Reliable operation of a modern magnetic disk drive depends critically on maintaining a controlled spacing between the magnetic recording head and the recording medium. In the world's first magnetic-disk drive, the IBM RAMAC 305, this was achieved by statically pressurizing a slider in which the recording head was embedded. In modern drives, the recording transducers are positioned at the end of a small ceramic 'slider' with a carefully designed air bearings that is self-pressurized by the airflow of the rapidly spinning disk. Careful design of this air bearing and the head disk interface (HDI) is needed to reliably provide a physical spacing between the head's magnetic sensors and the disk down to almost 10 nanometers in today's drives. This is equivalent to a stack of just about 30 average atoms, and all that at relative speeds of up to 50 meters per second (over 100 miles/hour)!

In addition to providing this controlled head to medium spacing, the design of the components of the head-disk interface must provide sufficient durability for many years of operation including many thousands of drive start/stop cycles. This involves optimizing the disk roughness and waviness, the thin protective overcoats on disk and slider, and the molecularly thin lubrication scheme to both avoid wear and minimize static (stiction) and dynamic friction. As recording densities have increased, forcing the head-to-medium spacing to decrease, the requirements for reliable low-flying, long-term durability and low stiction have resulted in designs aimed at optimizing the interface as an integrated system. A prime example of this is the dynamic load/unload (L/UL) technology introduced in the 2.5" form factor Hitachi Travelstar drives. Using L/UL technology, the super smooth disk is optimized for magnetics and flyability. The head never lands on the disk in L/UL but retracts to the ramp position when it is not in use.

Future high-density magnetic-disk drives will require head-disk interface technology that can reliably support smaller magnetic spacing while operating in more stressful environments. One of the main missions of the Storage Research function at Hitachi San Jose Research Center is to develop this technology and to transfer it to the Storage Technology Division for use in Hitachi's advanced server, desktop and mobile storage products. At the Hitachi San Jose Research Center, state-of-the-art instrumentation and testing equipment is used to investigate key HDI issues pertaining to future high density magnetic recording. With the aid of various mechanical, optical and magnetic transducers, combined with high speed precision spin stands the head-disk interaction and wear mechanisms can be investigated under a wide range of environmental conditions. Research on alternative designs of air bearing and advanced head-disk material systems is conducted with the objective to achieve consistently low flying designs with high reliability and minimum sensitivities to altitude and contamination. All of these research activities are expected to propel magnetic recording densities in continuation of their phenomenal historic growth rates.