MIG Head Research Articles

Running characteristics of MIG heads against MP, barium ferrite and ME tapes

The running characteristics (signal stability) of MIG heads against MP, barium ferrite and ME tapes were studied by measuring friction force between a tape and head, head output and head contour. The tests were conducted in the still and streaming modes of operation. Some still mode testing was also conducted at different temperatures and humidities. Based on this study, running characteristics of MP and barium ferrite tapes appear to be superior to that of ME tapes. >

The gap recession reduced MIG head

In order to reduce the decrease of head output level during running, the wear recession formed on a composite material and MIG heads with various ferrite crystallographic orientations was investigated. It was found that wear recess depends mainly on the wear rate ratio of materials, and that the decrease in output level was in proportion to the spacing loss due to the formation of a level difference at the interface between the metal and the ferrite core. However, the decrease measured using tape different from the running tape was also affected by the unfitness between head and tape. It was also found that the damage caused to metal evaporated (ME) tape depends on the ferrite orientation of the head.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Agglomerates and media-noise of ultra-thin coated rigid disks

This paper discusses the media-noise properties of ultra-thin coated rigid disks and their origin. The ultra-thin coated rigid disks using Co-γFe 2O 3 fine particles were obtained after spin-coating Al-substrates with magnetic paints. Thickness values between 0.12 and 0.33 μm were obtained after controlled spin-coating. After removing high protrusions on disk-surfaces, the read/write properties of ultra-thin coated rigid disks were investigated using a MIG head. The media-noise properties of the ultra-thin coated disks were compared with those of a conventional particulate disk and a thin film disk. The signal-recorded noises, the dc-erase noise, and the reverse dc-erase (RDC) noises were measured. A peculiar recording density dependence for the signal-recorded noise was found. The signal-recorded noise of the ultra-thin coated disks has a maximum value at a density of 17.5 kFCI. In the region below 17.5 kFCI, the signal-recorded noise increases like a thin film disk as the recording density increases. In the region larger than 17.5 kFCI, the signal-recorded noise decreases like a conventional particulate disk as the recording density increases from 17.5 kFCI. This peculiar dependence is caused by cohered agglomerates which consist of randomly oriented magnetic particles in the magnetic layer of the ultra-thin coated disks.

Grain influences on domains and read-back pulse distortions of ferrite MIG heads

Direct observations using microellipsometry, Kerr microscopy, and electron backscatter diffraction are made for the first time on individual grains in the leading pole-tip region of polycrystalline ferrite MIG heads intended for narrow track (<or=10- mu m) data recording. These observations, compared with readback-after-write waveforms, indicate that waveform instabilities and asymmetry which can cause high error rate would be diminished by controlling grain size and orientation in this critical pole-tip region. When large grains (near the gap) exceed the single domain size ( approximately=5 mu m) but are oriented so their media-facing surface contains an easy-axis of magnetization, the head produces smaller asymmetry and instability than when missoriented (large) gap grains or multiple single-domain size grains are present.<<ETX>>

Application of MFM to Magnetic Recording: For D.C. Characterization

The magnetic field profiles of ferrite and MIG heads, and of magnetic media, were imaged by magnetic force microscopy (MFM) using a scanning tunneling microscope (STM) and a beam deflection sensor. On the basis of the profiles obtained, we discuss the force acting on the tip of the MFM and the magnetic structure of the tip. The MFM is a very powerful tool for observing detailed magnetic structures with high resolution without special sample preparation. However, some problems, considered in our conclusion, remain to be overcome.

In-contact magnetic recording performance of Pt/CoCrTa thin films on glass computer disks

CoCrTa films deposited on fcc Pt and Au underlayers show excellent c-axis orientation. The ‘epitaxial-growth’ mechanism may explain the origin of such an effect. The perpendicular MOKE and VSM coercivity, shape of hysteresis loops and contact recording results of such media are investigated and discussed together with the film structure. A first peak D 50 of 160 kFRPI has been realized by a single-layer Pt/CoCrTa rigid disk using an in-contact MIG head.

微細な結晶粒径を持つ磁気ヘッド用Ｍｎ‐Ｚｎフェライトの磁気特性

The Mn-Zn ferrite ceramics with high density above 99.8% and fine grain size below 5 μm have been obtained by sintering of hydrothermal-precipitated ferrite powders at lower temperature than that in the ordinary process. Mn-Zn ferrite ceramics with grain sizes below 3μm have relative permeabilities comparable to that of commercial one in a frequency range above 5MHz. The single side MIG heads composed of ferrite with fine grain(Gs=2.3μm) are manufactured. The output voltage of the heads composed of the developed ferrite are equal to those of the heads composed of the commercial ferrite. The asymmetry instabilities of the heads composed of the developed ferrite are almost equal to those composed of the single crystal Mn-Zn ferrite which seemed to be good for the asymmetry instabilities. Therefore, Mn-Zn ferrite with fine grain sizes and high density is expected to be useful as magnetic head material for high density recording.

