Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2000-05-23
2003-12-30
Letscher, George J. (Department: 2653)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06671140
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic information recording/reproducing field, particularly to a magnetic head and a magnetic recording/reproducing apparatus for recording/reproducing information on a magnetic recording medium by using the magnetic head, and more particularly to a magnetic head using a magnetoresistance effect based on ferromagnetic tunnel junction, a method of manufacturing the magnetic head, and a magnetic recording/reproducing apparatus using the magnetic head.
2. Description of the Related Art
In connection with recent compact and large-capacity design of magnetic recording/reproducing apparatuses, a magnetoresistance effect type head capable of realizing a large reproduction output (hereinafter referred to as “MR head”) has been practically used. The MR head has been disclosed in a paper titled “A Magnetoresistivity Readout Transducer” of “IEEE Trans. on Magn., MAG7 (1971) 150”, for example. NiFe film is generally used as the magnetoresistance effect material, and in the case of a magnetoresistance effect type element (hereinafter referred to as “MR element”) using the NiFe film, the magnetoresistance variation rate corresponding to the reproduction output of the head is equal to about 2 to 3%.
FIG. 14
is a cross-sectional view showing a composite magnetic head (hereinafter referred to as “composite head”) equipped with a reproducing head based on an MR element and a recording head based on an inductive element (induction type element), and
FIG. 15
shows the structure of the composite head which is viewed from the magnetic recording medium confronting face (generally called as “air bearing surface [ABS]”).
A magnetic shield
21
is formed on a base
31
serving as a slider, and an MR element is formed through an insulating layer used to establish electrical insulation. The MR element has a central area
22
for sensing the magnetic field from the magnetic recording medium, and an end portion area
23
comprising a ferromagnetic layer for applying bias magnetic field to the central area
22
and a conductive layer for supplying current. A magnetic shield
24
is further formed through an insulating layer. The above parts constitute a reproduction element portion
The magnetic shield
24
also functions as one of recording magnetic poles, and it is paired with the other recording magnetic pole
26
formed through a recording gap
25
. A coil
30
is provided between the magnetic shield
24
serving as one recording magnetic pole and the other recording magnetic pole
26
so as to be located slightly inside away from the ABS while insulated by insulators
28
,
29
such as photoresist or the like, and these recording magnetic poles are exited (magnetized) by the magnetic field occurring when current flows through the coil. The above parts constitute a recording element portion.
Recently, much attention has been paid to a GMR head which aims to enhance the recording density by using a giant magnetoresistance effect film (GMR film) at the central area of the MR head to further increase the output power. With respect to the GMR film, particularly a magnetoresistance effect, generally called as “spin valve effect” in which the resistance variation corresponds to the cosine defined by the magnetization directions of two adjacent magnetic layers is starting to be practically applied to next-generation MR heads because a large resistance variation can be obtained by a small operating magnetic field. The MR head using the spin valve effect is described in a paper titled “Design, Fabrication & Testing of Spin-Valve Read Heads for High Density Recording”, IEEE Trans. on Magn., Vol. 30, No. 6 (1994) 3801. The resistance variation rate of the GMR film using the spin valve is equal to about ten and several % at maximum, and thus the practical value in consideration of noises of a magnetic head (hereinafter merely referred to as “head”) is equal to about 7%.
A ferromagnetic tunnel junction element has such a structure that a tunnel barrier layer formed of an extremely thin insulator of nano-meter order is sandwiched between two ferromagnetic layers. According to the ferromagnetic tunnel junction element, when an external magnetic field is applied in the direction along the ferromagnetic layers while fixed current flows between the ferromagnetic layers sandwiching the tunnel barrier layer from both the sides thereof, there appears a magnetoresistance effect corresponding to the relative angle between the magnetization directions of the ferromagnetic layers (this phenomenon is hereinafter referred to as Recently, it has been reported that a magnetoresistance element exhibiting a magnetoresistance variation rate exceeding 20% is achieved by using a surface oxide film of Al as a tunnel barrier layer. For example, “Journal of Applied Physics, vol. 79, pp4724 to 4729, April 1996” has reported such a large magnetoresistance variation rate. According to this publication, a first ferromagnetic layer of CoFe is formed on a glass substrate by a vacuum deposition method using a deposition mask, and then the mask is exchanged by another to form an Al layer of 1.2 to 2.0 nm in thickness by the vacuum deposition method. The surface of the Al layer thus formed is exposed to oxygen to form a tunnel barrier layer made of alumina. Finally, a second ferromagnetic layer of Co is formed so as to be superposed on the first ferromagnetic layer through the tunnel barrier layer, thereby completing a cross-shaped electrode type ferromagnetic tunnel junction element. According to this method, it has been theoretically expected that the magnetoresistance variation rate of about 50% is achievable.
By applying the element using TMR as described above to a reproduction head, a magnetic head of higher output power than GMR can be implemented. However, IVR as described above needs to apply a voltage across two adjacent ferromagnetic layers between which an extremely thin insulating layer of 2 nm or less is sandwiched, and thus it has an extremely high risk of dielectric breakdown. Particularly the head to which the structure shown in
FIGS. 14 and 15
is applied has a higher risk of electrostatic breakdown of the tunnel barrier layer because the end face of the laminate film of TMR is exposed at the medium confronting face.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a magnetic head which can suppress occurrence of dielectric breakdown of a tunnel barrier layer while using TRR having a magnetoresistance variation higher than conventional GMR.
Further, another object of the present invention is to provide a composite magnetic head having a TMR reproducing magnetic head and an inductive recording magnetic head in which low-noise reproduction can be performed even when the gap between the head and a magnetic recording medium is small.
Still further, another object of the present invention is to provide a composite magnetic head having an inductive recording magnetic head and a TMR reproducing magnetic head in which high-density recording of a narrow track width can be performed on a magnetic recording medium.
In addition, a further object of the present invention is to provide a method of manufacturing the magnetic head as described above.
A further object of the present invention is to provide a magnetic recording/reproducing apparatus using the magnetic head as described above.
In order to attain the above objects, according to a first aspect of the present invention, there is provided a magnetic head comprising: a magnetic yoke film (magnetic yoke) forming a closed magnetic circuit containing a magnetic gap; a first magnetic layer which is laminated on the magnetic yoke film and magnetically coupled to the magnetic yoke film; a second magnetic layer laminated on the first magnetic layer through a magnetic separation layer; and a pair of electrodes which are formed so that the laminate comprising the magnetic yoke film, the first magnetic layer, the magnetic separation layer and the second magn
Hayes & Soloway P.C.
Letscher George J.
LandOfFree
Magnetic head using a magnetoresistance effect based on... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Magnetic head using a magnetoresistance effect based on..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Magnetic head using a magnetoresistance effect based on... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3123287