Ring-type Head Research Articles

鉄‐コバルト部分酸化物垂直磁気記録媒体の磁気特性と記録再生特性

Magnetic properties of partially oxidized Fe-Co sputtered films are comparable to those of CoCr films. We studied the relationships between magnetic properties and recording characteristics using a combination of ring-type head and single layer medium. Recording density D50 increased in proportion to anisotropy field Hk, and reproduced voltage depended on saturation magnetization 4πMs and Co content. Maximum reproduced voltage was obtained in the 4πMs region of 8500 to 11000 gauss at 60 at.% Co content. From X-ray diffraction analysis of these films, it is thought that reproduced voltage relates to microscopic structure of the films.

Single-turn perpendicular thin film heads

This paper describes the thin film heads, intended for use with CoCr perpendicular recording media, which were designed to bring forth highest possible efficiency both in ring-type and pole-type constructions. The heads are of single-turn structure to minimize the yoke length, and all the magnetic films are deposited on substantially the flat planes to avoid magnetic degradations. By employing such scheme, both ring-type and pole-type thin film heads are shown to have efficiency comparable to that of VHS-type ferrite video heads.

Ba-ferrite thin film rigid disk for high density perpendicular magnetic recording

A magnetoplumbite type of hexagonal Ba-ferrite films, whose c-axis of crystallites is well oriented perpendicularly to the film plane, have been prepared by means of a conventional rf diode sputtering system. Morphological and crystallographic characteristics of sputtered Ba-ferrite films depend strongly on preparation conditions such as the distance between target and substrate d T-S and partial pressure of oxygen gas P O2 during the deposition. Ba-ferrite films with smooth surface are prepared at the extended d T-S in the region of low P O2 . Read/write characteristics of Ba-ferrite thin film deposited on thermally oxidized silicon wafer with radius of two inches were evaluated with ring type head. Recording density D 50 of Ba-ferrite thin film rigid disk depends strongly on Δθ 50 . In this work, D 50 of 110 and 190 kfrpi for Δθ 50 of 4.8 and 2.8°, respectively, have been attained.

Read-After-Write Characteristics of Ring-Type Heads for Perpendicular CoCr Media

Research into the recording density and recording current characteristics of perpendicular CoCr media is reported. CoCr alloy films were either directly formed on a polyimide substrate or on intermediate layers of Ge, Si and Ti, 0.03 ?m thick. The recording reproduction properties where measured from the contact conditions of the head and media at relative speed of 2.5 m/s. It was found that it is possible to obtain high-density perpendicular recording reproduction, using a ring-type head composed of high-saturation magnetic flux density material near the optical gap together with CoCr media formed on a Ge base.

Head saturation effects in perpendicular and longitudinal recording

In this study we have investigated the effect of saturation of a narrow gap ring-type-head on the amplitudes and gradients of the horizontal and vertical head field components for both longitudinal and perpendicular magnetic recording systems. The head field calculations were performed by finite element analysis simulating the geometry of a narrow gap ferrite ring head. We found a remarkable difference between the behavior of the horizontal gradient of the longitudinal field component ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\partialHx/\partialx</tex> ) and vertical head field component ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\partialHy/\partialx</tex> ) as the head core is driven into saturation. From computational results of head field and experimental results of the signal output versus write current response, we found that a) we have to consider recording demagnetization and its dependency on <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\partialHy/\partialx</tex> in "quasi-perpendicular" recording systems, i.e., ring-type head with Co-Cr media, as well as longitudinal recording systems, and b) we have to choose the high Hc medium in the range where the head can achieve saturation recording to reduce the influence of record demagnetization and the dependence of signal output on write current.

Comparison of sensitivity functions for ideal probe and ring-type heads

Analytical models of ideal infinitesimally thin probe-type heads have been presented and compared with a model of an ideal ring-type head. It is shown that with respect to readback resolution the characteristics of probe models are inferior to those of the ring model. It is also shown that resolution of the probe model is reduced further if media with a soft magnetic underlayer is used.

