Patent Application
20060203381
This application claims priority from Japanese Patent Application No. JP2005-069143, filed Mar. 11, 2005, the entire disclosure of which is incorporated herein by reference.
The present invention relates to a magnetic head used for recording and reading magnetic recording media, also to a method of manufacturing the same magnetic head and to a hard disk drive mounting the same magnetic head.
A hard disk drive reads and writes data from and to the recording disks using magnetic heads. In view of increasing the recording capacity per unit area of a magnetic disk, it is essential to improve an a real recording density to higher density. However, the present longitudinal recording system has a problem that the a real recording density cannot be raised due to thermal fluctuation in the magnetization of a medium, if the recording bit length becomes small. As a method for solving this problem, the perpendicular recording system has been proposed, in which the magnetization signal is recorded in the perpendicular direction to the surface of a medium. In this perpendicular recording system, a giant magneto-resistive head can be used to read the data. Moreover, a tunneling magneto-resistive head which can provide larger read output and a CPP (Current-Perpendicular-to-Plane) type GMR head which causes the current to flow perpendicularly to the film surface can also be used.
Meanwhile, a single pole head must be used for recording of data. Even in the perpendicular recording, both track density and linear recording density must be increased in order to improve the a real recording density. For increasing the linear recording density, the gradient of recording magnetic field of the recording head must be increased. As a method of this purpose, it has been proposed to form a structure in which the double-layer is employed for a recording medium and a soft-magnetic layer is provided as the lower layer. However, in order to achieve the higher recording density exceeding 200 Gb/in2, increase in the magnetic field gradient from the recording head and control of spread in writing of data or the like are also required. For the increase in the magnetic field gradient, it has been proposed, for example, to introduce a structure that a trailing shield is provided at the area near the main pole. For the control of spread in the writing of data, US2002/0176214A1 discloses an example of the magnetic head for perpendicular recording in which a side shield is provided. Moreover, JP-A No. 127480/2004 discloses an example of the magnetic head for perpendicular recording in which the side shield is also provided. In addition, JP-A Nos. 34916/2001 and 182226/2000 disclose an example of the structures in which the double-layer is employed for the read shield. Moreover, JP-A No. 20916/2000 describes a magnetic head in which a lower magnetic core which is also used in common as an upper shield film of the read shield is formed of two layers of magnetic layer via a non-magnetic layer.
In the case of providing a trailing shield or a side shield to a recording head, it is preferable to provide a main pole 12 to the side nearer to a read head for improvement in format efficiency of a hard disk drive and convenience in connection between the trailing shield, side shield and a return pole 11. However, the study by the inventors has revealed that the magnetic field from the main pole 12 or a yoke 14 enters the upper read shield 17 of the read head and varies an output of the read head as indicated by an arrow mark 31 (see
US2002/0176214A1 and JP-A No. 127480/2004 do not explain influence of the magnetic field entering the read head from the recording head. Moreover, JP-A Nos. 34916/2001 and 182226/2000 relate to a magnetic head for longitudinal recording. JP-A No. 34916/2001 discloses a structure in which the double-layer is introduced for the shield of read head. However, in this case, a non-magnetic layer to control instability of the shield itself is not inserted between two layers. JP-A No. 182226/2000 shows an example wherein a highly thermal conductive material is used to radiate the heat generated from the magnetic head. JP-A No. 20916/2000 shows an example wherein generation of noise is controlled through difference of characteristics of two laminated layers of magnetic layer of the shield which is also used in common as a part of the recording head.
Considering the problems described above, a feature of the present invention is to provide a magnetic head for perpendicular recording which is freed from the influence on the read head of the magnetic field from the recording head and is also to provide a hard disk drive which has enhanced the format efficiency by mounting the magnetic head for perpendicular recording.
The present invention relates to a magnetic head for perpendicular recording having a main pole and a return pole to a read head, and a recording head utilizing the magnetoresistive effect, which is characterized in that the main pole is provided between the return pole and the read head, and a read shield provided nearer to the main pole of the read head is formed of three or more layers including a lower shield layer, a non-magnetic layer, and an upper shield layer. The layers of three or more layers of the read shield 3 may also be formed of the plating process.
According to the present invention, the magnetic head for perpendicular recording which has suppressed variation in the read output of the read head due to the magnetic field from the main pole can be obtained and the hard disk drive having improved the format efficiency can also be obtained by reducing the distance between the main pole of the magnetic head for perpendicular recording and the read element.
a-7g are diagrams showing manufacturing processes of the magnetic head for perpendicular recording according to an embodiment of the present invention.
a-10b are diagrams for comparing the conventional magnetic head for perpendicular recording with the magnetic head for perpendicular recording of the present invention when the coil is formed in double-layer.
