The Simulation On Properties Of Magnetization Dynamics Of Surface Modified Ferromagnetic Particles

In recent years,large capacity data storage and data reading are becoming more and more popular because of its vast market and application value.The system of periodic array of magnetic particles has an important application in high density memory.The study of the dynamic flip characteristics of the spin of a single domain magnetic particle is of great significance to the performance of the magnetic memory.The stability of the magnetization of the particles and the speed of the magnetization reversal directly affect the performance of the magnetic memory.In this paper,two kinds of magnetic particle models are mainly established:the cubic magnetic particle model of the simple cubic structure and the magnetic particle model of the six corner dense pile structure.In the establishment of the model,we consider the difference between the spin of the ferromagnetic core and the anisotropy of the surface spin.The spin anisotropy of the ferromagnetic core has a fixed anisotropic parameter along the direction of the Z axis.The anisotropic parameters and exchange effects of different surface modification are also different.For the sixcorner dense heap structure,the surface spin has a small anisotropy perpendicular to the surface in addition to the anisotropy along the Z axis.In this paper,we deduce the LLG equation of single spin.We use the four order Runge-kutta method to solve multiple spin differential equations,and deduce the AC susceptibility of magnetic materials in AC field.We have different surface modification on different magnetic particle models.When the interface conditions and external field conditions are changed,the hysteresis loops and magnetization reversal of magnetic granular system are calculated.The magnetization reversal field,turnover speed and AC susceptibility of ferromagnetic core and shell under different conditions are discussed.It is shown that the simple cubic structure of magnetic particle model in antiferromagnetic surface modification,increasing the interfacial exchange strength can increase the switching field;adding transverse alternating field,at a certain frequency,can accelerate the turnover speed of ferromagnetic surface modification of magnetic particle spin,can accelerate the turnover speed in the antiferromagnetic surface modification.For the six angle lattice structure of magnetic particle model:increase the antiferromagnetic surface modification of interface exchange interaction can increase the turnover,increase of iron magnetic surface modification of interface exchange interaction can reduce the switching field;transverse alternating field with certain frequency can reduce the switching field;adding transverse AC field at a frequency is added after the lateral exchange after the field,magnetic particle system will appear two turn transitions;anisotropy of the core-shell spin,AC susceptibility of two peaks.