A new W-shaped single-pole head and a high density flexible disk perpendicular magnetic recording system

A new single-pole head with no auxiliary pole was developed for perpendicular magnetic recording. The head is called WSP head (W-shaped Single Pole head) because the head has a W-shaped side core which contributes to increase the recording and reproducing sensitivitiy. The head field of the new head has the same distribusion as that of an auxiliary pole head[1]. The recording and reproducing sensitivity of the head is equal to or higher than that of a ring-type video head. The head eliminates mechanical problems which prevent its application in perpendicular magnetic recording because we can locate the head on one side of the recording medium. As a possible application of the WSP head, a 3 1/2-inch flexible disk recording system was constructed. A linear recording density of the flexible disk system was 65.5 kbits/inch. This density is equivalent to 8 times that of the existing high-density 3 1/2-inch micro-floppy and 11 times that of a 5 1/4-inch floppy disk. In termes of information storage, this density gives a 4 megabyte unformated capacity on one side of a 3 1/2-inch flexible disk. The overwrite signal-to-noise ratio was greater than 30 dB and the peakshift displacement was less than 10 % at the linear dinsity of 65.5 kbits/inch.

Rare earth - transition metal alloys: Another way for perpendicular recording

Many investigators have chosen CoCr alloys or other Co-based alloys to study perpendicular magnetic recording. Although the perpendicular magnetic anisotropy of Co alloys is quite convenient for this use, the demagnetizing fields are high because of high saturation magnetization and then the squareness of the perpendicular M-H loops is poor. To study another kind of perpendicular anisotropic alloy, we tested sputtered amorphous Fe 1-x-y Tb x Gd y (X = y) thin films as a perpendicular recording medium. Several thicknesses with and without a FeNi underlayer were tested. Although a conventional ring-type head was used, with a low trackwidth (20 μm) and a coil with 2 × 13 turns, 162 KFci could be recorded and read and a 1,600 μ Vpp output signal was read at 10 KFci.

Co-Cr/Ni-Fe系二層膜媒体の垂直磁気記録特性

The effects of magnetic properties and thickness of Co-Cr/Ni-Fe double-layered medium on perpendicular magnetic recording are investigated. Experiments are performed using a single-pole-type head for recording and a ring-type head for reproducing. Our experiments show that: (1) Thickness of the Ni-Fe layer is required to be greater than half of thickness of the head pole to obtain the maximum reproduced voltage. (2) Reproduced voltage Ep is proportional Hc0.6 (Hc: coercive force of the Co-Cr layer in the film normal direction). (3) Ep/Hc0.6 to (≡Ep′) is independent of saturation magnetization of the Co-Cr layer. (4) Ep′ increases with thickness of the Co-Cr layer δp at long recording wavelength. (5) Ep′ is independentof δp when the recording wavelength is short. The relationships (2) to (4) are close to those suggested by calculation based on magnetization model of the medium and a reciprocal theorem. But the relationship (5) a does not agree with the result of our calculation probably because of the incorrectness of the magnetization model for short recording wavelength. The calculation shows that magnetic interaction between the ring head and the medium has an important effect on the reproducing characteristics.

Thin permalloy film - bulk ferrite composite head for perpendicular magnetic recording

A composite head of thin permalloy film and bulk ferrite has been developed for perpendicular magnetic recording, which is designed to operate from only one side of the recording medium. This head has been fabricated mostly by means of vacuum evaporation, sputtering and photo-lithography. The writing and reading efficiencies have been confirmed to be as good as for a ferrite ring type head, by using Co-Cr films with a soft magnetic layer of amorphous Co-Mo-Zr. Higher bit density is obtained by a thinner pole tip head, though there is a sacrifice of output at lower bit densities. The highest bit density, D 50 , of 57 kBPI has been attained with a pole tip thickness of 0.3 μm. Computer analysis shows that a decrease of output at lower bit densities with decreasing pole tip thickness is attributed to the magnetic saturation of the pole tip. It is thus concluded that in order to improve head performance, it is necessary to increase the saturation induction of the pole tip material.

