【発明の詳細な説明】[Detailed description of the invention]
本発明は磁気記憶媒体に書き込まれた磁気的情
報を、いわゆる磁気抵抗効果を利用して読み出し
を行う強磁性磁気抵抗効果素子（以下、MR素子
と称す）を備えた磁気抵抗効果ヘツド（以下、
MRヘツドと称す）に関する。
MRヘツドは、磁気記録における記録密度の向
上に大きく貢献するものとして注目されている。
しかし、周知の如く、MR素子を磁気記憶媒体に
書き込まれた磁気的情報に対して、線形応答を呈
する高効率の再生用ヘツドとして用いる場合に
は、MR素子に流すセンス電流ＩとMR素子の磁
化Ｍの成す角度（以下バイアス角度と称す）θを
所定の値（望ましくは45゜）に設定するバイアス
手段を具備しなければならない。
従来、前述のバイアス手段を呈する具体的方法
に、MR素子に近接対向（或いは接触）させて、
磁気的にハードな磁性体、又は電気的良導体を配
置し、これらの磁性体、又は電気的良導体に流す
電流から生ずる磁界をバイアス磁界としてMR素
子の磁化Ｍの角度θをセンス電流Ｉと略45゜に設
定する方法が知られている。しかし、これ等のバ
イアス方法は比較的大きな磁界を必要とし、この
大きな磁界が磁気記憶媒体上の情報を変化させる
恐れがあつた。特に前者の磁気的にハードな磁性
体をMR素子に近接対向（或いは接触）させた場
合は、バイアス角度θを厳密にしかも再現性よく
45度に設定するのが困難であり、又、後者の電気
的良導体をMR素子に近接対向（或いは接触）さ
せた場合は電気的良導体に比較的大電流を流す必
要があり、従つて、MR素子の電気抵抗が熱的ド
リフトを起し、かつ熱雑音の原因にもなつてい
た。これ等の問題点を解決するため、前述した外
部磁界によるバイアス法と対照的に、第１図及び
第３図に示す如く、MR素子の長手方向に流すセ
ンス電流Ｉに対して、始めからMR素子の磁化Ｍ
を略45度に設定する手法が知られている。この方
法は外部から、バイアス磁界を印加するための
MR素子に付属するバイアス手段が不要になるた
め、MRヘツドを小型化でき、更にシールド構成
としたときに狭ギヤツプ化ができる等の利点があ
る。
第１図は特開昭46−5580に開示されたMRヘツ
ドのMR素子部の概略斜視図である。
この手法によれば、センス電流ＩとMR素子１
の磁化容易軸Ｅ・Ａの成す角を予めバイアス角以
上に設定し、MR素子１の幅方向反磁界Hdと異
方性磁界Hkとの間にHd／Hk＜１を満すように
MR素子１の寸法及び材質を選定することによ
り、所定のバイアス状態が実現される。
また、第２図は第１図に示すMR素子１の幅Ｗ
方向に外部磁界Ｈ（横軸）を印加し、これによる
抵抗変化ΔRをMR素子１の最大抵抗変化ΔRm
（即ち、磁化Ｍがセンス電流Ｉと平行な場合にお
けるMR素子の抵抗値と磁化Ｍがセンス電流Ｉと
垂直な場合における抵抗値の差）で規格化した値
（縦軸）との関係を示す磁界Ｈ−抵抗変化特性曲
線図である。第２図の測定に用いたMR素子１
は、表面の滑らかな、Ａ面を主面とする単結晶サ
フアイヤ基板（図示せず）上にNi82％−Fe12％
（いずれも重量パーセント）の組成からなるパー
マロイを膜厚tM＝400Åで被着せしめ、長さ50μ
ｍ、幅Ｗ＝10μｍの寸法を有するストライプ形状
に加工し、その長さ方向とパーマロイの磁化容易
軸Ｅ・Ａの成す角θ0を45゜に設定したものである。
得られたMR素子１の幅Ｗ方向の反磁界Hdは約
40pe、異方性磁界Hkは60peであり、従つてHd／
Hkは0.67に設定されている。第２図に示す磁界
Ｈ−抵抗変化ΔR特性曲線において、ΔR／ΔRm
＝１及びΔR／ΔRm＝０はそれぞれMR素子１の
磁化Ｍとセンス電流Ｉが平行な場合、及び垂直な
場合を意味する。
第２図から明らかな様に確かに印加磁界Ｈに対
して線形応答する領域（例えば曲線ABもしくは
曲線A′B′上）が存在し、バイアス状態が実現さ
れている。しかし、磁界Ｈに対して有効に寄与す
るMR素子の抵抗変化ΔRは、最大抵抗変化ΔRm
より小さな値となるため、抵抗変化の利用率
（ΔR／ΔRm）が小さく、直線性の良い応答を呈
する磁界範囲が小さくなつている。こう言つた現
象は既にフイジカ・ステイタス・ソリデイ
〔Physica Status Solidi(a)〕1981年、第64巻、
513〜517ページに記載のO.Gebhardt氏等による
