Impact of head thermal movement to adjacent track encroachment measurement

Abstract

The impact of the head thermal movement to adjacent track encroachment (ATE) measurement with spin stand is studied. At head-gimbal assembly (HGA) and head-stack assembly (HSA) levels, the current technique measures the track amplitude reduction after continuously writing the adjacent tracks in the nominal write current and full write gate condition. However, the head thermal movement could result in a big problem for ATE value and stability with the spin stand. From the one-side adjacent track encroachment experiment, head thermal movement is the major reason for quick rising ATE when the adjacent track writing iteration increases. The experimental data also show strong correlation between ATE and adjacent track write gate and write current. Further work shows that the writer trace is the major reason for this thermal movement. However, ATE is much more stable when the write gate total open rate is less than 25%. A technique, which inserts the idle revolutions among adjacent track writing, is proposed to reduce the head thermal movement during ATE test. This methodology has been applied to a spin stand software module for HGA/HSA level ATE measurement.