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IBM Journal of Research and Development

Issue 6 • Date Nov. 1974

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Displaying Results 1 - 21 of 21
  • Preface

    Publication Year: 1974 , Page(s): 479
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (204 KB)  

    This issue contains a group of papers on a wide range of research and development topics in magnetic recording. These papers, rather than being the outgrowth of a single development program, report new and innovative results from the various disciplines in disk file and tape file technologies. View full abstract»

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  • Aerodynamic Aspects of Disk Files

    Publication Year: 1974 , Page(s): 480 - 488
    Cited by:  Papers (25)  |  Patents (9)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (902 KB)  

    Airflows between centrally clamped, rotating, rigid disks are investigated with respect to the type of flow pattern, the parameters that influence nonuniform flow, and the effects of various flow patterns on disk stability. The experimental method uses a water-flow modeling technique for the airflow. The observed flow patterns are highly unsteady. The configuration and position of the shroud and slider arm are found to be the major parameters that influence flow characteristics. A reduction of disk flutter by a factor of 12 can be achieved when the unsteady flow pattern is changed to a steady flow pattern. View full abstract»

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  • Engineering Design of a Disk Storage Facility with Data Modules

    Publication Year: 1974 , Page(s): 489 - 505
    Cited by:  Papers (13)  |  Patents (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1398 KB)  

    The design of the IBM 3340 Direct Access Storage Facility with IBM 3348 Data Modules incorporates new concepts and required the development of several innovative components, including newly designed magnetic read-write heads. The heads start and stop in contact with the disk and use a tri-rail, air-bearing slider having a low mass. Each data module includes read-write heads, a head carriage, disks, and a disk spindle. The rationale is discussed for the design concepts and for several components, including the data module, head and arm assembly, and the moving-coil linear actuator. A method of improving data integrity, utilizing a “disk-defect skipping” procedure, is described and its performance implications discussed. View full abstract»

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  • Design of a Disk File Head-Positioning Servo

    Publication Year: 1974 , Page(s): 506 - 512
    Cited by:  Papers (24)  |  Patents (36)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (615 KB)  

    The engineering design of a head-positioning system for an interchangeable-medium disk file is considered. Emphasis is placed upon three specific functions within the positioning system: (1) encoding and demodulation of information from the dedicated servo surface, (2) compensation and dynamics of the track-following control system, and (3) implementation of control electronics for a quasi-time-optimal, track-accessing control system. The examples used are taken from the IBM 3340 Disk Storage Facility. View full abstract»

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  • Dynamic Response of Self-acting Foil Bearings

    Publication Year: 1974 , Page(s): 513 - 520
    Cited by:  Papers (9)  |  Patents (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (744 KB)  

    A new approach to the analysis of wide foil bearings is investigated. The equation of motion for a finite length of tape is coupled to the transient lubrication equation for the air film between the tape and the recording head. Compressibility and slip flow are retained in the fluid mechanics equation; flexural rigidity and high-speed dynamic effects are retained in the tape equation. The steady-state solution to the coupled equations is obtained as the limiting case of the transient initial value problem. Describing the system equations relative to the undeflected tape (as opposed to conventional foil-bearing theory, which uses the head as the reference surface) permits investigation of noncircular head geometries. In addition, wave propagation effects in the tape and the interaction of waves in the tape with the air-bearing region may be studied. View full abstract»

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  • White Light Interferometry of Elastohydrodynamic Lubrication of Foil Bearings

    Publication Year: 1974 , Page(s): 521 - 528
    Cited by:  Papers (1)  |  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (737 KB)  

    This paper describes an experiment performed to verify the one-dimensional model of elastic foil behavior developed by Stahl, White, and Deckert. In the experiment, a loop of tape one-inch wide passes over a stationary recording head, and the air-film thickness between the head and the foil is determined using white light interferometry. Measured data for various experimental conditions are compared with the predictions of the model and also with prior foil-bearing analyses. The influence of parameters such as tape thickness, head radius, tape tension, etc. on the nature of the spacing field is demonstrated. View full abstract»

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  • Infrared Laser Interferometer for Measuring Air-bearing Separation

    Publication Year: 1974 , Page(s): 529 - 533
    Cited by:  Papers (12)  |  Patents (10)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (572 KB)  

    The design and characteristics are presented for an infrared instrument capable of measuring air-bearing separation distances over a mechanical bandwidth ranging from dc to 30 kHz. The measurement technique involves monitoring optical intensity variations of the interferometric cavity formed by two air-bearing surfaces. This intensity varies between a minimum at zero separation and a maximum at a distance equal to one-quarter of the optical wavelength. For air-bearing distances less than 1 µm, a convenient source is the 3.391 µm infrared line of the helium-neon laser. By continually monitoring a fraction of the intensity of the optical source, a real-time analog division can be performed on the spacing signals to produce an output independent of laser intensity variations. Room-temperature indium arsenide detectors were selected for their high responsivity and rapid rise time. View full abstract»

