Cylindrical magnetic nanowires (NWs) constitute a viable component of 3D nanoscale magnetic devices and engineering their response to external stimuli is necessary for their future functionalization. Here, by means of micromagnetic simulations, we study the dynamical response of vortex–antivortex and Bloch point domain walls under the action of an applied magnetic field in curved arc-shaped NWs varying the saturation magnetization value. Our results provide evidence that, in the range considered in this work, the curvature has no influence on the critical diameters, delimiting different domain wall types. However, it has a relevant effect on the domain wall dynamics. Specifically, the vortex–antivortex domain wall oscillates back and forth while rotating around the nanowire, and the frequency and amplitude can be tuned by curvature and applied field. On the contrary, Bloch point domain wall dynamics does not show any oscillatory behavior, and the domain wall is rapidly expelled from the nanowire with velocities similar to that of the straight cylindrical nanowires. These results allow engineering magnetic response of cylindrical nanowires with curvature.

Using numerical simulations, we explore the static and dynamic response of hopfions to an external magnetic field in cylindrical and toroidal nanorings. Results evidence that the nucleation and stability of hopfions are intricately linked to geometry. When including an external field, due to the Dzyaloshinskii–Moriya interaction and the field direction-dependent annihilation mechanism, the hopfion displays distinct behavior under magnetic fields pointing along opposite directions. We have also obtained the spin wave resonance modes of the magnetization patterns nucleated in both nanorings and show the impact of geometry on the suppression of some of them. The interplay between curvature, topology, and magnetization dynamics opens new possibilities toward hopfion-based spin torque oscillator fabrication.

This work analyzes the nucleation and stabilization of torons in cylindrical nanopillars with bulk DMI and easy-plane anisotropy. A micromagnetic study reveals the dependence of toron chains on the nanopillar length and the different behaviors when nucleating an even or odd number of torons in a magnetic nanopillar. Spin wave resonant modes in these systems are explored, evidencing differences according to the number of torons. The interplay between torons, chiral bobbers, and their associated spin wave modes is analyzed, which is relevant for applications demanding dynamical modes in the range of gigahertz.

Magnetic domain walls (DW) are interesting for several technologies requiring perfect control of their propagation along a nanostructure. Therefore, it is necessary to better understand their dynamics. In this paper, using micromagnetic simulations, we analyze the DW propagation along nanowires (NWs) with triangular cross-section, clarifying the role of cross-section symmetry on the DW velocity. Our results evidence that the lowest DW velocity occurs for equilateral triangles. Such behavior is strongly associated with changes in the magnetic energy of the system during DW rotation around the NW axis. Since fully regular cross-sections cannot be easily fabricated, studying the DW dynamics in NWs with non-regular cross-sections could be useful for experimental works.

This work analyzes the propagation of a transverse domain wall (DW) motion under the action of an electric current along a nanowire (NW) with a curvature gradient. Our results evidence that the curvature gradient induces a chiral spin-transfer torque (CSTT) whose effect on the DW motion depends on the direction along which the DW points. The origin of the CSTT is explained in terms of a position and phase-dependent effective field associated with the DW profile and the electric current direction. Finally, our results reveal that this chiral mechanism can also affect the behavior of other magnetization collective modes, such as spin waves. This work shows the emergence of curvature-induced chiral spin transport and highlights a new phenomenon to be considered for designing spintronic devices.

This work analyzes the magnetic configurations of cylindrical nanowires with a bulk Dzyaloshinskii–Moriya interaction and easy-plane anisotropy. We show that this system allows the nucleation of a metastable toron chain even when no out-of-plane anisotropy exists in the nanowire’s top and bottom surfaces, as usually required. The number of nucleated torons depends on the nanowire length and the strength of an external magnetic field applied to the system. The size of each toron depends on the fundamental magnetic interactions and can be controlled by external stimuli, allowing the use of these magnetic textures as information carriers or nano-oscillator elements. Our results evidence that the topology and structure of the torons yield a wide variety of behaviors, revealing the complex nature of these topological textures, which should present an exciting interaction dynamic, depending on the initial conditions.

