Head-Disk Dynamics in the Flying, Near Contact, and Contact Regimes

Abstract

To achieve an areal density approaching 50 Gb/in.2 for the magnetic storage of data in hard disk drives requires reduced mechanical and magnetic spacing. Off-track jitter caused by airflow or contact can cause track misregistration on the order of 20–70 nm which may be excessive for adequate servo performance. The magnetic signal can be used to identify both the vertical spacing modulation due to the air bearing modes and off-track jitter due to suspension modes with nanometer resolution. We find that the off-track jitter in the flying regime is driven by airflow and is a strong function of the disk velocity and the suspension type. In the contact regime, the vertical spacing modulation and off-track jitter increase due to contact. Using a laser Doppler vibrometer we identified the leading contribution to the off-track jitter to be primarily the first torsional mode (T1) and to a lesser extent the first bending mode (B1) of the suspension.

Adhesive transition from noncontacting to contacting elastic spheres: extension of the Maugis–Dugdale model

“…For example, in HDI applications where a recording slider is flying over a rotating disk (using an air-bearing design) at very small separations of the order of few nanometers, hysteric behavior between "touchdown" (slider transitions from flying to contact with decreasing disk velocity) and "take-off" (slider transitions from contacting the disk to flying with increasing disk velocity) has been experimentally observed, e.g., [17]. In such HDI experiments, one observes a distinct difference in "touchdown" and "take-off" velocities, which make the slider contact or fly, respectively.…”

An elastic–plastic hybrid adhesion model for contacting rough surfaces in the presence of molecularly thin lubricant

“…Under such low-spacing conditions it has been experimentally observed that adhesive instabilities occur, causing the HDI to become unstable. Furthermore, it has been observed that the presence of adhesion at the HDI causes a hysteresis phenomenon, where the magnitude of the interfacial forces is different during touchdown (approach) and takeoff (departure) processes [23]. These instabilities have been investigated from the system dynamics point of view, e.g., numerically using an advanced air-bearing simulator (no roughness effects) [24].…”

“…In rough surface adhesive modeling δ A is usually ignored; however, it is considered in this paper, where for a specific material pair, the value of δ A is obtained using Eqs. (23) and (25) from Ref. [9].…”

“…It was found [9] that under displacement control, the "jump-on" and "jump-off" points are the same for adhesion parameter values λ < 0.95 and different for λ > 0.95. In magnetic storage HDIs, such adhesive instabilities have been experimentally observed [23] and also numerically modeled [24]. However, the literature on the instability of adhesive rough surfaces in contact, as far as roughness effects are concerned, is absent.…”

Investigation of contact deformation and wear characteristics of discrete track recording media

“…To prevent failure, improvements in the wear characteristics of the head disk interface are essential. Many researchers have studied the effect of slider/disk contacts (Komvopoulos 2000;Wang et al 2001;Kohira et al 2001;Xu et al 2002) for conventional ''smooth'' media. However, little information is available on the problem of slider/disk contacts in the case of DTR media.…”