United States Patent [19J
`Noguchi et al.
`
`I lllll llllllll Ill lllll lllll lllll lllll lllll 111111111111111111111111111111111
`5,862,022
`Jan. 19, 1999
`
`US005862022A
`[11] Patent Number:
`[45] Date of Patent:
`
`[54] FERROMAGNETIC TUNNEL JUNCTION,
`MAGNETORESISTIVE ELEMENT AND
`:MAGNETIC HEAD
`
`4-103013
`4-103014
`8-21166
`
`4/1992
`4/1992
`3/1996
`
`Japan .
`Japan .
`Japan .
`
`[75]
`
`Inventors: Kiyoshi Noguchi; Taro Oike, both of
`Saku; Satoru Araki, Chiba; Manabu
`Ohta; Masashi Sano, both of Saku, all
`of Japan
`
`[73] Assignee: TDK Corporation, Tokyo, Japan
`
`[21] Appl. No.: 933,347
`
`[22]
`
`Filed:
`
`Sep. 19, 1997
`
`[30]
`
`Foreign Application Priority Data
`
`Sep. 19, 1996
`Dec. 10, 1996
`Mar. 7, 1997
`
`[JP]
`[JP]
`[JP]
`
`Japan . ... ... ... ............. ............. 8-248410
`Japan .................................... 8-330064
`Japan .................................... 9-053065
`
`[51]
`
`Int. Cl.6
`
`............................. GllB 5/39; GllC 11/00;
`HOlL 41i12
`[52] U.S. Cl . ........................... 360/113; 257/421; 365/158
`[ 58] Field of Search ............................. 360/113; 365/158;
`257/421
`
`[ 56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`5,018,037
`5,206,590
`5,729,410
`
`5/1991 Krounbi et al. .
`4/1993 Dieny et al. .
`3/1998 Fontana ................................... 360/113
`
`FOREIGN PAfENT DOCUMENTS
`
`4-42417
`
`2/1992
`
`Japan.
`
`OTHER PUBLICATIONS
`
`T. Miyazaki, et al., "Giant Magnetic Tunneling Effect In
`Fe/Al2 0 3 /Fe Junction", Journal of Magnetism and Mag(cid:173)
`netic Materials 139 (1995), pp. 231-234.
`M. Pomerantz, et al., "Strongly Coupled Ferromagnetic
`Resonances of Fe Films", Journal of Applied Physics, vol.
`61, No. 8, Apr. 15, 1987, pp. 3747-3749.
`S. Maekawa, et al., "Electron Tunneling Between Ferromag(cid:173)
`netic Films", IEEE Transactions on Magnetics, vol.
`MAG-18, No. 2, Mar. 1982, pp. 707-708.
`
`Primary Examiner-A. J. Heinz
`Attorney, Agent, or Firm--Oblon, Spivak, McClelland,
`Maier & Neustadt, P.C.
`
`[57]
`
`ABSTRACT
`
`This invention is directed to a ferromagnetic tunnel junction,
`an MR element and a magnetic head. A ferromagnetic tunnel
`junction is constituted by sequentially laminating a first
`ferromagnetic film, an insulating film and a second ferro(cid:173)
`magnetic film. These are laminated on an appropriate insu(cid:173)
`lating substrate. The present invention is characterized in
`that the barrier potential of the insulating film is set within
`a range of 0.5 to 3 e V. A ferromagnetic tunnel junction with
`which a high MR ratio can be achieved with good repro(cid:173)
`duction characteristics is provided.
`
`52 Claims, 27 Drawing Sheets
`
`e
`
`2
`
`e
`
`212
`
`210
`
`TDK Corporation Exhibit 1014 Page 1
`
`

`
`U.S. Patent
`
`Jan. 19, 1999
`
`Sheet 1of27
`
`5,862,022
`
`e
`
`e
`
`2
`
`212
`
`210
`
`FIG. 1
`
`FIG. 2
`
`TDK Corporation Exhibit 1014 Page 2
`
`

`
`U.S. Patent
`
`Jan. 19, 1999
`
`Sheet 2 of 27
`
`5,862,022
`
`MR ratio (%)
`~----,~H
`
`O H(Oe)
`
`FIG. 3
`
`M(Arb. Units) §
`,
`,
`
`§
`____.,
`•
`-H2
`
`-Hl
`
`H2
`
`I Hl
`
`·e H(Oe)
`
`~
`
`)
`
`FIG.4
`
`TDK Corporation Exhibit 1014 Page 3
`
`