An Influence of Head Field on the Transition Noise of Thin Film Disk

The dependence of a field gradient on media noise was demonstrated. Medium noise was degraded under the influence of a secondary field with low field gradient. This influence was confirmed by the investigation of changes in media noise, which are based on the intrinsic micromagnetic media properties, for different field gradients. Reverse dc modulation noise and transition noise of low-H c and high-H c disks were evaluated using a single-sided MIG and a ferrite mini-monolithic head. Reverse dc modulation noise showed different values for the two heads, despite the fact that the medium was the same. The ratio of increase of reverse dc demagnetization noise to dc saturation noise, i.e. the reverse dc modulation ratio, was higher when the medium was evaluated using the MIG head, which can generate sharper field gradients in each medium. However, transition noise was lower when using the MIG head than when using the ferrite head. As a result, both the reverse dc modulation increase ratio and the transition noise level, which has been regarded as an intrinsic property of the medium, were strongly correlated to the field gradient.

The analysis of the MIG heads

This paper studies the recording characteristics of MIG heads with various coercive force media and various recording frequencies. The MIG heads can saturate the media with high magnetic coercive force (up to H c = 1300 Oe). Overwrite is also discussed. In RLLC (2,7) coding methods, the linear bit density of MIG heads reached 36751 BPI (or 24500 FCI), the limiting conditions are: overwrite ≤ - 30 dB and resolution ≥ 70%.

Microstructural origin of the magnetically degraded layer in Sendust metal-in-gap recording heads

Microstructural studies using transmission electron microscopy have been performed on Sendust films deposited on both polycrystalline and single-crystal ferrites. A strain-induced contrast in both the ferrite and Sendust and a large number of dislocations in the ferrite region near the interface were observed. However, no intermediate layer of Al/sub 2/O/sub 3/ or SiO/sub 2/ was formed by interdiffusion at the interface. It was found that both the in-plane crystallographic texture and the microstructure of the Sendust films depend on the orientation of the underlying single-crystal ferrite substrates, even though the out-of-plane crystallographic texture appears to be independent of ferrite crystal orientation. A model has been proposed to explain the microstructural origin of the magnetically degraded layer formed at the interface of the Sendust film and ferrite cores in the MIG heads. >

Domain studies in single-crystal ferrite MIG heads with image-enhanced, wide-field, Kerr microscopy

The magnetic domain structure at the media-facing surfaces of the single-crystal ferrite MIG heads is investigated using the magnetooptical Kerr effect. Domain behavior depends strongly on the stress state and surface treatment of the head. The pole tips display coercive zig-zag domain walls, which are nucleated at the gap by write current pulses. For the samples studied, nucleation and motion of these walls are different between heads which exhibit small secondary pulses in the read-back signal and heads which do not.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Wiggles in transition response of MIG ferrite heads

The cause of wiggles in the read-back signal of a series of MIG heads has been studied. A digitizing signal analyzer was used to analyze the read-back signals of the heads. These heads were then studied on a scanning magnetooptic photometer system by measuring the magnetic activity on the air-bearing surfaces. Defects having strong magnetic effects were observed in both the ferrite and the Sendust. It is shown that these defects are responsible for the wiggles in the read-back signal of these heads. It is believed that some defects in the Sendust are caused by variations of magnetic properties from grain to grain, and some are caused by diffusion of interface layer material taking place during the glass bonding process. The defects in ferrites are believed to be caused by inclusions.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

RF-sputtered FeSiAl films for MIG head

This paper reports the effects of rf-magnetron sputtering conditions, annealing and aging on magnetic properties of FeSiAl alloy films with compositions close to that of Sendust. We have optimized conditions for sputtering and annealing, and have made some samples of rf-sputtered FeSiAl thin film with magnetic parameters satisfying the design requirements for a MIG head.

Improvement in soft magnetism of Sendust sputtered films for high performance MIG head

Sendust thin films with relative permeability μ r up to 6000 were prepared by using the facing targets sputtering (FTS) system which is one of the plasma-free sputtering methods. The optimum values of the argon gas pressure P Ar, the substrate temperature T s and the bias voltage to the substrate V b were found.

