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The dynamic properties of vertically coupled vortices in two magnetic nanodisks were studied using numerical simulations and analytical calculations. If the core polarizations of the two vortices are parallel, there exist two distinct normal modes with two distinct eigenfrequencies corresponding to the apparent complex motions of two vortices. Conversely, only a degenerate mode with a single eigenfrequency exists when the cores have opposite polarization. We show that the gyration eigenfrequencies can be tuned by changing the coupling strength, i.e., the separation between the disks. The dependence of the normal modes and the eigenfrequencies on the relative vortex-state configuration can be well understood based on the analytic model. [ABSTRACT FROM AUTHOR]

We have studied vortex core switching in a Permalloy disk with a cavity defect using micromagnetic simulation and analytical calculation methods. It is demonstrated that the existence of a cavity that can attract and pin the vortex core in the nanodisk plays an important role in controlling the reversal of the vortex core by coherent excitation. The diagram of the vortex core switching with different cavity radii is presented based on the calculation of the effective potential energy. It is shown that there are three cases that are dependent on the distance between the cavity and the disk centers. For a smaller distance, the reversal cannot occur without applying a second sufficiently strong field pulse with the direction opposite to the orientation of the first pulse, and the amplitude of the second field pulse that can release and reverse the polarity of the vortex core increases with increasing of the radius of the cavity. Then, for a critical distance range, the vortex core can be released from the cavity and reverse automatically. When the distance is large enough the vortex core cannot be attracted and pinned by the cavity, the reversal cannot be controlled by the cavity. [ABSTRACT FROM AUTHOR]

A model is presented that accounts for the observation of periodic lubricant ripples formed when a slider is flying on-track over a lubricated disk surface. It is shown that lubricant flow modulation from the air shear stress due to the low flying slider acting as a spring is responsible for the observed corrugation, as repeated flying over the same track enhances the effect. This is somewhat moderated by the relaxation of the lubricant perturbation, by surface diffusion. Depending on the relative magnitude of the shear and diffusion processes, the system can find itself into regions of stability where small perturbations decay away, or regions of instability where they increase exponentially. Instability is enhanced for lower fly height and higher disk rotational frequency, making it a challenge for future growth in disk drive performance and areal density. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Laser-induced structural decompositions of hydrogenated amorphous carbon films deposited by dc-magnetron sputtering on magnetic hard disks were studied using a microbeam Ar[sup +] laser (514.5 nm). The laser had varying powers between 3.0 and 0.3 mW at a focused circular spot of 2.5 µm diameter, corresponding to approximate fluence rates between 6 × 10[sup 4] to 6 × 10[sup 3] J cm[sup -2] s[sup -1]. The effect of laser power on decomposition rate could be expressed by an exponential equation. Based on the relationship between laser power and temperature, relative apparent activation energies for film decompositions were obtained and found to decrease with the increase of film hydrogen content and the elapse time of laser irradiation. All the films irradiated with laser powers between 0.75 and 0.3 mW followed the apparent first-order reaction. The reaction order tended to increase at higher laser powers and hydrogen content in the films. [ABSTRACT FROM AUTHOR]

Studies the surface roughness of a computer disk using atomic force microscopy (AFM) and light scattering. Anisotropic rough surfaces and experimental techniques; AFM measurements; Light scattering measurements.

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. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Focuses on a study of interface reactions between the magnetic layer and the protective carbon coating, and the influence of these interactions on magnetic properties of rigid disk media for magnetic data storage. Background of the study; Experimental details; Results of the study.

Deals with a study which described the physical and magnetic characteristics of rigid single layer perpendicular recording media. Comparison between the desired physical and magnetic parameters for perpendicular media with those for longitudinal media; Impact of the differences on production techniques; Production considerations.

Provides information on a study which discussed the characteristics of a magnetic disk drive with 10 gigabit per square inch density. Requirements for high track density; Use of flyheads and longitudinal recording; Servos and actuators.

Provides information on a study which described a range of possible partial-response maximum-likelihood detection schemes for the signal processing of magnetic disk recording systems. Methods; Results and discussion; Conclusion.

Deals with the magnetic media for 10 gigabyte per square inch hard disk storage. Recording format and magnetic requirements; Status of media development as of April 1996; Discussion of media structure preparation approach.

Presents information on a study that examined the production of carbon dioxide from the sliding interface of a carbon-coated thin-film magnetic recording disk. Methodology of the study; Results and discussion on the study.

Presents a study which addressed the topographic effect of surface roughness of a rotating magnetic disk on the flying height of a slider. Effect of the surface roughness of a magnetic disk on the instability of the air bearing; Approach used in examining fluctuations in flying height induced by disk topography; Details on the dynamics of a slider attached to a cantilever suspension; Characteristics of surface roughness and stochasticity.