Hopfions are localized and topologically non-trivial magnetic configurations that have received considerable attention in recent years. Through a micromagnetic approach, we analyze the scattering of spin waves by magnetic hopfions. We show that the spin waves experience an emergent electromagnetic field related to the topological properties of the hopfion. We find that spin waves propagating along the hopfion symmetry axis are deflected by the magnetic texture, which acts as a convergent or divergent lens, depending on the spin wave propagation direction. The effect differs for spin waves propagating along the plane perpendicular to the symmetry axis. In the last case, they respond with a skew scattering and a closely related Aharonov-Bohm effect. This allows probing the existence of a magnetic hopfion by magnonic holography.

Spintronic devices using domain walls (DWs) as information carriers require stable high speeds and a clear understanding of their dynamics. The latter strongly depends on the geometry of the magnetic element hosting the DW. This work aims to determine the effects of the geometry on the width of a transverse DW nucleated in a bent magnetic nanowire with a rectangular cross-section. Our results show that a geometry-induced effective anisotropy is responsible for shrinking or stretching the DW width, depending on the direction along which the DW center points (DW phase).

An off-center shift of the magnetic hysteresis loop, usually known as exchange bias, develops in an asymmetric nanodisk due to the Dzyaloshinskii-Moriya (DM) interaction. Results exhibit the onset of bias in a system without material interfaces, originating from the relation between the chirality defined by the DM interaction and the geometry. In addition, programmable magnetization bias by the variation of an external field emerges as a possibility. Our simulations, carried out using Mumax3 code, also yield double hysteresis loops, evidencing a magnetization reversal driven by vortex nucleation and annihilation. Bias in a homogeneous nanodisk and its control seem promising for applications.

In this work, we present a theoretical model for domain wall (DW) oscillations in a curved magnetic nanowire with a constant curvature under the action of a uniaxial magnetic field. Our results show that the DW dynamics can be described as that of the mechanical pendulum, and both the NW curvature and the external magnetic field influence its oscillatory frequency. A comparison between our theoretical approach and experimental data in the literature shows an excellent agreement. The results presented here can be used to design devices demanding the proper control of the DW oscillatory motion in NWs.

In this paper, we address the skyrmion-bimeron dynamical transformation during the propagation of such structures along a magnetic nanotrack with anisotropy gradients. Using a micromagnetic approach and simulations, we observe that a skyrmion continuously transforms into a bimeron, and vice versa (in a reversible way). Furthermore, our results show that the topological charge and the velocity of the intermediary magnetic textures emerging during the transformation are constant. These results can contribute to understanding the dynamic transformation between solitonic magnetic textures with the same topological charge.

Three dimensional magnetic textures are a cornerstone in magnetism research. In this work, we analyze the stabilization and dynamic response of a magnetic hopfion hosted in a toroidal nanoring with intrinsic Dzyaloshinskii-Moriya interaction simulating FeGe. Our results evidence that unlike their planar counterparts, where perpendicular magnetic anisotropies are necessary to stabilize hopfions, the shape anisotropy originated on the torus symmetry naturally yields the nucleation of these topological textures. We also analyze the magnetization dynamical response by applying a magnetic field pulse to differentiate among several magnetic patterns. Finally, to understand the nature of spin wave modes, we analyze the spatial distributions of the resonant mode amplitudes and phases and describe the differences among bulk and surface modes. Importantly, hopfions lying in toroidal nanorings present a non-circularly symmetric poloidal resonant mode, which is not observed in other systems hosting hopfions.

