Vortex is considered as a promising candidate for nonvolatile magnetic random storage devices due to its unique binary state and high thermal stability. The control of vortex polarity and chirality is key to the devices based on vortex. In this work, the switching of magnetic vortex state in Permalloy nanodisks has been investigated by micromagnetic simulation employing in-plane alternating magnetic fields. During the switching of magnetic vortex state, an antivortex is formed, and the antivortex and vortex will not annihilate together. The formation of antivortex and the annihilation of initial vortex lead to the switching of magnetic vortex state. The switching of vortex state depends on magnetic field and disk size. The switching time of magnetic vortex state declines with the enhancement of magnetic field amplitude or magnetic field frequency. All the switching can be completed within 1.4 ns, indicating that the alternating magnetic field driving can induce the rapid switching of vortex state. This work provides an effective method for the fast switching of magnetic vortex state, which benefits the potential storage applications in vortex-based spintronic devices.
The synthetic antiferromagnetic (SAF) racetracks can perfectly suppress the skyrmion Hall effect, but the congestion phenomenon of the skyrmions at the end of the racetracks will seriously hinder the development of the skyrmion-based magnetic storage technology. In this paper, we have designed and investigated three racetrack structures of double-layer triangular notch, single-layer triangular notch (SLTN) and square hole-triangular notch (SHTN) in SAF racetracks by micromagnetic simulations. The critical current density that annihilates skyrmions in a racetrack with triangular notches is closely related to the angle of the triangular notches and decreases with the decrease of the angles. If a skyrmion in the top ferromagnetic (FM) layer of SLTN structure is annihilated, its counterpart in the bottom FM layer will also be annihilated due to the interlayer antiferromagnetic exchange coupling. Compared with the critical current density of 3.0 × 10 12 A m −2 in a normal racetrack, the critical current density of SHTN structure can be dropped to 6.0 × 10 10 A m −2 . The results reveal that all the three structures can significantly reduce the critical current density, which can effectively solve the skyrmion congestion at the end of the racetracks.
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