Magnetic thin film having non-magnetic spacer layer that is provided with SnO2 layer

A magnetic thin film has: a pinned layer whose magnetization direction is fixed with respect to an external magnetic field; a free layer whose magnetization direction is changed in accordance with the external magnetic field; and a non-magnetic spacer layer that is sandwiched between said the pinned layer and the free layer, wherein sense current is configured to flow in a direction that is perpendicular to film surfaces of the pinned layer, the non-magnetic spacer layer, and the free layer. The non-magnetic spacer layer has a first layer which includes SnO2, and a pair of second layers which are provided to sandwich the first layer, the second layers being made of a material which exhibits a higher corrosion potential than Sn.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a magnetic thin film that is used for a CPP-GMR (Current Perpendicular to the Plane Giant Magneto Resistance) element (hereinafter called a “CPP element”) which constitutes a thin-film magnetic head, and more particularly relates to the structure of a non-magnetic spacer layer.

2. Description of the Related Art

A CPP element is known as one of the magnetic field detecting elements which are used in a thin-film magnetic head. A CPP element has a pinned layer whose magnetization direction is fixed with respect to an external magnetic field, a free layer whose magnetization direction is changed in accordance with the external magnetic field, and a non-magnetic spacer layer that is sandwiched between the pinned layer and free layer (also called a “spacer layer”). In this specification, a stacked structure of layers that are comprised of a pinned layer, a non-magnetic spacer layer, and a free layer is called a “magnetic thin film.” A magnetic thin film is a central part of a CPP element for generating changes in magneto resistance by the GMR effect. A magnetic thin film forms a CPP element together with other metal layers. Sense current is configured to flow in a direction that is perpendicular to the film surfaces of the pinned layer, the non-magnetic spacer layer, and the free layer. A CPP element is sandwiched between a pair of shield layers. The shield layers also have the function of electrode layers for supplying sense current. Since the CPP element is physically connected with the shield layers, the CPP element has a high efficiency for heat radiation, and a large capacity for sense current. Further, the CPP element exhibits a larger electric resistance and a larger change in resistance in accordance with a decrease in cross section. Accordingly, the CPP element is more suitable for a narrow track width.

Techniques have been disclosed for improving the MR (Magneto Resistance) ratio of the CPP element. The specification of Japanese Patent No. 3293437 discloses a technique to vary the electric resistance of a non-magnetic spacer layer two-dimensionally in the film surface. The specification of Japanese Patent Laid-down Publication No. 2003-298143 and 2006-261306 discloses a non-magnetic spacer layer that is provided with a region that is made of oxides of Sn, Sb etc. and a region that is made of Cu, Ag etc. so that the electric resistance of the non-magnetic spacer layer is varied two-dimensionally in the film surface. According to these techniques, since most sense current flows through the region of smaller electric resistance, an effect can be achieved that is similar to the effect that would be obtained if the cross-section of the element was actually reduced. However, local migration is more likely to occur because current density is increased in the region of lower electric resistance because of the concentration of sense current in this region. For this reason, the CCP element of this type is disadvantageous in term of reliability.

As another technique for improving the MR ratio of a CPP element, Japanese Patent No. 3565268 discloses a non-magnetic spacer layer for which a semiconductor or half metal is used.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a magnetic thin film which achieves a large MR ratio as well as improved reliability. Another object of the present invention is to provide a magnetic field detecting element, a slider, a hard disk drive and so on in which such a magnetic thin film is used.

According to an embodiment of the present invention, a magnetic thin film comprises: a pinned layer whose magnetization direction is fixed with respect to an external magnetic field; a free layer whose magnetization direction is changed in accordance with the external magnetic field; and a non-magnetic spacer layer that is sandwiched between said pinned layer and said free layer, wherein sense current is configured to flow in a direction that is perpendicular to film surfaces of said pinned layer, said non-magnetic spacer layer, and said free layer. Said non-magnetic spacer layer has a first layer which includes SnO2, and a pair of second layers which are provided to sandwich said first layer, said second layers being made of a material which exhibits a higher corrosion potential than Sn.