`
`U.S. Patent
`
`Jan. 19, 1999
`
`Sheet 3 of 27
`
`5,862,022
`
`MR ratio (%)
`8
`
`-300
`
`0 0
`H(Oe) Hab
`
`300
`
`FIG. 5
`
`8 ---~\
`_ _._-r-214
`e
`
`e
`
`' \
`
`7
`
`212
`
`210
`
`215
`
`8 ----~
`
`FIG. 6
`
`TDK Corporation Exhibit 1014 Page 4
`
`

`
`U.S. Patent
`
`Jan. 19, 1999
`
`Sheet 4 of 27
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`5,862,022
`
`FIG. 7
`
`210
`
`4
`
`FIG. 8
`
`TDK Corporation Exhibit 1014 Page 5
`
`

`
`U.S. Patent
`
`Jan. 19, 1999
`
`Sheet 5 of 27
`
`5,862,022
`
`M2 /
`
`FIG. 9
`
`TDK Corporation Exhibit 1014 Page 6
`
`

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`U.S. Patent
`
`Jan. 19, 1999
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`Sheet 6 of 27
`
`5,862,022
`
`1 1
`
`e
`
`e
`
`212
`
`210
`
`11 --\
`
`F I G. 1 0
`
`FIG. 11
`
`212
`
`214
`
`211
`
`FIG. 12
`
`TDK Corporation Exhibit 1014 Page 7
`
`

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`U.S. Patent
`
`Jan. 19, 1999
`
`Sheet 7 of 27
`
`5,862,022
`
`MR ratio (%)
`
`-H2
`
`+H2
`FIG. 13
`
`+H6
`
`FIG. 14
`
`-H2
`
`0
`H(Oe)
`
`+H2
`
`TDK Corporation Exhibit 1014 Page 8
`
`

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`U.S. Patent
`
`Jan. 19, 1999
`
`Sheet 8 of 27
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`5,862,022
`
`17 ----\.
`
`---~
`\
`
`\ 16
`
`17 ---·~
`
`FIG. 15
`
`FIG. 16
`
`210
`
`FIG. 17
`
`TDK Corporation Exhibit 1014 Page 9
`
`

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`U.S. Patent
`
`Jan. 19, 1999
`
`Sheet 9 of 27
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`5,862,022
`
`M1
`~
`
`FIG. 18
`
`TDK Corporation Exhibit 1014 Page 10
`
`

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`U.S. Patent
`
`Jan. 19, 1999
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`Sheet 10 of 27
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`5,862,022
`
`21··-·\.
`
`e
`
`212
`
`215
`
`21---:\
`
`FIG. 19
`
`216
`
`FIG. 20
`
`FIG. 21
`
`TDK Corporation Exhibit 1014 Page 11
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`

`
`U.S. Patent
`
`Jan. 19, 1999
`
`Sheet 11 of 27
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`5,862,022
`
`M2 y
`
`FIG. 22
`
`TDK Corporation Exhibit 1014 Page 12
`
`

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`U.S. Patent
`
`Jan. 19, 1999
`
`Sheet 12 of 27
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`5,862,022
`
`11
`
`FIG. 23
`
`TDK Corporation Exhibit 1014 Page 13
`
`

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`U.S. Patent
`
`Jan. 19, 1999
`
`Sheet 13 of 27
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`5,862,022
`
`36
`
`32
`
`13 or
`
`FIG. 24
`
`TDK Corporation Exhibit 1014 Page 14
`
`

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`U.S. Patent
`
`Jan. 19, 1999
`
`Sheet 14 of 27
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`5,862,022
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`TDK Corporation Exhibit 1014 Page 15
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`

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`U.S. Patent
`
`Jan. 19, 1999
`
`Sheet 15 of 27
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`5,862,022
`
`63
`
`62
`
`61
`
`22
`
`FIG.26
`PRIOR ART
`
`--o--Tunnel
`-fr--AMR
`
`52
`72
`23
`
`51
`
`1. 2
`
`1
`o. 8
`o. 6
`
`0.4
`
`o. 2
`
`,,........
`:::J
`co
`'--"
`t-
`::J
`~
`t-
`::J
`0
`c
`UJ
`N
`_J <
`:::I!: a::
`0 :z
`
`0
`
`0
`
`50
`
`250
`150
`100
`200
`RECORDING DENSITY (kFCI)
`
`300
`
`FIG. 27
`
`TDK Corporation Exhibit 1014 Page 16
`
`

`
`U.S. Patent
`
`Jan. 19, 1999
`
`Sheet 16 of 27
`
`5,862,022
`
`FIG. 28
`
`/ 21
`
`210
`
`211
`
`FIG. 29
`
`TDK Corporation Exhibit 1014 Page 17
`
`