Coal cutting by a ring-type jet head

Coal cutting by a ring-type jet head

A low inductance strip-line recording head

A prototype high energy-efficiency recording head for use in a high packing density recording system has been developed. The operation of the head in the writing mode depends on the magnetic field round a thin strip conductor rather than flux leakage from the magnetic circuit as in a conventional ring-type head. The presence of ferrite in the vicinity of the strip increases the field produced for a given strip current. Since its low input impedance is unsuitable for direct connection to electronic circuits, it has been necessary to use an intermediate pulse transformer. By making this transformer an integral part of the recording head, a very compact unit is realizable. Care has been taken in the design of the structure to minimize any stray inductance which may be comparable to that of the head element. Advantages of the proposed head are its good high-frequency performance and suitability for high track densities.

A low inductance strip-line recording head

A prototype high energy-efficiency recording head for use in a high packing density recording system has been developed. The operation of the head in the writing mode depends on the magnetic field round a thin strip conductor rather than flux leakage from the magnetic circuit as in a conventional ring-type head. The presence of ferrite in the vicinity of the strip increases the field produced for a given strip current. Since its low input impedance is unsuitable for direct connection to electronic circuits, it has been necessary to use an intermediate pulse transformer. By making this transformer an integral part of the recording head, a very compact unit is realizable. Care has been taken in the design of the structure to minimize any stray inductance which may be comparable to that of the head element. Advantages of the proposed head are its good high-frequency performance and suitability for high track densities.

Magnetic Recording Head with dc Response

A magnetic recording head has been developed to directly record and play back low-frequency signals, down to and including zero cps, without using amplitude, frequency, or pulse width modulation. Two problems are encountered in dc magnetic recording. The more obvious problem is caused by the small voltage induced in the playback head when the flux changes at a very slow rate. At low frequencies, the output of a conventional playback head is proportional to the time rate of change of flux in the head; therefore, at dc the playback signal has zero amplitude. The second problem encountered in reproducing dc signals is the disappearance of the magnetic field at the gap of a ring-type head when wavelengths of considerable lengths are recorded on the tape. The magnetic field at the gap of a ring-type head becomes too small to be used when a recorded wavelength is longer than a few inches. Combining a perpendicular head with flux sensitive playback has eliminated these two problems. A perpendicular head magnetizes the recording tape perpendicularly to the direction of tape motion, i.e., the tape is magnetized through its thickness. The pole pieces of the head are spring loaded and pressed against the tape to maintain consistent contact while the tape passes through the head. Vicalloy, in the form of a thin, homogeneous metal tape, was selected for this purpose because it contains many of the magnetic and physical characteristics desired, including a high coercive force, high remanence, and mechanical flexibility when it is rolled into a thin tape. A frequency response of dc (0 cps to 10 cps) is achieved at a tape speed of 0.027 in./sec. Pre-emphasis is not required in recording and equalization is not used during playback. Cross talk between adjacent heads in a multichannel system is below 50 db at moderate track separations.

Magnetic drum recording of digital data

MAGNETIC recording has attained an important position in the field of digital data storage because of its simplicity and economy. Information is handled in binary form, requiring a discrimination between only two states. These states correspond to two opposite senses of saturation, and new information is then merely recorded over that previously contained, erasing being unnecessary. This paper is primarily concerned with the development of a useful mathematical description of the process of magnetic recording of binary information. A concept of this process is developed which furnishes an analytical basis for design evaluation. While a large part of the following is applicable to binary storage on a continuous magnetic medium in general, the paper is specifically concerned with a magnetic drum unit using a ring-type magnetic recording head, wherein the type of magnetization is referred to as longitudinal. This is at present the most common form for a magnetic drum memory system.

A Magnetic Record-Reproduce Head

It is the purpose of this paper to discuss various features of a combination magnetic record-reproduce head of the ring-shaped type, known as MI-10794, with emphasis more on the general principles of construction than details of assembly. Shown in the paper are various lamination shapes for ring-type heads; the change of head inductance with change of front-gap and back-gap spacer thickness; the lamination stacking factor as a function of lamination thickness; the shape of the lamination employed for the subject head; flux distribution patterns about the front-gap of a record head for various thicknesses of front-gap spacer; the “gap effect” of a reproduce head; the output voltage and inductance of a reproduce head as a function of the front-gap reluctance; and a photograph of the finished record-reproduce head.