Integrated thin film magnetic head

Abstract: In an integrated thin film magnetic head; a write pole or inductive head (I h ) includes a first and a second magnetic cores (1,5) magnetically coupled to form a magnetic circuit and a coil (3) formed between said first and second magnetic cores (1,5); and a MR element read pole or MR head MR h includes a first and a second yoke (14,5), a MR element (12) and a bias conductor (10) for applying a biasing magnetic field on said MR device; wherein said first magnetic core (1) or said second magnetic core (5) of said write pole also constituting said second yoke (5) of said read pole.

Description: FIELD OF THE INVENTION AND RELATED ART STATEMENT 1. FIELD OF THE INVENTION The present invention relates to an integrated thin film magnetic head used in a magnetic writing and reading apparatus. 2. DESCRIPTION OF THE PRIOR ART With the development of the magnetic writing/reading apparatus directed to the high recording density, demand for a thin film magnetic head adapted to narrow track width and multiple tracks system has remarkably been growing. Of the known thin film magnetic head, there are generally two types; one is an inductive head which uses a coil similar to that used in a bulk head, and the other is a magneto-resistive head (MR head) of read-only type which utilizes a magneto-resistive effect (MR effect). Since the output level of the inductive head using the coil is proportional to the relative velocity of the recording medium against the magnetic head, it is low in the case of a small relative velocity. Therefore it cannot read the magnetically recorded information unless the velocity is sufficiently large. On the other hand, the MR head utilizing the MR effect has an advantage in that it can produce a signal of a constant output level irrespective of relative velocity of the recording medium to head because it can perform a magneto-electric conversion which is made by varying of the resistance value of a magneto-resistive effect element (MR element) in response to the magnetic flux entering into the device from the recording medium. However, since the magneto-resistive conversion is irreversible, the MR head cannot write information onto the recording medium. And thus a magnetic writing/reading apparatus provided with the MR head requires a separate recording head. Therefore, in order to perform both the recording and reading by a head of one tip, it is required to laminate a recording (write) pole and a read pole on a single substrate. Hereinafter, an elucidation will be made on an example of the conventional integrated thin film magnetic recording head comprising a write pole and a read pole formed on a single tip, First, the inductive head which serves as the write pole is formed such that, on a magnetic substrate, which serves as a first magnetic core layer, a coil is formed interposing a first insulator layer inbetween. And then a second magnetic core layer is formed thereon interposing a second insulator layer inbetween. At a front gap of said inductive head, its gap length or distance in the gap is determined by thickness of the second insulator layer. At a back gap, the second magnetic core is magnetically coupled to the magnetic substrate. On top the thus-deposited inductive head or write pole, there is deposited an isolation layer composed of non-magnetic substance. Then, in advance to the formation of the overlying MR head on said isolation layer, the surface of said isolation layer must be smoothed by lapping, because unevenness of the underlying inductive head is replicated as it is on said surface. The conventional MR head comprises a lower yoke formed on the isolation layer, and thereon a third insulator layer, a bias conductor and a fourth insulator layer are laminated in this sequential order. In order to supply a sense current on the MR element, two lead conductors formed by a layer are formed on both ends of said MR device. And an upper yoke for applying a signal magnetic field of the recording medium is formed on the device interposing a fifth insulator therebetween. At a front gap of said MR head, its gap length is determined by the fifth insulator layer. And at a back gap, the lower yoke is magnetically coupled with the upper yoke. With any of the conventional integrated thin film magnetic head it has been difficult to reproduce the recorded information with a satisfactory frequency characteristics, because the write pole is completely isolated and independent from the read pole. In other words, in the case where the wavelength of the recorded information is in an integer times of the thickness of the isolation layer, the magnetic flux of the recording medium does not effectively enter into the reading pole owing to a possible interaction with the magnetic core of the write pole. Therefore, the conventional integrated thin film magnetic head has such a disadvantage that the output level is low for the signal component having the wavelength of integer times the thickness of the isolation layer. In addition to this, the conventional integrated thin film magnetic head has such other disadvantages that it