Presents a study which analyzed the behavior of liquid lubricant films on the disk surfaces in magnetic recording using the concepts of disjoining and capillary pressure. Schematic representation of a particulate disk drives; Details on the disjoining pressure; Distribution of liquid lubricant; Types of pressure gradients or forces to drive the lubricant flow.

Presents a study which addressed the depletion of thin liquid films due to the combined effect of centrifugation, surface roughness, and air shear. Uses of magnetic disk systems; Construction of the surface asperities; Mathematical model of viscous flow.

Examines the dependence of the domain size and domain size scattering on the write energy and external magnetic field for gadolinium terbium iron magneto-optical recording disks. Information on magneto-optical recording; Experimental conditions; Results and discussion; Conclusions.

Heat Assisted Magnetic Recording (HAMR) has been proposed to extend the storage areal density beyond 1 Tb/in.2 for the next generation magnetic storage. A near field transducer (NFT) is widely used in HAMR systems to locally heat the magnetic disk during the writing process. However, much of the laser power is absorbed around the NFT, which causes overheating of the NFT and reduces its reliability. In this work, a two-stage heating scheme is proposed to reduce the thermal load by separating the NFT heating process into two individual heating stages from an optical waveguide and a NFT, respectively. As the first stage, the optical waveguide is placed in front of the NFT and delivers part of laser energy directly onto the disk surface to heat it up to a peak temperature somewhat lower than the Curie temperature of the magnetic material. Then, the NFT works as the second heating stage to heat a smaller area inside the waveguide heated area further to reach the Curie point. The energy applied to the NFT in the second heating stage is reduced compared with a typical single stage NFT heating system. With this reduced thermal load to the NFT by the two-stage heating scheme, the lifetime of the NFT can be extended orders longer under the cyclic load condition. [ABSTRACT FROM AUTHOR]

Thermal flying-height control (TFC) sliders have been recently used in commercial hard disk drives (HDDs) to increase the HDDs’ capacity. The design of this new class of sliders depends on the numerical prediction of their flying performance, which requires a model for heat flux on the surface of the slider facing the disk. The currently widely used heat flux model is based on a first order slip theory and is believed to lack sufficient accuracy due to its limitation of applicability. This paper implements an improved heat flux model and compares numerical predictions of a TFC slider’s flying performance based on these two models with experiments. It is found that the numerical prediction based on the currently used model has a relative error less than 10% for a state-of-the-art TFC slider. It is suggested that the currently used model might cause large errors for the sliders which do not have a pressure peak near the transducer. [ABSTRACT FROM AUTHOR]

In this study, the interaction of the magnetic head slider and magnetic disk defects were studied as the function of the head flying height controlled by the dynamic flying height (DFH) control method. In the conventional glide test, the flying height is set as a function of the rotational velocity. However, in the glide test using the DFH control method, the flying height could be set as a function of DFH power on a constant rotational velocity. A magnetic disk with two types of defects—a crater and a 5 nm bump—was prepared. The acoustic emission (AE) signal at the slider-defect contacts from the conventional glide test and the DFH glide test were then compared. The results of the experiment indicated that the DFH glide test could detect these defects at a few nanometers flying height, but the conventional glide test could not detect them. This was because the AE signal burst below a flying height of 3 nm. The AE signal output of the DFH glide test was higher than that of the conventional glide test, and the AE signal of the defect contact increased at a greater rotational velocity. It was concluded that the DFH control glide testing was one of the most important techniques for the future high-density recording disks. [ABSTRACT FROM AUTHOR]

In this paper, the real time thermal effect of the heat-assisted magnetic recording (HAMR) on the slider is investigated with the HAMR platform. The net temperature rises of the slider caused by laser absorption and heat radiation of the locally heated recording magnetic disk are studied by monitoring the calibrated read sensor resistances in different rotation speeds. The maximum slider temperature increase of about 3.5 °C caused by the locally heated recording disk is obtained when the media net temperature increase is 85 °C at 2000 rpm rotation speed. A higher temperature case is also discussed. [ABSTRACT FROM AUTHOR]

