JP2004334921A - Magnetoresistive effect magnetic head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the corrosion resistance of a magnetoresistive effect magnetic head and maintain a high magnetoresistive effect rate. <P>SOLUTION: In the magnetoresistive effect magnetic head 20, the magnetization fixing layer of a spin valve film 40 is a laminated ferrimagnetism fixing layer. In this case, the material of an antiferromagnetic coupled layers which is sandwiched between the magnetization fixing layers is specified, and the corrosion potential of the spin valve film 40 is +0.4(V vs SHE) or larger to a standard hydrogen electrode when measured in a 0.1 mol/L NaCl solution. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０１１８】
表１に示すように、反強磁性結合層４７をＲｕ、Ｒｈ、Ｉｒによって形成したサンプル１〜３においては、いずれも目視試験により表面に腐食が確認されず、濃度０．１ｍｏｌ／ＬのＮａＣｌ溶液中に液浸されたときに測定される標準水素電極に対する腐食電位が＋０．４〔Ｖ ｖｓ ＳＨＥ〕以上であり、また腐食試験前後における抵抗変化がなく、極めて耐食性に優れていることがわかった。
【０１１９】
なお、反強磁性層結合層４７はＲｕ、Ｒｈ、Ｉｒ、及びこれらの合金からなる群から選択された材料に、Ａｌ、Ｔａ、Ｉｎ、Ｂ、Ｎｂ、Ｈｆ、Ｍｏ、Ｗ、Ｒｅ、Ｐｔ、Ｐｄ，Ｇａ、Ｚｒ、Ｉｒ、Ａｇ、Ｎｉ、Ｃｒから選ばれる少なくとも一種または二種以上の元素が添加されたものであってもよい。
【０１２０】
反強磁性結合層４７の膜厚は、０．３〜１．５ｎｍであることが好ましく、更には、０．５〜１．１ｎｍであることが望ましい。反強磁性結合膜４７の膜厚が０．３ｎｍ未満であると、磁化固定層４３Ａ、４３Ｂが反強磁性的に交換結合しなくなる。一方、反強磁性結合層４７が１．５ｎｍよりも厚く形成されていると、反強磁性的に交換結合しなくなり、ノイズの原因となる。
【０１２１】
なお、本発明は、例えば磁気抵抗効果型磁気ヘッド上に、電磁誘導を利用したインダクティブ型磁気ヘッドが積層されてなる複合型磁気ヘッドにも適用可能である。
また、本発明は、絶縁層を介して一対の磁性層を積層し、一方の磁性層から他方の磁性層に流れるトンネル電流のコンダクタンスが一対の磁性層の磁化の相対角度に依存して変化する磁気トンネル接合素子を備える磁気トンネル効果型磁気ヘッドにも適用可能である。
【０１２２】
【発明の効果】
本発明によれば、スピンバルブ膜の磁化固定層を、積層フェリ固定層とした構成を有する磁気抵抗効果型磁気ヘッドに関し、高記録密度化にともないトラック幅を狭くし磁化自由層を薄くしたときも、磁化固定層からの漏洩磁界を抑制することができ、さらには、スピンバルブ膜を構成し磁化固定層に介在されている反強磁性結合層の材料を選定し、スピンバルブ膜について、濃度０．１ｍｏｌ／ＬのＮａＣｌ溶液中に液浸されたときに測定される標準水素電極に対する腐食電位を、＋０．４〔Ｖ ｖｓ ＳＨＥ〕以上であるものとしたことにより、優れた耐食性が実現でき、かつ高い磁気抵抗効果を得られ、テープストリーマに適用する場合において、磁気記録媒体と摺接される面に保護膜を形成しなくても、優れた耐食性が実現できた。
【図面の簡単な説明】
【図１】磁気テープ用の記録再生装置の概略平面図を示す。
【図２】記録再生装置を構成するヘッドドラムの概略斜視図を示す。
【図３】本発明の磁気抵抗効果型磁気ヘッドの概略斜視図を示す。
【図４】ＧＭＲヘッドを媒体摺接面側から見た端面図を示す。
【図５】（ａ） ボトム型積層フェリ型スピンバルブ膜の概略断面図を示す。
（ｂ） トップ型積層フェリ型スピンバルブ膜の概略断面図を示す。
【図６】腐食電位の定義についての説明図を示す。
【図７】腐食電位と腐食試験前後の抵抗変化率との関係、及び表面観察結果を示す。
【図８】非磁性層をＡｕ、ＣｕＡｕとしたときの組成比と標準水素電極に対する腐食電位との関係を示す。
【図９】非磁性層をＣｕＡｕとしたときの組成比と、腐食試験前後の抵抗変化率、表面観察結果を示す。
【図１０】非磁性層をＣｕＰｄとしたときの組成比と標準水素電極に対する腐食電位との関係を示す。
【図１１】非磁性層をＣｕＰｄとしたときの組成比と、腐食試験前後の抵抗変化率と表面観察結果、電気抵抗測定結果の特性図を示す。
【図１２】非磁性層をＣｕＰｔとしたときの組成比と標準水素電極に対する腐食電位との関係を示す。
【図１３】非磁性層をＣｕＰｔとしたときの組成比と、腐食試験前後の抵抗変化率と表面観察結果、電気抵抗測定結果の特性図を示す。
【図１４】非磁性層をＣｕＲｕとしたときの組成比と標準水素電極に対する腐食電位との関係を示す。
【図１５】非磁性層をＣｕＲｕとしたときの組成比と、腐食試験前後の抵抗変化率と表面観察結果、電気抵抗測定結果の特性図を示す。
【図１６】非磁性層をＣｕＮｉとしたときの組成比と標準水素電極に対する腐食電位との関係を示す。
【図１７】非磁性層をＣｕＮｉとしたときの組成比と、腐食試験前後の抵抗変化率、表面観察結果、電気抵抗測定結果との関係図を示す。
【図１８】非磁性層をＣｕＲｈとしたときの組成比と標準水素電極に対する腐食電位との関係を示す。
【図１９】非磁性層をＣｕＲｈとしたときの組成比と、腐食試験前後の抵抗変化率、表面観察結果の特性図を示す。
【図２０】非磁性層をＣｕＲｈとしたときの組成比と電気抵抗の特性図を示す。
【図２１】磁化固定層及び磁化自由層に関して、組成比を変化させた場合の腐食試験結果を示す。
【図２２】磁化固定層及び磁化自由層に関して、腐食を効果的に防止する好適な組成比の範囲を示す。
【符号の説明】
１……磁気テープ装置、２……磁気テープ、３……供給リール、４……巻取リール、５ａ〜５ｆ……ガイドローラ、５ｇ……ピンチローラ、６……キャップスタン、６ａ……キャップスタンモータ、７……ヘッドドラム、８……駆動モータ、９……回転ドラム、１０……固定ドラム、１１ａ，１１ｂ……記録用磁気ヘッド、１２ａ，１２ｂ……再生用磁気ヘッド、２０……ＧＭＲヘッド、２１……第１のコア部材、２２……保護膜、２３……第２のコア部材、２４，２５……磁気シールド層、２６……ギャップ層、２７……ＧＭＲ素子、２８ａ，２８ｂ……永久磁石膜、２９ａ，２９ｂ……低抵抗化膜、３０ａ，３０ｂ……導体部、３１ａ，３１ｂ……外部接続用端子、４０……スピンバルブ膜、４１……下地層、４２……反強磁性層、４３Ａ……磁化固定層、４３Ｂ……磁化固定層、４４……非磁性層、４５……磁化自由層、４６……保護層、４７……反強磁性結合層[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a magnetoresistive head using a spin valve film as a magnetic sensing element for detecting a magnetic signal while sliding on a magnetic recording medium.
[0002]
[Prior art]
2. Description of the Related Art A magnetoresistive element (hereinafter, referred to as an MR element) utilizes a so-called magnetoresistive effect in which a resistance value changes depending on the magnitude and direction of an external magnetic field, and detects, for example, a signal magnetic field from a magnetic recording medium. Used in a magnetic head or the like as a magnetic sensing element.
A magnetic head having such an MR element is generally called a magnetoresistive head (hereinafter, referred to as an MR head).
[0003]
As such an MR element, an element utilizing the anisotropic magnetoresistance effect has been conventionally used, but an element exhibiting a larger MR ratio is desired because the magnetoresistance ratio (MR ratio) is small. In recent years, a giant magnetoresistance effect element (hereinafter, referred to as a GMR element) using a spin valve film has been proposed (for example, see Non-Patent Document 1 and Patent Document 1).
[0004]
The GMR element has a spin-valve film in which a non-magnetic layer is sandwiched between a pair of magnetic layers, and the conductance of a so-called sense current flowing in an in-plane direction with respect to the spin-valve film causes a so-called conductance of a magnetization of the pair of magnetic layers. It utilizes a so-called giant magnetoresistance effect that changes depending on the relative angle.
