Study of slider-defect interaction at ultralow flying height by dynamic flying height control

Abstract

In this study, the interaction of the magnetic head slider and magnetic disk defects were studied as the function of the head flying height controlled by the dynamic flying height (DFH) control method. In the conventional glide test, the flying height is set as a function of the rotational velocity. However, in the glide test using the DFH control method, the flying height could be set as a function of DFH power on a constant rotational velocity. A magnetic disk with two types of defects—a crater and a 5nm bump—was prepared. The acoustic emission (AE) signal at the slider-defect contacts from the conventional glide test and the DFH glide test were then compared. The results of the experiment indicated that the DFH glide test could detect these defects at a few nanometers flying height, but the conventional glide test could not detect them. This was because the AE signal burst below a flying height of 3nm. The AE signal output of the DFH glide test was higher than that of the conventional glide test, and the AE signal of the defect contact increased at a greater rotational velocity. It was concluded that the DFH control glide testing was one of the most important techniques for the future high-density recording disks.