Frequency and transient response of yoke flux for 45/55 NiFe and CoTaZr thin film write heads

This paper describes measurement and modeling of the frequency and transient response of the yoke flux in plated 45/55 NiFe and amorphous CoTaZr thin film write heads. The frequency response of the flux was determined from impedance measurements without any assumptions about the form of magnetic impedance. The transient response was calculated (i) from the frequency domain response using a inverse Fourier transform and (ii) from the frequency and inductance-current measurements using a nonlinear eddy current model. In all cases, the CoTaZr head showed better high-frequency and highspeed response than the 45/55 NiFe head. In addition, at higher DC bias currents (>60 mA) the CoTaZr flux frequency response shows spin dynamic damping; the NiFe head flux response shows only eddy current damping for all measured bias currents,.