Specifically, the spin valve film is composed of an antiferromagnetic layer, a magnetization fixed layer in which magnetization is fixed in a predetermined direction by an exchange coupling magnetic field acting between the antiferromagnetic layer, and a magnetization direction according to an external magnetic field. And a nonmagnetic layer that magnetically isolates between the fixed magnetization layer and the magnetization free layer.
[0005]
In a GMR element using a spin valve film, when an external magnetic field is applied, the magnetization direction of the magnetization free layer changes according to the magnitude and direction of the external magnetic field. When the magnetization direction of the magnetization free layer is opposite (antiparallel) to the magnetization direction of the magnetization fixed layer, the resistance value of the sense current flowing through the spin valve film becomes maximum. On the other hand, when the magnetization direction of the magnetization free layer is in the same direction (parallel) as the magnetization direction of the magnetization fixed layer, the resistance value of the sense current flowing through the spin valve film becomes minimum.
[0006]
Therefore, in a magnetic head including a GMR element as described above (hereinafter, referred to as a GMR head), when a constant sense current is supplied to the GMR element, the GMR element responds to a signal magnetic field from a magnetic recording medium. The voltage value of the sense current flowing through the magnetic recording medium changes. By detecting the change in the voltage value of the sense current, a magnetic signal from the magnetic recording medium can be read.
[0007]
The initial GMR head described above uses a spin valve film composed of a magnetization free layer, a nonmagnetic layer, a magnetization fixed layer, and an antiferromagnetic layer as a GMR element.
However, in order to improve the recording density, the recording and reproducing track width must be reduced. When the thickness of the magnetization free layer is reduced in order to improve sensitivity, which is indispensable for achieving high density, the leakage magnetic field from the magnetization fixed layer causes a shift in the operating point, and this shift It becomes difficult to correct the amount by the current magnetic field with high yield.
[0008]
On the other hand, there has been proposed a so-called laminated ferri-fixed layer (synthetic AF) having a two-layer configuration in which a fixed magnetization layer is antiferromagnetically coupled by interposing a predetermined magnetic coupling layer (for example, Patent Document 2). reference.).
According to this, in the magnetization fixed layer that is antiferromagnetically coupled, there is an advantage that the operating point can be easily secured because the operating point can be reduced to zero in principle.
[0009]
That is, of the two ferromagnetic layers in the magnetization fixed layer, the ferromagnetic layer A on the nonmagnetic layer side and the ferromagnetic layer B on the antiferromagnetic layer forming side, In the laminated ferri-fixed layer structure in which the magnetic film thickness of the layer B, that is, the product of the film thickness and the saturation magnetization is equal, the leakage magnetic fields of the ferromagnetic layers A and B cancel each other, so that the leakage magnetic field becomes substantially zero. In addition, since the magnetization fixed layer becomes insensitive to the magnetic field, there is an advantage that the fixed magnetization is excellent up to a blocking temperature Tb near the exchange bias at which the exchange bias of the antiferromagnetic layer disappears stably.
[0010]
Patent Documents 1 and 2 disclose examples in which a GMR head is used for a hard disk drive.
A hard disk drive has, for example, a structure in which a GMR head is mounted on a head slider attached to the tip of a suspension, and receives a flow of air generated by the rotation of a magnetic disk so that the head slider moves over a signal recording surface of the magnetic disk. While flying, the GMR head mounted on the head slider reads a magnetic signal recorded on the magnetic disk, thereby performing a reproducing operation on the magnetic disk.
[0011]
The use of the GMR head is not limited to a magnetic disk device, and in recent years, use of a magnetic tape device such as a tape streamer has been studied.
For example, a tape streamer adopting a helical scan system has a structure in which a GMR head is arranged on an outer peripheral surface of a rotating drum so as to be oblique to an azimuth angle with respect to a direction substantially perpendicular to a running direction of a magnetic tape. ing.
In the tape streamer, the rotating drum is rotated while the magnetic tape runs obliquely with respect to the rotating drum, and the GMR head mounted on the rotating drum slides on the magnetic tape and is recorded on the magnetic tape. By reading the magnetic signal, a reproducing operation for the magnetic tape is performed.
[0012]
In a tape streamer, it is preferable to reduce the distance between the GMR head and the magnetic tape, that is, the so-called spacing. Therefore, from this viewpoint, it is desirable to smooth the surface of the magnetic tape.
[0013]
However, as the surface of the magnetic tape becomes mirror-finished, the contact area between the magnetic tape and the outer peripheral surface of the rotating drum increases, the frictional force acting between the magnetic tape and the rotating drum during running increases, and Sticking to the rotating drum occurs, and smooth running of the magnetic tape becomes difficult.
Therefore, fine protrusions are provided on the surface of the magnetic tape with SiO ₂ filler, organic filler, or the like, to reduce the contact area with the outer peripheral surface of the rotating drum, and to reduce the frictional force acting between the magnetic tape and the rotating drum. Ingenuity has been made.
On the surface of the magnetic tape, a protective film such as a DLC film for preventing the occurrence of scratches, corrosion and the like is formed.
[0014]
By the way, in the hard disk drive described above, the reproducing operation is performed in a state where the GMR head is not in contact with the signal recording surface of the magnetic disk. In addition, Cu is usually used for the non-magnetic layer constituting the spin valve film. Conventionally, a DLC (Diamond Like) for preventing corrosion of Cu is provided on a medium facing surface of a GMR head facing a magnetic disk. A protective film such as a Carbon film is formed.
[0015]
[Non-patent document 1]
Physical Review B, Vol. 43, No. 1,
p1297-p1300 "Giant magnetoresistance effect in soft magnetic multilayer film"
(Giant Magnetoresistance in Soft Ferromagnetic Multilayers)
[Patent Document 1]
Japanese Patent Application Laid-Open No. 8-111010 [Patent Document 2]
JP-A-7-169026
[Problems to be solved by the invention]
However, in a tape streamer in which application of a GMR head is currently being studied, since the reproducing operation is performed while the GMR head is in contact with the magnetic tape, the medium sliding surface of the GMR head that slides on the magnetic tape. If a protective film for preventing the above-mentioned corrosion or the like is formed on the magnetic tape, the protective film will be worn due to contact with minute projections or the protective film formed on the surface of the magnetic tape during the reproducing operation.
Further, since the protective film formed on the medium sliding surface of the GMR head serves as a spacing with the magnetic tape, it causes deterioration of the short-wavelength recording / reproducing characteristics of the GMR head.
[0017]
Therefore, in a magnetic tape device such as a tape streamer, it is considered inappropriate to form a protective film on the medium sliding surface of the GMR head.
For this reason, in the magnetic tape device, the medium sliding surface of the GMR head comes into direct contact with the air, and there is a problem that corrosion or the like is likely to occur under severe use conditions such as high temperature and high humidity or in a seawater atmosphere. Was.
[0018]
The sensitivity of the GMR head is determined by the sense current flowing through the spin valve film. Further, the thickness of each layer constituting the spin valve film is formed on the order of nm, and even if a slight corrosion occurs in each layer, the electric resistance of each layer changes. Therefore, the occurrence of corrosion on the medium sliding surface of the GMR head greatly deteriorates the head characteristics of the GMR head.
[0019]
In Patent Document 1, although a study has been made to improve the corrosion resistance of a magnetoresistive effect type magnetic head applied to a hard disk, in a hard disk drive, the magnetic head may slide directly on a medium. Therefore, it is clear that the amount of damage caused by friction of the magnetic head is larger in the tape system.
Further, in the hard disk drive, since the medium is sealed by packaging without being exposed to the outside air, the tape system is more serious in terms of the influence of the breakage of the magnetic head due to fine dust and the like. It is believed that there is. Therefore, it can be said that improving the corrosion resistance of the GMR head applied to the magnetic tape device is more important than the hard disk drive.
[0020]
In view of the above-described problems, the present invention relates to a magnetoresistive effect type magnetic head having a configuration in which a magnetization fixed layer of a spin valve film is formed as a laminated ferrimagnetic layer. In this case, excellent corrosion resistance is realized and a high rate of change in magnetoresistance is maintained.
[0021]
[Means for Solving the Problems]
The magneto-resistance effect type magnetic head of the present invention is a magneto-sensitive element that detects a magnetic signal while slidingly contacting a magnetic recording medium, and is provided with a predetermined coupling coupling magnetic field acting between the anti-ferromagnetic layer and the anti-ferromagnetic layer. A magnetization fixed layer whose magnetization is fixed in the direction of the magnetization, a magnetization free layer whose magnetization direction changes according to an external magnetic field, and a non-magnetic layer that magnetically isolates the magnetization fixed layer from the magnetization free layer are stacked. In the fixed magnetization layer, an antiferromagnetic coupling layer that couples the fixed magnetization layer antiferromagnetically is interposed, and the fixed magnetization layer separated by the antiferromagnetic coupling layer is provided. Suppose a spin-valve film is provided which is adapted to maintain the magnetization of one of the layers in a desired direction.