Hopfions are localized and topologically nontrivial magnetic configurations that have received considerable attention in recent years. In this Letter, we use a micromagnetic approach to analyze the scattering of spin waves (SWs) by magnetic hopfions. Our results evidence that SWs experience an electromagnetic field generated by the hopfion and sharing its topological properties. In addition, SWs propagating along the hopfion symmetry axis are deflected by the magnetic texture, which acts as a convergent or divergent lens, depending on the SWs' propagation direction. Assuming that SWs propagate along the plane perpendicular to the symmetry axis, the scattering is closely related to the Aharonov-Bohm effect, allowing us to identify the magnetic hopfion as a scattering center.

This paper focuses on the dynamics of a domain wall (DW) displacing along an elliptically bent nanowire (NW) under the action of spin-polarized electric currents and external magnetic fields. Our results evidence that a curvature gradient induces an exchange-driven effective tangential field responsible for pinning a DW at the maximum curvature point in the NW. However, the competition between the torques produced by the external stimuli and the curvature-induced effective fields changes the DW equilibrium position and phase. Therefore, when the external stimuli are below a certain threshold, the DW follows a damped harmonic oscillation around the new equilibrium position. Above this threshold, DW displaces along the NW under an oscillatory translational motion.

The dynamics of several systems in nature occurs under some constraints and symmetries that ensure the appearance of constants of motion. In this work, we discuss the dynamics of the magnetic domain wall (DW) under the Walker regime (i.e., when its position oscillates as a function of time) in bent cylindrical magnetic nanowires (NWs) with constant curvatures. It is shown that the DW position sweeps, in relation to the curvature center, the same area for different NW curvatures. This phenomenon appears due to an exchange-driven curvature-induced interaction. The translational DW motion is accompanied by its rotation around the NW axis, leading to a periodic curvature-independent angular momentum, from which one obtains an area's law for the DW motion.

Understanding and mastering the magnetic properties of domain walls in cylindrical nanowires is a fundamental pillar for developing novel 3D information technologies. For this purpose, a good comprehension of domain wall (DW) dynamical properties, which are strongly dependent on its type and size, is needed. In this work, by means of micromagnetic simulations, we focus on the accurate determination of DW types (transverse, vortex-antivortex, and the Bloch point) and DW widths and present a state diagram as a function of the diameter and the nanowire material. Using different initial states and trajectories we find a large region of metastability where the Bloch-point domain wall co-exists with either transverse or a more energetical vortex-antivortex one. We determine the domain wall width and its dependence on the nanowire diameter either for the transverse or the vortex-antivortex domain wall showing that it is always larger than the nanowire diameter. We also find simple expressions for the DW widths and the critical diameter for the transition between different DW types which agree well with direct simulations. Our results are useful for the experimental design of cylindrical nanowires for multiple applications.

Using numerical simulations, we studied the dynamics of two skyrmions nucleated in a double-disk structure. Depending on the geometry and the electric current, different regimes for the dynamical behavior of the skyrmions were obtained. Our results evidence that there are four main dynamic regimes depending on the geometry and current: stagnation points, oscillatory motion, and two types of skyrmion annihilation: partial and total. Our findings are explained as a result of the different forces that skyrmions are subject to and are shown in a state diagram of the dynamical states that allow an adequate understanding of the associate phenomena.

In this work we analyze the influence of curvature on the dynamic properties of the magnetization in bent nanotubes. Our results show that both the resonance frequencies and the number of resonant peaks have a strong dependence on the ground state of the magnetization created by the curvature. Our results can be understood from the analysis of the effective anisotropy and the Dzyaloshinskii–Moriya interaction (DMI) induced by curvature. The ability to control the dynamic properties of these curved ferromagnets makes them excellent candidates for developing applications based on resonant modes of spin waves.

The search for magnetic hopfions has been the focus of intense research during the last years. In this direction, and using micromagnetic simulations, we studied the magnetization reversal mechanism in toroidal nanoparticles under the action of an Oersted magnetic field. Our results evidence the nucleation of four magnetic configurations as a function of geometry, two of them being hopfion-like textures. These mechanisms are preferred for large toroidal structures. The annihilation of such texture is indicated by strong changes in the energy, which characterizes a topological transition.