| With the rapid development of communications and computer technology,the amount of data generated by human society is increasing exponentially.In order to meet the challenge of mass data storage,magnetic random access memory based on spintronics research is designed.Meanwhile,because of its low energy consumption,high read/write speed and storage density,it is considered to have great application potential and development value in solving the problem of mass information storage and processing.For spintronics devices regulated by spin and charge current,it is common to use different magnetization states to represent the"0"and"1"logical states in information storage devices.In magnetic materials,this spontaneous formation of the same alignment configuration of magnetic moments is the magnetic domain.Therefore,in order to understand the working principle of magnetic random access memory,it is very important to study the magnetic domain structure in magnetic thin film materials.Magneto-optical Kerr microscope is one of the main methods to characterize the domain structure of magnetic thin film materials.It can directly observe the domain structure in the scale range of 1-100μm.Therefore,magneto-optical Kerr microscope is widely used by researchers to study the behavior of magnetic sample domain structure under the effect of spin-orbit torque,spin-transfer torque and other electric current effects,because it can in-situ observe the domain structure while applying current to the material.In this paper,the domain behavior of ferromagnetic TbFeCo films in the process of current-induced magnetic switching and the rich domain structures which are spontaneous generate in Co Fe B films were investigated by using the magneto-optical Kerr microscope.1.The heavy metal/ferromagnet metal bilayer structure is a classical structure for the study of magnetic switching caused by spin-orbit torque.In this paper,two kinds of heavy metals with different spin hall angles,W and Pt,were selected as the heavy metal layer of ferromagnetic amorphous Tb Fe Co bilayer with strong perpendicular magnetic anisotropy,and the domain behavior of these two bilayer samples in the process of magnetic switching induced by spin-orbit torque were observed using the magneto-optical Kerr microscope.It was found that the larger the spin hall angle of the heavy metal layer,the higher the switching efficiency of the bilayer sample.In addition,the Dzyaloshinskii-Moriya interaction equivalent field was quantitatively measured by the magneto-optical Kerr microscope,and the existence of DMI in the Tb Fe Co/W bilayer was qualitatably proved.This verifies the physical image that chiral Néel domain walls due to DM interactions are a prerequisite for the occurrence of high efficiency magnetic switching induced by spin-orbit torque.2.Ta/CoFeB/MgO thin films with stable perpendicular magnetic anisotropy are widely used in the manufacture of magnetic tunnel junctions and the design of high-density magnetic storage units.In this paper,a wedge-shaped Ta/Co Fe B/Ta(t Ta)/Mg O/Ta sample with uniform gradient variation in the thickness of the Ta capping layer was grown.The distribution of magnetic domains in different regions of the sample has been observed by the magneto-optical Kerr microscope.It is concluded that skyrmion-type magnetic bubbles can be generated spontaneously at the region with a transition from out of-plane to in-plane magnetic anisotropy of the wedge-shaped Co Fe B film sample.Then a series of multi-period Ta/Co Fe B/Mg O samples were grown and the domain structure of these Co Fe B film samples with different period numbers were observed systematically.It was found that with the increase of the period number of the sample,that is,the artificially regulated interlayers DM interaction increases,film samples tend to generate thinner and denser labyrinth domains. |
