Measuring core losses in thin film heads

Increasing data rates are requiring magnetic transducers to perform at higher frequencies. "Core losses"-the combined effect of eddy current losses, damped domain wall motion, and decreasing rotation susceptibility, act to reduce yoke permeance at high frequencies. In this work, we describe a technique for measuring core loss and demonstrate its application to a variety of heads. The method involves least-squares fitting measured head impedance vs. frequency spectra to the response from an equivalent magnetic circuit having a complex and frequency-dependent inductance. The result is a description how the complex inductance varies with frequency, thereby characterizing the core loss.