Head design considerations for lower thermal pole tip recession and alumina overcoat protrusion

The magnetic/mechanical spacing between the transducer and the disk significantly decreases due to thermal expansion of pole tips at stressed high temperature and high humidity tests. The protruded pole tips and alumina overcoat result increased thermal asperities and can interfere with the higher disc asperities and be damaged due to high contact. The damage at the head-disk interface due to protruded pole tips and alumina overcoat may become a major roadblock in the drive mechanical performance when flying height is below 10 nm. In this study, the thermal PTR defined as change in PTR with temperature is measured using an optical profiler and an AFM for heads having stack design with single and dual layers of writer coil. The pole tips protrude above the ABS surface by 3–4 nm when the temperature of the head is raised by 50°C. Heads with single layer of writer coil exhibit significantly lower thermal PTR than those with dual layers of coils.