In this work, a five-layer HDI configuration was employed to derive a simple way to relate the multilayer Hamaker constant to an effective surface energy of the HDI. Specifically, the five layers of the HDI include two layers on the slider [diamondlike carbon (DLC) overcoat, Al2O3–TiC] and two layers on the disk (lubricant, DLC overcoat) as well as the air gap (or flying height). Following the formulation for two equivalent homogeneous surfaces, one can derive the effective surface energy of the five-layer model. To investigate the effect of the topmost layer thicknesses of the slider and disk on the surface energy, they were first varied from 2 to 5 nm and from 0.5 to 2 nm, respectively. It was found that the surface energy depends largely on the disk lubricant thickness while it has little dependence on the slider DLC thickness. Lubricant pickup by the slider and its effect on the surface energy was also investigated and it was found that the overall surface energy of the interface is lower when there is lubricant pickup. [ABSTRACT FROM AUTHOR]

We employed micro-Hall magnetometry and micromagnetic simulations to investigate magnetic vortex pinning at single point defects in individual submicron-sized Permalloy disks. Small ferromagnetic particles containing artificial point defects can be fabricated by using an image reversal electron beam lithography process. Corresponding micromagnetic calculations, modeling the defects within the disks as holes, give reasonable agreement between experimental and simulated pinning and depinning field values. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We systematically compare the magnetic properties of epitaxial and polycrystalline Co disks and rings with varying width (110–730 nm) for a fixed Co thickness and outer diameter (16 nm and ∼1.6 μm, respectively) by magneto-optical Kerr microscopy and photoemission electron microscopy. The magnetic hysteresis loops of the epitaxial (fcc Co) samples exhibit much larger switching fields and broader switching field distributions than the polycrystalline structures. This behavior is attributed to the different origin of the pinning fields in, respectively, the epitaxial and polycrystalline structures. Our results show also that for epitaxial rings, the magnetic global easy axis is along the magnetocrystalline hard axis. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

This article compares three patterns for position error signal generation in hard disk drives: the conventional amplitude pattern, the chevron phase pattern, and the frequency pattern. The three approaches were evaluated for sensitivity to fabrication variation and noise using simulations. The motivation was to determine which of the approaches would be most suitable for preformatted media. The study showed that the phase approach was least sensitive to the dominant forms of variation in preformatting. However, the performance of the frequency pattern was only slightly worse than that of the phase, while the performance of the amplitude pattern was significantly worse. [ABSTRACT FROM AUTHOR]

Further reducing the head-disk spacing down to 3-4 nm will be needed for future extremely high-density magnetic recording systems of areal densities of 800-1000 Gbits/sq[SUP2]. On the other hand, it is important to not only reduce the head-disk spacing but also retain the stability of the head-disk interface. This article reports an observation of the spacing change caused by thermal induced nanodeformation of the slider body even when writing current and the writing frequency are just within their value range in normal writing operations. Results indicate that the combination of the internal heating generated by writing operation with the cooling effect of the airflow over the air-bearing surface leads to not only local protrusion of the area around the transducer but also the variation of the crown value of the slider and, therefore, the change of the head-disk spacing. A crown deformation model is proposed and the validity of the proposed model is confirmed by both computer modeling and experimental observations. [ABSTRACT FROM AUTHOR]

Pole tip recession (PTR), which is caused by differences in wear resistance of the various phases in magnetic disk and tape heads, must be reduced because it is probably the main impediment to reduction of spacing. Here, a numerical model of PTR is presented. Experimental results suggest that three-body abrasion, which leads to primarily plastic wear, is the mode responsible for PTR. In the model, the authors assume this wear mode, and assume that wear is a function of load, sliding distance, hardness of the worn surface, and dimensionless wear coefficients. As sliding proceeds, PTR increases continuously, which leads to a continuous change in contact between three-body abrasives and poles; the load carried by the poles decreases as PTR increases. This is modeled by assuming that asperities of the head and medium deform and wear plastically to accommodate passage of particles through the interface. The pole wears less as PTR increases since the opening for sliding particles increases. This accounts for the decreasing rate of change of PTR with sliding distance found for disk and tape heads numerically and experimentally. For tape heads, the model predicts that each of the following leads to higher PTR: increasing the thickness of three-body particles, increasing tape tension, decreasing pole hardness, and increasing the pole wear coefficient. [ABSTRACT FROM AUTHOR]

Pole tip recession (PTR), which is caused by differences in wear resistance of the various phases in magnetic disk and tape heads, must be reduced because it is probably the main impediment to reduction of spacing. Here, a numerical model of PTR is presented. Experimental results suggest that three-body abrasion, which leads to primarily plastic wear, is the mode responsible for PTR. In the model, the authors assume this wear mode, and assume that wear is a function of load, sliding distance, hardness of the worn surface, and dimensionless wear coefficients. As sliding proceeds, PTR increases continuously, which leads to a continuous change in contact between three-body abrasives and poles; the load carried by the poles decreases as PTR increases. This is modeled by assuming that asperities of the head and medium deform and wear plastically to accommodate passage of particles through the interface. The pole wears less as PTR increases since the opening for sliding particles increases. This accounts for the decreasing rate of change of PTR with sliding distance found for disk and tape heads numerically and experimentally. For tape heads, the model predicts that each of the following leads to higher PTR: increasing the thickness of three-body particles, increasing tape tension, decreasing pole hardness, and increasing the pole wear coefficient. [ABSTRACT FROM AUTHOR]

