Roger F. Hoyt

Future trends in hard disk drives

Magnetic hard disk drives have significantly improved in size, performance and cost due to many technological innovations; including magnetoresistive heads, low noise thin film disks, PRML channels and advanced mechanical actuators and motors. By analyzing specification trends of each new disk drive design, a perspective of this evolution can be developed and design characteristics of future disk drives can be estimated.

Direct measurement of recording head fields using a high‐resolution inductive loop (invited)

A method is described for direct measurement of the magnetic microfield from a recording head. The method employs a thin film ‘‘microloop’’ as a transducer which by induction senses the recording head field. Measurements are presented on both a thin film and a ferrite head. Fits to the data allow the absolute efficiency to be determined. Data on the frequency dependence of head efficiency are also presented.

Precise side writing measurements using a single recording head

A method is presented by which the write width of a recording head may be determined using a single head alone. Analysis of data from a thin film and a ferrite head on a 3380-like particulate disk indicates the thin film head tends to write a narrower track due to the finite pole thickness and lack of a taper angle.

Motion pictures of air bearing dynamics under stressed conditions

We present here a study of the motion of an air-bearing slider at low flying heights as it accesses over a particulate disk and interacts with asperities on the surface. The measurements are made using a capacitance technique, with a specially made multi-sensor slider and high bandwidth electronics. The sliders motion is captured using a fast digitizer and reconstructed in motion picture format. Three data sets are discussed as examples of the different types of motion which can occur due to the slider-disk interaction.

Microloop measurements of recording head fields versus current

Using the microloop technique, measured results are presented for the first time of recording head fields versus current for several thin‐film heads. It is found that the field increases linearly with current, becoming nearly constant as the flux density in the head core material reaches the saturation value.