needs an etching process of exposuring the layer of coil for producing coil terminals, that the etching process takes a long time when the isolation layer has a large thickness, and that the making of the isolation layer takes a considerable time which leads to a high cost. An integrated thin film magnetic head of the kind defined by the precharacterizing features of the claim is known from the JP-A-2-91 807. The thin film write pole of this known magnetic head is required to form a predetermined configuration by a patterning process. As a result, before the formation of the overlapping a magneto-restrictive effect element, the integrated thin film magnetic head has a complicated stress distribution. When the thin film read pole of the magneto-resistive effect element is formed on the isolation layer, the magneto-resistive effect element does receive the influence of the complicated stress distribution, and a magnetic property of the magneto-resistive effect element changes to an undesirable property. For example, many magnetic domain walls appear in the magneto-resistive effect element, and an increase of noise, such as a Barkhausen noise, occurs, caused by imbalance movements of the magnetic domain walls. Further, a gap for the thin film write pole is formed between the upper yoke and the lower yoke having a gap for the thin film read pole. A further integrated thin film magnetic head of the kind defined by the precharacterizing features of claim 1 is known from the JP-A-62-145 527. Since the thin film read pole is provided on the thin film write pole in this known magnetic head, a protective layer is required to further laminate on the thin film read pole for protecting the thin film read pole. This protective layer is fixed to the thin film read pole by a resin or the like. The protective layer and the resin have a complex stress distribution in case that the integrated thin film magnetic head is heated for increasing the magnetic properties. Thereby, problems arise when a MR element and an upper side yoke are adversely, affected by the protective layer and the resin. From the EP-0-423 878 A1 a thin film magnetic head is known, comprising a magnetic yoke having first and second flux conductors and a magnetic-resistance element, located remotely from a head face. An edge portion of the magneto-resistance element is located closer to the head face than a second edge portion. The first flux conductor extends from the head face to close to the first edge portion and the second flux conductor extends from the head face at least to the second edge portion. The magnetic head furthermore comprises a third flux conductor which extends from the head face to close to an end portion of the first flux conductor located near the first edge portion. A transducing gap and an inductive element are located between the first and the third flux conductors. OBJECT AND SUMMARY OF THE INVENTION The present invention intends to overcome the above-mentioned disadvantages inherent to the conventional magnetic heads and has as an object the provision of an integrated thin film magnetic head of the kind defined by the precharacterizing features of the claim having an excellent frequency characteristics. This object is attained by the characterizing features of the claim. As being configured as mentioned above, in the integrated thin film magnetic head built in accordance with the present invention, the upper magnetic layer of the write pole also works as the lower magnetic layer of the read pole, and thus the isolation layer is dispensed with. This magnetic head has an advantage that it can reproduce the recorded information with a preferable frequency characteristics because it is free from the drop in the output level at a specified frequency range attributable to the existence of the isolation layer. In addition to this, the integrated thin film magnetic head of the present invention has another advantage that it can reduce the overall thickness of the thin films and thus reduce the amount of the uneven wear of the thin film layer. Further, the integrated thin film magnetic head of the present invention has a further advantage that it can easily expose the terminals such as coil terminals formed on the lower layer, bias terminals for the read pole and lead terminals, etc., because the thickness of the underlayer for flattening can be reduced as compared with the conventional ones including an isolation layer disposed between the inductive head part and the overriding MR head. While the novel features of the invention are set fourth particularly in the appended claims, the invention, both as to organization and content, will be better understood and appreciated, along with other objects and features thereof, from the following detailed description taken in conjunction with the drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 and FIG. 1a are side cross-sectional views of an integrated thin film magnetic head of an embodiment built in accordance with the prior art during its manufacturing process. FIG. 1b is a side cross-sectional view of the integrated thin film magnetic head shown in FIG. 