Molecular Magnetism Research, And Some Of The Theories Of Magnetic Multilayers

This thesis consists of two parts, involving the field of molecular magnetism and spindynamic simulation of microscropic magnetic structure in ferromagnetic multilayers.In the first part, we study some problems, such as macroscropic quantum effects(quantum resonant tunneling), staircase hysteresis loop, (?) magnetization relaxationbehavior, transverse anisotropy, hyperfine effects, dipolar interaction effects, temperature effects and so on, in the field of molecular magnetism. This part is arranged as follows: In chapter 1, we give a brief review of the progress of theory and experiment on single-molecule magnets (smm's), including Mn₁₂, Fe₈, Mn₄ andsupermolecular magnetic cluster [Mn₄]₂. In chapter 2, we introduce some basic theoretical descriptions about quantum resonant tunneling and some experimental results, taking example for Mn₁₂ system. In chapter 3, we give a study of thestaircase hysteresis loop of Mn₁₂ system based on Landau-Zener (LZ) model and numerically calculation method of exact diagonalization of Hamiltonian. In chapter 4, we study the quantum resonant tunneling in supermolecular magnetic cluster [Mn₄]₂system by means of the numerically exact solution of the time-dependent Schrodinger equation. In chapter 5, we study the dynamical process of thermally assisted quantumresonant tunneling in Mn₁₂ system, by introducing a phenomenological localthermal equilibrium approach.In the second part of this thesis, we give a study of microscropic magnetic configuration in magnetic multilayers based on spin dynamical simulation. Spin vortex configuration is a very common structure founded in ferromagnetic multilayers. This kind of vortex spin configuration will shift easily by applied an in-plane field. We take efforts to study if this kind of spin vortex can be pinned to be more stable for the purpose of potential technological applications. This part is arranged as follows:...