中文摘要：

基于微磁学基本方程Landau-Lifshitz-Gilbm（LLG）方程，我们建立了软磁薄膜体系顺磁-铁磁转变过程中涡旋数目随时间的变化关系模型．磁化强度运动方程采用了传统的Runge-Kutta数值方法求解．计算结果发现：不同的交换场下，涡旋数变化可以分为两个阶段：第一阶段涡旋数目随时间急剧减少；第二阶段涡旋数目缓慢减少，直至不再变化，交换系数越小剩余的涡旋数会越多．退磁能对相变过程影响甚微，只有在交换系数（1．3E-12）较小时有可观察到的效应：有退磁场涡旋数目稍小．

英文摘要：

A model was build about the relation of the Vortex Number and time in the process of paramagnetic - ferromagnetic transition in the soft ferromagnetic permalloy （Py） thin films based on, LLG equations （LLG）. Equation of the magnetization was solved by numerical methods of Runge-Kutta. The results shows： the process of vortex number vs time can be divided into two stages： in the first stage, vortex number reduces drastically, in the second stage, the vortex numbers slowly decrease to a steady state. The smaller exchange coefficient is, the more remaining Vortex Numbers will be. Demagnetization has little effects on the process of phase change, Vortex number decrease can be observed only in the smallest exchange foffieient （1.3E-12） situation.