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Here we evaluate some of the problems likely to be encountered for flying magnetic recording heads over unplanarized patterned media. We demonstrate: (i) current air bearing codes developed for flying heads over smooth disks can be extended to patterned surfaces; (ii) the method for detecting contact at the head-disk interfaces within disk drives will likely need to be more sensitive for unplanarized patterned media; and (iii) the disk lubricant is more likely to be picked up on a head slider surface when flying over patterned surfaces. While our experiments and simulations were carried for discrete track media (DTM), we also discuss the implications for future bit patterned media (BPM) technology programs and possible solutions to these tribological problems.

Accurate touchdown power detection is a prerequisite for read-write head-to-disk spacing calibration and control in current hard disk drives, which use the thermal fly-height control slider technology. The slider air bearing surface and head gimbal assembly design have a significant influence on the touchdown behavior, and this paper reports experimental findings to help understand the touchdown process. The dominant modes/frequencies of excitation at touchdown can be significantly different leading to very different touchdown signatures. The pressure under the slider at touchdown and hence the thermal fly-height control efficiency as well as the propensity for lubricant pickup show correlation with touchdown behavior which may be used as metrics for designing sliders with good touchdown behavior. Experiments are devised to measure friction at the head-disk interface of a thermal fly-height control slider actuated into contact. Parametric investigations on the effect of disk roughness, disk lubricant parameters, and air bearing surface design on the friction at the head-disk interface and slider burnishing/wear are conducted and reported.

Well-defined, three-dimensional (3D) flowerlike metallic Co microcrystals with several radiating hexagonal-tapered petals assembled by particles size of 150–250 nm were fabricated via a facile hydrothermal reduction route under a fixed basic condition. The morphology and structure of the products were characterized by scanning electronic microscopy (SEM), energy-dispersive X-ray (EDX), transmission electron microscopy (TEM), selected area electron diffraction (SAED), X-ray photoelectron spectroscopy (XPS) and powder X-ray diffraction (XRD). The probable formation mechanism of the flowerlike Co microcrystals was discussed based on the experimental results. Magnetic properties of Co microcrystals were investigated by a commercial Physical Properties Measurement System (PPMS). The flowerlike products exhibited ferromagnetic characteristics with a saturation magnetization of 128.1 emu/g and a coercivity of 232.5 Oe at room temperature. Compared to the coercivity value of bulk Co, the products displayed a remarkable enhanced value due to their special morphology.

Here we demonstrate a new approach to bring the disk drive recording head close to the disk media, while achieving tight control of the final head-media separation. The slider in this approach has a miniature Wear-In-Pad (WIP) at its trailing edge, encapsulating the read/write elements. As the slider flies over the disk, the slider overcoat and head recession are quickly worn off, resulting in the bottom of read and write elements clearing the disk roughness by only a few nanometers. We show that the Wear-In-Pad is a viable way to achieve the sub 7 nm head-media separations believed to be necessary for Tb/in/sup 2/ recording.

To achieve an areal density approaching 50 Gb/in.2 for the magnetic storage of data in hard disk drives requires reduced mechanical and magnetic spacing. Off-track jitter caused by airflow or contact can cause track misregistration on the order of 20–70 nm which may be excessive for adequate servo performance. The magnetic signal can be used to identify both the vertical spacing modulation due to the air bearing modes and off-track jitter due to suspension modes with nanometer resolution. We find that the off-track jitter in the flying regime is driven by airflow and is a strong function of the disk velocity and the suspension type. In the contact regime, the vertical spacing modulation and off-track jitter increase due to contact. Using a laser Doppler vibrometer we identified the leading contribution to the off-track jitter to be primarily the first torsional mode (T1) and to a lesser extent the first bending mode (B1) of the suspension.

We demonstrated recording performance at greater than 10 Gb/in/sup 2/ with data rates up to 25 MB/s, using a single combined write and read head (Merge Notched head).

