Dynamics in the Bridged State of a Magnetic Recording Slider

Abstract

A novel region of tribological interaction is explored by inducing near contact between the magnetic recording slider and disk. In this study, we performed frictional measurements over a wide range of subambient air pressure and disk rotation rate. Since the slider is supported over the disk by an air bearing, it has been found that cycling from ambient to subambient and then back up to ambient pressure over several minutes of time forms a frictional hysteresis loop. The high-friction branch of the loop, referred to as the bridged state, is characterized by an average frictional displacement and resonant vibration of the suspension mount assembly. The bridged state is currently employed for accelerated wear testing of magnetic slider/disk/lubricant systems. Future magnetic recording systems designed to operate at increasingly lower physical spacing will need to take into account these frictional forces which accompany the incipient contact between the lubricated disk and slider with finite surface roughness. A single degree of freedom model is solved to determine the equivalent dynamic friction force on the slider as an impulse series with random impulse frequency and amplitude from the measured frictional displacement in the bridged state. The mean slider-disk spacing in the bridged state is derived from the experimental friction force, the spacing probability density function, and the adhesion stress from the Lifshitz model for dispersion interaction energy.

Adhesion and Friction Behaviors of Probes Approaching Magnetic Disk Surfaces

“…The curves of friction force as a function of load force at , and nm obviously agreed with themselves and the repeatability of the measurement was confirmed from this figure. The relationship between the two forces can also be described by (2), which is derived from the JKR model, and (3), which defines the friction force…”

“…Thomas et al measured the tribological interaction by inducing near contact between the magnetic recording slider and the disk [2]. They observed that there is a sudden transition to high friction and vibration (bridged state) at some low touchdown pressure when the ambient pressure is decreased, with the magnetic recording slider initially flying over the lubricated disk surface.…”

Adhesion and Friction Properties of Molecularly Thin Perfluoropolyether Liquid Films on Solid Surface

“…Therefore, we must better understand and accurately measure the friction and adhesion properties of the lubricant films at small scales. − The friction properties at a small scale have thus far been usually discussed on the basis of measurements obtained using a surface force apparatus (SFA) or an atomic force microscope (AFM). Brunner et al discussed the relationship between the adhesive force and the surface energy on the magnetic disk surfaces having a PFPE lubricant film by AFM force curve measurements . They reached an interesting conclusion that the adhesive force was proportional to the surface energy.…”

Numerical Analysis of Surface Force of Diamond-Like Carbon Surface Coated with Monolayer Lubricant Film

“…Experimental evidence of the formation of a macroscopic lubricant bridge between the head surface and the spinning disk was also reported in some papers [21,22]. The lubricant pickup and transfer to the head surface caused by van der Waals forces have been big obstacles to achieving a smaller flying height [23,24].…”