Dominant higher-order vortex gyromodes in circular magnetic nanodots.

The transition to the third dimension enables the creation of spintronic nanodevices with significantly enhanced functionality compared to traditional 2D magnetic applications. In this study, we extend common two-dimensional magnetic vortex configurations, which are known for their efficient dynamical response to external stimuli without a bias magnetic field, into the third dimension. This extension results in a substantial increase in vortex frequency, reaching up to 5 GHz, compared to the typical sub-GHz range observed in planar vortex oscillators.

Giant supermagnonic Bloch point velocities in cylindrical ferromagnetic nanowires.

Achieving high velocities of magnetic domain walls is a crucial factor for their use as information carriers in modern nanoelectronic applications. In nanomagnetism and spintronics, these velocities are often limited either by internal domain wall instabilities, known as the Walker breakdown phenomenon, or by spin wave emission, known as the magnonic regime. In the rigid domain wall model, the maximum magnon velocity acts as an effective "speed of light", providing a relativistic analogy for the domain wall speed limitation.

Spin-wave spectroscopy of individual ferromagnetic nanodisks.

The increasing demand for nanoscale magnetic devices requires development of 3D magnetic nanostructures. In this regard, focused electron beam induced deposition (FEBID) is a technique of choice for direct-writing of complex nano-architectures with applications in nanomagnetism, magnon spintronics, and superconducting electronics. However, intrinsic properties of nanomagnets are often poorly known and can hardly be assessed by local optical probe techniques.

Single Chiral Skyrmions in Ultrathin Magnetic Films.

The stability and sizes of chiral skyrmions in ultrathin magnetic films are calculated accounting for the isotropic exchange, Dzyaloshinskii⁻Moriya exchange interaction (DMI), and out-of-plane magnetic anisotropy within micromagnetic approach. Bloch skyrmions in ultrathin magnetic films with B20 cubic crystal structure (MnSi, FeGe) and Neel skyrmions in ultrathin films and multilayers Co/X (X = Ir, Pd, Pt) are considered. The generalized DeBonte ansatz is used to describe the inhomogeneous skyrmion magnetization.

Information processing in patterned magnetic nanostructures with edge spin waves.

Low dissipation data processing with spins is one of the promising directions for future information and communication technologies. Despite a significant progress, the available magnonic devices are not broadband yet and have restricted capabilities to redirect spin waves. Here we propose a breakthrough approach to spin wave manipulation in patterned magnetic nanostructures with unmatched characteristics, which exploits a spin wave analogue to edge waves propagating along a water-wall boundary.

Nonlinear magnetic vortex dynamics in a circular nanodot excited by spin-polarized current.

We investigate analytically and numerically nonlinear vortex spin torque oscillator dynamics in a circular magnetic nanodot induced by a spin-polarized current perpendicular to the dot plane. We use a generalized nonlinear Thiele equation including spin-torque term by Slonczewski for describing the nanosize vortex core transient and steady orbit motions and analyze nonlinear contributions to all forces in this equation. Blue shift of the nano-oscillator frequency increasing the current is explained by a combination of the exchange, magnetostatic, and Zeeman energy contributions to the frequency nonlinear coefficient.

Higher order vortex gyrotropic modes in circular ferromagnetic nanodots.

Magnetic vortex that consists of an in-plane curling magnetization configuration and a needle-like core region with out-of-plane magnetization is known to be the ground state of geometrically confined submicron soft magnetic elements. Here magnetodynamics of relatively thick (50-100 nm) circular Ni80Fe20 dots were probed by broadband ferromagnetic resonance in the absence of external magnetic field. Spin excitation modes related to the thickness dependent vortex core gyrotropic dynamics were detected experimentally in the gigahertz frequency range.

Microstructural and magnetic properties of CoCu nanoparticles prepared by wet chemistry.

Co(10)Cu(90) nanopowder alloys have been prepared by the sonochemical wet method. In this way, Cu/Co bimetallic nanocrystallites with average diameter of 10-20 nm, presenting a homogeneous metastable solid solution of Co in Cu, were produced. Their structural characterization by X-ray diffraction, transmission electron microscopy and inductive coupled plasma-atomic emission spectrometry techniques has been used.

Universal criterion and phase diagram for switching a magnetic vortex core in soft magnetic nanodots.

The universal criterion for ultrafast vortex-core switching between the up- and down-core bistates in soft magnetic nanodots is investigated by micromagnetic simulations along with vortex-core switching that occurs whenever the velocity of vortex-core motion reaches its critical velocity, upsilon cri = (1.66 +/- 0.18) gamma mean square root of Aex (e.

Dynamic origin of azimuthal modes splitting in vortex-state magnetic dots.

A spin-wave theory explaining experimentally observed frequency splitting of dynamical spin excitations with azimuthal symmetry of a magnetic dot in a vortex ground state is developed. It is shown that this splitting is a result of the dipolar hybridization of three spin-wave modes of a dot having azimuthal indices |m|=1: two high-frequency azimuthal dipolar modes of the in-plane part of the vortex with indices m = +/-1 and a low-frequency (Goldstone-like) gyrotropic mode, describing translational motion of the vortex core and having index m = +1. The analytically calculated magnitude of the frequency splitting is proportional to the ratio of the dot thickness to its radius and quantitatively agrees with the results of time-resolved Kerr experiments.

Dynamic origin of vortex core switching in soft magnetic nanodots.

The magnetic vortex with in-plane curling magnetization and out-of-plane magnetization at the core is a unique ground state in nanoscale magnetic elements. This kind of magnetic vortex can be used, through its downward or upward core orientation, as a memory unit for information storage, and thus, controllable core switching deserves some special attention. Our analytical and micromagnetic calculations reveal that the origin of vortex core reversal is a gyrotropic field.

Strong radiation of spin waves by core reversal of a magnetic vortex and their wave behaviors in magnetic nanowire waveguides.

We conducted micromagnetic numerical studies on the strong radiation of spin waves (SWs) produced by the magnetic-field-induced reversal of a magnetic vortex core, as well as their wave behaviors in magnetic nanowires. It was found that the radial SWs can be emitted intensively from a vortex core in a circular dot by virtue of localized large torques employed at the core, and then can be injected into a long nanowire via their contact. These SWs exhibit wave characteristics such as propagation, reflection, transmission, interference, and dispersion.

Field evolution of tilted vortex cores in exchange-biased ferromagnetic dots.

We developed an analytical model for the magnetization reversal via vortex nucleation and annihilation in double-layer ferromagnetic/antiferromagnetic cylindrical dots. The coupling of the ferromagnet to the antiferromagnet is modeled by means of an interfacial exchange field. The nonuniformity of the magnetization reversal mode perpendicular to the layers is explicitly included and results in a tilted vortex core (tilted Bloch line).