The antiferromagnetic coupling layer is made of any one of Ru, Rh, and Ir, and the spin valve film is provided with respect to a standard hydrogen electrode measured when immersed in a 0.1 mol / L NaCl solution. Assume that the corrosion potential is +0.4 [V vs. SHE] or more, and the magnetic signal is detected while sliding on a tape-shaped magnetic recording medium.
[0022]
According to the magneto-resistance effect type magnetic head of the present invention, the magnetization fixed layer of the spin valve film is configured to be a laminated ferrimagnetic pinned layer. The material of the magnetic coupling layer was selected, and the corrosion potential of the spin valve film measured with respect to the standard hydrogen electrode when immersed in a 0.1 mol / L NaCl solution was +0.4 [V vs. SHE]. By adopting the above, excellent corrosion resistance can be realized, and a high magnetoresistance effect can be obtained, and when applied to a tape streamer, a protective film is not formed on a surface that is in sliding contact with a magnetic recording medium. Also, excellent corrosion resistance can be realized.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a magnetoresistive head according to the present invention will be described in detail with reference to the drawings.
[0024]
First, an example of a magnetic tape device to which the magnetoresistive head according to the present invention is applied will be described.
A magnetic tape device 1 shown in FIG. 1 records and / or reproduces signals on a magnetic tape 2 by a helical scan method.
In the magnetic tape device 1, a supply reel 3 for supplying the magnetic tape 2, a take-up reel 4 for winding the magnetic tape supplied from the supply reel 3, and a magnetic tape between the supply reel 3 and the take-up reel 4. The magnetic tape 2 is provided with a plurality of guide rollers 5a to 5f for running the magnetic tape 2 so that the magnetic tape 2 runs in the direction of arrow A in the figure.
[0025]
Further, between the guide roller 5e and the guide roller 5f, as a tape running means, a pinch roller 5g on which the magnetic tape 2 is wrapped, a cap stand 6 for sandwiching the magnetic tape 2 together with the pinch roller 5g, And a cap stun motor 6a for driving the rotation of the motor 6 is provided.
The magnetic tape 2 is sandwiched between the pinch roller 5g and the capstan 6, and the capstan 6 is rotated by the capstan motor 6a in the direction of arrow B in FIG. And run under tension.
[0026]
The magnetic tape device 1 includes a head drum 7 that performs a signal recording operation or a signal reproducing operation on the magnetic tape 2 between the guide rollers 5c and 5d.
As shown in FIG. 2, the head drum 7 has a rotating drum 9 that is driven to rotate in the direction of arrow A in the figure by a driving motor 8, and a fixed drum 10 that is fixed to a base (not shown). The outer peripheral surface 9a of the rotating drum 9 and the outer peripheral surface 10a of the fixed drum are continuous.
[0027]
The magnetic tape 2 is guided by the guide rollers shown in FIG. 1 and runs while being helically wound around the outer peripheral surface portions 9a and 10a of the rotating drum 9 and the fixed drum 10 at an angle range of approximately 180 °. It has been made.
A lead guide 10b for guiding the magnetic tape 2 is provided on an outer peripheral surface portion 10a of the fixed drum 10, and the magnetic tape 2 runs obliquely with respect to the rotation direction of the rotary drum 9 along the lead guide 10b. It is supposed to.
[0028]
A pair of recording magnetic heads 11a and 11b for recording signals on the magnetic tape 2 and a pair of reproducing magnetic heads for reproducing signals on the magnetic tape 2 are provided on the outer peripheral surface 9a of the rotating drum 9. Heads 12a and 12b are attached.
The recording magnetic head 11a and the reproducing magnetic head 12a and the recording magnetic head 11b and the reproducing magnetic head 12b are opposed to the outer peripheral surface 9a of the rotary drum 9 with a phase difference of 180 ° from each other.
The recording magnetic heads 11a and 11b and the reproducing magnetic heads 12a and 12b have their recording gap and reproducing gap oblique to the direction substantially perpendicular to the running direction of the magnetic tape 2 according to the azimuth angle. Are located in
[0029]
Therefore, in the head drum 7, the magnetic tape 2 hung on the outer peripheral surface portions 9a, 10a of the rotating drum 9 and the fixed drum 10 travels in the direction of arrow A in FIG. 2, the pair of recording magnetic heads 11 a and 11 b and the pair of reproducing magnetic heads 12 a and 12 b mounted on the rotary drum 9 slide on the magnetic tape 2 while rotating in the direction indicated by arrow C. A recording operation or a reproducing operation is performed.
[0030]
Specifically, at the time of recording, one recording magnetic head 11a forms a recording track with a predetermined track width while applying a magnetic field according to a recording signal to the magnetic tape 2, and the other recording magnetic head 11b A recording track is formed with a predetermined track width while applying a magnetic field corresponding to a recording signal adjacent to the recording track.
The recording magnetic heads 11 a and 11 b form recording tracks repeatedly on the magnetic tape 2, so that signals are continuously recorded on the magnetic tape 2.
[0031]
On the other hand, during reproduction, one reproducing magnetic head 12a detects a signal magnetic field from the recording track recorded by the recording magnetic head 11a, and the other reproducing magnetic head 12b detects A signal magnetic field is detected from a recording track recorded by the magnetic head 11b. When the reproducing magnetic heads 12a and 12b repeatedly detect the signal magnetic field from the recording track, the signals recorded on the magnetic tape 2 are continuously reproduced.
[0032]
Next, the magnetoresistive head of the present invention will be described in detail with reference to FIGS.
[0033]
The magnetoresistive head 20 shown in FIG. 3 includes a giant magnetoresistive element (hereinafter, referred to as a GMR element) using a spin-valve film as a magnetosensitive element for detecting a magnetic signal from a magnetic recording medium. Is a so-called giant magnetoresistive magnetic head (hereinafter referred to as a GMR head).
[0034]
The GMR head 20 has a higher sensitivity than an inductive magnetic head or an anisotropic magnetoresistive magnetic head that performs recording and reproduction using electromagnetic induction, has a large reproduction output, and is suitable for high-density recording. Therefore, in the recording / reproducing apparatus 1 for a magnetic tape described above, by using the GMR head 20 as the pair of magnetic heads for reproduction 12a and 12b, higher density recording can be achieved.
[0035]
Specifically, as shown in FIG. 4, the reproducing magnetic heads 12a and 12b are provided on the first core member 21 by using various thin film forming techniques using a magnetic shield layer 24, a GMR element 27, a gap layer 26, and a shield layer. It is assumed that the layer 25 has a structure in which a layer 25 is sequentially formed and a second core member 23 is attached via a protective film 22.
Also, in the reproducing magnetic heads 12a and 12b, the medium sliding surface 20a that is in sliding contact with the magnetic tape 2 has a curved surface that is curved in a substantially arc shape along the running direction of the magnetic tape 2 indicated by an arrow A in FIG. I have. The reproducing gap facing the outside from the medium sliding contact surface 20a is arranged to be oblique to the direction substantially perpendicular to the running direction of the magnetic tape 2 according to the azimuth angle θ.
[0036]
The pair of reproducing magnetic heads 12a and 12b have the same configuration except that their azimuth angles θ have opposite phases. Therefore, in the following description, the pair of reproducing magnetic heads 12a and 12b will be collectively described as a GMR head 20.
[0037]
As shown in FIG. 4, the GMR head 20 has a structure in which a magnetoresistive element (GMR element 27) is sandwiched between a pair of upper and lower magnetic shield layers 24 and 25 with a gap layer 26 interposed therebetween.
[0038]
The pair of magnetic shield layers 24 and 25 are formed of a soft magnetic film having a width sufficient to magnetically shield the GMR element 27. Out of the signal magnetic field of the GMR element 27.
That is, in the GMR head 20, a signal magnetic field that is not to be reproduced with respect to the GMR element 27 is guided to the pair of magnetic shield layers 24 and 25, and only the signal magnetic field that is to be reproduced is guided to the GMR element 27. . Thereby, the frequency characteristics and the reading resolution of the GMR element 27 are improved.
[0039]
The gap layer 26 is made of a non-magnetic non-conductive film that magnetically isolates the GMR element 27 from the pair of magnetic shield layers 24 and 25, and the gap between the pair of magnetic shield layers 24 and 25 and the GMR element 27. Is the gap length.
[0040]
The GMR element 27 utilizes a so-called giant magnetoresistance effect in which the conductance of a sense current flowing in the in-plane direction with respect to the spin valve film 40 changes depending on the relative angle of the magnetization of the pair of magnetic layers. .