`
`U.S. Patent
`
`Jan. 19, 1999
`
`Sheet 17 of 27
`
`5,862,022
`
`FIG. 30
`
`51
`
`\~--101
`
`FIG. 31
`
`i::::;;:::z:z::::;z:::::z;:z::::z:zz:~:z:::::;~:z:z:::;z::::;~:;zz~-71
`51
`
`FIG. 32
`
`TDK Corporation Exhibit 1014 Page 18
`
`

`
`U.S. Patent
`
`Jan. 19, 1999
`
`Sheet 18 of 27
`
`5,862,022
`
`11-E~W~~2ti~~~~W~~-22
`51
`
`FIG. 33
`
`71--E:::z::;::;::z:z:::::z:::::z;::::::.;:::::::::;::::::2:£3t:ti~ZEiZB~~-22
`51
`
`FIG. 34
`
`2 0
`211
`71~~~~~~~~~~~a--22
`51
`
`FIG. 35
`
`TDK Corporation Exhibit 1014 Page 19
`
`

`
`U.S. Patent
`
`Jan. 19, 1999
`
`Sheet 19 of 27
`
`5,862,022
`
`211
`
`212
`
`23
`
`71
`
`FIG. 36
`
`51
`
`\ ;;,__, 01
`FIG. 37
`
`51
`
`\ ..).,_101
`
`FIG. 38
`
`TDK Corporation Exhibit 1014 Page 20
`
`

`
`U.S. Patent
`
`Jan. 19, 1999
`
`Sheet 20 of 27
`
`5,862,022
`
`2 2
`
`23
`
`212
`
`23
`
`72
`
`FIG. 39
`
`FIG.40
`
`TDK Corporation Exhibit 1014 Page 21
`
`

`
`U.S. Patent
`
`Jan. 19, 1999
`
`Sheet 21 of 27
`
`5,862,022
`
`212
`
`23
`
`72
`
`51
`
`\
`
`~101
`
`FIG. 41
`
`X1
`
`212
`
`34
`
`I
`
`X1
`
`FIG.42
`
`TDK Corporation Exhibit 1014 Page 22
`
`

`
`U.S. Patent
`
`Jan. 19, 1999
`
`Sheet 22 of 27
`
`5,862,022
`
`44
`
`FIG. 43
`
`TDK Corporation Exhibit 1014 Page 23
`
`

`
`U.S. Patent
`
`Jan. 19, 1999
`
`Sheet 23 of 27
`
`5,862,022
`
`51
`
`71
`
`211
`
`210
`
`FIG.44
`
`212 72
`
`52
`
`FIG.45
`
`TDK Corporation Exhibit 1014 Page 24
`
`

`
`U.S. Patent
`
`Jan. 19, 1999
`
`Sheet 24 of 27
`
`5,862,022
`
`FIG.46
`
`FIG.47
`
`TDK Corporation Exhibit 1014 Page 25
`
`

`
`U.S. Patent
`
`Jan. 19, 1999
`
`Sheet 25 of 27
`
`5,862,022
`
`V(arb. unit)
`
`V (a rb. uni t)
`
`H(Oe)
`
`FIG.48
`
`H(Oe)
`
`FIG.49
`
`TDK Corporation Exhibit 1014 Page 26
`
`

`
`U.S. Patent
`
`Jan. 19, 1999
`
`Sheet 26 of 27
`
`5,862,022
`
`-
`
`-
`
`'-
`
`'-
`
`,,-...
`+-'
`c
`::l
`...0
`'-
`ca
`'-'
`ca
`c
`O'> ·-en
`
`j
`
`l
`
`J
`
`l
`
`1
`
`f
`
`l
`
`I
`
`J l
`
`Time
`
`-.
`FIG. 50
`
`Time-----
`
`FIG. 51
`
`TDK Corporation Exhibit 1014 Page 27
`
`

`
`U.S. Patent
`
`Jan. 19, 1999
`
`Sheet 27 of 27
`
`5,862,022
`
`IJ,\
`
`I
`
`I
`I
`
`,, r1
`
`I
`
`I
`
`--
`--
`--
`--
`
`'\
`
`I
`
`.~
`I
`
`I
`I
`
`I
`
`'\1
`
`Time----
`
`FIG. 52
`
`TDK Corporation Exhibit 1014 Page 28
`
`

