Micromagnetic Simulations Of Magnetic Skyrmion-based Microwave Detector

Magnetic skyrmions are topological protected spin structures discovered in recent years.Due to its small size and extreme low manipulation current density,magnetic skyrmions are expected to be used in application of the racetrack memory(RM)and other spintronic devices.At present,lots of spintronic devices based on magnetic skyrmion have been proposed,such as magnetic random access memories(MRAMs),spin transfer nano-oscillators(STNOs),and Racetrack Memories(RMs),etc.In addition to the advantages in power consumption,there are some problems needed to be resolved for skyrmion in practical applications.In the application of STT-MRAM,most reported skyrmion nucleation and reversal time is quite long,which limits the speed of information access.In skyrmion based microwave detector,its sensitivity is relatively low compared to that based on ferromagnetic resonance(FMR).In this work,we mainly focus our attention on these two problems,the details are as follows: 1.Magnetic skyrmion based MRAMWe proposed a specific spin valve structure to nucleate and switch the magnetic skyrmion rapidly,in which the magnetization configurations of reference layer exhibit a spatially varied polarization with skyrmion-like structure.In such device,the critical current density for the skyrmion nucleation and reversal is extremely low,and the time of reversal can be greatly reduced.The proposed device can be used in MRAM as a basic unit,which provides a new way for the design of magnetic skyrmion based MRAM.2.Magnetic skyrmion based microwave detectorWe introduce bias current and bias magnetic field in traditional magnetic tunnel junction(MTJ)structure,and investigate its effect on the performance of skyrmionbased microwave detectors.Moreover,to improve the sensitivity of the magnetic skyrmion-based microwave detector,we made some optimizations on the MTJ structure.First,we considered a ring-shaped electrode instead of the circular electrode.Second,we added another magnetic reference layer to the traditional MTJ structure,which exhibits vortex-like magnetization configurations.Both of the two optimizations greatly improve the sensitivity of the skyrmion-based microwave detector.Above all,our proposals and investigations offer a new method for the designing of skyrmion based microwave detectors,which are useful in the developments of spintronic devices.