[0041]
As the spin valve film 40, for example, as shown in FIG. 5A, an underlayer 41, an antiferromagnetic layer 42, a magnetization fixed layer 43B, an antiferromagnetic coupling layer 47, a magnetization fixed layer 43A, a nonmagnetic layer 44 , A magnetization free layer 45, and a protective layer 46 are sequentially stacked, and a bottom type ferri-type spin valve film 40 a having a structure in which the underlayer 41, the magnetization free layer 45, A top-type laminated ferri-type spin valve film having a structure in which a nonmagnetic layer 44, a magnetization fixed layer 43A, an antiferromagnetic coupling layer 47, a magnetization fixed layer 43B, an antiferromagnetic layer 42, and a protective layer 46 are sequentially laminated. 40b and the like.
[0042]
When the magnetization fixed layer 43A and the magnetization fixed layer 43B constituting the spin valve film have a stacked ferri-fixed layer structure having the same film thickness, that is, the product of the film thickness and the saturation magnetization, the magnetization fixed layer 43A and the magnetization fixed layer 43B are formed. Since the stray fields cancel each other out, the stray field is substantially zero.
Since the magnetization fixed layer 43B is disposed adjacent to the antiferromagnetic layer 42, the magnetization is fixed in a predetermined direction by an exchange coupling magnetic field acting between the magnetization fixed layer 43B and the antiferromagnetic layer 42.
The magnetization fixed layer 43A is brought into a state where the magnetization is fixed in a predetermined direction by an exchange coupling magnetic field acting between the magnetization fixed layer 43A and the magnetization fixed layer 43B via the antiferromagnetic coupling layer 47.
[0043]
On the other hand, the magnetization free layer 45 is magnetically isolated from the magnetization fixed layer 43A via the nonmagnetic layer 44, so that the magnetization direction can be easily changed with respect to a weak external magnetic field. .
[0044]
The thickness of the antiferromagnetic coupling film 47 is appropriately selected according to the combination of the materials forming the magnetization fixed layer 43A, the magnetization fixed layer 43B, and the antiferromagnetic coupling layer 47. The magnetization fixed layer 43B is antiferromagnetically coupled.
[0045]
Therefore, when an external magnetic field is applied to the spin valve film 40, the magnetization direction of the magnetization free layer 45 changes according to the magnitude and direction of the external magnetic field. When the magnetization direction of the magnetization free layer 45 is opposite (antiparallel) to the magnetization direction of the magnetization fixed layer 43A, the resistance value of the current flowing through the spin valve film 40 becomes maximum.
On the other hand, when the magnetization direction of the magnetization free layer 45 is in the same direction (parallel) as the magnetization direction of the magnetization fixed layer 43A, the resistance value of the current flowing through the spin valve film 40 becomes minimum.
[0046]
As described above, since the spin valve film 40 changes its electric resistance in accordance with the applied external magnetic field, the spin valve film 40 functions as a magnetic sensing element for detecting a magnetic signal from the magnetic tape 2 by reading this change in resistance. I have.
[0047]
The underlayer 41 and the protective layer 46 are for suppressing an increase in the specific resistance of the spin valve film 40, and are made of, for example, Ta.
[0048]
In addition, in order to stabilize the operation of the GMR element 27, as shown in FIGS. 3 and 4, a pair of biasing magnetic fields is applied to both ends of the spin valve film 40 in the longitudinal direction. Of the permanent magnet films 28a and 28b are provided.
The width of the portion sandwiched between the pair of permanent magnet films 28a and 28b is the reproduction track width Tw of the GMR element 27. Further, on the pair of permanent magnet films 28a and 28b, a pair of resistance reducing films 29a and 29b for reducing the resistance value of the GMR element 27 are provided.
[0049]
In particular, in the GMR head in which the laminated ferrimagnetic pinned layer is provided on the magnetization pinned layer in the present invention, the reproduction track width Tw of the GMR element 27 is preferably 1.0 μm or less, and more preferably 0.8 μm or less.
[0050]
Further, in order to supply a sense current to the spin valve film, the GMR element 27 includes a pair of conductor portions 30a and 30b having a pair of permanent magnet films 28a, 28b, And are provided so as to be connected to the low-resistance films 29a and 29b.
A pair of external connection terminals 31a and 31b connected to an external circuit are provided on the other end side of the conductors 30a and 30b.
[0051]
The protective film 22 covers the main surface of the first core member 21 on which the GMR head 20 is formed, except for portions where the external connection terminals 31a and 31b face the outside. The first core member 21 and the second core member 23 are joined.
[0052]
The GMR head 20 shown in FIG. 3 and FIG. 4 is illustrated with the periphery of the GMR element 27 enlarged for easy understanding of the characteristics, but actually, the first core member 21 and the second core member 21 are not shown. The GMR element 27 is very fine as compared with the core member 23 of the first embodiment, and the GMR head 20 faces the outside on the medium sliding surface 20a almost entirely with the first core member 21 and the second core member 23. Is only the upper end face against which the.
[0053]
The GMR head 20 configured as described above is attached to a chip base (not shown), and a pair of external connection terminals 31a and 31b are electrically connected to connection terminals provided on the chip base. . The GMR head 20 provided on the chip base is attached to the rotating drum 9 shown in FIG. 2 as a pair of reproducing magnetic heads 12a and 12b.
[0054]
By the way, in the magnetic tape device 1, the reproducing operation is performed in a state where the GMR head 20 is in direct contact with the magnetic tape 2. A protective film such as a Like Carbon film cannot be formed. For this reason, in the related art, the medium sliding surface of the GMR head comes into direct contact with the atmosphere, and there has been a problem that corrosion or the like is likely to occur under severe use conditions such as high temperature and high humidity or in a seawater atmosphere.
[0055]
In view of the above, in the present invention, a spin valve film which shows excellent corrosion resistance and maintains a high magnetoresistance ratio even when a protective film is not formed on the medium sliding surface 20a of the GMR head 20 is applied. This makes it possible to perform an appropriate reproducing operation on the magnetic tape 2.
[0056]
Specifically, as a material for forming the antiferromagnetic layer 42 constituting the spin valve film 40, PtMn showing excellent corrosion resistance is preferable.
For the antiferromagnetic layer 42, NiO having excellent corrosion resistance, IrMn, CrMnPt, α-Fe ₂ O ₃ , RhMn, NiMn, PdPtMn, or the like can be applied in addition to PtMn.
[0057]
It is assumed that the nonmagnetic layer 44 constituting the spin valve film 40 is formed of an Au or Cu alloy having excellent corrosion resistance and high conductivity.
Examples of the Cu alloy include CuAu, CuPd, CuPt, CuNi, CuRu, and CuRh.
[0058]
When the nonmagnetic layer 44 is made of CuAu, the composition ratios of Cu and Au are (100-a ₁ ) and a ₁ (a ₁ represents atomic%), respectively. The range is preferably 25 ≦ a ₁ <100, more preferably 25 ≦ a ₁ ≦ 75, and further preferably 25 ≦ a ₁ ≦ 45.
[0059]
When the nonmagnetic layer 44 is made of CuPd, the composition is such that the composition ratio of Cu and Pd is (100-a ₂ ) and a ₂ (a ₂ represents atomic%). Preferably, the range is 5 ≦ a ₂ ≦ 25.
[0060]
When the nonmagnetic layer 44 is made of CuPt, the composition ratios of Cu and Pt are (100−a ₃ ) and a ₃ (a ₃ represents atomic%), respectively. Preferably, the range is 5 ≦ a ₃ ≦ 20.
[0061]
When the nonmagnetic layer 44 is made of CuRu, the composition ratios of Cu and Ru are (100-a ₄ ) and a ₄ (a ₄ represents atomic%), respectively. The range is preferably set to 3 ≦ a ₄ ≦ 15.
[0062]
The non-magnetic layer 44, if it is assumed consisting of CuNi is, Cu, the composition ratio of Ni, respectively _{(100-a 5),} when _{a 5} (a 5 represents an atomic%.) Was the composition The range is preferably 25 ≦ a ₅ ≦ 50.
[0063]
When the non-magnetic layer 44 is made of CuRh, the composition ratios of Cu and Rh are (100-a ₆ ) and a ₆ (a ₆ represents atomic%), respectively. It is preferable that the range is 7 ≦ a ₆ ≦ 20.
[0064]
The spin valve film 40 was subjected to a corrosion test using an electrochemical method to measure the change in magnetoresistance before and after the corrosion test, and to observe the surface after the corrosion test to check for the occurrence of corrosion.
In this corrosion test, the standard hydrogen electrode (SHE: Standard Hydrogen Electrode) was used as a reference electrode, and the corrosion potential for the standard hydrogen electrode measured when immersed in a 0.1 mol / L NaCl solution was measured. It was to be measured.
