| Magnetic skyrmion and radial vortex both are new nanoscale magnetization with topological protected property.They are widely used in the development of next generation spintronics devices,including racetrack memory and spin transfer nanooscillators.They have attracted the interest of a growing number of researchers due to the huge advantages,for example small size,easily to integrate,low drive current density,and high stability.However,overcoming the skyrmion Hall effect in the racetrack memory and increasing the oscillation frequency of the spin transfer nanooscillator have always been the key for practical applications.In this work,we propose some results of solving above problems by means of micromagnetic simulations.We also investigated the switching process of radial vortex driven by microwave magnetic field and spin polarization current,and further explored spin wave modes of kπ radial vortex excited by pulse microwave magnetic field.For the 2π and 3π radial vortex,the in-plane counterclockwise and clockwise modes and the out-of-plane breathing modes appeared under the excitation of the pulse microwave magnetic field.And the number of spin wave modes increase with increasing the k.In the radial vortex switching process under the effect of microwave magnetic field,it can be found that the response of magnetization to the microwave magnetic field is very strong when the frequency is close to eigenfrequencies.The dynamic switching process under the microwave magnetic field at different eigenfrequencies are divided into breathing mode,spin wave mode and mixed mode.It is also found the precession mode when the spin polarization current is applied to the nanodisk.Then we applied the high magnetocrystalline anisotropy materials to boundary of nanodisk to achieve continuous precession motion by overcoming switching of core.Thus,the spin transfer nano-oscillator with high oscillation frequency is designed.In addition to the above single frequency signal generator based on radial vortex,we also propose the structures that can excite multi-frequency microwave signals.For the skyrmion pair based oscillator assisted by the vertical magnetic field,it is found that the larger size skyrmion starts breathing when the size difference of the skyrmion pair is big enough.This behavior excites a multi-frequency microwave signal.In addition,spin wave mode of elliptical skyrmion has radial asymmetric breathing mode,so the elliptical skyrmion occurs breathing behavior in the precession process under the effect of spin polarization current.Thus,these two types of oscillator output single-frequency and multi-frequency microwave signals.For the study of racetrack memory,we first design the structure based on synthetic antiferromagnetic skyrmion pair,which effectively avoids the skyrmion Hall effect.And it is found that spin polarized current density,damping content and interlayer antiferromagnetic coupling strength are all important factors affecting the speed of skyrmion.In addition,the skyrmioniun and skyrmion are applied synchronously to avoid information loss and errors,which caused by high temperature.And it is found that they have faster speed and higher stability in synthetic antiferromagnetic structures.These results provide reference significance for further research on static characteristics with topological magnetic structures and their application in spintronics. |