According to an embodiment, said first layer consists of SnO2. According to another embodiment, said first layer consists of SnO2and Sb2O5. According to yet another embodiment, said first layer consists of SnO2to which F is added.

A magnetic field detecting element according to the present invention comprises said magnetic thin film mentioned above.

A slider according to the present invention comprises said magnetic field detecting element mentioned above.

A wafer according to the present invention has said magnetic thin film formed thereon.

A head gimbal assembly according to the present invention comprises said slider mentioned above and a suspension for resiliently supporting said slider.

A hard disk drive according to the present invention comprises said slider mentioned above and a device for supporting said slider and for positioning said slider with respect to a recording medium.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of a CPP element using a magnetic thin film of the present invention will be described with reference to the drawings. While the following embodiment will be described in connection with a thin-film magnetic head for a hard disk drive, the magnetic field detecting element of the present invention may also be applied to a magnetic memory element, a magnetic sensor assembly etc.

Reference Embodiment

First, the inventors made a CPP element having a non-magnetic spacer layer in a three-layer structure of Cu/ZnO/Cu, in which a semiconductor or half metal is used. The CPP element was annealed at 250° C. or higher in order to crystallize the ZnO layer. The thickness of the ZnO layer was chosen from a range between 1.2 and 1.6 nm. It was confirmed that the CPP element, in which ZnO is used as a part of the non-magnetic spacer layer, exhibits a larger MR ratio than a conventional CPP element in which Cu is used alone for the non-magnetic spacer layer. It is generally known that ZnO exhibits n-type semi-conducting characteristics due to the emission of electrons from inter-lattice zinc and oxygen deficiency. The defect is represented by the Kröger-Vink notation which is expressed by Equations (1), (2):

ZnZn* Zn which exists at the site of Zn;

Zni* Zn which exists between lattices and which has emitted one valence electron;

VO* Oxygen hole which has trapped one positive hole; and

OO* O which exists at the site of O.

Equation (1) represents the generation of inter-lattice zinc, and Equation (2) represents the generation of oxygen deficiency. It can be understood from these equations that one free electron is emitted and the number of carriers of an n-type semiconductor is increased. However, there are various theories on the origin of manifestation of n-type characteristics, and the above equations merely represent one model among many.

The non-magnetic spacer layer in a three-layer structure of Cu/ZnO/Cu is able to exhibit a large MR ratio, and is less susceptible to degradation in reliability that may occur due to local migration. However, the following disadvantages still exist. A slider is fabricated by dicing a wafer, on which a plurality of layers that constitute CPP elements are formed, into bars, then lapping the diced surface to form an air bearing surface, and subsequently dicing the bar into sliders. The surface that is lapped is in contact with lapping solvent, and is chemically affected by the solvent. The above-mentioned ZnO does not have sufficient chemical resistance, particularly, to acid. Specifically, the lapped surface may be corroded by the acidic lapping solvent, and part of ZnO may elute. Although this problem does not occur as long as the lapping solvent is neutral, pH of the lapping solvent may actually be changed by the material that is lapped and the lapping solvent may be acidified. A mild alkalescent lapping solvent may be used for this reason. However, variation in pH may cause degraded characteristics and lower yield. Thus, the inventors further developed a magnetic thin film that is less susceptible to degradation in reliability that may occur due to local migration, that exhibits a large MR ratio, and that has large chemical resistance.

First Embodiment

FIG. 1is a partial perspective view of a thin-film magnetic head in which a magnetic thin film of the present invention is used. Thin-film magnetic head1may be a read only head, or may be an MR/inductive composite head which additionally has a write head portion. Magnetic field detecting element2is a CPP element. Magnetic field detecting element2is sandwiched between upper electrode/shield3and lower electrode/shield4, and the leading end thereof is disposed opposite to recording medium21. Magnetic field detecting element2is configured such that sense current22flows in a direction that is perpendicular to the film surfaces under a voltage that is applied between upper electrode/shield3and lower electrode/shield4. The magnetic field of recording medium21at a position opposite to magnetic field detecting element2is changed in accordance with the movement of magnetic medium21in moving direction23. Magnetic field detecting element2detects the change in magnetic field as a change in electric resistance based on the GMR effect, and reads magnetic information that is written in each magnetic domain of recording medium21.