[0065]
Incidentally, the corrosion potential changes depending on the type and concentration of the solution. In particular, the corrosion potential of metals and alloys greatly changes depending on the presence or absence of reaction with Cl. Therefore, in this corrosion test, attention was paid to the occurrence of corrosion under severe environments such as high temperature and high humidity and in a seawater atmosphere, and in order to avoid this, a polarization curve in the case of using a 0.1 mol / L NaCl solution was used. Was measured.
FIG. 6 shows a polarization curve measured using a predetermined sample. In this polarization curve, the potential extrapolated from the polarization curve when the current density at the sample side electrode flows at 0.1 mA / cm ² or more was defined as the corrosion potential (Reference: Physical properties of spin valve material, Satoru Oikawa et al. , The Institute of Electronics, Information and Communication Engineers MR96-91 (1997-01) pp21-28).
[0066]
In this corrosion test, Ag · AgCl was used as a reference electrode, and Pt was used as a measurement electrode, and the corrosion potential was measured at room temperature (about 20 ° C.). Then, the measured corrosion potential was corrected to a standard hydrogen electrode (SHE), and this was defined as the corrosion potential in the main corrosion test. Note that the potential rise rate at the time of measurement is about 0.5 mV / sec. The thickness of the sample of the monolayer film was about 100 nm, and the pH of the NaCl solution was 7.
[0067]
In addition, the corrosion potential and the resistance change before and after the corrosion test are examined in order to examine the film properties, to measure each layer constituting the spin valve film 40 with a single layer film, or to examine the compatibility of the film in consideration of the local battery effect and the like. Measurement with a laminated film in which the magnetization fixed layer 43 and the magnetization free layer 45, which are the main parts of the spin valve film 40, are laminated via the non-magnetic layer 44, or with the laminated film in which each layer of the spin valve film 40 is laminated Among them, those measured by any method may be used. Here, the corrosion potential and the resistance change before and after the corrosion test were determined by measuring a single layer film of each layer constituting the spin valve film 40.
[0068]
In addition, in the surface observation, a test using a single-layer film described above and a test using a laminated film in which each layer is stacked on a base film made of a metal having a high corrosion potential, for example, Au, in consideration of the local battery effect, are performed. Was. This is because the laminated film in contact with Au tends to cause corrosion more easily than the single-layer film due to the local battery effect.
[0069]
With respect to the spin valve film having the configuration shown in FIGS. 5A and 5B, various samples were prepared by changing the material composition and film thickness, and the corrosion potential measured for each sample and the resistance change before and after the corrosion test were measured. 7 and the results of surface observation before and after the corrosion test are shown in FIG. In FIG. 7, ○ indicates the case where no change due to corrosion occurred on the surface, △ indicates the case where slight discoloration occurred on the surface, and × indicates the case where corrosion occurred on the surface.
[0070]
As shown in FIG. 7, it can be seen that the resistance change and the surface observation result before and after the corrosion test greatly change at the corrosion potential +0.4 [V vs. SHE]. That is, when the corrosion potential is +0.4 [V vs. SHE] or more, occurrence of corrosion is not confirmed on the surface of the spin valve film 40, and there is almost no change in resistance before and after the corrosion test.
On the other hand, when the corrosion potential was lower than +0.4 [V vs. SHE], corrosion occurred on the surface of the spin valve film 40, and the resistance change before and after the corrosion test rapidly increased. When the corrosion potential was further lowered, the corrosion progressed to a state where resistance could not be measured.
More specifically, for the bottom-type laminated ferri-type spin valve film 40a shown in FIG. A sample having a thickness of 0.8 nm was prepared, the corrosion potential and the resistance change before and after the corrosion test were measured, and the surface was observed before and after the corrosion test. vs. SHE] or more, no corrosion was observed on the surface, and there was little change in resistance before and after the corrosion test, indicating that excellent corrosion resistance was obtained.
[0071]
As described above, in the spin valve film 40, the corrosion potential with respect to the standard hydrogen electrode measured when immersed in a 0.1 mol / L NaCl solution is +0.4 [V vs. SHE] or more. Preferably. As a result, in the GMR head, the occurrence of corrosion of the spin valve film is avoided, and a high magnetoresistance ratio is maintained.
[0072]
Next, the relationship between the material composition ratio and the corrosion potential when the nonmagnetic layer 44 constituting the spin valve film was formed of any of Au, CuAu, CuPd, CuPt, CuRu, CuNi, and CuRh was examined.
[0073]
[When the nonmagnetic layer is formed of Au or CuAu]
FIG. 8 shows measurement results of the corrosion potential [V vs. SHE] of the nonmagnetic layer 44 with respect to the standard hydrogen electrode when the amount of Au added to Cu was changed.
[0074]
As shown in FIG. 8, the proportion of Au to Cu and the corrosion potential are substantially proportional to each other, and it has been confirmed that the corrosion potential increases as the amount of Au added to Cu increases. It was found that by setting the amount to 25 atomic% or more, the corrosion potential with respect to the standard hydrogen electrode described above became +0.4 [V vs. SHE] or more.
[0075]
Next, in the case where the nonmagnetic layer 44 was made of CuAu, the change in the electric resistance of the nonmagnetic layer 44 before and after the above-described corrosion test and the results of surface observation are shown in FIG. In FIG. 9, ９ indicates the case where no corrosion was confirmed on the surface, and ■ indicates the case where corrosion was confirmed on the surface.
[0076]
As shown in FIG. 9, when the nonmagnetic layer 44 is formed of CuAu, from the measurement results of the resistance change rate before and after the corrosion test and the surface observation results, by adding at least 25 atomic% of Au, before and after the corrosion test. It was found that the rate of change in resistance was suppressed, and no corrosion was observed in surface observation, indicating that excellent corrosion resistance was obtained.
[0077]
When the nonmagnetic layer 44 is made of CuAu, the magnetoresistive effect rate is higher when the amount of Au added is reduced.
From the above, when the composition ratios of Cu and Au are (100-a ₁ ) and a ₁ (where a represents atomic%), the composition ranges are 25 ≦ a ₁ ≦ 100. It is more preferable that 25 ≦ a ₁ ≦ 75, and more preferably 25 ≦ a ₁ ≦ 45. Thus, even when a protective film is not formed on the medium sliding surface 20a of the GMR head 20, the occurrence of corrosion of the nonmagnetic layer 44 can be prevented, and excellent corrosion resistance and an excellent magnetoresistance effect can be obtained.
[0078]
[When the non-magnetic layer is formed of CuPd]
FIG. 10 shows measurement results of the corrosion potential [V vs. SHE] of the nonmagnetic layer 44 with respect to the standard hydrogen electrode when the amount of Pd added to Cu was changed.
[0079]
As shown in FIG. 10, the amount of Pd added to Cu and the corrosion potential are substantially proportional to each other, and by setting the amount of Pd added to 5 atomic% or more, the corrosion potential with respect to the standard hydrogen electrode becomes +0. 4 [V vs. SHE] or more.
[0080]
Next, in the case where the nonmagnetic layer 44 was made of CuPd, FIG. 11 shows the resistance change rate of the nonmagnetic layer 44 before and after the corrosion test, surface observation results, and electric resistance of the nonmagnetic layer.
In FIG. 11, １１ indicates a case where no change occurred on the surface, and ■ indicates a case where corrosion occurred on the surface. The electric resistance was represented by a ratio with Cu.
[0081]
As shown in FIG. 11, when the nonmagnetic layer 44 is formed of CuPd, corrosion is caused by adding Pd in an amount of 5 atomic% or more based on the measurement results of resistance change before and after the corrosion test and the surface observation results. It was found that excellent corrosion resistance could be obtained without using this method.
[0082]
Note that, as indicated by the symbol 図 in FIG. 11, the electric resistance of CuPd increases with an increase in the amount of Pd added. If the addition amount of Pd exceeds 25 atomic%, the electric resistance of the nonmagnetic layer 44 becomes large enough to cause a practical problem of the spin valve film, and the magnetoresistance effect is reduced. From this, in order to further reduce the electric resistance value to a practically good value, it is desirable that the addition amount of Pd is selected to be about 25 at% or less, more preferably about 20 at% or less.
As described above, when the nonmagnetic layer 44 is formed of CuPd, the composition ratios of Cu and Pd are respectively (100−a ₂ ) and a ₂ (a ₂ represents atomic%). In this case, the composition range is preferably set to 5 ≦ a ₂ ≦ 25.
[0083]
[When the non-magnetic layer is formed of CuPt]
FIG. 12 shows the measurement results of the corrosion potential [V vs. SHE] of the nonmagnetic layer 44 with respect to the standard hydrogen electrode when the amount of Pt added to Cu was changed.
