Gary C. Rauch

Lubricant replenishment on carbon coated discs

The replenishment of a lubricant on a carbon coated disc was characterized through theoretical modeling employing experimentally acquired diffusion coefficient data. To quantify the reflow behaviour of a lubricant film, a parameter, the critical reflow time, was defined as the time to replenish a depleted hole of 1 /spl mu/m diameter in a 2 nm thick lubricant film. The results based on solving 2D diffusion equations showed that the critical reflow time is a strong function of the endgroup polarity and molecular weight of a lubricant, as well as the H and N content in the carbon film. Based on these results, design criteria have been provided for enhanced wear durability of magnetic media.

Slip sliding away: A novel head–disk interface and its tribology (invited)

The continuous reduction of head–disk spacing has made the use of supersmooth media a necessity in gaining ultrahigh magnetic recording areal density. To overcome the stiction barrier associated with supersmooth disks without compromising the head flyability requirement, texture features can be transferred from the disk surface to the slider surface, creating a new type of head–disk interface, the padded slider interface. The tribology of a padded slider interface is in many ways different from that of the traditional head–disk interface with texture on the disk only. In this article, various unique tribological aspects of the padded slider interface are discussed in detail. Both theoretical modeling results and experimental data are presented to elucidate the stiction, friction, and wear behaviors of this novel head–disk interface. It is shown that the padded slider technology offers a viable alternative to the ramp load technology as a head–disk interface solution for the ultrahigh areal density.

Ion beam deposition of carbon overcoats for magnetic thin film media

Ion beam deposited carbon has been investigated for its use as an overcoat for magnetic thin film media. By using a gridless end-Hall ion source, carbon has been deposited that possesses hardnesses to 18 GPa, stress to 4.5 GPa, and densities up to 2.6 g/cc. Contact-start-stop testing of ion beam deposited carbon to fifty thousand cycles shows a marked improvement in failure rate compared to hydrogenated and nitrogenated carbon. Energetic deposition of carbon thin films can lead to implantation of energetic species into the magnetic layer. Simulations have been performed to assess the vulnerability of the magnetic layer to energetic implantation of carbon. In addition, the effect of the partial pressure on the magnetic performance is assessed and a critical impurity concentration defined.

Properties and durability of thin a-C:H overcoats produced by plasma enhanced chemical vapor deposition

Abstract Radio-frequency plasma enhanced chemical vapor deposition (RF-PECVD) technique was used to deposit thin amorphous hydrogenated carbon (a-C:H) overcoats on glass ceramic disc substrates. Raman spectroscopy results showed that higher sp3 carbon content films can be obtained by applying appropriate kinetic energy of ion bombardment (∼100 eV) during film growth. However, a higher content of hydrogen was also observed in such films. The results suggest that a certain fraction of sp3 carbon bonds is likely to be terminated by hydrogen and become dangling bonds. These dangling bonds may be important to the durability performance in the tribo-contact interface. The highly hydrogenated carbon overcoats (∼40 at.%) showed significant improvement in tribological performance compared with the less hydrogenated films. The contact-start-stop test at ambient environment of such overcoats showed good durability over 10 K cycles at the film thickness of 3.6 nm.

Texture evolution in CoCrPtTa/Cr/NiAl magnetic recording media

Crystallographic textures in a CoCrPtTa/Cr/NiAl multilayer magnetic recording media were studied by electron diffraction. It was found that texture quality evolves through the thickness of the films. A large improvement of texture quality was discovered at the interface of the Cr and NiAl layers. Surprisingly, there remains a portion of randomly oriented grains in the CoCrPtTa layer, in addition to the anticipated grains of [1010] texture. The texture quality of the CoCrPtTa layer remains similar to that of the underlying Cr layer.

17 Gb/in/sup 2/ areal density demonstration at 214 Mb/s

We have simultaneously demonstrated high areal density and high data rate, in an experiment that closely mimics the operation of disc drive products. The system involves thin-film media, GMR merged heads, broad bandwidth electronics, and an EPR4 channel with post-processing. The results presented reflect a statistical sample of components, rather than one-of-a-kind devices. In order to determine the areal density accomplished, we demanded that the bit error rate performance be insensitive to significant deviations of the head position from the recorded track center. We present a thorough description of the components and the SNR budget. The areal density accomplished varies between 15.1 Gb/in/sup 2/ at 193 Mb/s, and 17.1 Gb/in/sup 2/ at 214 Mb/s. A series of areal density capability assessments was obtained by applying various margin conditions. This was done to demonstrate robust experimental results. The outcome of this work may be applied to product development.

Novel quantitative MFM technique to study orientation ratio in longitudinal recording media

A quantitative MFM technique to determine the magnetic orientation in longitudinal media at the microscopic level is described. The remanent magnetization orientation ratio measured by this MFM technique correlates well with the orientation ratio measured using a VSM. The analysis used to determine the orientation ratio from MFM images is based on the disorder noise model. The experimental results show that orientation is reflected in medium noise and interaction effects, as measured using the delta M technique.

23.8 Gb/in.2 areal density demonstration

We have demonstrated 23.8 Gb/in.2 areal density using a merged read-write grant magnetoresistive head, with an oriented thin film medium tested with broadband electronics and enhanced EPR4 channels. The medium had high signal to noise ratio metrics that was robust unto temperatures as high as 75u200a°C. A unique aspect of the head design at such a narrow track width is the simultaneous enhancement of the transducer sensitivity while keeping product and system manufacturability in the forefront. The areal density was demonstrated at a track density of 45.8 k tracks/in., using photolithographically defined poles and linear density of 520 k bits/in.

Recording performance enhancement via in-situ annealing of multilayer media structures

A novel technique for incorporating rapid thermal annealing into media sputter fabrication has facilitated the production of flyable media samples. Discs are fabricated with standard processing techniques to control physical grain size and crystallite texture. A CrMn caplayer ranging in thickness between 0.5 and 5 nm is subsequently deposited to provide the Mn-diffusant necessary to achieve post-treatment exchange decoupling. While still in-situ and before application of protective overcoats, the discs are exposed to temperatures between 200/spl deg/C and 350/spl deg/C compatible with most media production processes. A threefold increase in coercive force (peak reaching /spl sim/3800 Oe) and 10 dB improvement in medium signal-to-noise ratio is observed for the optimized process.