`
`1
`FERROMAGNETIC TUNNEL JUNCTION,
`MAGNETORESISTIVE ELEMENT AND
`:MAGNETIC HEAD
`
`5,862,022
`
`15
`
`BACKGROUND OF THE INVENTION
`1. Field of the Invention
`The present invention relates to a ferromagnetic tunnel
`junction, a magnetoresistive element (hereafter referred to as
`MR element) which employs the ferromagnetic tunnel junc(cid:173)
`tion as a sensing portion and it also relates to a magnetic 10
`head employing this element.
`2. Discussion of Background
`Magnetoresistive heads (hereafter referred to as MR
`heads) that utilize the anisotropic magnetoresistance
`(hereafter referred to as AMR) effect are in commercial
`production as magnetic heads for high density magnetic
`recording. However, since an AMR head typically employs
`an AMR effect film such as NiFe to constitute the magnetic
`film, its magnetoresistive ratio (hereafter referred to as MR
`ratio) and sensitivity are low, at approximately 2% and
`0.5%/0e respectively. Therefore, development of magne(cid:173)
`toresistive films (hereafter referred to as MR films) with a
`higher MR ratio and a higher sensitivity is required.
`As a technology that will meet this requirement, a new
`phenomenon, i.e., the giant magnetoresistance effect
`(hereafter referred to as GMR effect), has come to light in
`recent years and since it affords a greater MR ratio compared
`to the AMR effect film in the prior art, much research into
`this phenomenon has been conducted. In particular, the 30
`GMR effect achieved by utilizing a spin valve (SV) film has
`become the focus of great interest. Since a spin valve film
`with a film structure constituted of ferromagnetic film/non(cid:173)
`magnetic metallic film/ferromagnetic film/antiferromagnetic
`film, which creates the GMR effect, demonstrates charac- 35
`teristics with a high degree of sensitivity, at 2 to 5%/0e, it
`is thought to have potential as a reproduction element in a
`next generation magnetic head and further research has
`commenced toward achieving practical utilization thereof.
`Apart from the GMR effect, the phenomenon knov.'11 as 40
`the ferromagnetic tunneling effect, whereby a tunneling
`effect manifests depending upon the relative angles of
`magnetization of two ferromagnetic films in a junction
`constituted of a ferromagnetic film/insulating film/
`ferromagnetic film, is of interest and research into develop- 45
`ment of an MR element utilizing this phenomena has been
`in progress. Since a ferromagnetic tunneling effect film
`provides an extremely high degree of magnetic field
`sensitivity, it has potential to be adopted as a reproduction
`magnetic head in ultra high density magnetic recording on 50
`the order of 10 Gbit/inch2
`. In IEEE Trans. Magn., MAG-18,
`707 (1982), S. Maekawa, V. Gafvert et. al. demonstrated
`theoretically and through experiment that the manifestation
`of the tunneling effect depends upon the relative angles of
`magnetization of the two magnetic films in a magnetic 55
`film/insulating film/magnetic film junction.
`Japanese Unexamined Patent Publication (KOKAI) No.
`42417/1992 discloses a magnetic head provided with a
`ferromagnetic tunneling effect film capable of detecting
`minute changes in leaked magnetic flux with a higher degree 60
`of sensitivity and a higher degree of resolution than an MR
`head in the prior art and also discloses that the reproduction
`sensitivity can be further improved by reducing the junction
`area to reduce the incidence of pinhole formation in the
`insulating film.
`In addition, Japanese Unexamined Patent Publication
`(KOKAI) No. 103014/1992 discloses a ferromagnetic tun-
`
`2
`neling effect film that applies a bias magnetic field from an
`antiferromagnetic film to a magnetic film and a magnetic
`head employing this ferromagnetic tunneling effect film.
