Measuring Core Losses in Thin Film

Increasing data rates are requir- ing magnetic transducers to perform at higher fre- quencies. "Core losses" - the combined effect of eddy current losses, damped domain wall motion, and decreasing rotation susceptibility, act to re- duce 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 induc- tance. The result is a description how the complex inductance varies with frequency, thereby charac- terizing the core loss.