1a in its completed form. FIG. 1c is a front view of the integrated thin film magnetic head shown in FIG. 1b. FIG. 2 and FIG. 2a are side cross-sectional views of the integrated thin film magnetic head of an embodiment built in accordance with the present invention during its manufacturing process. FIG. 2b is a side cross-sectional view of the integrated thin film magnetic head shown in FIG. 2a in its completed form. FIG. 2c is a front view of the integrated thin film magnetic head shown in FIG. 2b. DESCRIPTION OF THE PREFERRED EMBODIMENTS Example 1. In the following several paragraphs, an embodiment of an integrated thin film magnetic head in accordance with the prior art will be elucidated with reference to FIGs. 1, 1a, 1b and 1c of the drawings. [Configuration] A write pole, which is the inductive head, is configured as follows: At first, on a magnetic substrate 1 of a ferrite, a first insulator layer 2 of SiO 2 is formed by a known lithographic method so as to have a predetermined pattern which is designed for making an inductive head or writing head. The thickness of the first insulator layer 2 is preferably from 0.5 µm to 1.0 µm. Thereafter, a coil layer 3 of 1.0 µm gold is formed on selected part of the first insulator 2 by a known vapor deposition method using a lithographic method. Then, on the substrate having the first insulator layer 2 and the coil layer 3, a second insulator layer 4 of 1.0 µm thickness is formed with a predetermined pattern having an opening 41 by a known lithographic method. Thereafter, a second magnetic core layer 5 of 6 µm thickness Co-based amorphous patterned to have a given shape, which determines the write track width by its shape, is formed. In order to obtain a very even and flat surface necessary for subsequent forming of an overriding structure of MR head, the underlayer for flattening 8 is formed on the second insulator layer 4, in a manner to fill the regions not covered by the second magnetic core layer 5. The filler layer 8 is made of alumina (Al 2 O 3 ) and has a thickness equal to or slightly larger than that of the second magnetic core layer 5. After the forming of the filler layer 8, the surfaces of the second magnetic core layer 5 and the filler layer 8 are smoothed by lapping to produce a continuous even flat surface. The above-mentioned configuration form the writing head which is an inductive type head. In the inductive head, the gap length at the front gap part 6 is determined by the thickness of the second insulator layer 4. At the back gap part 7, the second magnetic-layer 5 is magnetically coupled to the magnetic substrate 1. On the above-mentioned inductive head part I h , the below-mentioned MR head part MR h is configured. The MR head part MR h , or the read pole, is configured as follows: At first a third insulator layer (SiO 2 ) 9 is deposited on the second magnetic core 5, and then a bias conductor 10 of gold is deposited on the insulator layer 9. Thereafter, a fourth insulator layer 11 of SiO 2 is formed further thereon. Then a MR element 12 of permalloy layer is formed thereon. A pair of lead wires (not shown in FIG. 1) of gold are connected to both end of the MR element 12 in order to flow a sense current through the MR element 12. Thereafter, a fifth insulator layer 13 of SiO 2 is formed. And then, a yoke 14 of Co-based amorphous, which is for applying the signal magnetic field derived from the recorded information on the recording medium, is laminated on the MR element 12. The yoke 14 determines the read track width by its shape. At the front gap 15 of the reading pole, the gap length is determined by thickness of the fifth insulator layer 13. And at the back gap 16 the yoke 14 contact directly and is magnetically coupled with the second magnetic core 5. After the deposition of the yoke 14, a protective layer 17 of alumina (Al 2 O 3 ) is deposited as shown in FIG.1b. Since the unevenness of the yoke 14 is replicated on the surface of the protective layer 17 as it is, the surface is smoothed by lapping. And further thereon a protective substrate 18 of alumina is bonded. Then, the resultant laminated body is cut along a slightly convex sliding face (this sliding face is formed as a slightly convex cylindrical face of very small curvature in order to give a tape a good contact to the head), as shown by a line α-α including the front gaps 6 and 15 to expose a sliding surface shown by the front view of the head of FIG. 1c. The sliding surface is thereafter finished to have a given shape and surface condition convenient for contacting the recording medium. [Operation] Hereinafter, the operation of the above-mentioned integrated thin film magnetic head will be described. During recording, when a write current flows in the coil 3, a signal magnetic flux induced by the current and thereby flows a signal magnetic flux through a magnetic circuit composed of the magnetic substrate 1 (serving as the first magnetic core) and the second magnetic core 5, and produce a signal magnetic field at the front gap 6 of the write pole, whereby an information is stored on a recording medium. During the readback, a D.C. current is