論文に報告されており、第２図に示した例に限ら
ず、前述の特開昭46−5580に開始されたMRヘツ
ド一般にみられる。
更に、この手法は、MR素子の磁化をセンス電
流Ｉと所定の角度に再現性よく設定するのが困難
で、又、同時に作製したMR素子間の再生特性に
バラツキが生じ易く、生産性の点で不都合であつ
た。一方、第３図は特願昭57−050586に開示され
ている本出願人による「ジヨツグMR素子」の概
略斜視図である。このMR素子は、１個又は複数
個の相互に平行で直線状の溝（凹部）３が設けら
れた基板２上にMR素子１を設け、前記溝３によ
つて生ずるMR素子１の形状反磁界を利用し、
MR素子１の磁化Ｍとセンス電流Ｉとのなす角θ
を制御するものである。
第４図は第３図に示すMRヘツドの磁界Ｈ−抵
抗変化ΔR特性曲線の実測データである。測定方
法は第２図に示した特性曲線と全く同じである。
第４図の測定に用いたMR素子１は、フオトレ
ジスト及びイオンミリング装置を用いて通常の光
学露光法により、深さS.H＝370Å、幅ｌ＝1.5μ
ｍ、l′＝1.5μｍ、即ちピツチ3μｍの複数の直線的
な溝３を形成したガラス基板を基板２として、こ
の上にNi82％−Fe12％（いずれも重量パーセン
ト）の組成からなるパーマロイを膜厚tM＝400Å
で被着せしめ、長さ50μｍ、幅Ｗ＝10μｍの寸法
を有するストライプ状に加工し、その長さ方向と
溝３の直線方向の成す角θ0を45゜に設定したもの
である。尚、この場合、MR素子１の磁化容易軸
E.Aの方向は、溝３の直線方向と略平行に設定し
ている。又、溝３が形成されていないガラス基板
上のパーマロイ膜の異方性磁界Hkは4peである。
第４図から明らかな様に、第３図に示す構成に
よるバイアス法も印加磁界Ｈに対して線形応答す
る領域が存在し、バイアス状態が実現されてい
る。しかも、第２図に比較して、磁界Ｈに対して
有効に寄与するMR素子の抵抗変化ΔRは最大抵
抗変化ΔRmと同等になるまで変化する。即ち、
磁化Ｍは印加磁界Ｈに対して、スムーズな回転を
起している。しかし、バイアス角θは十分でな
く、線形応答する領域が狭くなつており、その分
だけダイナミツクレンジが小さい。これは、再生
波形歪が発生しやすいことを意味する。
この問題を解決するには、溝３のピツチを更に
小さくし、例えばピツチを1μｍ以下に設定すれ
ば良い。これによつて、溝３によつて生ずるMR
素子１の形状反磁界を更に大きくし、MR素子１
の長手方向と溝３の直線方向の成す角θ0にバイア
ス角θを一致せしめることができる。しかし、前
述の極めて小さなピツチを有する溝３の加工には
レーザホログラフイ又は電子線露光等の特殊な技
術及び装置が必要となり多大な工数が要求される
ので、歩留りの劣化、製作時間が長くなる等の欠
点を有し、その結果、MRヘツドは高価にならざ
るを得なかつた。
本発明の目的は、前記従来の欠点を解決した、
再生波形歪が少なくダイナミツクレンジが広く、
しかも、抵抗変化の利用率の高いバイアス状態を
実現した磁気抵抗効果ヘツドを提供することであ
る。
本発明によれば、強磁性磁気抵抗効果素子の検
出磁界方向における形状反磁界Hdと前記磁気抵
抗効果素子自体の有する異方性磁界Hkが
Hd／Hk＜１
の関係を満たすように、前記強磁性磁気抵抗効果
素子の材料または前記強磁性磁気抵抗効果素子を
形成する基板が選定され、前記基板の表面が１個
又は複数個の相互に平行で直線状の凸部又は凹部
を有することを特徴とする磁気抵抗効果ヘツドを
提供できる。
以下、本発明の実施例を図面を用いて、詳細に
説明する。尚、本発明の構成を説明するに当り、
再び第３図を用いる。
第３図においては、絶縁性基板材２の表面がフ
オトレジスト及びエツチング液又はイオンミリン
グ等周知の方法により幅ｌ、深さS.Hピツチｌ＋
l′の値で多数の直線的な溝（凹部）３がそれぞれ
略平行となるように形成されている。ついで、こ
の溝３を覆うように、厚みtMの強磁性体薄膜から
なるMR素子１がスパツタ、蒸着等の手法により
形成されている。前記MR素子１は、幅Ｗの寸法
を有するストライプ状に加工され、MR素子１の
長さ方向と溝３の直線方向のなす角は所定の値θ0
に設定されている。又、MR素子１の長さ方向の
両端にセンス電流を導入するための２つの電気端
子４が接続されている。従つて、電気端子４から
導入されるセンス電流Ｉは溝３の直線方向とθ0の
角度を成す。
