Measurement of Velocity-Dependent Adhesive Force Exerted on Magnetic Disk Using Micro-Probe of SPM

Abstract

A novel method for measuring the velocity-dependent adhesive force exerted on a magnetic disk has been developed using the micro-probe of a scanning probe microscope (SPM). The deformation of a cantilever having a diamond tip was measured based on the Michelson laser interferometry, wherein an interference fringe pattern was formed over the cantilever. The fringe images were captured by an ultra-high speed CCD camera, and then the deformation of the cantilever was accurately captured through image processing for extracting ridgelines from the fringe pattern. The high-speed camera enabled observation of the fringe image variation while the tip was being separated from a target surface, and identification of the transient response of the cantilever arising after separation by using the regression analysis. Then, the separation instant and the separation force were identified as the values of the initial condition of the transient response. Finally, this novel method was applied to the measurement of the separation force exerted on a magnetic disk coated with a molecularly thin lubricant film. As a result, the separation force was found to be approximately proportional to the square root of the retractive velocity.