This work reports a novel method for the visualization of slider-disk or slider-particle-disk interactions. The method is based on a special testing disk which is same as the conventional magnetic disk media except using a layer of magneto-optical (Me) material to replace the magnetic layer of the magnetic disk media. The magnetization in the Me layer will be switched by a small external field applied if the temperature generated by the interactions is higher than the Curie temperature of the Me material. The proposed method and corresponding setup were used successfully in the experimental study of slider-disk and slider-particle-disk interactions. [ABSTRACT FROM AUTHOR]

A potential approach to extending current thin film media to 100 Gbits/in2 recording density is physical patterning of the media, perhaps via an etching technique. An advantage of patterning is the capability of creating advanced position error signal (PES) patterns that are difficult or impossible to generate with writing by a recording head. This study uses spin stand tester to investigate various PES patterns generated by a focused ion beam etching technique on conventional thin film disks. For all practical purposes, the patterned PES eliminates transition noise, track edge noise, and erase band, therefore, demonstrates a much better PES signal than conventionally written servo patterns. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

This paper reports results of experimental investigations into the head–disk interface dynamics for the combination of the stiction free slider with super-smooth disk and the influences of disk roughness and lubricant thickness on the flying performance of stiction-free slider. The experiments were carried out with an optical head–disk interaction tester with which the tribologically interface used in the tester is still identical to the actual disk drive case The results indicate that the pad height on the air-bearing surface of the slider is one of the key parameters that determines the take-off and landing velocity of the slider. The flying performance of the slider strongly depends on the lubricant thickness when the disk speed is around the take-off velocity. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

With its precisely controlled contact geometry, the head–disk interface with laser zone texture affords a model system for the study of dynamic friction. By using two types of head sliders, i.e., the conventional slider and the padded slider, and a matrix of hard disks with a wide range of laser zone texture parameters, head–disk contacts involving a small number as well as a large number of bumps are realized. A rich variety of dynamic friction behavior is observed with respect to bump height and bump density dependence. A satisfactory explanation of these friction behaviors requires that both the deformational component and the adhesive component of friction be considered on equal footings. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Spinstand level testing has demonstrated a failure mechanism that may go undetected using standard strain gage and acoustic emission methods of data capture. Since normally static friction is higher than dynamic friction, dynamic friction measurements are often ignored, filtered, or sampled at a much lower data rate than static friction measurements. In this study, dynamic friction peak values significantly higher than the static friction were recorded during take-off of Pico heads on laser-textured media. Furthermore, data collected using an optical surface analyzer (OSA) showed a greater degree of wear on disks exhibiting high dynamic friction. FFT was employed to analyze the signal modulation of the high dynamic friction event. Resonance at a frequency of approximately 1050 Hz was found to be associated with the high dynamic friction. Experiments were designed to reveal factors that influence this resonance occurrence. The factors identified that contribute to this resonance were natural frequency of the head load arm, disk bump pitch, and lubricant thickness. The head/disk interface system is believed to be excited by an improper bump pitch if the lubricant layer is not thick enough to reduce the friction value. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Slider disk impact, especially the impact with particles in between, generates flash temperatures at the contact area and creates thermal stress in the magnetic layer of disk media. By modeling the effective magnetic fields of the thermal stress and the thermal agitation, the flash temperature induced magnetic degradation is studied via micro-magnetic simulation. It is noticed that the recorded bit pattern can be fully erased near the area of the maximum thermal stress if the flash temperature approaches 673 K (grain size: 12 nm). The bit patterns with higher bit density corresponds to higher likelihood of data erasure if other conditions are the same. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Asymmetric “S-shaped” bumps are formed in the presence of a significant temperature gradient on the disk surface during the laser-texture process. The production of S-shaped bumps is of particular interest for low-glide magnetic media, for which the desired high bump densities require the use of high spindle speeds. The formation of S-shaped bumps as a function of laser-pulse energy (0.1–4.5 μJ), pulse width (350–5000 ns), and rotation speed of the spindle (1184–4737 rpm) was investigated. The results show that within the accessible energy range the peak-to-mean bump height increases with the pulse energy. For a constant pulse energy, larger bump heights are obtained for shorter pulse widths. In addition, higher bumps are also obtained for slower spindle speeds if the pulse width is 2000 ns or longer, but this changes as the pulse width is reduced. The full-width-at-half-maximum diameter of the trailing bump cone monotonically increases with the pulse energy for 350–1000 ns pulse width, but shows a local minimum for 2000 and 5000 ns pulse width, which is shifted to smaller pulse energies as the spindle speed is reduced. An investigation of the height shrinkage during the sputter process showed that the shrinkage is larger for 15 nm high bumps textured with 500 ns pulse width and 0.26 μJ pulse energy than for bumps of the about the same height textured with 1000 ns pulse width and 0.40 μJ pulse energy. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Focuses on a study of protective properties of 3-5 nm thick carbon overcoat layers deposited on magnetic hard disks by ion beam deposition (IBD) and plasma-enhanced chemical vapor deposition (PECVD). Effect of the reduction of the surface concentration of cobalt ions; Evaluation of the tribological performance of the disks lubricated with perfluoropolyether lubricant; Information on corrosion properties.