本発明における溝３のピツチｌ＋l′は通常の光
学的露光で形成できる数μｍのオーダでよく、レ
ーザホログラフイ、又は電子線露光等の特殊な技
術及び装置を特に必要としない。
又、本発明におけるMR素子１の異方性磁界
HkはMR素子の幅Ｗ方向の反磁界Hdより大きく
成る様に選定される。ここで反磁界Hdは溝３が
存在しない場合の値が用いられ、周知の如くHd
≒4πMtM／Ｗで与えられる。ただしＭは飽和磁化を
あらわす。MR素子１の寸法特に幅Ｗが規定され
た場合（通常数μｍ〜十数μｍ程度に選定され
る。）反磁界Hdより大きい異方性磁界Hkは、例
えば、単結晶基板のある特定の結晶面にMR素子
を被着した場合やMR素子の材質としてNi−Co
合金を用いた場合、更にはこれ等を組み合せた場
合に得られ、数十Oe以上の値が達成される。
次に、本発明の効果を明らかにするため、具体
的実施例を以下に説明する。
第３図において、表面の滑らかな、Ａ面を主面
とする単結晶サフアイヤ基板を基板２とし、その
表面にフオトレジスト及びイオンミリング装置を
用いて通常の光学露光により、深さS.H＝370Å、
幅ｌ＝1.5μｍ、l′＝1.5μｍ即ち、ピツチ3μｍの複
数の直線的な溝３を形成した。その後、この溝３
を覆うようにNi82％−Fe12％（いずれも重量パ
ーセント）の組成からなるパーマロイ膜を膜厚tM
＝400Åで被着せしめた。
尚、この時パーマロイ膜の磁化容易軸E.Aは溝
３の直線方向と平行になるように、溝３を形成し
た。溝３が形成されていない基板２上のパーマロ
イ膜の異方性磁界Hkは60peであつた。つづいて
パーマロイ膜をフオトエツチングによつて長さＬ
＝50μｍ、幅Ｗ＝10μｍの寸法を有し、その長さ
方向とパーマロイの磁化容易軸E.Aの成す角（即
ち、溝３の直線方向と成す角）θ0が45゜となるス
トライプ状にパターン化してMR素子１を形成し
た。得られたMR素子１の飽和磁化Ｍは
800emu／c.c.であつた。従つてMR素子１の幅方
向反磁界Hdは約40peとなる。即ち、Hd／Hkは
0.67の値を有し、Hd／Hk＜１の条件を満す。
つづいて、MR素子１の長さ方向の両端に電気
端子４を形成し、幅Ｗ方向に印加する磁界Ｈに対
する抵抗値の変化分ΔRを測定した。その磁界Ｈ
−抵抗変化ΔR特性を第５図に示す。尚、ΔRの
値はMR素子１が有する最大抵抗変化ΔRmで規
格化している。
第５図から明らかな様に、本発明では、印加磁
界Ｈに対して線形応答する磁界領域が大きく改善
され、しかも、磁界Ｈに対して有効に寄与する
MR素子の抵抗変化ΔRは最大抵抗変化ΔRmと同
等になるまで変化しており、磁化Ｍは磁界Ｈに対
して、スムーズな回転を呈している。
本発明の効果を更に理解するため、第２図及び
第４図に示した従来例と第５図に示す本発明の磁
界Ｈ−抵抗変化ΔR特性を定量的に比較し、表に
示す。表中、許容信号磁界とは、抵抗変化ΔRが
線形性を保つ磁気記憶媒体磁からの信号磁界Hs
の範囲を意味し、抵抗変化利用率とは、上記許容
信号磁界を印加した時の、信号として利用可能な
抵抗変化の最大抵抗変化ΔRmに対する割合を意
味する。即ち、第２図，第４図及び第５図中に示
す曲線AB上もしくは曲線A′B′上の磁界範囲と抵
抗変化の範囲を示している。
The present invention provides a magnetoresistive head (hereinafter referred to as "MR element") equipped with a ferromagnetic magnetoresistive element (hereinafter referred to as MR element) that reads magnetic information written on a magnetic storage medium using the so-called magnetoresistive effect.
(referred to as MR head). MR heads are attracting attention as a device that greatly contributes to improving recording density in magnetic recording.