flown through the bias conductor 10 for applying a biasing magnetic field to the MR element 12, and a signal magnetic field produced in response to the recorded information on the recording medium enters through the front gap 15 of the read pole. The signal magnetic flux flows through a magnetic circuit composed of the second magnetic core 5 and the yokes 14 having the MR element 12 at its gap 141. At that time, the resistance value of the MR element varies in response to the signal magnetic field applied to the MR element, and this variation in the resistance value is taken out as a voltage signal from the lead conductors. In this Example 1, since the second magnetic core 5 of the write pole or the inductive head also serves as the second yoke of the reading pole or the MR head, the isolation layer is dispensed with, thereby decreasing total thickness and further the recorded information is reproduced with a preferable frequency characteristics. In addition to this, since the overall layer thickness of the thin films is reduced, the amount of the uneven wear of the thin films can also be reduced. Further, in manufacturing the exemplified head, it is easy to expose the coil 3 to form the coil terminals by etching the underlayer for flattening 8, because the thickness of the under-layer for flattening 8 is the same as that of the second magnetic layer 5. Thus the etching itself is performed easily. In this Working Example, although the substrate made of the magnetic substance is used, it is needless to mention that the same advantage will be obtained by using a non-magnetic substrate having the first magnetic core laminated thereon and configuring the integrated thin film magnetic head based on this first magnetic core in the similar configuration. Example 2. In the following paragraphs, an embodiment of the present invention will be elucidated with reference to FIGs. 2, 2a, 2b and 2c of the drawings. In this example, the order of the inductive head part I h and the MR head part MR h are different from those of the Example 1, but the natures and thicknesses thereof are substantially the same as those of Example 1. [Configuration] The MR head, which is the read pole, is configured as follows: At first, as shown in FIG. 2 a layer 22 of a first yoke of Co-based amorphous having openings is deposited on a non-magnetic substrate 21. After filling a first insulator layer of silicon dioxide (SiO 2 ) 23 in the openings in the first yoke 22 for obtaining a flat face theretogether, a second insulator layer (SiO 2 ) 24 of a selected pattern is formed thereon, and further thereon a MR element 25 made of a permalloy layer is formed. A pair of lead conductors of gold layer (not shown in the drawing) are provided by known method to both ends of the MR element 25 so as to flow a sense current therethrough. Then a third insulator layer (SiO 2 ) 26 is formed thereon, and a bias conductor 27 of gold is formed further thereon. Thereafter, a fourth insulator layer 28 of SiO2 is formed so as to cover the bias conductor 27. And further thereon, a first magnetic core layer 29 of Co-based amorphous is formed. This first magnetic core layer 29 also serves as a second yoke. The yoke 22 is patterned to have a given shape for determining the read track width by its shape. But, unevenness of the read pole is replicated on the surface of the first magnetic core layer 29 as it is when having been formed. In order to obtain a very even and flat surface necessary for subsequent forming of an overriding structure of inductive head, a filler layer 30 is formed on the first yoke 22 and the second insulator layer 28, in a manner to fill the regions not covered by the first magnetic core layer 29. The filler layer 30 is made of alumina (Al 2 O 3 ) and has a thickness equal to or slightly larger than that of the first magnetic core layer 29. After the forming of the filler layer 30, the surfaces of the first magnetic core layer 29 and the underlayer for flattening 30 are smoothed by lapping to produce a continuous even flat surface. At the front gap 31 of the read pole, its gap length is determined by thickness of the fourth insulator layer 28; and at the back gap 32, the first magnetic core 29 is magnetically, coupled to the first yoke layer 22. A write pole, which is the inductive head, is configured as follows: At first, a fifth insulator layer 33 of SiO 2 is formed on the first magnetic core 29 and on the filler layer 30. Then, the fifth insulator layer 33 is etched so as to form a front gap 37 and a back gap 38. At the front gap 37, the gap length is determined by a sixth insulator layer 35 of SiO 2 , and at the back gap 38 the first magnetic core 29 is magnetically coupled to the second magnetic core 36. On the fifth insulator layer 33, there are formed a sixth insulator layer 35, and further thereon a coil 34 of gold and the second magnetic core layer 36 is piled up. The second magnetic core 36 is patterned so as to have a given shape in order to control the write track width by the shape. After the deposition of the second magnetic core 36, a protective layer 39 of alumina Al 2 O 3 is deposited as shown in