[0084]
As shown in FIG. 12, the corrosion potential with respect to the above-mentioned standard hydrogen electrode became +0.4 [V vs. SHE] or more by setting the addition amount of Pt to Cu at 5 atomic% or more.
[0085]
Next, in the case where the nonmagnetic layer 44 is made of CuPt, FIG. 13 shows the resistance change rate of the nonmagnetic layer 44 before and after the corrosion test, surface observation results, and electric resistance of the nonmagnetic layer.
In FIG. 13, ○ indicates a case where no change occurred on the surface, and ■ indicates a case where corrosion occurred on the surface. The electric resistance was represented by a ratio with Cu.
[0086]
As shown in FIG. 13, when the nonmagnetic layer 44 is made of CuPt, from the measurement result of the resistance change before and after the corrosion test and the surface observation result, by adding Pt at 5 atomic% or more, No corrosion occurred, and excellent corrosion resistance was obtained.
[0087]
In the spin valve film 40, the antiferromagnetic layer 42 must be exchange-coupled with the magnetization fixed layer 43. Therefore, when PtMn is used for the antiferromagnetic layer 42, ordered annealing is required.
When the nonmagnetic layer 44 is made of CuPt, if Pt is more than 20 atomic%, CuPt is transformed into a tetragon by the above-described ordered annealing.
In addition, as indicated by ◆ in FIG. 13, the electric resistance of CuPt increases as the amount of Pt added increases. If the added amount of Pt exceeds 20 atomic%, the electric resistance of the non-magnetic layer 44 becomes large enough to hinder the practical use of the spin valve film, and the magnetoresistive effect decreases. Therefore, in order to reduce the electric resistance value to a practically good value, it is desirable that the addition amount of Pd is selected to be about 20 at% or less, more preferably about 15 at% or less.
As described above, when the nonmagnetic layer 44 is formed of CuPt, the composition ratios of Cu and Pt are (100-a ₃ ) and a ₃ (a ₃ represents atomic%). The composition range is preferably set to 5 ≦ a ₃ ≦ 20.
[0088]
[When the nonmagnetic layer is formed of CuRu]
FIG. 14 shows the measurement results of the corrosion potential [V vs. SHE] of the nonmagnetic layer 44 with respect to the standard hydrogen electrode when the amount of Ru added to Cu was changed.
[0089]
As shown in FIG. 14, the corrosion potential increases as the amount of Ru added to Cu increases. By setting the amount of Ru added to 3 atomic% or more, the corrosion potential with respect to the above-described standard hydrogen electrode is reduced. , +0.4 [V vs. SHE] or more.
[0090]
Next, in the case where the nonmagnetic layer 44 was made of CuRu, the change in resistance of the nonmagnetic layer 44 before and after the corrosion test, the results of surface observation, and the electrical resistance of the nonmagnetic layer were shown in FIG. In FIG. 15, １５ indicates the case where no change occurred on the surface, and ■ indicates the case where corrosion occurred on the surface. The electric resistance was represented by a ratio with Cu.
[0091]
As shown in FIG. 15, when the nonmagnetic layer 44 is formed of CuRu, corrosion is generated by adding 3 atomic% or more of Ru from the measurement results of resistance change before and after the corrosion test and the surface observation results. It was found that excellent corrosion resistance was obtained.
[0092]
In addition, as shown by the triangle in FIG. 15, the electric resistance of CuRu increases as the amount of added Ru increases.
If the addition amount of Ru is more than 15 atomic%, the electric resistance of the nonmagnetic layer 44 becomes high enough to hinder the practical use of the spin valve film, and the magnetoresistance effect decreases. For this reason, in order to reduce the electric resistance to a practically good value, it is desirable that the amount of Ru added be 15 atomic% or less, more preferably about 10 atomic% or less.
As described above, when the nonmagnetic layer 44 is made of CuRu, the composition ratios of Cu and Ru are respectively (100-a ₄ ) and a ₄ (a ₄ represents atomic%). In this case, the composition range is preferably set to 3 ≦ a ₄ ≦ 15.
[0093]
[When the nonmagnetic layer is formed of CuNi]
FIG. 16 shows the measurement results of the corrosion potential [V vs. SHE] of the nonmagnetic layer 44 with respect to the standard hydrogen electrode when the amount of Ni added to Cu was changed.
As shown in FIG. 16, the amount of Ni added to Cu and the corrosion potential are substantially proportional to each other. By setting the amount of Ni added to 25 at% or more, the corrosion potential with respect to the standard hydrogen electrode described above is increased to +0. 4 [V vs. SHE] or more.
[0094]
Next, in the case where the nonmagnetic layer 44 is made of CuNi, FIG. 17 shows a change in resistance of the nonmagnetic layer 44 before and after the above-described corrosion test, a surface observation result, and an electric resistance of the nonmagnetic layer.
In FIG. 17, １７ indicates a case where no change occurred on the surface, and ■ indicates a case where corrosion occurred on the surface. The electric resistance was quantified in comparison with the case where the nonmagnetic layer 44 was made of Cu.
[0095]
As shown in FIG. 17, when the nonmagnetic layer 44 is formed of CuNi, corrosion does not occur by adding 25 atomic% or more of Ni from the measurement results of the resistance change before and after the corrosion test and the surface observation results. It was found that excellent corrosion resistance was obtained.
[0096]
In addition, as indicated by ◆ in FIG. 17, it can be seen that the electric resistance of CuNi increases as the amount of Ni added increases.
If the addition amount of Ni is more than 50 atomic%, the electric resistance of the nonmagnetic layer 44 becomes high enough to hinder the practical use of the spin valve film, and the magnetoresistance effect decreases. For this reason, in order to further reduce the electric resistance value to a practically good value, the amount of Ni added is desirably 50% by weight or less, and more desirably 45% by atom or less.
As described above, when the nonmagnetic layer 44 is formed by a CuNi is, Cu, the composition ratio of Ni, when each _{(100-a 5), a} 5 (a 5 represents an atomic%.) Was The composition range is preferably set to 25 ≦ a ₅ ≦ 50.
[0097]
[When the nonmagnetic layer is formed of CuRh]
FIG. 18 shows the measurement results of the corrosion potential [V vs. SHE] of the nonmagnetic layer 44 with respect to the standard hydrogen electrode when the amount of Rh added to Cu was changed.
As shown in FIG. 18, the corrosion potential with respect to the above-mentioned standard hydrogen electrode becomes +0.4 [V vs. SHE] or more by setting the addition amount of Rh to 7 atom% or more.
[0098]
Next, in the case where the nonmagnetic layer 44 is formed of CuRh, FIG. 19 shows a change in resistance and a result of surface observation of the nonmagnetic layer 44 before and after the above-described corrosion test, and shows the relationship between the amount of added Rh and the electric resistance. 20 is shown.
In FIG. 19, ○ indicates a case where no change occurred on the surface, and ■ indicates a case where corrosion occurred on the surface. The electric resistance in FIG. 20 is represented by the ratio to Cu.
[0099]
As shown in FIG. 19, when the non-magnetic layer 44 is made of CuRh, corrosion does not occur by adding 7 atomic% or more of Rh from the measurement results of resistance change before and after the corrosion test and the surface observation results. It was found that excellent corrosion resistance was obtained.
[0100]
In addition, as shown by the triangle in FIG. 20, the electric resistance of CuRh increases as the amount of Rh added increases. If the added amount of Rh exceeds 20 atomic%, the electric resistance of the nonmagnetic layer 44 becomes extremely large as compared with the case where the nonmagnetic layer 44 is made of only Cu, which may hinder the practical use of the spin valve film. The magnetoresistance effect is reduced as much as it comes. For this reason, in order to further reduce the electric resistance value to a practically good value, it is desirable that the amount of Rh added be about 20 atomic% or less.
As described above, when the nonmagnetic layer 44 is formed of CuRh, the composition ratios of Cu and Rh are (100-a ₆ ) and a ₆ (a ₆ represents atomic%), respectively. At this time, the composition range is preferably set to 7 ≦ a ₆ ≦ 20.
[0101]
Note that the nonmagnetic layer 44 is formed by adding Au, Al, Ta, In, B, Nb, Hf, Mo, W, Re, Pt, Pd, Rh, Ga, Zr to a Cu alloy or Au having the above-described composition ratio. , Ir, Ag, Ni, Ru, at least one element or two or more elements may be added.
[0102]
Next, the magnetization fixed layer 43A, the magnetization fixed layer 43B, and the magnetization free layer 45 constituting the spin valve film shown in FIGS. 5A and 5B will be described.
The magnetization fixed layers 43A and 43B and the magnetization free layer 45 are made of a material exhibiting excellent corrosion resistance and good soft magnetic characteristics. It is assumed that the part or all is made of one or both of NiFe and CoNiFe.