However, as is well known, when an MR element is used as a highly efficient reproduction head that exhibits a linear response to magnetic information written on a magnetic storage medium, the sense current I flowing through the MR element and the A bias means must be provided for setting the angle θ formed by the magnetization M (hereinafter referred to as bias angle) to a predetermined value (preferably 45°). Conventionally, a specific method of providing the above-mentioned bias means is to make the MR element closely face (or come into contact with) the MR element.
A magnetically hard magnetic material or a good electrical conductor is arranged, and the magnetic field generated from the current flowing through the magnetic material or the electrically good conductor is used as a bias magnetic field, and the angle θ of the magnetization M of the MR element is defined as the sense current I and approximately 45 There is a known method for setting the value to ゜. However, these biasing methods require relatively large magnetic fields, which can alter the information on the magnetic storage medium. In particular, when the former magnetically hard magnetic material is placed close to (or in contact with) the MR element, the bias angle θ must be set strictly and with good reproducibility.
It is difficult to set the angle at 45 degrees, and if the latter electrically conductive material is placed close to (or in contact with) the MR element, it is necessary to pass a relatively large current through the electrically good conductor. The electrical resistance of the element causes thermal drift and is also a cause of thermal noise. In order to solve these problems, in contrast to the bias method using an external magnetic field described above, as shown in FIGS. 1 and 3, the MR element is Magnetization M of the element
A known method is to set the angle at approximately 45 degrees. This method involves applying a bias magnetic field externally.