FIG. 2is a side view of the magnetic field detecting element viewed from A-A direction inFIG. 1, i.e., from the air bearing surface. The air bearing surface refers to a surface of thin-film magnetic head1which is opposite to recording medium21. Table 1 shows an exemplary layer configuration of magnetic field detecting element2. Table 1 shows the layers in the order of stacking from buffer layer5at the bottom row, which is in contact with lower electrode/shield4, to cap layer10at the top row, which is in contact with upper electrode/shield3.

Magnetic field detecting element2is a stacked structure in which buffer layer5, anti-ferromagnetic layer6, pinned layer7, non-magnetic spacer layer8, free layer9, and cap layer10are stacked in this order on lower electrode/shield4, which is made of a NiFe layer and has a thickness of approximately 1 μm. Pinned layer7, non-magnetic spacer layer8, and free layer9constitute magnetic thin film15. Pinned layer7is a layer whose magnetization direction is fixed with respect to an external magnetic field. Free layer9is a layer whose magnetization direction is changed in accordance with the external magnetic field. Sense current22flows in the direction that is perpendicular to the film surfaces of pinned layer7, non-magnetic spacer layer8, and free layer9, i.e., magnetic thin film15. The magnetization direction of free layer9forms an angle relative to the magnetization direction of pinned layer7in accordance with the external magnetic field. Spin dependent scattering of conduction electrons is varied in accordance with the relative angle, and change in magneto resistance is caused. Thin-film magnetic head1detects the change in magneto resistance so that it reads magnetic information on a recording medium.

Pinned layer7is constructed as a so-called synthetic pinned layer. Specifically, pinned layer7has outer pinned layer71, inner pinned layer73that is disposed closer to non-magnetic spacer layer8than outer pinned layer71, and non-magnetic intermediate layer72that is sandwiched between outer pinned layer71and inner pinned layer73. The magnetization direction of outer pinned layer71is fixed due to exchange coupling with anti-ferromagnetic layer6. Further, inner pinned layer73is anti-ferromagnetically coupled to outer pinned layer71via non-magnetic intermediate layer72. Thus, the magnetization direction of inner pinned layer73is firmly fixed. In this way, in the synthetic pinned layer, a stable magnetization state is maintained in pinned layer7, and effective magnetization of pinned layer7is limited as a whole.

Non-magnetic spacer layer8is a layer in three-layer structure in which first layer82, which is made of SnO2(tin oxide), is sandwiched between a pair of second layers81,83which are made of Cu (copper). It is known that SnO2, similarly to ZnO, exhibits n-type semi-conducting characteristics due to the emission of electrons from inter-lattice tin or oxygen deficiency. The defect is represented by the Kröger-Vink notation expressed by Equations (3), (4):
SnO2→Sni*+e−+O2(3)
SnO2→SnSn*+VO*e−+O2(4)

SnSn* Sn which exists at the site of Sn;

Sni* Sn which exists between lattices and which has emitted one valence electron

VO* Oxygen hole which has trapped one positive hole; and

OO* which exists at the site of O.

Equation (3) represents the generation of inter-lattice tin, and Equation (4) represents the generation of oxygen deficiency. It can be understood from these equations that one free electron is emitted and the number of carriers in an n-type semiconductor is increased. Further, a CPP element in which SnO2is used as first layer82exhibits a MR ratio that is equivalent to or larger than that of a CPP element in which ZnO is used as first layer82, as will be later described. The inventors think that this is because of the tendency of SnO2to preserve spin information of conduction electrons.

FIG. 3shows a comparison of etching rates between ZnO and SnO2. The data were collected in the following manner. First, a seed layer (Cu, 5 nm thick) was deposited on a silicon substrate, then a ZnO layer or a SnO2layer each having a thickness of 50 nm was deposited on the seed layer. Next, resist was formed on the ZnO layer and the SnO2layer, respectively, and the layers were dipped in oxalic acid (10 wt % concentration) for a predetermined time. After taking the layers out of the oxalic acid, the resist was removed, and recesses were measured to evaluate etching rates. It can be seen from the graph that SnO2, which presents an etching rate that is approximately one fifth of that of ZnO, has excellent chemical resistance.FIG. 3also shows the etching rate of ATO (Antimony doped Tin Oxide), as will be later described. The etching rate of ATO was measured in the same manner as for ZnO and SnO2.

