Effects Of Defects On Dynamic Behaviors Of Skyrmions In Synthetic Ferrimagnetic And Synthetic Antiferromagnetic Materials

Due to magnetic skyrmion are topologically protected nanoscale magnetizaion configuration and can be driven by low current,so there are expected to become the next generation of magnetic storage device units.Ferromagnetic（FM）skyrmion will drift from the center of nanotrack or even annihilate at the edge of the nnotrack under driving current due to the skyrmion Hall effect（Sk HE）.The synthesized antiferromagnetic（SAF）bilayer skyrmions driven by electric current can restrain the Sk HE and move in a straight line in the direction of the track.However,experiments show that the pinning effect of SAF skyrmions is so large that the required threshold driving current increases accordingly.In this work through micromagnetic simulations,we find the reason of the large pinning effect of SAF skyrmions and solve it by using synthetic ferrimagnetic（SFIM）skyrmions.We compare the motion behavior of FM,SAF and SFIM skyrmions driven by electric currents in detail.It is showed that the Sk HE of SFIM skyrmions is smaller than FM skyrmions and do not annihilate at the edge of the nanotrack under current driving.In addition,the critical current for SFIM skyrmions getting through the pinning region is ten times smaller than SAF skyrmions.Furthermore,the relationship between the ability of SFIM skyrmions to cross defects and the Sk HE shows that the ability of SFIM skyrmions to cross the defect can be enhanced by manipulating the saturation magnetic moment of FM layer.And by changing the polarity of FM layer,we can design the offset direction of SFIM skyrmions to suit our needs.In this paper,a signal reading amplifier based on SAF skyrmions is proposed.It is found that the ability of the magnetic tunnel junction to recognize the magnetic skyrmion can be effectively enhanced by properly regulating the potential well region.Our results could have significant implications for fundamental physics and help design future racetrack storage devices with ultra-low energy consumption and ultra-high memory density.