Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2001-03-09
2003-10-21
Klimowicz, William (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
C360S125330, C360S121000
Reexamination Certificate
active
06636390
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application claims benefit of priority under 35USC §119 to Japanese Patent Application No. 2000-70265, filed on Mar. 14, 2000, the contents of which are incorporated by reference herein.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a magnetic head and a magnetic recording and reproducing system. More specifically, the invention relates to a recording and reproducing magnetic head capable of carrying out an effective recording and reproducing with low noises in a vertical magnetic recording system, and a recording and reproducing system using the same.
2. Description of Related Art
In recent years, magnetic recording systems, such as hard disk drives (HDDs), are rapidly miniaturized and densified, and expected to be further densified in future. In order to increase the density in magnetic recording, it is required to narrow the recording track width to enhance the recording track density, and it is required to enhance the recording density in longitudinal directions of the recording track, i.e., the “track recording density”.
However, in a so-called inplane recording system (longitudinal recording system), as the recording density increases, there are remarkably caused problems in that the diamagnetic field increases, the regenerative output decreases, and stable recording operations can not be carried out. As a system for eliminating these problems, the vertical recording system is proposed. The vertical recording system is designed to magnetize in directions substantially perpendicular to the surface of a recording medium to record signals, and has advantages in that even if the recording density increases, the influence of the diamagnetic field is small and the lowering of the regenerative output is suppressed as compared with the inplane recording system.
In either of the inplane recording system or the vertical recording system, an inductive head is conventionally used for reproducing signals which have been recorded on medium. However, the anisotropic magnetoresistive (AMR) head, which uses the magnetoresistance effect and which has a high regenerative sensitivity, is developed to be used as a shielded reproducing head so that a sufficient regenerative signal output can be obtained even if the recording track width becomes narrower and the magnitude of recorded magnetization decreases with the increase of density. In recent years, the spin-valve-type GMR head utilizing the giant magnetoresistance effect is used. Moreover, a magnetic head using the tunneling magnetoresistance effect (TMR), which is expected to have a higher regenerative sensitivity, is developed and studied for practical use. Thus, magnetic heads having a high regenerative sensitivity have been developed. By using these magnetic heads, a recording signal begins to be able to be recorded even if it has a very small recording bit size.
By the way, in order to enhance the track recording density which is the density in longitudinal directions of a recording track, it is required to narrow the gap of a magnetic head. However, in the above-described conventional magnetic heads using the magnetoresistance effect, a magnetoresistance effect element is provided in a head gap. Even in the case of the AMR head or the spin-valve GMR head, the thickness of the magnetoresistance effect element must be about 30 nm, and 100 nm between shields in view of insulation from shields. For that reason, in the conventional type of magnetic heads, the thickness of the magnetoresistance effect element capable of narrowing the head gap is limited to about 100 nm. Therefore, there is a severe limit to the enhancement of track recording density.
Accordingly, it is desired to provide a magnetoresistance effect type magnetic head of a type capable of sufficiently narrowing a head gap without providing a magnetoresistance effect element in the gap of a magnetic head, for incorporating a magnetic flux from recorded magnetization by means of a head gap portion to guide the magnetic flux into the magnetic head by means of a magnetic yoke to transmit a magnetoresistance effect element which is arranged in the rear portion of the magnetic head, i.e., a magnetoresistance effect type magnetic head of “yoke type”. Since this yoke type magnetic head can sufficiently decrease the head gap, it is expected that the yoke type magnetic head can improve the resolution in reproduction and can correspond to a high track recording density. With respect to the track density, although a conventional type magnetic head defines a regenerative track width by intervals of leads which are provided for supplying a sense current to both ends of a magnetoresistance effect element, the yoke type magnetic head can define a track width by the thickness of a yoke film, so that the yoke type magnetic head can more easily narrow the track width than the conventional type magnetic head. From these facts, it is expected that the yoke type magnetic head can particularly sufficiently adapt to the enhancement of recording density in future.
On the other hand, it is also required to provide a recording head for writing in order to construct a magnetic head for HDD. Although there is the same advantage in a recording head in the case of a planar type head capable of a track width by a thickness, it is very difficult to provide this recording head with a coil for generating a magnetomotive force. Although it is required to provide the coil so as to pass above and below a magnetic pole, the process for producing the coil is not only complicated, but it is also not easy to increase the turn number of the coil. In order to eliminate these problems, the coil may be prepared in the plane of a substrate. However, in this case, a reproducing head must be prepared on the side of the substrate, so that the process is more complicated.
Particularly in the case of the vertical recording system, there is proposed a recording medium disk having a double-layer film structure wherein a “magnetically soft backing layer” is provided below a magnetizing recording layer in order to enhance recording and reproducing efficiencies. Using such a medium, the demagnetization field at the tip of the magnetic head can be reduced by the magnetic interaction between the magnetic head and the magnetically soft backing layer. Therefore, a greater generated magnetic field can be obtained during a recording operation, and a greater regenerative signal can be obtained during a reproducing operation.
However, in such a vertical magnetic recording system using the double-layer recording medium having the magnetically soft backing layer, there is a problem in that noises are generated due to the magnetically soft backing layer. These noises are generated by the variation in magnetized state of the magnetically soft backing layer. Typical noises are Barkhausen noises caused by the movement of magnetic domain walls.
Since a relatively strong magnetic flux passes through the backing layer during a recording operation, the magnetized state at that place is disturbed to cause the generation of noises during a reproducing operation. In particular, when the recording density is high and when a sensitive magnetoresistance effect element is used as a reproducing head, the recording bit size is small, so that the quantity of magnetic fluxes generated by the recording layer is small. Therefore, there are problems in that the influence of noises increases, so that S/N decreases during a reproducing operation.
By the residual magnetization of a recording pole, a magnetic circuit is always formed by the main pole of the recording head, the magnetically soft backing layer and a return yoke although it has a smaller magnetic field than that during a recording operation. During a recording operation, there is no problem since a stronger magnetic field is generated. However, during a reproducing operation, the source of magnetomotive force only has recording bits of the recording layer. In particular, as the recording density increases,
Funayama Tomomi
Hori Akio
Koizumi Takashi
Osawa Yuichi
Yoshikawa Masatoshi
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