A Method for Characterizing the Head-Disk Interface Dynamics Near the Touchdown Conditions Using the Magnetic Fly-Height

Recent growth in the cloud storage industry has created a massive demand for higher capacity hard disk drives (HDD). A sub-nanometer head media spacing (HMS) remains the most critical pre-requisite to achieve the areal density needed to deliver the next generation of HDD products. Designing a robust head-disk interface (HDI) with small physical clearance requires the understanding of slider dynamics, especially when the head flies in proximity to the disk surface. In this paper, we describe a method using the magnetic read-back signal to characterize the head fly-height modulations as it undergoes a transition from a free-flying state to soft contact with the disk surface. A technique based on the magnetic fly-height sensitivity is introduced for the identification of the transition plane that corresponds to the onset of the touchdown process. Additionally, the proposed magnetic spacing based meteorology is used to study the effect of the air bearing stiffness on the magnitude of the slider vibrations induced by intermittent head-disk interactions. The information about the minimum spacing while maintaining the stable flying conditions can help in reducing the head-disk interaction risk that can enable a low clearance interface.

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.

A Facile Approach of Fabricating Ultra-Thin Wear Resistant Si/SiNx/C Overcoats for Magnetic Tape Recording Heads

Magnetic tape recording is one of the oldest data storage technologies, and it is still used today due to its low cost and long data storage life. Magnetic tape recording is a contact recording technology, where a thin flexible magnetic tape medium is pulled across an Al2O3/TiC (AlTiC) recording head surface at a high velocity while in direct physical contact with each other. As a result, one of the inherent problems faced in magnetic tape recording systems is an increase in the magnetic spacing over time with prolonged usage, due to continuous wear of the tape bearing head surface, which in turn leads to a deterioration of the magnetic readback signal [1]. The increase in the magnetic spacing at the head-tape interface can be due to several factors, such as pole tip recession (PTR), accumulation of wear debris on the head and surface roughness of the head and tape medium. Out of these factors, PTR is a major contributor to the magnetic spacing loss, due to a higher rate of wear of the softer magnetic read and write poles at the head-tape interface [2].

Experimental Study of Suspension and Slider Vibrations Measured by Laser Doppler Vibrometer

The magnetic spacing of Hard Disk Drives (HDD) needs to be reduced for high recording density. On the other hand, it is necessary to prevent contact between the slider and disk for reliability of HDDs. Various research was carried out for the flying stability of the slider [1–3]. Furthermore, the magnetic track width also needs to be narrowed for high recording density. The Dual Stage Actuator (DSA) servo system is used for high positioning accuracy [4]. The DSA servo system uses a piezoelectric actuator on a suspension in addition to Voice Coil Motor (VCM). In this study, we measured vibrations to the slider and suspension caused by the PZT and VCM actuations. Two Laser Doppler Vibrometers (LDV) were used for the measurement. Moreover, we performed a numerical analysis to estimate the roll moment of the Air Bearing Surface (ABS) of the slider caused by PZT actuation. As results, we confirmed that the ABS vibrated in vertical direction due to the suspension’s vibrations caused by PZT and VCM actuations.

Nanorheometry of Molecularly Thin Liquid Lubricant Films Coated on Magnetic Disks

Molecularly thin lubricant films are used for the lubrication of head disk interfaces in hard disk drives. The film thickness is reduced to 1-2 nm to minimize the magnetic spacing, and optimal, precise design is required to obtain sufficient lubrication. However, until now, there was no generally applicable method for investigating such thin films. Therefore, we developed a highly sensitive shear force measuring method and have applied it to the viscoelastic measurement of lubricant films coated on magnetic disk surfaces. In this paper, we review the method and summarize the useful findings we have demonstrated so far.