Microcracks of the alumina of the thin-film head: study and simulation

A study of the microcracks found in the alumina of a magnetic thin film head is presented. A model of the alumina fatigue crack initiation and growth is proposed. Thermal expansion of the energized wires leads to high stress at the pole tip area. Crack initiation usually occurs at the outer edge of the alumina, due to the mechanical damage caused by the rotating disk surface. Further crack growth is caused by fatigue in the alumina. The crack is attracted to the pole tip area, affecting the magnetic head performance. Magnetic Force Microscopy is used to study the effects of the crack on the magnetic fringe field of the head.