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  • Transition from Boundary Lubrication to Hydrodynamic Lubrication of Slider Bearings

    Publication Year: 1974 , Page(s): 534 - 540
    Cited by:  Papers (13)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (646 KB)  

    The transition from boundary lubrication to fully hydrodynamic lubrication is investigated for air-lubricated slider bearings using the electrical resistance method. Intermittent contacts are shown to exist even under conditions for which the numerical solution of the Reynolds equation or white light interferometry predicts steady state spacings in the spacing region from 0.125 to 0.25 µm. The transition is similar to the one found in the presence of liquid films, being influenced for a given surface roughness of disk and slider by load, speed, and hydrodynamic design. View full abstract»

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  • Hand-held Magnetoresistive Transducer

    Publication Year: 1974 , Page(s): 541 - 546
    Cited by:  Papers (8)  |  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (655 KB)  

    The initial design of a vertical magnetoresistive head in a hand-held wand for reading magnetically encoded price tags and credit cards is discussed. The performance of the head (e.g., resolution, signal shape and amplitude, and signal-to-noise ratio) is analytically and experimentally evaluated as a function of the configuration of the sensor, head-to-medium interface, and sensor processing and materials. View full abstract»

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  • Thermally Induced Pulses in Magnetoresistive Heads

    Publication Year: 1974 , Page(s): 547 - 550
    Cited by:  Papers (21)  |  Patents (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (582 KB)  

    The thermal response of a magnetoresistive head is analyzed for frictional heating between the head surface and dust particles or other asperities on the recording medium surface during relative motion of head and medium. A theoretical model is presented showing that pulses are induced in the output of a magnetoresistive head as a result of this frictional heating. The model predicts the dependence of these noise spikes on the thermal properties of the substrate and cover chip for the magnetoresistive head, the dimensions of the magnetoresistive stripe, the head-medium relative velocity, and the rate of frictional heat generation. Experimental verification of the theoretical model is obtained by scanning a focused laser beam across a head. View full abstract»

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  • Numerical Analysis of the Shielded Magnetoresistive Head

    Publication Year: 1974 , Page(s): 551 - 555
    Cited by:  Papers (10)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (499 KB)  

    Numerical computations for the shielded magnetoresistive head are reported and compared with previous analytic and experimental results. Linear resolution is found to be essentially the same as for inductive heads. Output amplitude is in the range 50 to 175 V per meter track width for a sense current density of 5 × 1010 A/m2. View full abstract»

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  • Ferrite Film Recording Surfaces for Disk Recording

    Publication Year: 1974 , Page(s): 556 - 562
    Cited by:  Papers (8)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (656 KB)  

    Ferrite thin films have been prepared using a chemical deposition process; hematite and substituted hematite films were formed by spin coating a diluted solution of the metal nitrates on a substrate and subsequently heating the substrate in air to 300°C to crystallize the film. Magnetic ferrite films were formed by reducing the films in a wet hydrogen atmosphere. Process parameters, which have evolved from studies on spin coating and reduction on 7.62- and 35.56-cm substrates, have been determined that result in desirable magnetic properties. Experimental studies of film composition and morphology are reported. It has been determined both theoretically and experimentally that film thickness near 0.125 µm is optimum for high-density recording with heads with gap lengths of approximately 1 µm spaced about 0.5 µm from the film. A TiO2 undercoat (0.125 µm) on the Al-Mg alloy substrate was prepared by chemical vapor deposition and resulted in improved magnetic properties. Magnetic properties of the films and magnetic recording performance of disks using Ti and Al substrates with the TiO2 undercoat are reported. View full abstract»

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  • The Remanent State of Recorded Tapes

    Publication Year: 1974 , Page(s): 563 - 569
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (627 KB)  

    Measurements are reported on the in-plane and the perpendicular components of the remanence a tape acquires on passing through the steady field of a recording head. The tape coatings were oriented and unoriented particles of γ-Fe2O3, oriented CrO2 and unoriented Co-substituted γ-Fe2O3. The two writing heads used had 10 µm- and 2.25 µm-gaps, respectively. In each case the in-plane magnetization increases at first with increasing writing current, and eventually reaches a peak that is less than the maximum in-plane remanence produced on the same sample by an electromagnet. For higher values of writing current, in-plane magnetization in the tape actually decreases. The perpendicular remanence is not large enough to explain the difference between the in-plane remanence acquired from the head and the remanence acquired in a magnet. The perpendicular component of the field from the writing head is shown to have two adverse effects on the remanence of the tape. First, it produces a perpendicular magnetization that ranges from 2 percent to 15 percent of the in-plane component. Second, it causes a reduction in the in-plane component to occur near the surface of the tape closest to the writing head. The reduction can be as large as 15 percent of the maximum in-plane remanence and will obviously have an adverse effect on recording performance, particularly at high densities. View full abstract»