In the case of a magnetic head for perpendicular recording in which a main pole is provided between a read head and a return pole, it has been revealed that the magnetic field formed by the main pole enters the read head to shift a magnetic domain in a read shield resulting in influence on a read element formed, for example, of a giant magnetoresistance film and thereby a read output is varied.
The inventors have manufactured in trial a magnetic head for perpendicular recording which is schematically illustrated in
The inventors also manufactured in trial the two kinds of magnetic head for perpendicular recording having the interval d between the upper surface of the read head and the lower surface of the yoke 14 of 4 μm and 8 μm. Recording has been conducted in various recording frequencies to a double-layer perpendicular medium including a soft-magnetic underlayer using this magnetic head for perpendicular recording and thereafter changing rates of output from the read header have been measured. Here, the changing rate of output of the read head is expressed by measuring a read output, when the recording and reading operations have been conducted for 10,000 times in a certain recording frequency using a spin-stand apparatus and by dividing a difference between the maximum value and the minimum value of such read output with an average value thereof.
Results of measurements are illustrated in
In the magnetic head for perpendicular recording as illustrated in
In view of suppressing variations in output of this read head, the present invention employs a structure where a non-magnetic layer is allocated between magnetic layers by forming the read shield located nearer to the main pole is formed in the structure of three or more layers. According to this structure, when the magnetic field generated by the main pole enters the read shield, the magnetic domain of the shield nearer to the read element is never disturbed and thereby variation in output of the read element can be suppressed because even if the magnetic domain of the shield nearer to the main pole is disturbed, a non-magnetic layer is provided under such shield. Employment of this structure enables that the distance between the main pole and read element is shortened, format efficiency of a hard disk drive is improved, and storage capacity of the drive is increased.
The shield of three or more layers in the read head can be formed with a method in which a resist frame is formed after formation of a seed layer for plating and a magnetic layer, a non-magnetic layer, and a magnetic layer are plated using this resist frame. Moreover, as the other applicable method, it is possible that a magnetic layer, a non-magnetic layer, and a magnetic layer are formed to the entire surface of the wafer with the plating method or sputtering method, and a pattern is formed with the etching process using a resist pattern as the mask. As the magnetic layer, NiFe, FeNi, and FeNiCo may be applicable. As the magnetic layer nearer to the main pole of the read shield of three or more layers, FeNi or FeNiCo may be applicable as the materials having a smaller linear expansion coefficient. In the case of the FeNi material, desirable composition of Ni is about 30 to 50 at %. In the case of the FeNiCo material, the desirable composition of Ni is about 30 to 50 at % and the desirable composition of Co is about 3 to 10 at %.
In addition, as the non-magnetic layer, Cu, Au, Ru, Rh, Pd, Ta, NiP, NiPd, and NiP are applicable as the material allowing the plating process. Moreover, an oxide film of Al2O3, SiO2, Ta2O5, TiO2 or the like formed by the sputtering method or a non-magnetic metal of Cr, Ta, W, Cu, Au, Ru, Rh, Pd, Ta, NiP, NiPd and NiP or the like are also applicable. Adequate film thickness of the non-magnetic layer is about 20 nm to 200 nm, because it is desirable for the non-magnetic layer to have the thickness as decoupling the magnetic layers adjacent to upper and lower sides of the non-magnetic layer, namely as not giving influence on the magnetic layer in the side nearer to the read element in the case where the magnetic field enters the magnetic layer nearer to the main pole.
In regard to the film thickness of magnetic layer, the desirable thickness for both magnetic layers nearer to the read element and nearer the main pole is about 0.2 to 1 μm. It is because the film thickness almost equal to that having the magnetic characteristic as the magnetic shield is required and it is also required to consider the distance between the main pole and the read element by lowering the film thickness not to deteriorate the thermal protrusion (TPR) characteristic which is the phenomenon that the element is protruded due to the heat.
The magnetic head for perpendicular recording of the present invention is capable of improving the format efficiency of a magnetic recording apparatus and increasing storage capacity of each apparatus because the distance between the main pole and read element can be made shorter than that of the existing magnetic head for perpendicular recording. Moreover, the magnetic head for perpendicular recording of the present invention is characterized in that the distance between the main pole and read element does not change even when a coil is laminated in two or more layers. The reason of this characteristic is that the coil is manufactured after formation of the read head and main pole. Accordingly, the magnetic recording apparatus having improved the recording performance can be manufactured without deterioration of the format efficiency even if the coil is laminated in two or more layers in view of improving the recording performance.
Moreover, in the case of the head structure of the present invention, thermal protrusion results in a problem because the return pole is located at the lowest point when a slider floats to the trailing side, namely to the location near to the flowing end part. In order to avoid this problem, it is desirable to use FeNi or FeNiCo in the adequate composition of Fe, Ni, and Co for the return pole. When the FeNi material is used, the desirable composition of Ni is about 30 to 50 at %. When the FeNiCo material is used, the desirable composition of Co is about 3 to 10 at %, while the desirable composition of Ni is about 30 to 50 at %.
