Study Of The Magnetization Reversal Mechanism Of Magnetic Nanowire

Magnetic nanowires with high shape anisotropy have attracted extensive interests for their potential application as high density perpendicular magnetic recording medium. And, the magnetization reversal mechanism of magnetic nanowires has been always the focus of researches. As is shown in this paper, a chain of truncated ellipsoids model is proposed to study the magnetization reversal mechanism of the magnetic nanowire in accordance with real topological structure. In this model, we take into account the accurate magnetostatic interaction energy between magnetic poles on the surface of the truncated ellipsoids, uniaxial magnetocrystalline anisotropy energy and Zeeman energy resulting from the interaction between applied magnetic field and magnetization. The contact angle of ellipsoids and the shape factor Of single ellipsoid become adjustable parameters according to the real topological structure of nanowire. Based on this model, the expressions of critical field for the irreversible reversal magnetization and the coercive force are derived for both the parallel rotation and symmetric fanning mechanism. The influences of the contact angle of the ellipsoids, the uniaxial magnetocrystalline anisotropy, the angle between the applied magnetic field and the chain axis, the number of ellipsoids and the shape factor of single ellipsoid on critical field and coercive force are discussed. The results based on this model indicate that the magnetization reversal process of the Ni nanowire may be the symmetric fainting mechanism. Another focus of this dissertation discusses the magnetization reversal of magnetic nanowire with specific shapes in view of the micro-magnetic simulations. Micro-magnetism finite element method, an effective method to study the magnetization reversal process, can study the relationship between microstructure and magnetic properties quantitatively. Using the micro-magnetism simulating software OOMMF based on finite element method, we simulate the magnetization reversal process of nanowire with the shape of chain of spheres, chain of ellipsoids and chain of truncated ellipsoids, with their hysteresis loops obtained, finding that for the nanowire with specific figure based on theoretical models, shape anisotropy of single cell plays an important role, the whole chain reversal magnetization begins from the two ends of the nanowire and, the reversal magnetization of real nanowire can be well approximated by chain of truncated ellipsoids with large contacted angle.