RESUMEN
The spin torque nano-oscillator (STNO), a nanosize microwave signal generator, have caught the attention of a number of researchers due to its obvious advantages. Recently a chiral bulk material with twisted skyrmion has been discovered in studies with different helicity degrees. In this work, we design a new STNO based on twisted skyrmion existing in free layers of magnetic tunnel junction structure. We first investigate the effect of the magnetic moment of fixed layer on the twisted skyrmion and frequency of STNO. Although the magnetic moment of fixed layer does not affect the state of the twisted skyrmion but affects the precession frequency of STNO. Later, the current, external magnetic field and Dzyaloshinskii-Moriya interaction strength are changed to regulate the oscillation frequency of STNO. Our result may be favorable for the design of new twisted skyrmion-based STNO.
RESUMEN
Skyrmion bags as spin textures with arbitrary topological charge are expected to be the carriers in racetrack memory. Here, we theoretically and numerically investigated the dynamics of skyrmion bags in an anisotropy gradient. It is found that, without the boundary potential, the dynamics of skyrmion bags are dependent on the spin textures, and the velocity of skyrmionium withQ = 0 is faster than other skyrmion bags. However, when the skyrmion bags move along the boundary, the velocities of all skyrmion bags with differentQare same. In addition, we theoretically derived the dynamics of skyrmion bags in the two cases using the Thiele approach and discussed the scope of Thiele equation. Within a certain range, the simulation results are in good agreement with the analytically calculated results. Our findings provide an alternative way to manipulate the racetrack memory based on the skyrmion bags.
RESUMEN
The 2π isolated chiral skyrmion is a magnetic configuration. Since the total topological charge is zero, the 2π isolated skyrmion driven by a spin-polarized current propagates strictly along the racetrack. The manipulation of 2π-skyrmion, e.g., pinning/depinning at a specific position of the racetrack, is significant. Here, we investigated the 2π-skyrmion pinning in a racetrack using exchange bias. A series of transversal AFM wires were set above the ferromagnetic (FM) racetrack. Spin waves were employed to induce 2π-skyrmion motion to study the dynamics of the 2π-skyrmion pinning. The AFM wires induce exchange bias at the AFM/FM crossing points, which can act as pinning sites. The working window for a 2π-skyrmion in a racetrack was investigated as a function of the exchange bias field, the frequency and amplitude of the oscillating magnetic field for exciting spin waves. The interaction mechanism between the 2π-skyrmion and the exchange bias was also studied. This work may provide guidance for the design of next-generation spintronics.