The magnetization free layer 45 may have a laminated structure in which these alloys are laminated, or a laminated ferri-structure in which these alloys are alternately laminated with a nonmagnetic film made of, for example, Ru, Rh, Ir, or the like.
[0103]
The magnetization fixed layers 43A and 43B and the magnetization free layer 45 are formed of NiFe or CoNiFe, and samples in which the composition ratio of Co, Ni, and Fe is changed are manufactured. A corrosion test was performed using a 0.1 mol / L NaCl solution, and the surface was observed after the corrosion test to check whether or not corrosion had occurred.
[0104]
FIG. 21 shows the evaluation results of the corrosion test when the composition ratio of Co, Ni, and Fe was changed. In FIG. 21, ○ indicates that no corrosion occurred on the surface, and the corrosion potential with respect to the standard hydrogen electrode measured when immersed in a 0.1 mol / L NaCl solution was +0.4 [V vs. SHE]. The above cases are shown, and the black circles show the cases where corrosion occurred on the surface.
[0105]
Further, Δ indicates a case where the coercive force Hc is higher than 10 Oe (796 A / m), and ▲ indicates a case where the coercive force becomes a bcc phase (body-centered cubic structure). When Hc> 10 Oe, the magnetoresistance effect deteriorates due to an increase in coercive force.
In addition, the magnetoresistance effect of NiFe or CoNiFe is higher when both have the fcc phase (face-centered cubic structure). On the other hand, in the case of another crystal structure, lattice mismatch occurs at the interface, and the magnetoresistance effect deteriorates. Also, when the fcc phase and the bcc phase are mixed, lattice mismatch occurs at the interface, and the magnetoresistance effect deteriorates.
[0106]
As shown in FIG. 21, when the Co content is greater than 75 at% and the Ni content is less than 15 at% with respect to Co, Ni, and Fe, the magnetization fixed layer 43 and the magnetization free layer 45 are reduced. It was found that corrosion was more likely to occur. When the Ni content is more than 95 atomic% and the Fe content is less than 5 atomic% with respect to Co, Ni and Fe, the magnetization fixed layers 43A and 43B and the magnetization free layer 45 are protected. It was found that the magnetic force Hc increased and the magnetoresistance effect deteriorated.
Further, it was found that when the content of Fe was more than 40 atomic% with respect to Co, Ni, and Fe, corrosion was easily generated in the magnetization fixed layers 43A and 43B and the magnetization free layer 45.
[0107]
As described above, when the magnetization fixed layers 43A and 43B and the magnetization free layer 45 are formed of FeNi or CoNiFe, the composition ratios of Co, Ni, and Fe are b, c, d (b, c, d, respectively). Each represents an atomic%), and the composition ranges are preferably 0 ≦ b ≦ 75, 15 ≦ c ≦ 95, 5 ≦ d ≦ 40 (b + c + d = 100 atomic%). .
[0108]
That is, in the magnetization fixed layer 43 and the magnetization free layer 45, as shown in FIG. 22, the composition ratio of Co, Ni, and Fe is point A (Co = 0 atomic%, Ni = 95 atomic%, and Fe = 5 atomic%). %), Point B (Co = 0 atomic%, Ni = 60 atomic%, Fe = 40 atomic%), point C (Co = 45 atomic%, Ni = 15 atomic%, Fe = 40 atomic%), point D ( Range of solid line surrounded by five points: Co = 75 at%, Ni = 15 at%, Fe = 10 at%) and point E (Co = 75 at%, Ni = 20 at%, Fe = 5 at%) It is preferable that the By selecting such a composition ratio, even when a protective film is not formed on the medium sliding surface 20a that slides with the magnetic tape 2, the magnetization fixed layers 43A and 43B constituting the spin valve film and the magnetization Corrosion of the free layer 45 can be prevented.
[0109]
Further, in the magnetization fixed layers 43A and 43B and the magnetization free layer 45, the composition ranges of Co, Ni, and Fe are 20 ≦ b ≦ 75, 20 ≦ c ≦ 75, and 5 ≦ d ≦ 40, that is, in FIG. F (Co = 20 atomic%, Ni = 75 atomic%, Fe = 5 atomic%), point G (Co = 20 atomic%, Ni = 40 atomic%, Fe = 40 atomic%), point H (Co = Within the range of the dashed line surrounded by four points of 40 atomic%, Ni = 20 atomic%, Fe = 40 atomic%) and point E (Co = 75 atomic%, Ni = 20 atomic%, Fe = 5 atomic%) Preferably, there is.
Thereby, in the magnetoresistive head 20 of the present invention, the magnetization fixed layers 43A and 43B and the magnetization free layer 45 exhibit excellent corrosion resistance and can maintain a high magnetoresistance effect rate. In particular, it is possible to increase the magnetoresistance change rate by increasing the proportion of Co.
[0110]
Furthermore, in the magnetization fixed layers 43A and 43B and the magnetization free layer 45, the composition ranges of Co, Ni, and Fe are 40 ≦ b ≦ 75, 20 ≦ c ≦ 65, and 5 ≦ d ≦ 30, that is, FIG. Medium, point I (Co = 30 atomic%, Ni = 65 atomic%, Fe = 5 atomic%), point J (Co = 30 atomic%, Ni = 40 atomic%, Fe = 30 atomic%), point K (Co = 50 atomic%, Ni = 20 atomic%, Fe = 30 atomic%) and point E (Co = 75 atomic%, Ni = 20 atomic%, Fe = 5 atomic%) By doing so, the magnetization fixed layers 43A and 43B and the magnetization free layer 45 exhibit excellent corrosion resistance and can maintain a high magnetoresistance effect rate, and have excellent corrosion resistance and a high magnetoresistance effect rate. Can be balanced in a higher dimension.
[0111]
The magnetization free layer 45 and the magnetization fixed layers 43A and 43B constituting the spin valve film may be made of Co-based amorphous or microcrystalline alloy having excellent corrosion resistance other than NiFe or CoNiFe.
[0112]
The magnetization fixed layers 43A and 43B and the magnetization free layer 45 constituting the above-described spin valve film 40 are formed by adding Au, Ir, Pt, Al, Rh, Cr, Pd, and Ru to NiFe or CoNiFe having the above-described composition ratio. At least one element or two or more elements selected from the above may be added.
[0113]
Further, the magnetization fixed layers 43A and 43B and the magnetization free layer 45 of NiFe or CoNiFe having the above-described composition ratio may be different from each other in the spin bubble 40, or may be constituted by a plurality of combinations. Good.
[0114]
As the spin valve film 40 satisfying the above-described conditions, specifically, for example, Ta as the underlayer 41, Ni ₈₀ Fe ₂₀ and Co ₅₀ Ni ₃₀ Fe _{20 as} the magnetization free layer 45, and the nonmagnetic layer become _Cu 70 and _{Au 30,} magnetization fixed layer 43A to become _Co 50 _Ni 30 _{Fe 20,} antiferromagnetic coupling layer 47 and becomes Ru, a magnetization fixed layer 43B _Co 50 _Ni 30 _{Fe 20,} the antiferromagnetic layer 42 Provided with a spin valve film 40 formed by sequentially laminating PtMn to become a protective layer 46 and Ta to become a protective layer 46, exhibiting excellent corrosion resistance, and providing a protective film on the medium sliding surface 20a that slides on the magnetic tape. Therefore, even when the magnetic tape 2 is not formed, it is possible to prevent the occurrence of corrosion or the like under high temperature and high humidity or in a seawater atmosphere, and it is possible to perform an appropriate reproducing operation on the magnetic tape 2. It was confirmed that it was a function.
At this time, the track width Tw of the GMR head 20 was set to 0.7 μm.
In particular, when such a GMR head was applied as the reproducing magnetic heads 12a and 12b in the magnetic tape device 1 using the helical scan method, excellent corrosion resistance could be obtained.
[0115]
Next, the antiferromagnetic coupling layer 47 interposed between the magnetization fixed layers in the spin valve film will be described.
The antiferromagnetic coupling layer 47 is formed of a material selected from the group consisting of Ru, Rh, Ir, and an alloy thereof.
[0116]
Samples in which the antiferromagnetic coupling layer 47 was formed of Ru, Rh, and Ir were prepared, and a corrosion test was performed on these samples using a 0.1 mol / L aqueous NaCl solution as described above. Table 1 below shows the corrosion evaluation of the surface of these samples after the corrosion test and the corrosion potential with respect to the standard hydrogen electrode measured when immersed in a NaCl solution.
The pH value of the NaCl solution used for the measurement was 7.0. The corrosion test in a NaCl solution was performed by combining a two-layer film with Au in consideration of the local battery effect as described above. The thickness of the sample was about 100 nm.