The present invention will be explained more practically with reference to the accompanying drawings.
Moreover, the distance between the main pole 12 and the read element 15 of read head also applies influence on the format efficiency of hard disk drive. When the distance between the main pole 12 and the read element 15 of read head is large, the format efficiency becomes small. As a result, the storage capacity of hard disk drive becomes smaller. Accordingly, an interval between the main pole and the read head should be reduced.
A read shield 21 (upper shield) near to the main pole is formed of three layers of a lower shield layer 18 consisting of a magnetic material, a non-magnetic layer 19, and an upper shield layer 20 consisting of a magnetic material.
When the upper read shield is formed of such three-layer structure, only the upper shield layer 20 nearest to the main pole 12 is influenced but the lower shield layer 18 via the non-magnetic layer 19 is never influenced even when the magnetic field from the main pole 12 enters the upper read shield 21 and thereby variation in output of the read head is never generated.
For the measurements, the read outputs have been measured, as in the case of
The upper shield layer 20 in the side nearer to the main pole in the upper read shield 21 is separated magnetically from the lower shield layer 18 with the non-magnetic layer 19 and therefore a material can be selected from wide range of materials and a material having the smaller linear expansion coefficient can be applied. In general, the materials called the invar or super-invar are also applicable and these materials are formed of FeNi or FeNiCo. In the case of the FeNi material, the composition of Ni is about 30 to 50 at %. In the case of the FeNiCo material, the composition of Ni is about 30 to 50 at % and the composition of Co is about 3 to 10 at %. The conventional materials such as permalloy (Ni81Fe19) and Fe55Ni45 can naturally be used. When these materials are used, the upper shield 21 can be formed continuously with the plating method using the resist frame plating method.
It is of course possible to adopt the method in which the magnetic material for lower shield layer 18, non-magnetic material for non-magnetic layer 19 and the magnetic material for upper shield layer 20 are formed with the sputtering method to the entire part of the wafer without use of the plating method and thereafter a pattern is formed. In this case, for the non-magnetic layer 19, Al2O3, SiO2, Ta2O5, TiO2, Cr, Ta, and W can also be used in addition to Cu, Au, Ru, Rh, Pd, Ta, NiP, and NiPd or the like described above.
Here, regarding film thickness of the magnetic film constituting the upper and lower shield layers 18, 20, it is desirable to form both magnetic film (lower shield layer) 18 near the read element and the magnetic film (upper shield layer) 20 near the main pole in the thickness of about 0.2 to 1 μm. The reason is that it is required to provide the magnetic characteristic as the magnetic shield, to reduce thickness of the layer not to deteriorate the thermal protrusion characteristic, and to consider the distance between the main pole and the read element. In addition, the desirable thickness is about 20 nm to 200 nm for the non-magnetic layer 19. It is desirable for the non-magnetic layer to have the thickness to decouple the upper shield 20 and lower shield layer 18 located in the upper and lower portions of the non-magnetic layer 19.
The distance (L1, L2) between the read element 15 of read head and the main pole 12 is important for determining the format efficiency of the magnetic recording apparatus. As is apparent from the figure, L1 is clearly larger than L2 and the hard disk drive having more excellent format efficiency, namely the hard disk drive having larger storage capacity may be attained by utilizing the magnetic head for perpendicular recording of the present invention. In the case of the conventional magnetic head for perpendicular recording, L1 is typically 8 to 10 μm. Meanwhile, in the case of the magnetic head for perpendicular recording of the present invention, L2 becomes 1.02 μm when the film thickness of the lower shield layer 18 near the read element 15 is 0.2 μm, the film thickness of the non-magnetic layer 19 is 20 nm, the film thickness of the upper shield layer 20 near the main pole 12 is 0.2 μm, the interval between the upper shield layer 20 and main pole 12 is 0.2 μm, the film thickness of the yoke 14 is 0.2 μm, and the film thickness of the main pole 12 is 0.2 μm. As the typical value, L2 is 1 to 4 μm; however, since the format efficiency is 0.3% per distance of 1 μm between the read element and main pole, the format efficiency of 1.2 to 2.7% can be increased. On the other hand,
In order to raise the writability of the recording head, it is required to increase a current value flowing into the coil or to increase the number of turns of the coil. However, when the size of coil is restricted, the current value is also restricted. Meanwhile, the number of turns of the coil can be increased but when importance is laid in the high-frequency characteristic, it is more desirable to make shorter the length from the air bearing surface of the main pole and return pole by forming the coil in two layers. In this case, as is apparent from
It is to be understood that the above description is intended to be illustrative and not restrictive. Many embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined not with reference to the above description, but instead should be determined with reference to the appended claims along with their full scope of equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005-069143 | Mar 2005 | JP | national |