We have successfully demonstrated magnetic recording at areal densities as high as 12 Gb/in/sup 2/ at a data rate of 14/spl sim/15 MB/s using separate spin-valve read heads and narrow pole-tip inductive write heads on low noise Co alloy thin film disks. In this work, the nominal target densities were 350 Kbpi/spl times/34 Ktpi. To make these densities possible, large signal-to-noise gains were attained with the use of high performance spin-valve read heads and low noise thin film media. At the same time, very narrow track write heads were designed and fabricated by extending conventional photolithographic techniques. Finally, small magnetic spacings between the head and the disk were attained with low flying ABS designs and improved head and disk surfaces. Recording tests showed satisfactory writability and large readback signal of around 2 mV//spl mu/m. The 50% rolloff densities were as high as 10 Kfc/mm, while the write and read trackwidths were as narrow as 0.7 and 0.5 /spl mu/m respectively. An overall assessment of the parametric recording results indicated an areal density capability of at least 10 Gb/in/sup 2/. This projection was confirmed by error rate testing with an EPR-4 channel, where very low ontrack errors of 10/sup -10//spl sim/10/sup -9/ were achieved at 315/spl sim/380 Kbpi. Furthermore, squeeze measurements revealed well-defined 747 behavior with offtrack maxima at 0.7/spl sim/0.8 /spl mu/m trackpitch. The product of linear and track densities for the write and read head combinations tested indeed showed that an areal density of 11/spl sim/12 Gb/in/sup 2/ has been achieved.

We introduced vapor corrosion inhibitor (VCI) into a disk drive to improve the resistance of the components to corrosion in repeated condensation cycles. VCI also significantly reduced the defect smears in the disks during accelerated life test. VCI is well known to cover up exposed metal surfaces. Thus the first means by which a VCI prevents corrosion is by forming a hydrophobic adsorbed film over exposed metal (e.g. Co, Cu) alloy. VCI also blocks the pathway for metal dissolution into the electrolyte.

As magnetic recording density increases toward hundreds of Gb/in/sup 2/, both the magnetic spacing and head-disk clearance decrease to

The effect of ryegrass (Lolium perenne L.) root-exudates concentration on pyrene degradation and the microbial ecological characteristics in the pyrene contaminated soil was investigated by simulating a gradually reducing concentration of root exudates with the distance away from root surface in the rhizosphere. Results showed that, after the root-exudates were added 15 d, the pyrene residue in contaminated soil responded nonlinearly in the soils with the same pyrene contaminated level as the added root-exudates concentration increased, which decreased first and increased latter with the increase of the added root-exudates concentration. The lowest pyrene concentration appeared when the root exudates concentration of 32.75 mg kg(-1) total organic carbon (TOC) was added. At the same time, changes of microbial biomass carbon (MBC, C(mic)) and microbial quotient (C(mic)/C(org)) were opposite to the trend of pyrene degradation as the added root-exudates concentration increased. Phospholipid fatty acid (PLFA) analysis revealed that bacteria was the dominating microbial community in pyrene contaminated soil, and the changing trends of pyrene degradation and bacteria number were the same. The changing trend of endoenzyme-dehydrogenase activity was in accordance with that of soil microbe, indicating which could reflect the quantitative characteristic of detoxification to pyrene by soil microbe. The changes in the soils microbial community and corresponding microbial biochemistry characteristics were the ecological mechanism influencing pyrene degradation with increasing concentration of the added root-exudates in the pyrene contaminated soil.

As magnetic recording areal density increases the mechanical spacing between the head and the disk continues to shrink. Head protrusion, induced by write current heating of the coil and yoke during recording at operating temperature, may interfere with the disk. In this work, we have measured the head temperatures as a function of write current, frequency and flying conditions. The rise in coil temperature for a flying head was found to be much less than a head on the load/unload ramp. The measured temperature coefficient was consistent with the simulation. The amount of head protrusion was measured as a function of the write current. The head-disk interaction of the interface after 100000 write current bursts resulted in alumina wear. Some of the effects of head protrusion on the interface reliability are discussed.

As the magnetic recording areal density approaches 10 Gb/in/sup 2/, the mechanical spacing between the head and the disk is expected to reduce rapidly below 20 nm. This lends to an increase of head-disk interaction which may induce an unacceptable level of interfacial wear. In this study experimental air bearing sliders were designed and fabricated to fly in close proximity or substantial contact with the disk. The durability of the interface decreased with decreasing mechanical clearance. The amount of head and disk wear was determined. The metrology and some of the challenges in maintaining a functional interface are presented.

Nanoindentation data are presented for three different but interrelated components of the thin film disk magnetic recording system-the air bearing slider/recording head, the disk substrate, and the sputter deposited thin film disk recording medium. Hardness traces across the slider trailing edge demonstrate the hardness of the NiFe, sputtered Al/sub 2/O/sub 3/, and the ceramic Al/sub 2/O/sub 3//TiC are 8, 10 and 24-40 GPa, respectively. Lapping under non-optimum, aggressive conditions can lead to significant recession in these components which is directly related to their hardness. The hardness and modulus have been measured for a number of alternate substrate materials ranging from AlMg/NiP to glass and glass ceramic. The ability of these substrates to resist damage from slider shock forces is presented and generally increases with substrate hardness, although other criteria (fracture toughness and plasticity initiation) rue required to rationalize all the data. Finally, hardness and modulus of carbon overcoat films are presented which have been sputtered under various conditions. The process variations lead to variations in hardness, the hardness/modulus (H/E) parameter, and tribological performance in slider/disk testing. The applicability of these mechanical property parameters to the wear degradation is discussed.

