Based on the physics computation model in this work, we firstly calculated the signal field and magnetization distribution in free layer using transmittance line model and micro-magnetic theory, and then we discussed the effect of size and magnetic parameters on the magnetic flux and signal field; 本文基于建立的物理计算模型,首先利用传输线方法和微磁学理论对铁磁自由层中信号场和磁化强度分布进行了计算,优化了材料性能参数;