Presents information on a study which focused on the fabrication of nickel (Ni) perpendicular quantized magnetic disks using nanoimprint lithography and electroplating. Fabrication of Ni pillar array; Results and discussion.

Presents information on a study which examined the recording performance of barium ferrite media in a Winchester-type disk form. Coercivity and particle size of barium-ferrite powder; Noise behavior of the media; Results and discussion; Conclusions.

Presents a bias scheme analysis of shielded magnetoresistive (MR) heads for disk recording. Possible schemes for biasing a MR head; Description of the nature of the signal flux entering the MR film; Response of the MR head at high densities.

Presents a study which evaluated the magnetic read/write characteristics of Ba-ferrite thin film disk. Experimental procedure; Results of the study; Conclusions.

Deals with rough surface contact analysis and its relation to plastic deformation at the head-disk interface. Effects of sampling resolution on contact pressure and contact area; Details of the experimental techniques used; Role of surface texture in controlling friction and durability at the head-disk interface.

Provides information on a study that explored the possibility of modifying friction and wear properties of diamondlike cardbon coated magnetic disk by ion implantation. Experimental procedure; Results and discussion.

Presents a study that investigated structure, magnetic properties and recording characteristics of the cobalt platinum boron(oxygen) rigid disk media with various underlayers. Experimental procedure; Results and discussion; Conclusions.

Presents a study which developed an eddy-current technique for determining conductivity of disks from complex active current (AC) susceptibility measurements. Systematic study done for disks; Measurements for nonmagnetic and weakly magnetic disks; Theoretical consideration of thin disks; Measurement of low-field external complex AC susceptibility.

Presents information on a study which investigated the patterned media structures formed on cobalt-alloy disks by sputter etching or ion milling. Experimental details; Results and discussion; Conclusions.

Explains the type of head crash which wipes out data on one track after thousands of hours of stable operation. Illustration of the head-disk configuration; Derivation of a differential equation that governs the motion of the initial particle in the space between the head and disk.

Presents information on a study which investigated the dependence of noise in thin metallic longitudinal disks on the transition density. Methodology of the study; Results and discussion; Conclusion.

This paper introduces a form of non-linear distortion (NLD) in rotating magnetic storage. This NLD is inherent to the read back process, and is caused by a non-linear field versus amplitude response in the read element. This is different than traditional NLD inherent to the write process, or non-linear 'saturation' effects in the read back process. Because of these differences, standard methods of mitigating NLD performance losses do not work on magneto-resistive non-linear distortion (MR-NLD). As of today there is no method of mitigating performance losses due to MR-NLD in any shipping hard drive. [ABSTRACT FROM AUTHOR]

A magnetic vortex core confined in a micron-scale magnetic disk is resonantly excited by both spin-polarized rf current and rf field. We found that rectifying voltage spectra caused by the resonance of vortex core are dependent not only on the core polarity, but also the chirality. These experimental results can be explained by analytically calculating the anisotropic magnetoresistance effect induced by the motion of the vortex core. [ABSTRACT FROM AUTHOR]

Presents an abstract of a study on the effects of nanoscale trenches and mesas patterned in a substrate on domain structures of magnetic films and ion applications in magnetic disk tracking. Non-requirement of etching of ferromagnetic film on the track marks.

Presents an abstract of the study 'Plastic Substrate Preembossed 100 kbpi, 3.4 μ Track Width Magnetic Disk,' by O. Ishizaki, T. Ohnuki, K. Adachi, K. Akagi, H. Momiji, O. Komoda and N. Ohta.