The adoption of dual zone texturing on magnetic disks allows the flying height of the head to be reduced over the data zone compared to a fully textured disk. Laser texture offers a technique far precise topography control and the placement of the landing zone. In this study the effects of the clearance between the head and the disk, and the presence or absence of overcoat on the air bearing surface on contact start-stop performance are evaluated. The wear mechanism of the laser bump by the head was investigated with in situ monitors and followed by surface analysis. Acceptable durability and stiction performance for contact start-stop operation is feasible with a few nm of clearance.

The incorporation of a limited amount of hydrogen in the amorphous carbon (a-C:H) overcoat improves the CSS durability of thin film media lubricated with perfluoropolyether (PFPE). A mechanism is proposed to explain this phenomenon. With increasing H content in C, the likely bonding sites for the lubricant such as the carboxyl end groups and dangling bonds decrease in the carbon films. Mobility of the lubricant measured by two different techniques was found to increase with increasing H. The improved interface durability is attributed to the enhanced lubricant mobility on hydrogenated carbon.

The effect of hydrogen in the carbon overcoat on the CSS durability of thin film media lubricated with perfluoropolyether (PFPE) is reported. A strain-gauge force transducer and optical surface analyzer (OSA) were employed to investigate the failure mechanism. The OSA provided in-situ monitoring of lubricant migration and modification as well as carbon wear. Durability improved with increasing hydrogen content over the range from 12 to 36 at% of H. The improvement is attributed to changes in lubricant bonding and mobility as a function of hydrogen content.

Summary form only given. As the mechanical flying height (FH) decreases towards sub-10 nm in hard disk drives, it is crucial to maintain adequate clearance between the head and the disk for the integrity of the head-disk interface (HDI). Hard disk drives (HDD) with experimental 10 nm flying sliders were tested at ambient condition for 1000 hours at /spl sim/60/spl deg/C. The effects from the radial profile of the FH, the drop in FH at altitude of the slider, the radial variation of take-off height (TOH), the type of lubricant and the curvature of the disks on the mechanical spacing and reliability of the interface are presented.

As the magnetic recording density increases towards hundreds of Gb/in2, both the magnetic spacing and head-disk clearance decrease to < 10 nm. By one estimate, the magnetic spacing for 1 Tb/in2 is about 6 nm and the read width is ∼ 30 nm. There are at least two different approaches to achieving this. The first one is an extension of the traditional flying interface and the second is contact recording. In the former case one needs to be concerned about maintaining adequate clearance both at sea level and at higher elevation whereas in the latter case the wear and corrosion of the heads and disks may pose major challenges. In the flying regime, an accelerated test to assess the relative integrity of the head-disk interface is described here. This is accomplished by monitoring the acoustic emission, capacitance or friction between the head and the disk as the ambient pressure is reduced. The pressure at which an abrupt change in the above signals takes place is called take-off pressure (TOP). This is also known as altitude avalanche measurement. With this method it is possible to compare different disk and head designs at the full velocity of the slider. We present results correlating the TOP with disk roughness and the influence of disk lubricant. An example of how head-disk interference takes place in a disk drive will be given for an experimental 10 nm flying slider. The effects of radial flying height profile, take-off height of the disk, and the disk curvature on mechanical spacing are presented. The results of changes occurring on the air bearing surface and the disks after long term flyability test are discussed.

Experimental I-V curves of microwave-driven Josephson tunnel junctions with resistive shunts are reported. The results are in very good agreement with numerical calculations using the resistively shunted junction model. In the low-frequency regime there are three distinct regions in the I-V curves and two different types of Shapiro steps. It is demonstrated that the overall shape of the I-V curves can be explained by using an adiabatic interpretation of the junction response. The two different types of Shapiro steps are related to a compensation effect between dc and rf bias currents.