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  • Noise in Disk Data-recording Media

    Publication Year: 1974 , Page(s): 570 - 575
    Cited by:  Papers (9)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (570 KB)  

    Measurements were made of recording medium noise in erased disks using an in-contact magnetoresistive element and an inductive head supported on an air bearing slider. Four types of coatings on aluminum disks were examined: thin, transition-metal alloy film, CrO2, FeCo particle, and γ-Fe2O3. Results obtained by means of three measurement techniques are in qualitative agreement and indicate that: (1) dc-erased noise of alloy film disks is 14 to 20 dB lower than that of particulate disks measured; (2) dc-erased noise of particulate disks measured is 6 to 16 dB above their bulk-erased noise; (3) although dc noise of particulate disks increases with write current, dc noise of alloy film disks is independent of write current; (4) the shapes of the noise spectra are similar in dc-erased particulate γ-Fe2O3 disks and FeCo particle coated disks; and (5) significant modulation noise is detected on particulate disks but not on alloy film disks. The observed dc-erased noise spectrum is compared with the model for small particle noise and is then used to estimate the size of particle agglomerates or voids. View full abstract»

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  • Switching Speeds in Magnetic Tapes

    Publication Year: 1974 , Page(s): 576 - 578
    Cited by:  Papers (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (408 KB)  

    Comparative measurements are reported on the switching speeds of three different magnetic tape materials, as determined by application of short field pulses of well-defined duration and magnitude. A sensitive measure of the change in magnetization is the length of applied pulse required for the peak readback signal to drop from 60 percent to 40 percent of its peak value. This pulse length was 2.6 ns for a γ-Fe2O3 tape, 4.1 ns for a CrO2 tape, and 1.4 ns for a cobalt-substituted γ-Fe2O3 tape. View full abstract»

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  • Optimal Rectangular Code for High Density Magnetic Tapes

    Publication Year: 1974 , Page(s): 579 - 588
    Cited by:  Papers (16)  |  Patents (7)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1264 KB)  

    IBM's 6250 bpi 3420 series tape units require a powerful error-correcting code for the standard 9-track format. The optimal rectangular code (ORC), presented here, is designed to correct any single-track error or, given erasure pointers, any double-track error in the tape. The code achieves this by conforming to a rectangular codeword of which two orthogonal sides are check bits. The code is specially tailored from a general class of b-adjacent codes. The ORC can be implemented without a buffer for encoding and offers a simple error-correction mechanism. The code can be generalized to multiple-channel applications. View full abstract»

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  • Recent papers by IBM authors

    Publication Year: 1974 , Page(s): 589 - 592
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (490 KB)  

    Reprints of the papers listed here can usually be obtained by writing directly to the authors. The authors' IBM divisions are identified as follows: ASDD is the Advanced Systems Development Division; DPD, Data Processing Division; FED, Field Engineering Division; FSD, Federal Systems Division; GPD, General Products Division; GSD, General Systems Division; OPD, Office Products Division; RES, Research Division; SDD, System Development Division; SPD, System Products Division; and WTC, World Trade Corporation. Papers are listed alphabetically by name of journal. View full abstract»

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  • Recent IBM patents

    Publication Year: 1974 , Page(s): 593 - 595
    Save to Project icon | PDF file iconPDF (365 KB)  
    Freely Available from IEEE
  • Author Index for papers Volume 18

    Publication Year: 1974 , Page(s): 601 - 602
    Save to Project icon | PDF file iconPDF (283 KB)  
    Freely Available from IEEE
  • Subject Index for papers Volume 18

    Publication Year: 1974 , Page(s): 603 - 604
    Save to Project icon | PDF file iconPDF (268 KB)  
    Freely Available from IEEE
  • Contents of previous issue

    Publication Year: 1974 , Page(s): 605
    Save to Project icon | PDF file iconPDF (204 KB)  
    Freely Available from IEEE

Aims & Scope

The IBM Journal of Research and Development is a peer-reviewed technical journal, published bimonthly, which features the work of authors in the science, technology and engineering of information systems.

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Editor-in-Chief
Clifford A. Pickover
IBM T. J. Watson Research Center