Microcracks of the thin-film head alumina: "L" cracks and "U" cracks

Two different types of microcracks in thin film head alumina were observed: cracks initiated at the alumina edges growing toward the head pole tips and cracks initiated at the head pole tip area and growing towards the leading edge of the alumina. Thermally induced cracks may cause degradation of magnetic head read/write performance due to the damage of the pole tip gap or corrosion of the head pole tips. Data from Ultrasonic AFM (UFM) indicate the difference in the subsurface structure of the observed cracks of the alumina.