`Furthermore, T. Miyazaki, N. Tezuka et. al. report in J.
`5 Magn. Magn. Mater. 139 (1995) L231 that an MR ratio of
`18% was achieved at room temperature in an Fe/Al2 0iFe
`tunnel junction. In addition, M. Pomerantz, J. C.
`Sloczewski, E. Spiller et.al. disclose an Fe/a-Carbon/Fe film.
`There are a number of problems that have yet to be
`addressed in the various types of ferromagnetic tunnel
`junctions that have been disclosed to date.
`Publications on the known art such as Japanese Unexam(cid:173)
`ined Patent Publication (KOKAI) No. 42417/1992, for
`instance, disclose several means for detecting minute
`changes in a magnetic flux with a high degree of sensitivity
`by employing an MR element provided with a ferromagnetic
`tunneling effect film in order to achieve a high, stable output.
`In one of such means, one of a pair of magnetic films
`constituting an MR film with a multilayer structure, namely,
`20 the magnetic film whose direction of magnetization changes
`due to leak magnetic flux from the medium, is required to
`have a reduced anisotropic dispersion angle and to have a
`single magnetic domain to ensure that the magnetization
`rotation occurs entirely and at once. To be more specific, a
`25 single magnetic domain is achieved by inserting an inter(cid:173)
`mediate film such as BN in the magnetic film.
`However, even with a film with a small anisotropic
`dispersion angle formed in this manner, there is still a
`problem in that when the film is patterned to a size of several
`,um to be operated in a high frequency magnetic field at or
`above several tens of MHz, disturbance in units of microns
`in the spinning direction occurs at the end portions of the
`finely patterned film, thereby forming a magnetic domain
`wall, which, in turn, disrupts the single magnetic domain
`structure and results in Barkhausen noise and the like.
`Next, in regard to the AMR magnetic head and the spin
`valve GMR magnetic heads in the prior art, a method for
`preventing Barkhausen noise by forming a magnetic domain
`control film at the two end portions of the MR film to apply
`a longitudinal bias has been disclosed (prior art publications:
`U.S. Pat. No. 5,018,037 and Japanese Examined Patent
`Publication No. 21166/1996). In these structures, the mag(cid:173)
`netic domain control films are formed in direct contact with
`the areas of the two end portions of the entire sensing
`portion, since as an AMR head or a spin valve GMR head
`is used with the current being supplied in a direction parallel
`to the surface of the MR element, no problem is posed in
`practical use, even if the magnetic domain control films are
`in contact with the two end portions of the sensing portion.
`However, in a ferromagnetic tunnel junction in which a
`first ferromagnetic film, an insulating film and a second
`ferromagnetic film are laminated in the vertical direction, a
`change in magnetoresistance occurs because of a tunnel
`current flowing in the direction of the lamination. Thus, if
`bias magnetic layers for magnetic domain control are placed
`in contact with the overall end portions of the sensing
`portion as in the prior art, the upper and lower ferromagnetic
`films, which are separated by the insulating film, become
`electrically shorted, cutting off the tunnel current and,
`consequently, no magnetoresistance change is achieved.
`In order to adopt a shield type magnetic head in high
`density recording/reproduction, it is necessary to reduce the
`distance between the shield<> at the ABS. In a shield type
`65 magnetic head, an insulating film constituted of alumina and
`so on, for instance, is normally provided in order to maintain
`insulation between the ferromagnetic tunnel junction and the
`
`TDK Corporation Exhibit 1014 Page 29
`
`

