Experimental Study of the Resonances of the Slider Modulations by Laser Doppler Vibrometer

The magnetic spacing of Hard Disk Drives (HDD) needs to be reduced for increasing areal density. It is therefore very challenging to maintain constant fly height at a sub-2nm clearance. Any resonance of the slider or suspension can cause modulations on fly height and thus impacting the writing efficiency. Various research was carried out for the flying stability of the slider [1–4], especially in the off-track direction caused by voice coil motor (VCM) as well as PZT actuation. However, the resonances of the slider modulations in vertical direction have not been well researched. In the study, a method of using heater oscillation to examine the slider resonances has been proposed. The experiments have been performed on two suspension designs and two air bearing designs to demonstrate the effectiveness of this approach. The experimental results showed a shift of resonance frequencies due to a design change of the suspension. The air bearing design also played a role in the heater time constant and thus affecting the magnitude of resonances. Further, larger resonances were observed in a lower clearance setting than passive fly.