Davide Guarisco

ESD sensitivity of GMR heads at variable pulse length

9 Gb/in/sup 2/ GMR heads were subjected to electrical overstress using square pulses of variable duration. The pulse length was varied between 4 ns and 80 ms. For each pulse length, the magnetic and physical failure thresholds were measured via a quasi-static test. It is found that for long pulses (/spl gsim/1 /spl mu/s) the GMR sensors fail at constant power, whereas at very short times (<100 ns), the system starts to gradually transition to an adiabatic regime where failure occurs at constant energy.

A Fast and Accurate Method for Measuring Adjacent-Track Erasure

This paper reports on a novel spin-stand method to measure adjacent-track erasure (ATE). The method divides a track into multiple sectors and makes use of the built-in servo system to ensure a highly accurate, amplitude-based measurement. By arranging subtracks uniformly across the range of interest around a center track, a quasi-continuous, detailed ATE profile can be obtained. We discuss the various features of this profile and how they depend on such parameters as skew angle, write current, frequency, and flying height. We then compare the ATE performance of state-of-the-art longitudinal and perpendicular recording components under realistic test conditions, such as may be used for a 250 GB/platter 95 mm desktop drive. We show that the perpendicular head and media compare favorably to longitudinal ones even though the track width is much narrower

High linear density in perpendicular recording

In the never-ending quest for higher areal recording density, perpendicular recording is viewed as the most likely candidate to supplant longitudinal recording. However, currently perpendicular recording is lagging longitudinal recording in terms of areal density by almost a factor of two. It is generally believed that the lack of optimized perpendicular head and media is hindering the progress of perpendicular recording in spite of its theoretical advantages. Recently, so-called oxide perpendicular media have become available. In such media, the perpendicularly oriented magnetic grains are physically isolated, e.g., in a SiO/sub 2/ phase, thus ensuring magnetic decoupling between the grains. This paper compares the recording performance of conventional and oxide perpendicular media, showing that the latter hold the promise of bridging the gap to longitudinal recording.

Perpendicular drive integration

This paper reports on progress in perpendicular drive integration. In the first part, the performance of a series of perpendicular media with different coercivity (5-6 kOe), nucleation field, and soft-underlayer thickness (120/80 nm) is compared using two different head designs. Good overwrite and bit error rate performance is achieved for all head/media combinations. Higher coercivity leads to lower linear density but higher track density, resulting in approximately equal areal density capability. The thinner soft underlayer causes wider erase bands and therefore a loss of areal density. Wide-area track erasure measurements were performed on all media. The media with lower coercivity do not show any measurable amplitude loss, due to their larger absolute value of the nucleation field and the smaller write current needed to write on them. Two types of single-head, 7200 RPM desktop perpendicular drives (40 and 80 GB capacity) were built using 95 mm perpendicular media. They both achieve good bit error rate and off-track capability in all zones. The thermal decay for the 40 GB drive was measured and compared to a similar longitudinal drive. It was found that the thermal decay rate is much smaller in the case of the perpendicular drive in the range -6/spl deg/C to +80/spl deg/C.

Drive integration in perpendicular recording (invited)

This paper reports on the progress in perpendicular drive integration. In the first part, an experiment comparing the effect of magnetic spacing variation between longitudinal and perpendicular recordings is discussed. First, it is shown that the Wallace equation applies to perpendicular recording provided that the density of the recorded signal is sufficiently high. Using a thermal actuator, the effect of separately changing the read and write magnetic spacings of longitudinal and perpendicular head and media is compared. It is shown that the bit error rate is more sensitive to write space variations versus read space variations. However, the dependence is similar between longitudinal and perpendicular components. In the second part, two types of single-head, 95mm, 7200rpm desktop perpendicular drives (40 and 80Gbyte capacity) are presented. They both achieve good bit error rate and off-track capability in all zones. The thermal decay rate of the 40Gbyte drive was measured and compared to a similar longi...

Side track erasure of stitched-pole magnetic recording heads

We studied the side track erasure of a stitched-pole head with writer pole P3 not recessed from the air-bearing surface and compared it with conventional designs. A method is presented to determine the degree of side track erasure. We found that side track erasure increases with increasing linear density, medium M/sub r//spl delta/, and DC erase current. This is consistent with the erasure being caused by the stray field generated at the corners of the P2/P3 interface in combination with the demagnetization field present in the transitions. The high degree of magnetization of P3 in the stitched-pole head has been confirmed by magneto-optic Kerr microscopy.

ESD sensitivity of GMR heads: effect of pulse length and number of events

GMR heads were subjected to electrical overstress using square current pulses of variable duration. The pulse length ranged from 4 ns to 80 ms. The number of events was varied as well between 1 and 10/sup 6/ pulses. For each stress condition, the magnetic and physical failure thresholds were determined using quasistatic testing. We examined two different types of heads, designed for recording densities of 9 Gb/in/sup 2/ and 23 Gb/in/sup 2/. It is found that for long pulses (/spl gsim/1 /spl mu/s) the GMR sensors fail at almost constant power, whereas at very short times (<100 ns) the system becomes more and more adiabatic.

Integration of high-performance PMR components

This work focuses on some of the design choices for heads and media for achieving high-density perpendicular magnetic recording (PMR) systems, competitive with or better than current state-of-the-art LMR technology. One of the purported advantages of PMR is the higher head write field, which should allow the use of higher-coercivity media, therefore taking advantage of smaller stable grains.