Two dimensional model of eddy currents and saturation in thin film write heads

A two-dimensional model of an MR write head has been constructed using a finite element model. The model includes the eddy currents as well as nonlinear saturation of recording head material. The recording head field (deep gap field) was calculated as a function of write-current frequency and amplitude for two recording-head materials, standard 80/20 NiFe and high saturation magnetization Ms material 50/50 NiFe. The analysis was also done in the time domain and was compared with experimental data on field response, using both a microloop apparatus and impedance measurements. Fair agreement was obtained between the model and the data. The deep gap field has a time delay relative to the write current, which varies as a function of current frequency and amplitude.