Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2001-03-14
2003-12-30
Whitehead, Jr., Carl (Department: 2813)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06671141
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a tunnel magnetoresistive effective element (hereinafter, often called as a “TMR element”), a thin film magnetic head, a magnetic head device and a magnetic disk drive device.
2. Related Art Statement
With the development of the recording density in hard disks (HDDs), it is required to enhance the sensitivity and the output power in the HDDs. Recently, attention is paid to TMR elements to satisfy the above requirements in the HDDs. The TMR element has a ferromagnetic tunnel film with a multilayered structure of a ferromagnetic layer/a tunnel barrier layer/a ferromagnetic layer. The ferromagnetic tunnel effective film is defined as the change of the tunnel current in the tunnel barrier layer depending on the relative angle between both of the ferromagnetic layers when flowing a current in between the ferromagnetic layers. In this case, the tunnel barrier layer is composed of such a thin insulating film that electrons can penetrate through the tunnel barrier layer with maintaining their spin conditions.
It is reported that the TMR element has a large resistance change ratio &Dgr; R/R of 12% and over. Then, the TMR elements are expected as next generation sensors to substitute for spin valve film (hereinafter, called as a “SV film”) elements, but they have been just applied for magnetic heads, so that as of now, it is required to take advantage of the TMR elements in the magnetic heads. That is, it is required to design a new magnetic head structure which is not proposed in the past because in using the ferromagnetic tunnel effective film of the TMR element, a current is flown in the stacking direction thereof.
U.S. Pat. Nos. 5,729,410, 5,898,547, 5,898,548 and 5,901,018 disclose conventional magnetic head structures using the TMR elements which are improved in order to realize their super high density recording. However, the requirement for the super high density recording in the TMR magnetic heads are increased, and recently, high-performance TMR magnetic heads are desired.
For example, in using the TMR element as a reading element of a thin film magnetic head, the tunnel barrier layer made of a thin insulating layer is exposed to a surface to be polished causes electric short circuit unfavorably in polishing step or after the polishing step. In order to remove the above matter, the inventors have proposed a flux-probe type TMR structure (Japanese Patent Application No. 11-188472), in which the ferro-magnetic tunnel effective film is arranged so as to recede the edge portion thereof from the surface to be polished, and the edge portion of the soft magnetic film directly connecting to the ferromagnetic tunnel film is drawn out, as a flux-probe portion, to the surface to be polished. In this way, the flux probe portion is made of the soft magnetic layer different from the ferro-magnetic tunnel effective film in size. Moreover, the flux-probe portion may be made of the part of the free layer of the ferromagnetic tunnel effective film.
The soft magnetic film to constitute the flux-probe portion also functions as a bias magnetic field-inductive portion to apply a longitudinal bias magnetic field from a hard magnet or an antiferromagnetic body to the free layer of the ferromagnetic magnetic tunnel effective film.
However, if the hard magnet or the like is contacted to the edge portion of the ferromagnetic tunnel effective film, an electric short circuit may occur between the ferromagnetic films due to the stacking structure thereof, so that the TMR change ratio is degraded.
On the contrary, if the hard magnet is contacted to either of the upper ferromagnetic film or the lower ferromagnetic film, the electric short circuit may not occur. However, a current is flown though the hard magnet, so that the TMR change ratio is degraded.
To avoid the above matter, the inventors have proposed the TMR structure in which the flux-probe is composed of a T-shaped soft magnetic film, and thus, the base portion of the flux-probe portion is elongated in a track width direction and has wider than the ferromagnetic tunnel effective film, and the hard magnet or the antiferromagnetic layer is formed at the both edges of the ferromagnetic tunnel effective film (Japanese Patent Application No. 11-171869).
Meanwhile, magnetic recording patterns in magnetic media are reduced with the development of the recording density and thus, it is required to reduce the size of the TMR element to be mounted on a reproducing head. For example, in order to realize a recording density of 40 Gbspi, the TMR element should be reduced to the size of about 0.4×0.4 (&mgr;m
2
). Such a minute TMR element can be made by patterning a metal film by ion milling with using a minute mask made by photolithography.
As mentioned above, however, if the flux-probe and the bias magnetic field-inductive portion are made of one soft magnetic film, the corner portion of the flux-probe is made round by the photolithography technique as the TMR element is milled to be miniaturized. In the case of using the TMR element as a reading element of a thin film magnetic element, since the reproducing track width is defined by the flux-probe width, the rounded corner portion of the flux-probe may cause the fluctuation in the track width unfavorably.
In order to avoid the above matter, EB exposing technique, etc. should be employed, but has very slow throughput and requires an expensive apparatus.
Moreover, the TMR element may be made of a rectangular soft magnetic film larger than the TMR element, instead of the above T-shaped soft magnetic film, but in this case, it is impossible to reduce the track width to a smaller size than the TMR element.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a TMR element, a thin film magnetic head, a magnetic head device and a magnetic disk drive device which are applicable for super high density recording.
It is an also object of the present invention to provide a TMR element, a thin film magnetic head, a magnetic head device and a magnetic disk drive device which can have their respective high precise reading track widths.
To iron out the above matters, a TMR element according to the present invention includes a ferromagnetic tunnel effective film, a bias magnetic field-inductive layer and a flux guide layer.
The ferromagnetic tunnel effective film includes a tunnel barrier layer, a free layer and a pinned layer, and the tunnel barrier layer is sandwiched between the free layer and the pinned layer.
The bias magnetic field-inductive layer applies a given bias magnetic field to the free layer, and has its larger width than that of the ferromagnetic tunnel effective film.
The flux guide layer is stacked with the bias magnetic field-inductive layer so that the long direction of the flux guide layer is crossed to the bias magnetic field from the bias magnetic field-inductive layer, and magnetically combined to the free layer. One end of the flux guide layer constitutes a flux probe portion which has its smaller width than that of the bias magnetic field-inductive layer as viewed from the bias magnetic field direction and projects from the ends of the bias magnetic field-inductive layer.
The TMR element according to the present invention has a ferromagnetic tunnel effective film composed of a multilayered structure of a free layer/a tunnel barrier layer/a pinned layer. Then, when a current is flown between the free layer and the pinned layer which sandwich the tunnel barrier layer, a tunnel current in the tunnel barrier layer changes, depending on a relative angle in the magnetizations of the free layer and the pinned layer (TMR effect). The magnetizations direction of the pinned layer is fixed, and the magnetization direction of the free layer changes on an external magnetic field. Therefore, when a current or a current change ratio in the TMR element is measured, the external magnetic field can be detected.
The TMR element according to the present invention includes a bias magnetic field-inductive layer to
Araki Satoru
Kasahara Noriaki
Shimazawa Koji
Dolan Jennifer M
Jr. Carl Whitehead
Oliff & Berridg,e PLC
TDK Corporation
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