| Magnetic material has a very wide range of applications. Especially in the rapid development of information technology and computer technology today, the magnetic material storaging and recording information has an irreplaceable role. With the advance of storage technology, the research of nano-scale storage media shows a rapid development trend. As we all know, information is stored by the direction of the particle magnetic moment, while the process of recording information depends on the change the direction of the particle magnetic moment, how to ensure the stability of stored information to overcome the superparamagnetic limit, but also easy to log information in the magnetic particles, is an important part of the current study. The microwave field assisted magnetic moment reversal is an effect way to accelerate the process of reversal and improved storage speed. In this paper, the LLG equation is used to simulate the dynamic process and hysteresis behavior of magnetic particles, study the effect of the various interactions between the spins and the external microwave field on the particle magnetic moment reversal. The main jobs and conclusions are as follows:1. The LLG equation as the theoretical basis, using fourth-order Runge-Kutta numerical method to solve this equation, simulate the dynamic process and the hysteresis behavior of a single particle magnetic moment, the reversal process of magnetic moment at different angle between anisotropic field and DC field, and the effect of microwave field on magnetic moment reversal process. The results showed that when the frequency of the microwave field is the natural resonance frequency, the particle magnetization reversal field is the smallest, and the time of magnetic moment reversal is shortest.2. The two particles system with interaction is studied. The effect of different angle between two anisotropic field on the particle magnetic moment reversal process is calculated. The results showed that when the angle between anisotropic fields is π/4, magnetization reversal of particles is most rapid. Like the situation of a single particle, when the frequency of the microwave field is the natural resonance frequency, the magnetic moment reverse is most easily and most quickly.3. The magnetic moment reversal process and hysteresis behavior of double layer system is studied. The effect of exchange interaction between spins within a layer or on two layers, the amplitude and frequency of the microwave field on magnetic moment reversal process and hysteresis behavior are calculated. The result showed that the exchange interaction between spins in the layer has a weaker effect on the magnetic moment reverse than the interlayer exchange effects,4. The magnetic moment reversal process and hysteresis behavior of magnetic nano-sphere composed of742spins is studied, and the effect of exchange interaction between spins and the microwave field is calculated. The reversal speed of magnetic moment is not always increase with the exchange interaction increasing. With the enhancement of exchange interaction between spins inside the sphere, the effect of this interaction on the hysteresis behavior shows a weakening trend, however the exchange interaction between spins in the surface and the exchange interaction between spins with one on the surface and the others in the internal has not such trend. The effect of the microwave field with natural resonance frequency on the magnetic moment reversal is obvious, but the effect of the microwave field with other frequency on the magnetic moment of reversal is very small. Increase of the amplitude of the microwave field will significantly promote the magnetic moment reversal. |
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