| Recently,with the development of spintronics,magnetic thin films with perpendicular anisotropy have attracted extensive interest.Compared with the magnetic thin film having in-plane anisotropy,the use of the thin film with perpendicular anisotropy is advantageous for miniaturization of a memory device.With the deepening of the understanding of the behavior of magnetic domains in such thin films,storage and logic devices based on magnetic domains and domain walls have been proposed and studied.Therefore,the manipulation of magnetic domain behavior in thin films with perpendicular magnetic anisotropy has become an important research topic.Although in recent years there have been reports on various methods of manipulating magnetic domains,such as current,voltage,and spin waves,these methods have disadvantages such as damage to the sample and difficulty in sample preparation.Therefore,in this thesis,we firstly studied the laws of the magnetic reversion and domain wall motion in thin films with perpendicular magnetic anisotropy,and then study the law of the magnetic reversion and domain wall motion under the influence of surface acoustic waves.The main research content and conclusions of this thesis are as follows:1.The magnetization reversal and domain wall motion in Pt/Co/Pt samples were systematically studied,and the effects of the thickness of the magnetic layer and the annealing temperature on the magnetization reversal and domain wall motion were analyzed respectively.A linear relationship between creep parameters was observed and a reasonable explanation was given.2.The study on the magnetization switching and domain wall motion of[Fe Co/Pt]nfilms shows that the state of the stripe domain in the magnetic film has a great influence on the magnetization switching.In the magnetic film with stripe domains in the flipping process,the magnetization switching process consists of two steps,and the coercive force of the film is greatly affected.The expansion velocity of the stripe domain boundary follows a similar law to the typical domains wall motion.Annealing increases the pinning strength of domain walls,makes the magnetic domain present fractal characteristics during the magnetization reverse process,and reduces the expansion velocity of the stripe domain boundary.The magnetization switching and domain wall motion in[Co/Ni]n films were subsequently studied.Due to their all-magnetic structure,[Co/Ni]n multilayers exhibit different characteristics from[Fe Co/Pt]n.Both the magnetization reversal and the domain wall motion velocity of[Co/Ni]n change greatly with the period number,which is caused by the accumulation of film disorder and the change of perpendicular anisotropy.Changing the thickness of the Ni layer has little effect on the sample,but changes the linear relationship between creep parameters.3.The effect of surface acoustic waves on Pt/Co/Pt thin films with perpendicular anisotropy was studied.Surface acoustic waves have a great influence on the magnetization reversal and domain wall motion of magnetic thin films.The effect of the substrate on the magnetization reversal in this type of film was studied,and it was found that the substrate affects the degree of domain wall energy reduction at film defects.Then the research was extended to the Pt/Co/IrMn system with exchange bias,the differences in magnetic domain evolution and domain wall motion speed between the two reversal processes were analyzed.The differences between the Pt/Co and IrMn/Co interfaces and the effect of unidirectional anisotropy are illustrated.The process of magnetization reverse conforms to the magnetic droplet model,and the addition of surface acoustic waves can increase the nucleation probability of reverse magnetic domains during the process of magnetization reversal.By fitting the experimental results,information on the nucleation position（defect）of the reverse magnetic domain can be obtained.The fitting results at multiple locations are in good agreement with the experimental results.Surface acoustic waves can significantly increase domain wall motion velocity.According to the linear relationship between creeping parameters,it can be speculated that there is a correlation between the microscopic pinning parameter fpin and perpendicular magnetic anisotropy.The third harmonic of the surface acoustic wave has a similar effect on the velocity of motion as the fundamental wave.When the power of the surface acoustic wave is relatively low,the effect of the third harmonic on the domain wall is slightly greater than that of the fundamental wave;when the power of the surface acoustic wave is relatively high,the fundamental wave has a greater impact on the domain wall. |
