The Dynamics Of Domain Wall In A Perpendicularly Magnetized Nanostructures

Spintronic devices which are based on domain walls are designed due to the properties of the spin electron.After the spin-transfer torque effect was discovered,electronic devices no longer relied on magnetic field.In spintronic devices field,STT-based devices generally have the advantages of small size,easy to integrate,low power consumption and faster propagation speed,so the STT effect has been widely used in the study of magnetic random access memory,track memory,microwave oscillator and other spintronic devices after it was discovered.Compared with in-plane magnetized nanostructures,perpendicular magnetized nanostructures have attracted much attention of researchers due to their simple spin structures,narrower domain walls and smaller threshold current.In view of that,this dissertation mainly studies the dynamics of domain wall oscillation in perpendicular magnetized nanostructures by means of micro magnetic simulation.The specific research results are as follows:?1?The oscillations of pinned domain wall in perpendicular magnetized nanowires were studied.The oscillating current decreases first and then increases as the depth of notch increases,and reaches the minimum value at a depth of h=12nm for rectanular notch,or h=18 for triangular notch or arc notch nm.The depinning current increases with the increase of notch depth.No matter what kind of shape for the notch,the oscillation frequency increases linearly while the current increases.When notch depth is large?h?12nm for rectanular notch or h?18nm for triangular/arc notch,the oscillation frequency will come to a stable plateau area–the increase of current will lead little change to frequency?.The frequency and amplitude of can mainly be regulated and controlled by current,notch shape and depth,and material of nanowire.?2?The dynamics of multiple pined domain wall in nanowires was investaged.It was found that stable synchronized oscillation of multiple domain walls can be reached manipulated the interval between domain walls and the depth of notches.The oscillation currents is not much different from single domain case.However,The microwave voltage signal can be effectively promoted by the distance between adjacent notches as well as the numbers of notches.It was also found that an proper applied magnetic field can further enhance the voltage signal.?3?The domain wall oscillations in nanowires compined with perpendicular and in-plane magnetizated parts were studied.The velocity of the domain walsl almost linearly increases while the current increases.The initial oscillation of the domain wall can be adjusted by the damping factor?,the non-adiabatic factor?,perpendicular anisotropy constant K_PMA,interfacial exchange constant A₁₂,and saturation magnetization Ms_PMA and Ms _IMA.The oscillation frequency and amplitude can be regulated by current,accessory magnetic field and material parameters K_PMA,?,?and so on.