Marker for detecting amount of working and process for producing thin film magnetic head

Abstract From the Canadian patent

A working amount detecting marker formed by laminating first and second marker layers each having a predetermined shape when seen from above. Two sides contouring the respective marker layers intersect each other at a point located at a specified position where working is to be completed. When the portion of a magnetic head to be opposed to magnetic recording media is formed by grinding or grooving, the sectional configuration appears on the ground surface, indicating whether the amount of grinding or grooving is insufficient or excessive. The point of intersection, when appearing on the ground surface, readily indicates completion of grinding or grooving with high accuracy.