High frequency dynamic imaging of domains in thin film heads

A wide-field magnetooptic domain observation system with a time resolution of 10 ns has been developed to study magnetization dynamics in thin-film heads. The instantaneous dynamic response on the top yoke of thin-film recording heads is examined at any chosen instant within the drive current cycle at frequencies up to 20 MHz. Different phase responses from different domain walls in the head are observed and interpreted in terms of hysteretic wall motion, effective field density variation in the head, and wall orientations relative to the flux conduction direction. Two different flux conduction mechanisms associated with two different domain structures in the central region of the head are observed and discussed. Flux conduction in the center of the head by motion of backgap walls and magnetization rotation for domain structures with and without the backgap walls was observed. The domain structure with the backgap walls is probably undesirable because the backgap wall motion may cause a decrease in head efficiency during high-frequency operation and could cause noise during read-back