FIG.2b. Since the unevenness of the second magnetic core 36 is replicated on the surface of the protective layer 39 as it is, the surface is smoothed by lapping. And further on the smoothly lapped surface a protective substrate 40 of alumina is bonded. Then, the resultant laminated body is cut along a slightly convex sliding face shown by a line β-β including the front gaps 31 and 37, thereby to expose a sliding surface as shown by the front view of the head of FIG. 2c. The sliding surface is thereafter finished in a manner to have given shape convenient for contacting the recording medium. [Operation] Hereinafter, the operation of the above-mentioned integrated thin film magnetic head will be described. During the recording, when a write signal current flows in the coil 34, a signal magnetic flux induced by the current flows through a magnetic circuit composed of the first magnetic core 29 and the second magnetic core 36 and makes a magnetic field at the front gap 37 of the write pole. Thereby, an information is stored on a recording medium which is driven sliding on the tape running face 99. During the readback, a D.C. current is flown through the bias conductor 27 for applying a biasing magnetic field to the MR element 25. Then a signal magnetic field is produced in response to the recorded information on the recording medium, and a magnetic flux flows from the front gap 31 of the read pole through a magnetic circuit composed of the yoke 22 and the first magnetic core 29. Therefore a signal magnetic field is induced at the gap 221 and this magnetic field is applied to the MR device. Accordingly, the resistance value of the MR device 25 varies in response to the signal magnetic field, and this variation in the resistance value induces a variance in the voltage to be sensed. In this Working Example, since the first magnetic core 29 of the write pole or the inductive head also serves as the second yoke of the read pole or the MR head, the isolation layer is dispensed with, thereby decreasing the total thickness and further the recorded information is reproduced with a preferable frequency characteristics. In addition to this, since the overall layer thickness of the thin films is reduced, the amount of the uneven wear of the thin films can also be reduced. Further, in manufacturing the exemplified head, it is easy to expose the bias conductor 27 and the lead terminal (not shown in the drawing) to form the bias terminals by etching the underlayer for flattening 30, because the thickness of the underlayer for flattening 30 is the same as that of the second magnetic layer 29. Thus the etching itself is performed easily. Although the invention has been described in terms of the presently preferred embodiment, it is to be understood that such disclosure is not to be interpreted as limiting. Various alterations and modifications, within the scope of the appended claims, will no doubt become apparent to those skilled in the art having read the above disclosure.

Claims: An integrated thin film magnetic head configured to combine at least one thin film write pole with at least one thin film read pole formed on a non-magnetic substrate (21) in a laminated relationship, wherein the thin film read pole comprises: a first yoke (22), a second yoke (29) and a magneto-resistive effect element (25) disposed at an adjacent location to the gap (221), the first and the second yokes (22, 29) and the magneto-resistive effect element (25) being magnetically coupled to form a first magnetic circuit, and a bias conductor (27) disposed at an adjacent location to the magneto-resistive effect element (25) for applying a biasing magnetic field on the magneto-resistive effect element (25), and a second front gap member (31) formed between the first and second yokes (22, 29), the second front gap member (31) being disposed to face the recording medium, and wherein the thin film write pole comprises: first and second magnetic cores (29, 36) which are magnetically coupled to form a second magnetic circuit, an electrically-conductive coil (34) formed between the first and second magnetic cores (29, 36), and a first gap member (37) formed between the first and the second magnetic cores (29, 36), the first gap member (37) being disposed to face a recording medium, and wherein the first and second magnetic cores (29, 36) of the thin film write pole and the first and the second yokes (22, 29) of the thin film read pole are magnetically coupled with each other, characterized in that the thin film read pole is provided on the non-magnetic substrate (21), and the thin film write pole is laminated further thereon, the first magnetic core (29) of the thin film write pole also constitutes the second yoke (29) of the thin film read pole, and the first yoke (22) of the read pole having a gap (221) therein is adjacent to the non-magnetic substrate (21).

Inventors: FUKAZAWA TOSHIO, MITANI SATORU, TOSAKI YOSHIHIRO, WADA KUMIKO, YANAGI TERUMI, FUKAZAWA, TOSHIO, MITANI, SATORU, TOSAKI, YOSHIHIRO, WADA, KUMIKO, YANAGI, TERUMI
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1992
Main classification: G11B5
IPC codes: G11B5