Magnetization Dynamics In Stoner Particle With Microwave

There are high requirements to the information storage devices such as hard disk and magnetic disk as the rapid development of modern science and technology. It is very important for researchers to try to design of faster and higher density of magnetic storage devices. Since a magnetic storage device has wide applications in our lives, the key point is trying to improve the storage performance of magnetic materials, which means finding some ways to improve the efficiency of magnetization reversal in the magnetic materials and to reduce the reversal field in the process of magnetic reversal. It is very complicated of magnetic reversal in the magnetic materials, therefore, we use a simplified uniaxial Stoner particle model to study the dynamics of magnetic reversal in order to simplify the studies, and it is useful not only in saving research time but also bringing certain guidance for practical application. This thesis mainly studied of magnetization reversal of Stoner particles under elliptically polarized microwave with variable frequencies and microwave field assisted magnetic reversal dynamics under tilted polarization spin-polarized current.The basic structure of the article is as follows: The first chapter is an introduction. We simply introduced the background and the development of this research field, and tried to deeply understand the research progress by reviewing the important related literatures in this field. The second chapter is the theoretical basis, where we mainly introduced the basic equation of magnetic reversal, the Landau-Lifshitz-Gilbert(LLG) equation and the Landau-Lifshitz-Gilbert-Slonczewski(LLGS) equation after considering the spin transfer torque(STT). In the third chapter, the magnetization reversal of Stoner particles is studied under elliptically polarized microwave with variable frequencies based on theLandau-Lifshitz-Gilbert equation. By applying variable frequency microwave field, we found the relationship between the variable frequency and the critical reversal field as well as determining the minimum critical field under the proper frequency. Studying the magnetization reversal of Stoner particles can improve the storage performance of magnetic materials and develop a new generation of magnetic memory. STT-induced magnetization reversal was studied in chapter 4. Taking into consideration the uniaxial magnetic anisotropy, the magnetization dynamics under a spin-polarized current that was polarized in an arbitrary direction were investigated by solving the Landau-Lifshitz-Gilbert-Slonczewski equation for a single-domain magnet. We found the relationship between the threshold current density and the amplitude and frequency of the microwave field in the process of magnetization reversal of different spin valves. Studies have shown that tilted spin valves can reduce the threshold current density of the free layer effectively in the process of magnetization reversal. The last chapter is the conclusion of this article. And some leftover problems were put forward. We also give some outlooks at last.