Study On The Spin Dynamics Of The Lateral Magnetic Domain Wall Driven By Spin Wave

In the information age, the shortcomings of traditional hard disk gradually exposed and has been unable to meet the requirements of people with people’s improving demand for data storage and speed of data reading, it will inevitably produce on the research of the new type of storage. Parkin et al. put forward the track memory, it uses the magnetic DW(DW) to store data, it can greatly improve the storage density because of its three-dimensional plane, it greatly improves the storage density, so the magnetic DW motion has great potential application value in the aspect of data storage and logic devices, which makes the magnetic DW of nanostructures and DW motion over the past few decades received wide attention and research. Magnetic DW dynamics also become the focus of people to scientific inquiry. At present, the three main methods used to drive the DW movement are magnetic filed, the polarization current and SW(SW), this paper mainly studies the DW motion driven by the SW.The first part of this paper mainly introduces the origin of the magnetism, the magnetic materials application and development in the field of information storage.The second chapter introduces the relevant theoretical knowledge and the existing conclusion and research results about DW motion, which including the DW motion induced by external field, current and SW.The third chapter concisely introduces the main basic simulation method used in this paper: spin dynamics simulation.The fourth chapter we study the DW motion rules, and discuss the mechanism of the DW motion induced by SW in magnetic nanostrip by micromagnetic simulations. The research shows the DW motions are always accompanied by an energy imbalance between two sides of the DW, at one side of the DW the energy density increases, at the other side the energy decreases. The DW motion can be attributed to the expansion of the low-energy-density area and the contraction of the high-energy-density area. We find in the area of the SW propagation, energy density increase over time, this is related to the energy injected. And in the region of the SW superposition and SW reflection, energy density will decrease with the increasing time, which is associated with energy dissipation. When the SW frequency is lower, there will be a big reflection and mall transmission, thus the SW superposition appears on the side of SW incident which reduces the energy density, at the transmission side energy density increase, so the DW motion direction is consistent with the SW propagation direction; when the SW frequency is higher, the transmission is big and the reflection is small at the position of DW, at the same time, the transmission will be reflected by the boundary and form in the superposition wave, the energy density at the side of SW incident increases, and the energy density at the transmission side decreases, so the DW direction is opposite to that of the SW. This energy imbalance mechanism can explain well all the regularity of DW motion.The fifth chapter introduces the difference of DW motion induced by the SW excited by different excitation, including the DW motion excited by different external filed with the same power and frequency,different filed with same amplitude and frequency and the same external field with different amplitude and same frequency. We find the SW excited by different external field with the same power have almost no influence to the peak of the DW motion and the threshold value of the amplitude of the external field that can drive the DW motion, but the velocity shows a little difference.When the frequency is lower, the velocity of the DW motion is the fastest induced by the SW excited by the square external field, and then is the velocity when the triangular external field works as excitation, and the velocity of the DW motion induced by the sine wave is the slowest, this is related with teh shape of SW. While the frequency is higher, the velocity of the DW motion induced by the SW excited by the triangular external field is the fastest and induced by the square external field is the lowest, this is related to the amplitude of SW. Beside, we also find that the velocity of the DW will increase with the increasing of the amplitude of the external field, but when the amplitude is larger than a certain value, it will stop increasing and keep unchanged which is relevant with the extrusion of the DW width. We find that the degree of extrusion is greater when the amplitude is lager, and the amount of extrusion is smaller with the increasing amplitude, the increment of velocity is also small, when the amplitude is large enough,The width of the DW almost keep unchanged, and the corresponding velocity is constant.