Mitsuhiro Shoda

Catastrophic damage of magnetic recording disk caused by slider-disk impact during loading/unloading

Catastrophic damage of a disk caused by impact between a slider and a disk during loading/unloading is investigated using many variations of disk samples with the different scratch resistances. At first, the accelerated loading/unloading test condition to increase disk damage was studied as the function of disk-runout during a disk rotation, rotational speed of a disk, and sweep velocity of a slider using disk samples with the same scratch resistance. Next, in accelerated test conditions, many kinds of disk samples with different scratch resistances were tested to find a relation between disk damage and scratch resistance of thin films. Flyability of a slider over a disk during a slider sweeping in these tests was monitored using an acoustic emission transducer. Disk surface and slider surface after the test was observed using an optical microscope and an optical surface analyzer. Scratch resistance of a disk was measured using a newly developed high-speed scratch tester. As a result, film-peeling damage broke out at the loading position of a disk with increasing disk-runout. Film-peeling damage broke out much more with decreasing scratch resistance of a disk. When scratch resistance of a disk was lower, flyability became bad suddenly during a slider sweeping over a disk; a sweep zone of the disk surface after the test shows damage, such as cross scratches. It is found that disk damage results in not only environmental contamination but also scratch resistance of a disk. This damage brakes out catastrophically. Finally, a mechanism of catastrophic damage is discussed.

Catastrophic damages on magnetic recording disks caused by slider-disk contacts during loading/unloading

Catastrophic damages on a disk caused by impacts between slider and disk during loading/unloading were observed using an optical microscope and an optical surface analyzer (OSA). Flyability of a slider during loading/unloading was studied using an acoustic emission (AE) transducer. If many film-peelings of a disk are broken out by loading/unloading, film particles peeled from the disk can adhered to the air bearing surface of a slider. Ultimately, slider-disk contacts are caused in the recording zone. In order to reduce these film-peelings, broken out by loading/unloading, it is necessary to increase the scratch resistance of thin films of a disk.

Control of bit error caused by slider vibration during continuous contact recording

Bit Error Rates (BER) and the slider vibration were measured changing the flying height with the variation of the environmental pressure using the current magnetoresistive head on three types of glass disks with different surface topography. The BER increased with the slider vibration, which increased with the reduction of the flying height on the disks. Neither the BER increase nor the slider vibration was observed on the disk which has controlled surface topography such as the centerline average and the peak heights. In the continuous contact recording, the control of the disk surface for the reduction of the slider vibration was found important on the aspect of lowering the BER as well as tribological reliability.