High-frequency write characteristics of thin film heads for HDDs

This paper looks at the significance of suppressing eddy currents in recording heads as means of achieving recording channels with both higher recording densities and higher data rates. We have experimentally investigated the write characteristics of thin film heads using CoNiFe and CoTaZr films with different values of resistivity and saturation flux density. Write characteristics were analyzed by studying recorded hits using sputtered magnetic particles and fringing field measurements using electron beam tomography. From the results of this study, it was found to be essential to increase the resistivity of the core itself for higher-density and higher-frequency recording. We found that heads using low resistivity film not only suffer from the phase delay of the recording field relative to the write current, but also from a intensity drop which results in degraded rolloffs and write sensitivity. The phase shift could be compensated by shifting the transition during the writing process, but this does not improve the intensity drop. Reliable high density recording systems for frequencies of up to 100 MHz were developed for heads using CoTaZr amorphous poles