Since the bias means attached to the MR element is not required, the MR head can be made smaller, and furthermore, when a shield configuration is used, the gap can be made narrower. FIG. 1 is a schematic perspective view of the MR element portion of the MR head disclosed in Japanese Patent Application Laid-Open No. 46-5580. According to this method, the sense current I and the MR element 1
The angle formed by the easy magnetization axes E and A is set in advance to be greater than the bias angle, so that Hd/Hk<1 is satisfied between the width direction demagnetizing field Hd and the anisotropic magnetic field Hk of the MR element 1.
By selecting the dimensions and material of the MR element 1, a predetermined bias state can be achieved. In addition, FIG. 2 shows the width W of the MR element 1 shown in FIG.
An external magnetic field H (horizontal axis) is applied in the direction, and the resulting resistance change ΔR is the maximum resistance change ΔRm of the MR element 1.
(In other words, the difference between the resistance value of the MR element when the magnetization M is parallel to the sense current I and the resistance value when the magnetization M is perpendicular to the sense current I) It is a magnetic field H-resistance change characteristic curve diagram. MR element 1 used for measurements in Figure 2
82% Ni-12% Fe on a smooth single-crystal sapphire substrate (not shown) with A-plane as the main surface.
Permalloy with a composition of
It is processed into a stripe shape having dimensions of m and width W = 10 μm, and the angle θ 0 between the length direction and the axis of easy magnetization E/A of permalloy is set to 45°.
The obtained demagnetizing field Hd in the width W direction of the MR element 1 is approximately
40 pe , the anisotropy field Hk is 60 pe and therefore Hd/
Hk is set to 0.67. In the magnetic field H-resistance change ΔR characteristic curve shown in Figure 2, ΔR/ΔRm
=1 and ΔR/ΔRm=0 mean the case where the magnetization M of the MR element 1 and the sense current I are parallel and perpendicular, respectively. As is clear from FIG. 2, there is certainly a region (for example, on curve AB or curve A'B') where there is a linear response to the applied magnetic field H, and a bias state is realized. However, the resistance change ΔR of the MR element that effectively contributes to the magnetic field H is the maximum resistance change ΔRm
Since the value is smaller, the utilization rate of resistance change (ΔR/ΔRm) is smaller, and the magnetic field range that exhibits a response with good linearity is smaller. This phenomenon has already been reported in Physica Status Solidi(a), 1981, Volume 64,
This is reported in the paper by Mr. O. Gebhardt et al. on pages 513-517, and is found not only in the example shown in FIG. 2 but also in general MR heads that were started in the above-mentioned Japanese Patent Application Laid-open No. 46-5580. Furthermore, with this method, it is difficult to set the magnetization of the MR element at a predetermined angle with respect to the sense current I with good reproducibility, and variations in the reproduction characteristics between MR elements fabricated at the same time tend to occur, which reduces productivity. It was inconvenient. On the other hand, FIG. 3 is a schematic perspective view of a "jogging MR element" disclosed in Japanese Patent Application No. 57-050586 by the present applicant. In this MR element, an MR element 1 is provided on a substrate 2 in which one or more mutually parallel linear grooves (recesses) 3 are provided, and the shape of the MR element 1 caused by the grooves 3 is Using magnetic field,
Angle θ between magnetization M of MR element 1 and sense current I
It controls the FIG. 4 shows actually measured data of the magnetic field H-resistance change ΔR characteristic curve of the MR head shown in FIG. The measurement method is exactly the same as the characteristic curve shown in FIG. The MR element 1 used for the measurement in FIG.