`
`5,862,022
`
`3
`shield films in addition to the ferromagnetic tunnel junction
`between the shields.
`Consequently, in order to reduce the distance between the
`shield<>, the thicknesses of the insulating film and the ferro(cid:173)
`magnetic tunnel junction must be set as small as possible.
`However, if the electrode film is made to be exposed at the
`ABS as disclosed in the publications on the known art, even
`with the thicknesses of the insulating film and the ferromag(cid:173)
`netic tunnel junction reduced, a certain distance is still
`required between the electrode film and the shield films, 10
`constituting an obstacle to reduction of the shield distance
`and, therefore, it is not suited for high density recording/
`reproduction.
`In the publications on the known art, the area over which
`the electrode film is provided is large to ensure that all
`current runs through the ferromagnetic tunnel junction.
`However, since it is necessary to assure resisting voltage
`equal to or greater than a specific level between the ferro(cid:173)
`magnetic tunnel junction and the shield films, if the elec(cid:173)
`trode film is made to be exposed at the ABS taking up a large 20
`area, as disclosed in the publications on the known art,
`dielectric breakdown due to static electricity tends to occur,
`and therefore it is not desirable.
`It is to be noted that the ferromagnetic tunnel junction
`according to the present invention is the same as the ferro(cid:173)
`magnetic tunneling effect film described above.
`
`4
`It is assumed that another contributing factor is a stable
`antiferromagnetically coupling between the first ferromag(cid:173)
`netic film and the second ferromagnetic film via the insu(cid:173)
`lating film within the barrier potential range described
`s above. Particularly advantageous results are achieved when
`the barrier potential is maintained within a range of 1.5 to
`2.5 eV.
`When the barrier potential exceeds 3 e V, a high MR ratio
`cannot be achieved. Although the reason for this is not yet
`clear, it is thought to be due to the fact that the tunnel current
`stops running when the barrier potential exceeds 3 e V.
`When the barrier potential falls below 0.5 e V, a high MR
`ratio, which is expected of this type of ferromagnetic tunnel
`junction, cannot be achieved. The reason for this is thought
`15 to be degradation in the uniformity of the insulating film
`with an increasing the number of pinholes.
`Now, the stable antiferromagnetically coupling formed
`between the first ferromagnetic film and the second ferro(cid:173)
`magnetic film via the insulating film within the barrier
`potential range of 0.5 to 3 e V in this ferromagnetic tunnel
`junction offers a great advantage when it is adopted as a read
`magnetic conversion element in a magnetic head.
`When antiferromagnetically coupling is generated, the
`25 magnetic field-magnetoresistance curves achieve the highest
`values for MR ratio in the area in the vicinity of zero
`magnetic field. Consequently, when this ferromagnetic tun(cid:173)
`nel junction is employed for a magnetic conversion read
`element in a magnetic head, a linear area is obtained in the
`30 vicinity of the zero magnetic field simply as a shape effect
`without having to apply a bias magnetic field. Thus, the
`structure of the magnetic head can be simplified.
`The MR element according to the present invention
`employs the ferromagnetic tunnel junction described above
`35 as a sensing portion. Consequently, it is possible to provide
`an MR element that can achieve a high MR ratio while also
`achieving simplification of the structure.
`The MR element according to the present invention is
`desirably provided \vith magnetic domain control films. The
`magnetic domain control films are provided adjacent to the
`two end portions of either the first ferromagnetic film or the
`second ferromagnetic film.
`Since, as described above, the magnetic domain control
`films are provided adjacent to the two end portions of either
`the first ferromagnetic film or the second ferromagnetic film,
`there is no room for an electrical short to occur between the
`first ferromagnetic film and the second ferromagnetic film.
`As a result, it is possible to supply a sufficiently large tunnel
`current to the ferromagnetic tunnel junction. Thus, a large
`50 MR ratio is achieved.
`Furthermore, with the magnetic domain control film, the
`ferromagnetic film provided with the magnetic domain
`control film can be set in a state of a single magnetic domain.
`55 This prevents Barkhausen noise which causes distortion in
`the output waveform, thereby achieving a noiseless and
`stable output.
`It is desirable that either of the first ferromagnetic film or
`the second ferromagnetic film, the ferromagnetic film with-
`60 out the magnetic domain control films is provided with a
`magnetization pinning film.
`This structure, in which either the first ferromagnetic film
`or the second ferromagnetic film constitutes a pinned fer(cid:173)
`romagnetic film provided with a magnetization pinning film
`and the other ferromagnetic film is made to operate as a free
`ferromagnetic film, allows the relative angle of the direction
`of magnetization of the first ferromagnetic film and the
`
`40
`
`SUMMARY OF THE INVENTION
`It is an object of the present invention to provide a
`ferromagnetic tunnel junction that can achieve a high MR
`ratio while also achieving good reproduction characteristics.
`It is a further object of the present invention to provide a
`ferromagnetic tunnel junction that, applied in an MR
`element, a magnetic head or the like, allows simplification of
`the overall structure.
`It is a still further object of the present invention to
`provide an MR element in which a sufficiently large tunnel
`current can be supplied to the ferromagnetic tunnel junction
`to achieve a high MR ratio.
`It is a still further object of the present invention to
`provide an MR element that achieves a good output wave(cid:173)
`form without distortion.
`It is a still further object of the present invention to
`provide an MR element that is capable of achieving a stable 45
`output without noise.
`It is a still further object of the present invention to
`provide a ferromagnetic tunnel junction type magnetic head
`that achieves a reduction in the distance between the shields
`and is suited for high density recording/reproduction.
`It is a still further object of the present invention to
`provide a ferromagnetic tunnel junction type magnetic head
`that effectively prevents dielectric breakdown which would
`occur between the electrode film and the shield films.
`In order to achieve the objects described above, according
`to the present invention, in a ferromagnetic tunnel junction
`constituted by sequentially laminating a first ferromagnetic
`film, an insulating film and a second ferromagnetic film, the
`barrier potential of the insulating film is set within a range
`of 0.5 to 3 eV.
`In the case of the present invention, in which the barrier
`potential is set within the range of 0.5 to 3 eV, a high MR
`ratio is achieved while al<>o achieving good reproduction
`characteristics. It is assumed that one of the reasons for this
`is that by maintaining the barrier potential within the range 65
`of 0.5 to 3 eV, formation of a consistent insulating film 210
`with an extremely small number of pinholes is assured.
`
`TDK Corporation Exhibit 1014 Page 30
`
`

