Shozo Saegusa

Optimized Design of Heaters for Flying Height Adjustment to Preserve Performance and Reliability

We developed a thermal flying-height control (TFC) slider to control the flying height of magnetic recording heads. The slider basically consists of a small heater fabricated near the read/write element. This study discusses the effect of heater size and heater location on the change in the flying height at the read/write element. We also discuss the resulting temperature rise due to the additional heat applied by the heater. Specifically, we have found that small heaters generally resulted in lower heater power per unit change in the flying height and lower head temperature rise per unit change in the flying height. In terms of heater location, we have found that a heater closer to the air-bearing surface (ABS) also tends to result in a larger change in the flying height because of the larger protrusion shape. However, the head temperature rose significantly. Therefore, shorter ABS/heater distance was a trade off lower power against higher rise in head temperature. We concluded that smaller heaters and the shorter ABS/heater distance are better as long as head reliability is ensured

Thermal displacement characteristics of a chip on suspension

A fundamental study on the temperature and slider displacement of a chip-on-suspension (COS) was performed. The results show that the temperature rise in the IC chip is almost proportional to the heating power and that the slider displacement in the tracking direction is almost proportional to the heating power applied to the chip. It takes several seconds for the temperature rise of the chip to saturate and the response of the slider displacement is less rapid than the temperature rise of the chip. The vibrational characteristics of the slider are not affected by the temperature rise.

Thermal Analysis for the Protrusion of Magnetic Head

The thermal protrusion of a magnetic head was investigated through, first a high-resolution measurement of temperature distribution over the air bearing surface (ABS) and head coil and, second, a numerical calculation of the head protrusion. It was found that the temperature on the ABS results in a “butterfly”-shaped distribution. It was also found that an eddy current induced by high frequency write-current significantly increases the temperature of read/write elements. Moreover, the point of maximum temperature changed from the head core to the write gap when the applied current was switched from DC to AC. It was also found that a write-current induced head protrusion caused more deformation of the alumina over coat in the horizontal direction and that an ambient-temperature-induced head protrusion caused more deformation around the read-write elements. Furthermore, it is clarified that film materials with higher elastic modulus, lower expansion rate, and higher thermal conductivity reduce the head thermal protrusion. Finally, to reduce write-current-induced head protrusion, a novel thermally improved head structure is proposed.Copyright