Niobium may be used as an electrode and wiring material in Josephson junction technology. For edge coverage of lines patterned in these films, it is critical to produce a controlled, tapered edge profile. Reactive etching is one of the feasible techniques to accomplish this goal. Plasma etching of niobium in a CF4/O2 gas plasma was studied using an anodically coupled parallel plate reactor. The edge angle was found to be dependent mainly on the etching rate ratio (ERR) of the photoresist to the underlying Nb. Factors which affect the etch rates of Nb and photoresist (thus ERR) such as Nb surface area, temperature of the substrate table, and oxygen concentration in CF4 will be discussed. Parametric studies on the effects of total gas flow rate and chamber pressure will also be reported.

This letter describes the first system level test vehicle in Josephson technology. The experiment consists of four circuit chips assembled on two cards in a high density, 3-dimensional, card-on-board package. A data path, which is representative of a critical path of a future prototype processor, was successfully operated with a minimum cycle time of 3.7ns. The path simulates a jump control sequence and a cache access in each machine cycle. This experiment incorporates the essential components of the logic, power and package portions of a Josephson technology prototype.

A large number of highly robust and reliable thin film DC SQUIDs have been designed and fabricated which have excellent low frequency noise properties. Measurements performed on isolated devices have yielded a limit on the low frequency (1/f) flux noise component which is at least a factor of 60 below the average value reported for devices of this kind. The corresponding energy factor in the white noise region is 770 h at 0.1 Hz. The input coil inductance is 0.7 μH and the coupling efficiency α = 0.9. The substantial reduction of the low frequency noise in these SQUIDs demonstrates that improvements in the performance of these devices in the white noise region can be obtained without sacrificing the low frequency resolution.

Packaging technology used to build the first system crosssection test vehicle in Josephson technology is described. A threedimensional modular card-on-board packaging approach has been selected to fabricate the test vehicle which incorporates all the essential features of the technology required to build a high performance processor prototype. Potential viability of the described packaging technology for the fabrication of such a prototype has been demonstrated by an experiment in which a critical data path has been successfully operated with a minimum cycle time of 3.7 ns.

Magnetic susceptibility measurements on cobalt(II) stellacyanin (Rhus vernicifera) have been performed between 2.2 and 50 K. The effective magnetic moment of Co(II) in the protein is 3.91 ± 0.12 (μB). Nonlinear behavior below 3 K evidences the presence of zero-field splitting attributable to a low-symmetry component of the ligand field. The results are consistent with a structural model based on a distorted tetrahedral Co(II) site involving one or more extremely covalent metal-ligand bonds.

The magnetic susceptibilities of oxy- and metaquohemerythrin in the range 3-200°K have been determined using an ultrasensitive superconducting quantum magnetometer, and for the first time their antiferromagnetic components have been conclusively resolved. The exchange coupling constants, J, between the two high-spin iron(III) atoms in each subunit are -77 and -134 cm^(-1), respectively. The electronic spectra of these two proteins in deuterium oxide have been measured from 800 to 1200 nm but no additional bands were obtained. After comparison to magnetic and spectroscopic data obtained previously for ferric dimer model complexes, it is concluded that the two iron(III) atoms in subunits of both oxy- and metaquohemerythrin are oxo bridged.

An equivalent circuit has been developed for the time-dependent dissipating state of superconductivity which accompanies quantum phase slip. This equivalent circuit is used here to analyze the superconducting thin-film ring magnetometer and to determine its operating characteristics in terms of measurable circuit parameters.

The magnetic susceptibilities of cobalt(II) and nickel(II) derivaties of carboxypeptidase A (CPA) follow the Curie law over a wide temperature range. The observed magnetic moments of Co(II)CPA and Ni(II)CPA are 4.77 ± 0.15 and 2.53 ± 0.10 Bohr Magnetons, respectively. The magnetic and spectral properties of Ni(II)CPA are consistent only with an octahedral ground-state geometry, whereas Co(II)CPA has a probable five-coordinate structure. The results establish ordinary metal-ion ground states for two metallocarboxypeptidase A derivatives which exhibit full peptidase activity.

The cross‐sectional model (CSM) is an experiment designed to test the electrical and technological issues that are representative of a proposed Josephson Signal Processor. This paper describes the thin films aspects of the CSM. The existing Pb‐alloy technology for logic and memory circuits was developed further (for both chips and package parts) to meet the additional demands for the CSM. This included more extensive use of regulator junctions for on‐chip power distribution, more precise target value objectives for current levels on chip, and extension of the thin film technology to new package part structures, including additional thermal and mechanical processing. The vacuum depositions and materials, photolithography, package parts diagnostics, and chip diagnostic aspects of the CSM are described.