`
`5,862,022
`
`s
`
`5
`direction of magnetization of the second ferromagnetic film
`to be changed simply by moving the direction of magneti(cid:173)
`zation of the free ferromagnetic film. In this case, it is
`preferable to set the directions so that the magnetic easy axis
`of the free ferromagnetic film is perpendicular to the exter-
`nal magnetic field and the magnetic easy axis of the pinned
`ferromagnetic film is parallel to the external magnetic field.
`Since this sets the direction of magnetization of the free
`ferromagnetic film and the direction of magnetization of the
`pinned ferromagnetic film perpendicular to each other when 10
`the external magnetic field is at zero, an output waveform
`with good symmetry is achieved. Furthermore, since the
`direction of magnetization of the free ferromagnetic film is
`changed in the magnetization rotation mode by an external
`magnetic field, a high degree of sensitivity is achieved and, 15
`at the same time, smooth magnetization reversal is executed,
`thereby reducing generation of Barkhausen noise resulting
`from the magnetic domain wall motion.
`The magnetic head according to the present invention
`comprises a slider and at least one magnetic conversion 20
`element. The slider is provided with an air bearing surface
`at the side facing opposite the magnetic recording medium.
`The magnetic conversion element includes the ferromag(cid:173)
`netic tunnel junction described above and an electrode film,
`and is supported by an insulating film that constitutes a 25
`portion of the slider.
`The ferromagnetic tunnel junction includes an insulating
`film, a first ferromagnetic film and a second ferromagnetic
`film. The first ferromagnetic film and the second ferromag-
`netic film are laminated via the insulating film.
`The electrode film includes a first electrode film and a
`second electrode film, with the first electrode film connected
`to the first ferromagnetic film and the second electrode film
`connected to the second ferromagnetic film. The first elec(cid:173)
`trode film and the second electrode film are provided so that
`they are not exposed at the air bearing surface.
`It has been learned that by achieving a structure in which
`the first electrode film and the second electrode film are not
`exposed at the ABS as described above, electrostatic break(cid:173)
`down becomes less likely to occur at the magnetic shield
`films and the ferromagnetic tunnel junction and, in
`particular, between the first electrode film and the second
`electrode film, improving the resisting voltage characteris(cid:173)
`tics.
`Furthermore, since the distance between the magnetic
`shield films and the ferromagnetic tunnel junction that
`constitutes the sensing portion can be reduced at the ABS,
`higher density recording/reproduction compared to the prior
`art becomes possible.
`
`30
`
`6
`FIG. 9 is a diagram illustrating the operation of the tunnel
`junction portion in the MR element shown in FIGS. 6 to 8;
`FIG. 10 is a perspective schematically showing another
`embodiment of the MR element according to the present
`invention;
`FIG. 11 is a cross section along line 11-11 in FIG. 10
`FIG. 12 is a cross section schematically showing another
`embodiment of the MR element according to the present
`invention;
`FIG.13 shows the magnetic field-MR ratio characteristics
`achieved when a soft ferromagnetic film with low coercivity
`is employed to constitute the free ferromagnetic film and
`when a hard ferromagnetic film with high coercivity is used
`to constitute the pinned ferromagnetic film;
`FIG. 14 shows the magnetic field-MR ratio characteristics
`achieved when a soft ferromagnetic film is employed to
`constitute both the free ferromagnetic film and the pinned
`ferromagnetic film with a magnetization pinning film lami(cid:173)
`nated adjacent to the pinned ferromagnetic film.
`FIG. 15 is a cross section showing another example of the
`ferromagnetic tunnel junction in the MR element according
`to the present invention;
`FIG. 16 is a cross section along line 17-17 in FIG. 15;
`FIG. 17 is a cross section along line 16-16 in FIG. 15;
`FIG. 18 is a diagram illustrating the operation of the
`tunnel junction portion in the MR element shown in FIGS.
`15 to 17
`FIG. 19 is a cross section showing another example of the
`ferromagnetic tunnel junction in the magnetic head accord(cid:173)
`ing to the present invention;
`FIG. 20 is a cross section along line 21-21 in FIG. 19;
`FIG. 21 is a cross section along line 20-20 in FIG. 19;
`FIG. 22 is a diagram illustrating the operation of the
`tunnel junction portion in the MR element shown in FIGS.
`35 19 to 21.
`FIG. 23 is a perspective of the magnetic head according
`to the present invention;
`FIG. 24 is an enlarged cross section of the magnetic
`conversion element portion of the magnetic head shown in
`40 FIG. 23;
`FIG. 25 is a perspective schematically showing the struc(cid:173)
`ture of a magnetic head employing the ferromagnetic tunnel
`junction according to the present invention;
`FIG. 26 is a cross section illustrating the structure of a
`45 magnetic head in the prior art which utilizes the AMR effect;
`FIG. 27 shows the reproduction characteristics of the
`reproduction magnetic head according to the present inven(cid:173)
`tion and the AMR head in the prior art;
`FIG. 28 is an enlarged cross section of the MR element
`50 portion;
`FIG. 29 is an enlarged perspective of the MR element;
`FIG. 30 is a diagram illustrating the method for manu(cid:173)
`facturing the magnetic head according to the present inven-
`55 tion;
`FIG. 31 is a diagram illustrating the method for manu(cid:173)
`facturing the magnetic head according to the present
`invention, showing a process following the process shown in
`FIG. 30;
`FIG . 32 is a diagram illustrating the method for manu(cid:173)
`facturing the magnetic head according to the present
`invention, showing a process following the process shov.'11 in
`FIG. 31;
`FIG. 33 is a diagram illustrating the method for manu-
`65 facturing the magnetic head according to the present
`invention, showing a process following the process shown in
`FIG. 32;
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a perspective schematically illustrating the
`ferromagnetic tunnel junction according to the present
`invention;
`FIG. 2 is a cross section along line 2 to 2 in FIG. 1;
`FIG. 3 shows the MR ratio characteristics in the ferro(cid:173)
`magnetic tunnel junction;
`FIG. 4 shows the magnetization curves in the ferromag-
`netic tunnel junction;
`FIG. 5 shows the MR ratio characteristics in the ferro-
`magnetic tunnel junction according to the present invention;
`FIG. 6 is a perspective schematically showing the MR
`element according to the present invention;
`FIG. 7 is a cross section along line 8-8 in FIG. 6;
`FIG. 8 is a cross section along line 7-7 in FIG. 6;
`
`60
`
`TDK Corporation Exhibit 1014 Page 31
`
`