The substrate 2 is a glass substrate on which a plurality of linear grooves 3 with m, l' = 1.5 μm, that is, a pitch of 3 μm is formed, and a permalloy film having a composition of 82% Ni-12% Fe (both weight percentages) is formed on this substrate. Thickness t M = 400Å
The groove 3 was coated with a stripe and processed into a stripe having a length of 50 μm and a width W of 10 μm, and the angle θ 0 between the length direction and the linear direction of the groove 3 was set to 45°. In this case, the easy axis of magnetization of MR element 1
The direction of the EA is set substantially parallel to the linear direction of the groove 3. Further, the anisotropic magnetic field Hk of the permalloy film on the glass substrate on which the groove 3 is not formed is 4 pe . As is clear from FIG. 4, even in the biasing method using the configuration shown in FIG. 3, there is a region in which linear response occurs to the applied magnetic field H, and a bias state is realized. Furthermore, compared to FIG. 2, the resistance change ΔR of the MR element that effectively contributes to the magnetic field H changes until it becomes equal to the maximum resistance change ΔRm. That is,
The magnetization M rotates smoothly with respect to the applied magnetic field H. However, the bias angle θ is not sufficient, and the region of linear response is narrow, and the dynamic range is correspondingly small. This means that reproduced waveform distortion is likely to occur. To solve this problem, the pitch of the grooves 3 may be made smaller, for example, by setting the pitch to 1 μm or less. This reduces the MR caused by groove 3.
By further increasing the shape demagnetizing field of element 1, MR element 1
The bias angle θ can be made to match the angle θ 0 formed between the longitudinal direction of the groove 3 and the linear direction of the groove 3 . However, machining the grooves 3 with the extremely small pitch described above requires special techniques and equipment such as laser holography or electron beam exposure, and requires a large number of man-hours, resulting in lower yields and longer production times. As a result, MR heads have to be expensive. The object of the present invention is to solve the above-mentioned conventional drawbacks.
Low playback waveform distortion and wide dynamic range.
Moreover, it is an object of the present invention to provide a magnetoresistive head that realizes a bias state with a high utilization rate of resistance change. According to the present invention, the strong magnetic field is adjusted such that the geometric demagnetizing field Hd in the detection magnetic field direction of the ferromagnetic magnetoresistive element and the anisotropic magnetic field Hk of the magnetoresistive element itself satisfy the relationship Hd/Hk<1. The material of the magnetic magnetoresistive element or the substrate forming the ferromagnetic magnetoresistive element is selected, and the surface of the substrate has one or more mutually parallel linear convex portions or concave portions. It is possible to provide a magnetoresistive head having the following properties. Embodiments of the present invention will be described in detail below with reference to the drawings. In addition, in explaining the configuration of the present invention,
Using Figure 3 again. In FIG. 3, the surface of the insulating substrate material 2 is etched with a width l and a depth SH pitch l+ by a well-known method such as photoresist and etching solution or ion milling.
A large number of linear grooves (recesses) 3 are formed so as to be substantially parallel to each other depending on the value of l'. Next, an MR element 1 made of a ferromagnetic thin film having a thickness t M is formed by a method such as sputtering or vapor deposition so as to cover this groove 3 . The MR element 1 is processed into a stripe shape having a width W, and the angle formed between the length direction of the MR element 1 and the linear direction of the groove 3 has a predetermined value θ 0
is set to . Further, two electrical terminals 4 for introducing a sense current are connected to both ends of the MR element 1 in the length direction. Therefore, the sense current I introduced from the electric terminal 4 forms an angle of θ 0 with the linear direction of the groove 3. The pitch l+l' of the grooves 3 in the present invention may be on the order of several micrometers, which can be formed by ordinary optical exposure, and special techniques and equipment such as laser holography or electron beam exposure are not particularly required. Moreover, the anisotropic magnetic field of the MR element 1 in the present invention
Hk is selected so as to be larger than the demagnetizing field Hd in the direction of the width W of the MR element. Here, the value of the demagnetizing field Hd when groove 3 does not exist is used, and as is well known, Hd
It is given by ≒4πMt M /W. However, M represents saturation magnetization. When the dimensions, especially the width W, of the MR element 1 are specified (usually selected from several μm to several tens of μm), the anisotropic magnetic field Hk, which is larger than the demagnetizing field Hd, is generated by, for example, a certain crystal of a single crystal substrate. When the MR element is attached to the surface or as the material of the MR element, Ni-Co
When alloys are used, or even when these are combined, values of several tens of O e or more can be achieved. Next, in order to clarify the effects of the present invention, specific examples will be described below. In FIG. 3, a single-crystal sapphire substrate with a smooth surface and A-plane as the main surface is used as the substrate 2, and its surface is exposed to a depth of SH=370 Å by ordinary optical exposure using a photoresist and an ion milling device.
