Study On The Thermodynamic Property And Magnetization Of Magnetic Bilayers

In recent years, as magnetic thin film has been widely applied to magnetic recording medium of super high density, magneto-optic recording medium, thin film magnetic head, sensor and so on, it has gained wide concern in both fundamental and application research. Motivated by recent experimental findings, this thesis adopts the classical Heisenberg model and Monte Carlo method to make a simulation study on the thermodynamic property of hard magnetic/soft magnetic bilayer system. It also adopts methods of micromagnetics to research the magnetization process of hard magnetic/soft magnetic bilayer system.With Monte Carlo method, it researches the interaction between layers of the hard magnetic/soft magnetic, the magnetocrystalline anisotropy of hard magnetic layer and the peak of thermodynamic property influence of external magnetic on hard magnetic/soft magnetic bilayer system. The results indicate that when the magnetocrystalline anisotropy of hard magnetic increases, the transformation temperature of the bilayer system will become higher with the influence of hard magnetic layer. At the same time, the peak of magnetic susceptibility and specific heat will shift right; with the impact of external magnetic field, the intensity of system magnetization will become larger with the increasing of the magnetic field. Magnetic susceptibility will be restrained by magnetic field. Specific heat will be restrained in low temperature and enhanced in high temperature. It researches the interaction between layers of the hard magnetic/soft magnetic, the magnetocrystalline anisotropy of hard magnetic and the peak of thermodynamic property influence of external magnetic on hard magnetic/soft magnetic bilayer system. The results indicate that when the magnetocrystalline anisotropy of hard magnetic increases, the transformation temperature of the bilayer system will become higher with the influence of hard magnetic layer. At the same time, the peak of magnetic susceptibility and specific heat will shift right; with the impact of external magnetic field, the intensity of system magnetization will become larger with the increasing of the magnetic field. Magnetic susceptibility will be restrained by magnetic field. Specific heat will be restrained in low temperature and enhanced in high temperature.This thesis adopts micromagnetics methods and tries to research the interaction between hard magnetic and soft magnetic, the influence of the angular of the external field on the magnetization process of hard magnetic/soft magnetic bilayer system. The results indicate that when coupling coefficient increases, the system hysteresis loop will become narrow; coercivity will become bigger gradually and verge to a constant value; with the increasing of angle between external field and easy axis of hard magnetic layer, coercivity become smaller. With the view of temperature changing will cause the random fluctuation of spin direction inside of the film, the author regulates the spin’s original state and simulates the influence of temperature on hysteresis loop hard magnetic/soft magnetic bilayer system with micromagnetic method. The result shows the research is generally fit to Monte Carlo method.