`
`5,862,022
`
`8
`insulating film 210 and a second ferromagnetic film 212.
`These are laminated on an appropriate insulating substrate 4.
`The present invention is characterized in that the barrier
`potential of the insulating film 210 is set within a range of
`s 0.5 to 3 eV.
`In a ferromagnetic tunnel junction, when an electron e
`passes from the first ferromagnetic film 211 via the insulat(cid:173)
`ing film 210 through the second ferromagnetic film 212
`while maintaining the direction of its spin (see FIGS. 1 and
`10 2), the transmittance of the electron e is determined based
`upon the amplitude square ratio of the incident wave and the
`transmitted wave by using a wave function which is deter(cid:173)
`mined taking into consideration the spin. Its tunnel conduc-
`tance G is expressed as:
`
`G~Go'(1 +Pl'-P2')cos 6
`
`In this expression;
`
`Pl'~[(Kl t-Kli)/((Kl t+KltJ)a1
`
`P2'=[(K2 f-K2t )/((K2 f +K2!)]a.2
`
`GO' : constant determined the wave number Kl f, Kl ! ,
`K2 f, K2 t of the electron and the barrier potential
`level within the two ferromagnetic films
`a.1, a.2: coefficients that are dependent upon the barrier
`potential heights;
`Pl', P2': effective spin polarizations of the two ferromag(cid:173)
`netic films 1 and 2 and
`Pl', P2': spin polarizations (fractional portions in the
`effective spin polarizations Pl', P2') of the two ferro(cid:173)
`magnetic films 1 and 2. The rate of change ti.GIGO in
`tunnel conductance is expressed as;
`
`~G/G-0~2·Pl'-P2'
`
`25
`
`35
`
`7
`F1G. 34 is a diagram illustrating the method for manu(cid:173)
`facturing the magnetic head according to the present
`invention, showing a process following the process shown in
`FIG. 33;
`F1G . 35 is a diagram illustrating the method for manu(cid:173)
`facturing the magnetic head according to the present
`invention, showing a process following the process shown in
`FIG. 34;
`F1G. 36 is a diagram illustrating the method for manu(cid:173)
`facturing the magnetic head according to the present
`invention, showing a process following the process shown in
`FIG. 35;
`FIG. 37 is a diagram illustrating the method for manu(cid:173)
`facturing the magnetic head according to the present 15
`invention, showing a process following the process shown in
`FIG. 36;
`FIG. 38 is a diagram illustrating the method for manu(cid:173)
`facturing the magnetic head according to the present
`invention, showing a process following the process shown in 20
`FIG. 37;
`FIG. 39 is a diagram illustrating the method for manu(cid:173)
`facturing the magnetic head according to the present
`invention, showing a process following the process shown in
`FIG. 38;
`F1G . 40 is a diagram illustrating the method for manu(cid:173)
`facturing the magnetic head according to the present
`invention, showing a process following the process shown in
`FIG. 39;
`F1G. 41 is a diagram illustrating the method for manu- 30
`facturing the magnetic head according to the present
`invention, showing a process following the process shown in
`FIG. 40;
`FIG. 42 is a diagram illustrating the method for manu-
`facturing the magnetic head according to the present
`invention, showing a process following the process shown in
`FIG. 41;
`F1G. 43 is an enlarged perspective showing another
`example of an MR element;
`F1G. 44 is a cross section along line 44--44 in FIG.