[0117]
[Table 1]

[0118]
As shown in Table 1, in samples 1 to 3 in which the antiferromagnetic coupling layer 47 was formed of Ru, Rh, and Ir, corrosion was not confirmed on the surface by a visual test, and NaCl having a concentration of 0.1 mol / L was used. The corrosion potential with respect to the standard hydrogen electrode measured when immersed in the solution was +0.4 [V vs. SHE] or more, and there was no change in resistance before and after the corrosion test, indicating that the corrosion resistance was extremely excellent. Was.
[0119]
The anti-ferromagnetic layer coupling layer 47 is made of a material selected from the group consisting of Ru, Rh, Ir, and an alloy thereof, including Al, Ta, In, B, Nb, Hf, Mo, W, Re, Pt, At least one element or two or more elements selected from Pd, Ga, Zr, Ir, Ag, Ni, and Cr may be added.
[0120]
The thickness of the antiferromagnetic coupling layer 47 is preferably from 0.3 to 1.5 nm, and more preferably from 0.5 to 1.1 nm. If the thickness of the antiferromagnetic coupling film 47 is less than 0.3 nm, the magnetization fixed layers 43A and 43B will not be antiferromagnetically exchange-coupled. On the other hand, if the antiferromagnetic coupling layer 47 is formed thicker than 1.5 nm, it does not antiferromagnetically exchange-couple and causes noise.
[0121]
The present invention is also applicable to a composite magnetic head in which, for example, an inductive magnetic head using electromagnetic induction is stacked on a magnetoresistive magnetic head.
Further, according to the present invention, a pair of magnetic layers are stacked via an insulating layer, and the conductance of a tunnel current flowing from one magnetic layer to the other magnetic layer changes depending on a relative angle of magnetization of the pair of magnetic layers. The present invention is also applicable to a magnetic tunnel effect type magnetic head having a magnetic tunnel junction element.
[0122]
【The invention's effect】
According to the present invention, a magnetoresistive magnetic head having a configuration in which a magnetization fixed layer of a spin valve film is a laminated ferrimagnetic pinned layer is used, and when a recording density is increased, a track width is reduced and a magnetization free layer is thinned. In addition, it is possible to suppress the leakage magnetic field from the magnetization fixed layer, and further, select the material of the antiferromagnetic coupling layer that constitutes the spin valve film and is interposed in the magnetization fixed layer, and adjusts the concentration of the spin valve film. By setting the corrosion potential with respect to the standard hydrogen electrode measured when immersed in a 0.1 mol / L NaCl solution to +0.4 [V vs. SHE] or more, excellent corrosion resistance can be realized. In addition, a high magnetoresistance effect can be obtained, and when applied to a tape streamer, excellent corrosion resistance can be realized without forming a protective film on the surface that is in sliding contact with the magnetic recording medium.
[Brief description of the drawings]
FIG. 1 is a schematic plan view of a recording / reproducing apparatus for a magnetic tape.
FIG. 2 is a schematic perspective view of a head drum constituting the recording / reproducing apparatus.
FIG. 3 is a schematic perspective view of a magnetoresistive head according to the present invention.
FIG. 4 is an end view of the GMR head as viewed from a surface in contact with the medium.
FIG. 5A is a schematic cross-sectional view of a bottom-type laminated ferri-type spin valve film.
(B) A schematic cross-sectional view of a top-stacked ferri-type spin valve film is shown.
FIG. 6 is an explanatory diagram for defining a corrosion potential.
FIG. 7 shows the relationship between the corrosion potential and the rate of change in resistance before and after the corrosion test, and the results of surface observation.
FIG. 8 shows the relationship between the composition ratio when the nonmagnetic layer is made of Au and CuAu and the corrosion potential with respect to a standard hydrogen electrode.
FIG. 9 shows a composition ratio when the nonmagnetic layer is made of CuAu, a resistance change rate before and after a corrosion test, and surface observation results.
FIG. 10 shows the relationship between the composition ratio when the nonmagnetic layer is made of CuPd and the corrosion potential with respect to a standard hydrogen electrode.
FIG. 11 shows a characteristic diagram of a composition ratio when the nonmagnetic layer is made of CuPd, a resistance change rate before and after a corrosion test, a surface observation result, and an electric resistance measurement result.
FIG. 12 shows a relationship between a composition ratio when a nonmagnetic layer is made of CuPt and a corrosion potential with respect to a standard hydrogen electrode.
FIG. 13 shows a characteristic diagram of a composition ratio when the nonmagnetic layer is made of CuPt, a resistance change rate before and after a corrosion test, a surface observation result, and an electric resistance measurement result.
FIG. 14 shows a relationship between a composition ratio when a nonmagnetic layer is made of CuRu and a corrosion potential with respect to a standard hydrogen electrode.
FIG. 15 shows a characteristic diagram of a composition ratio when the nonmagnetic layer is made of CuRu, a resistance change rate before and after a corrosion test, a surface observation result, and an electric resistance measurement result.
FIG. 16 shows a relationship between a composition ratio when a nonmagnetic layer is made of CuNi and a corrosion potential with respect to a standard hydrogen electrode.
FIG. 17 is a diagram showing a relationship between a composition ratio when a nonmagnetic layer is made of CuNi, a resistance change rate before and after a corrosion test, a surface observation result, and an electric resistance measurement result.
FIG. 18 shows a relationship between a composition ratio when a nonmagnetic layer is made of CuRh and a corrosion potential with respect to a standard hydrogen electrode.
FIG. 19 shows a characteristic diagram of a composition ratio when a nonmagnetic layer is made of CuRh, a resistance change rate before and after a corrosion test, and a surface observation result.
FIG. 20 is a characteristic diagram of composition ratio and electric resistance when the nonmagnetic layer is made of CuRh.
FIG. 21 shows the results of a corrosion test when the composition ratio of the magnetization fixed layer and the magnetization free layer was changed.
FIG. 22 shows a preferable composition ratio range for effectively preventing corrosion for the magnetization fixed layer and the magnetization free layer.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Magnetic tape device, 2 ... Magnetic tape, 3 ... Supply reel, 4 ... Winding reel, 5a to 5f ... Guide roller, 5g ... Pinch roller, 6 ... Capstan, 6a ... Cap Stan motor, 7 head drum, 8 drive motor, 9 rotary drum, 10 fixed drum, 11a, 11b magnetic recording head, 12a, 12b magnetic reproduction head, 20 GMR head, 21 first core member, 22 protective film, 23 second core member, 24, 25 magnetic shield layer, 26 gap layer, 27 GMR element, 28a, 28b ... permanent magnet film, 29a, 29b ... low resistance film, 30a, 30b ... conductor, 31a, 31b ... external connection terminal, 40 ... spin valve film, 41 ... underlayer, 42 ... ... Antiferromagnetic layer, 43 ...... magnetization fixed layer, 43B ...... magnetization fixed layer, 44 ...... nonmagnetic layer, 45 ...... magnetization free layer 46 ...... protective layer, 47 ...... antiferromagnetic coupling layer

Claims (4)

A magnetization fixed layer in which magnetization is fixed in a predetermined direction by an exchange coupling magnetic field acting between the antiferromagnetic layer and the antiferromagnetic layer as a magneto-sensitive element that detects a magnetic signal while sliding on a magnetic recording medium. And a magnetization free layer whose magnetization direction changes in accordance with an external magnetic field, and a non-magnetic layer magnetically isolating the magnetization fixed layer and the magnetization free layer from each other,
In the magnetization fixed layer, an antiferromagnetic coupling layer that antiferromagnetically couples the magnetization fixed layer is interposed,
A magnetoresistive magnetic head comprising a spin valve film adapted to maintain one magnetization of the magnetization fixed layer separated by the antiferromagnetic coupling layer in a desired direction,
The antiferromagnetic coupling layer is made of any one of Ru, Rh, and Ir;
The spin valve film has a corrosion potential with respect to a standard hydrogen electrode measured when immersed in a 0.1 mol / L NaCl solution of +0.4 [V vs. SHE] or more,
A magnetoresistive magnetic head, wherein a magnetic signal is detected while being in sliding contact with a tape-shaped magnetic recording medium. The nonmagnetic layer is formed of Au or a Cu alloy, and a part or all of the magnetization fixed layer and the magnetization free layer are made of one or both of NiFe and CoNiFe. Item 2. A magnetoresistive effect type magnetic head according to item 1. The nonmagnetic layer constituting the spin valve film has a corrosion potential with respect to a standard hydrogen electrode measured when immersed in a 0.1 mol / L NaCl solution of +0.4 [V vs. SHE] or more. 3. The magneto-resistance effect type magnetic head according to claim 1, wherein: 4. The magnetic sensing element according to claim 1, wherein the magnetic sensing element is mounted on a rotating drum and detects a magnetic signal while sliding on a tape-shaped magnetic recording medium by a helical scan method. Magnetoresistive magnetic head.

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