Comparison of written-in repeatable runout for servo-writing with different spindle speeds

With the increasing track density in hard disk drives (HDD), the head positioning mechanisms need to follow tracks more accurately. Due to limited servo bandwidth, the repeatable runout (RRO) induced from servo writing will be a significant track misregistration (TMR) source, especially the high frequency harmonics of RRO. In order to study the written-in RRO, an experimental test stand was developed to write servo pattern and measure track profile under different spindle speeds. Our experimental results showed that RRO was reduced 2.41% of track (0.41 /spl mu/m) with writing servo pattern at 3600 rpm compared to that at 5400 rpm.