Nanosecond and sub-nanosecond writing experiments

This paper explores the high speed and high power aspects of fast writing in magnetic data storage. It describes the experimental methods and instrumentation needed to exercise thin-film write heads at excessively large write currents (< 0.5 A), short pulse durations (greater than or equal to 200 ps) and high frequencies (< 1 GHz). The not commercially available instrumentation used is discussed in detail (avalanche pulse generator, head interconnect circuit). The thermal behavior of the head is investigated to ensure that the temperature of the hottest yoke leg (P-2) does not exceed 250 degrees C to avoid thermal degradation of the magnetic performance. The paper describes various pulse write, AC-bias write and AC-burst erase methods. As an example, experimental results obtained for an "industry-typical" head are reported and discussed, viz head footprints, saturation curves, write current needed for media magnetization reversal down to 200 ps, write field gradients, write field growth rates, high-frequency head efficiency, current levels needed for AC erasure versus frequency, and AC-bias writing results.