Recording Characteristics of Perpendicular Hard Disk Media Measured by MIG Head

Recording and reproducing characteristics of a Co-Cr perpendicular magnetic hard disk with a thin Fe-Co back layer were investigated using a non-flying type MIG head. The Co-Cr/Fe-Co composite media were prepared by rf sputtering onto glass substrate with a Cr underlayer. The results showed that a reproduced isolated pulse from the medium has a single peak with large amplitude. The head gap length was a dominant factor determining the upper limit of the recording density. Using a MIG head with a gap length of 0.15 ?m, a D 50 of 120 kFRPI and normalized output of 95 nV 0-p /?m-turn-m/s can be achieved. Furthermore, when the thickness of the Co-Cr layer was increased, the output voltage grew larger, but the overwrite characteristic deteriorated.

薄膜磁気ディスクの遷移ノイズへのヘッド磁界の影響

Dependence of field gradient on media noise was demonstrated. Medium noise was worsened by influence of secondary field, when the field gradient of the secondary field is considered to be the dullest one. The influence was confirmed by the investigation of change of media noise, which is based on the intrinsic micromagnetic media properties, against different field gradients. Reverse DC modulation noise and transition noise of low Hc and high Hc disks were evaluated by using a single sided MIG and a ferrite mini-monolithic head. The reverse DC modulation noises showed a different value for each head in spite of the same medium. The increasing ratio of the reverse DC demagnetized noise to the DC saturated noise, i. e., reverse DC modulation ratio, showed higher value when the medium was evaluated by using the MIG head which can generate a sharper field gradient in each medium. However, the transition noise was smaller by using the MIG head than by using the ferrite head. As a result, both the reverse DC modulation increasing ratio and the transition noise level which was believed to be an intrinsic property of media were strongly correlated to the field gradient.

磁気ヘッド用軟磁性薄膜の特性

Abstract Recent developments of soft magnetic thin films are reviewed from the viewpoint of magnetic head core applications. Many kinds of alloy films with high saturation flux density over 1.0 T have been investigated in the last decade together with conventional materials such as Fe-Al-Si (Sendust) films and Co-based amorphous alloy films. Almost all reported materials with high saturation flux density are Fe-based alloy, Fe-based micro-crystalline alloy and multilayered alloy films. This paper briefly describes the advantage of soft magnetic thin films with high saturation flux density in high frequency operation to avoid the natural ferromagnetic resonance. The advantage of isotropic Fe-based alloy film is also described for a practical MIG head application.

Influence of Head Fields and Media Properties on Transitions of Magnetization Reversals on Thin Film Disk

This paper describes a relationship between transition lengths and head fields for media of various coercivities. Signals with various transition lengths were written using a single-sided and a double-sided MIG head on three different thin film media, of coercivity 874, 1121 and 1270 Oe. The transition lengths were observed by the colloid SEM method. The head fields of the MIG heads were analyzed by the finite element method (FEM) with magnetic saturation taken into account. The following phenomena were discovered: (1) the secondary fields stray from the saturated ferrite region near the interface between the metal film and ferrite core of the MIG heads; (2) the transition lengths are elongated due to the influence of the secondary field when the strength of the secondary field is greater than half of the medium coercivity. On the other hand, if the medium coercivity is twice as great as the secondary field strength, then the transition length is closely related to the field gradient of the primary field in the recording zone.

Corrosion study of metal particle, metal film, and Ba-ferrite tape

The authors investigated the corrosion susceptibility of very high coercivity metal particle (MP) and metal evaporated (ME) tapes and Ba-ferrite tapes when exposed to 50 degrees C and 80% RH for 7.5 weeks. The tapes are used in 8-mm video and digital audio tape applications. The effects of corrosion were studied by measuring the error statistics at a density of 53 kfci (2100fc/mm) using an 8-mm helical scan recorder with MIG heads. A large increase in errors was observed for all the MP and ME tapes studied (typically by two orders of magnitude), but also a large variation in corrosion stability among the tapes from different manufacturers.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A Three-Dimensional Reconstruction of Stray Magnetic Fields of a Magnetic Head by Electron Beam Tomography

A new fast algorithm for reconstructing the stray magnetic field of a magnetic head by electron beam tomography, and applications of the method, are described. We had previously proposed a method for 3-D reconstruction of stray magnetic fields using an method of electron beam tomography. In this new algorithm, the magnetic field distribution in the measurement plane just beyond the gap is first reconstructed using the ART method. Then the entire magnetic field distribution is calculated numerically by the boundary element method, using the reconstructed magnetic field in the measurement plane as a boundary condition. Using this method, the total reconstruction time is shortened and reconstruction accuracy is improved considerably. An example of reconstruction of the magnetic field of a MIG head is described. From these results and the results of analyses by a 2-D finite element method, it is shown that the new algorithm is useful for comparatively accurate reconstruction of the entire magnetic field distribution.