A plurality of linear grooves 3 were formed with a width l=1.5 μm and l'=1.5 μm, that is, a pitch of 3 μm. Then this groove 3
A permalloy film with a composition of 82% Ni-12% Fe (both weight percentages) is coated with a film thickness t M.
= 400 Å. At this time, the grooves 3 were formed so that the axis of easy magnetization EA of the permalloy film was parallel to the linear direction of the grooves 3. The anisotropic magnetic field Hk of the permalloy film on the substrate 2 on which the groove 3 was not formed was 60 pe . Next, the permalloy film is photoetched to length L.
= 50 μm, width W = 10 μm, and a striped pattern in which the angle formed by the length direction and the permalloy's easy axis of magnetization EA (that is, the angle formed with the linear direction of the groove 3) θ 0 is 45°. Then, MR element 1 was formed. The obtained saturation magnetization M of the MR element 1 is
It was 800emu/cc. Therefore, the width direction demagnetizing field Hd of the MR element 1 is approximately 40 pe . That is, Hd/Hk is
It has a value of 0.67 and satisfies the condition of Hd/Hk<1. Subsequently, electric terminals 4 were formed at both ends of the MR element 1 in the length direction, and the change in resistance value ΔR with respect to the magnetic field H applied in the width W direction was measured. The magnetic field H
-Resistance change ΔR characteristics are shown in Figure 5. Note that the value of ΔR is normalized by the maximum resistance change ΔRm of the MR element 1. As is clear from FIG. 5, in the present invention, the magnetic field region that linearly responds to the applied magnetic field H is greatly improved, and moreover, it contributes effectively to the magnetic field H.
The resistance change ΔR of the MR element changes until it becomes equal to the maximum resistance change ΔRm, and the magnetization M exhibits smooth rotation with respect to the magnetic field H. In order to further understand the effects of the present invention, the magnetic field H-resistance change ΔR characteristics of the conventional example shown in FIGS. 2 and 4 and the present invention shown in FIG. 5 are quantitatively compared and shown in a table. In the table, the allowable signal magnetic field is the signal magnetic field Hs from the magnetic storage medium in which the resistance change ΔR maintains linearity.
The resistance change utilization rate means the ratio of the resistance change that can be used as a signal to the maximum resistance change ΔRm when the above-mentioned permissible signal magnetic field is applied. That is, it shows the magnetic field range and resistance change range on curve AB or curve A'B' shown in FIGS. 2, 4, and 5.
