnetic segments. As a consequence of the different reversal modes, a non-monotonic behavior of the annihilation field in function of the distance between the layers is evidenced. Thus, these results are important for the production of magnetic devices with multisegmented nanowire arrays.

The occurrence of equilibrium magnetic configurations in ferromagnetic low-symmetry nanoparticles has been investigated. T-shaped nanoparticles, which present strong configurational anisotropy, have been considered. It has been found that such particles exhibit four equilibrium magnetic states, whose stability at room temperature was estimated. The presence of structural imperfections, such as surface roughness, in those systems was also considered, resulting in no significant effects on the magnetic behavior of the particles. The present results are expected to be of relevance to magnetic storage.

A detailed numerical analysis of the magnetization reversal processes in T-shaped nanoparticles has been carried out. Attention has been focused on the influence of the symmetry of the particle on the formation, propagation, and interaction of internal magnetic structures such as domain walls, vortices, and antivortices. Results show that the lower the degree of symmetry of the particle, the more complex the reversal process is. Thus, symmetry represents an additional ingredient to control the magnetic properties of ferromagnetic nanoparticles.

During the last years, cylindrical structures like dots, wires, and tubes have been intensively investigated. However, stadium-shaped particles have been scarcely investigated because of the complexity associated to the control of its geometry. In this paper, we used a scaled atomistic representation with Monte Carlo simulations to investigate systematically the magnetization reversal process in stadium-shaped magnetic structures as a function of the size of the central volume. Different reversal mechanisms have been identified and its existence has been explained. The reversal process for short, almost circular, stadium structures occurs via the formation of a single vortex, whereas for longer stadium structures the reversal process involves either single vortices or vortex pairs. For the longest structures investigated, the reversal always involves two vortices that generate a central diamond region or a central antivortex, depending on the region of the nucleation of the vortices. Our results provide guidelines for the use of stadium-shaped particles in the control of vortex motion when a magnetic field is applied.

The investigation of interactions between magnetic nanotubes is complex and often involves substantial simplifications. In this letter an analytical expression for the magnetostatic interaction, taking into account the geometry of the tubes, has been obtained. This expression allows for the definition of a critical vertical separation for relative magnetization between nanotubes and can be used for tailoring barcode-type nanostructures with prospective applications such as biological separation and transport., Comment: 4 pages, 5 figures