The Simulation Study On Ac Susceptibility Of Magnetic Nanoparticle

Nanomaterials as a new type material has received extensive attention in recent years due to its unique capability in the optical, magnetical and electrical fields, therefore the study of ac susceptibility in nanomaterials has a guiding significance in preparation and improving performance of nanomaterials.In this paper, we have studied the ac susceptibility of magnetic nanoparticle system, exploring the frequency dependence of the ac susceptibility in this system. The paper is divided into three parts. In the first chapter, an overview of nano-magnetic materials and basic characteristics are briefly introduced. In the second chapter, we describe the object of nano-magnetic particles spherical model adopted in this paper. It composes of spins inside and outside of the sphere. The magnetic moment equation for each spin is established by LLG equation. Using Runge-Kutta method, we obtain the solution of magnetization of the spins. Then based on the integral formula, the final result of the ac susceptibility has been determined. In the third chapter, firstly we study the influences of damping factor and magnetic anisotropy on ac susceptibility of magnetic nanoparticles. Then under different exchange interactions, we study the effects of anisotropy on ac susceptibility. Finally the influences of exchange interaction on ac susceptibility have been investigated for various anisotropies.The results show that the magnetic anisotropy energy, surface exchange energy and damping coefficients have certain influence on ac magnetic susceptibility, consequently leading to a significant impact on the absorption of the nanomaterials as well. By regulating the structure of the nanoparticles can effectively improve absorptive characteristic and be applied to thin layer in the design of the absorbing material.