【表】
表から明らかな様に本発明では、許容信号磁
界、抵抗変化利用率のいずれも大きく改善されて
いる。
以上、実施例で明らかな様に、本発明による
MRヘツドは基板上に形成された溝３のピツチが
数μｍオーダであつても、MR素子の幅方向反磁
界Hdと異方性磁界Hkの間にHd／Hk＜１を満す
ことにより、再生波形劣を少なくし、抵抗変化の
利用率の高い、即ちダイナミツクレンジの大きい
バイアス状態が実現された。
又、本発明によるMRヘツドにおける異方性磁
界Hkの大きいMR素子として、上述した、実施
例の如く、Ａ面を主面とする単結晶サフアイヤ基
板上のNiFe合金膜に限らず、絶縁性のセラミツ
クス基板やガラス基板等に被着せしめたNiCo合
金薄膜や、特開昭57−24017に開示されている如
く、単結晶サフアイヤ基板に被着せしめたNiCo
合金薄膜を用いた場合でも同様の効果が確認され
た。
以上、本発明は通常の光学的露光で形成できる
数μｍオーダのピツチを有する溝を基板上に形成
し、その後に被着せしめるMR素子の幅方向の反
磁界HdをMR素子の異方性磁界Hkより小さくす
ることにより、ダイナミツクレンジの大きいバイ
アス状態を実現したMRヘツドを提供できる。し
かも、この溝によつて磁化の方向が一意的に決定
されるため、バイアス角を再現性良く設定した
MRヘツドが容易に提供できる。
更に、本発明は他のバイアス手段を必要としな
いため、シールド構成とした時のギヤツプが極め
て小さく設定でき、高記録密度再生に適したMR
ヘツドを提供できる。[Table] As is clear from the table, in the present invention, both the allowable signal magnetic field and the resistance change utilization rate are greatly improved. As is clear from the examples above, according to the present invention
Even if the pitch of the grooves 3 formed on the substrate is on the order of several μm, the MR head satisfies Hd/Hk<1 between the width direction demagnetizing field Hd and the anisotropic magnetic field Hk of the MR element. A bias state with reduced reproduction waveform defects and high utilization of resistance change, that is, a large dynamic range, has been realized. In addition, the MR element with a large anisotropic magnetic field Hk in the MR head according to the present invention is not limited to the NiFe alloy film on the single-crystal sapphire substrate with the A-plane as the main surface as in the above-mentioned embodiment; NiCo alloy thin films deposited on ceramic substrates, glass substrates, etc., and NiCo deposited on single crystal sapphire substrates as disclosed in JP-A-57-24017.
A similar effect was confirmed when using an alloy thin film. As described above, the present invention forms grooves with a pitch on the order of several μm on a substrate, which can be formed by ordinary optical exposure, and then converts the demagnetizing field Hd in the width direction of the MR element to the anisotropic magnetic field of the MR element. By making it smaller than Hk, it is possible to provide an MR head that realizes a bias state with a large dynamic range. Moreover, since the direction of magnetization is uniquely determined by this groove, the bias angle can be set with good reproducibility.
MR heads can be easily provided. Furthermore, since the present invention does not require any other bias means, the gap can be set extremely small when using a shield configuration, making it possible to set an MR system suitable for high recording density reproduction.
We can provide heads.
【図面の簡単な説明】[Brief explanation of drawings]
第１図は従来のMRヘツドのMR素子部分を示
す概略斜視図、第２図は従来のMRヘツドのMR
素子の磁界−抵抗変化特性曲線図、第３図は従来
及び本発明のMRヘツドのMR素子部分を示す概
略斜視図、第４図は従来のMRヘツドのMR素子
の磁界−抵抗変化特性曲線図、第５図は本発明の
MRヘツドのMR素子の磁界−抵抗変化特性曲線
図である。
図において、１…MR素子、２…絶縁性基板
材、３…溝（凹部）、４…電気端子。
Figure 1 is a schematic perspective view showing the MR element part of a conventional MR head, and Figure 2 is a schematic perspective view of the MR element of a conventional MR head.
3 is a schematic perspective view showing the MR element portion of the conventional MR head and the present invention. FIG. 4 is a diagram of the magnetic field-resistance change characteristic curve of the MR element of the conventional MR head. , FIG. 5 shows the structure of the present invention.
FIG. 3 is a magnetic field-resistance change characteristic curve diagram of the MR element of the MR head. In the figure, 1...MR element, 2...Insulating substrate material, 3...Groove (recess), 4...Electric terminal.