Second layers81,83are provided to prevent oxygen from being diffused from first layer82. Oxygen that is contained in SnO2of first layer82tends to be diffused into adjoining pinned layer7and free layer9. This is because Co and Fe, which form pinned layer7and free layer9, have lower corrosion potentials or standard electrode potentials than Sn. If oxygen that is contained in SnO2is diffused into pinned layer7and free layer9, SnO2will become more similar to pure Sn and will lose the nature of an oxide and the nature of a semiconductor. As a result, the electric resistance of magnetic thin film15, as well as the MR ratio, is decreased. Cu effectively prevents the diffusion of oxygen due to higher corrosion potential or higher standard electrode potential as compared with Sn. Accordingly, any materials which have higher corrosion potentials or higher standard electrode potentials than Sn may be used as second layers81,83. Second layers81,83may be formed of materials such as Au, Ag, Pt, Pd, Ir, Ru, Rh, Re, instead of Cu.

Buffer layer5is provided to ensure sufficient exchange coupling of anti-ferromagnetic layer6with outer pinned layer71. Cap layer10is provided to prevent deterioration of each of the stacked layers. Upper electrode/shield3, which is made of a NiFe film and is approximately 1 μm thick, is formed on cap layer10.

Hard bias films12are formed on the sides of magnetic field detecting element2via insulating films11. Hard bias film12is a magnetic domain control film for placing free layer9in the state of a single magnetic domain. Insulating film11is made of Al2O3, and hard bias film12is made of CoPt, CoCrPt or the like.

The CPP element of the present embodiment is a bottom type in which the pinned layer is deposited prior to the free layer. However, the present invention can similarly be applied to a top type CPP element in which the free layer is deposited prior to the pinned layer. Also, the pinned layer does not have to be a synthetic pinned layer, and a single-layer pinned layer without using anti-ferromagnetic coupling may be used.

The foregoing thin-film magnetic head is manufactured in the following manner. First, lower electrode/shield4is formed on a substrate, not shown, that is made of a ceramic material, such as Altic (Al2O3.TiC), via an insulating layer, not shown. Subsequently, the layers beginning with buffer layer5and ending with cap layer10are sequentially deposited by means of sputtering. A SnO2layer is deposited by sputtering using a SnO2target. After cap layer10is deposited, the SnO2layer is crystallized by annealing at 270° C. for three hours. Subsequently, the annealed layers are patterned into a column shape, then hard bias films12are formed on the side surfaces thereof, and the remaining portions are filled with an insulating layer. Subsequently, upper electrode/shield3is formed to complete the read head portion of the thin-film magnetic head, as illustrated inFIG. 2. A write magnetic pole layer and a coil are further formed if a write head portion is required. Subsequently, the entire structure is covered with a protection layer. Then, the wafer is diced, lapped, and separated into a stacked structure (slider) in which the thin-film magnetic head is formed.

Second Embodiment

First layer82of non-magnetic spacer layer8may also be made of SnO2and Sb2O5(antimony oxide). Sb2O5is doped into SnO2, and such a composition may be called “ATO.” In this specification as well, the above-mentioned composition may be called “ATO.” Table 2 shows an exemplary layer configuration of magnetic field detecting element2in which ATO is used for first layer82. Except for first layer82being made of ATO, the layer configuration of magnetic field detecting element2is similar to that shown in Table 1. Although second layer82is made of Cu, it may be formed of materials such as Au, Ag, Pt, Pd, Ir, Ru, Rh, Re, similarly to the first embodiment.

When Sb2O5is doped into SnO2, free electrons are further emitted due to the reaction expressed by Equation (5). As a result, the concentration of carrier is increased and the resistance ratio is reduced. Since the number of free electrons which are emitted is incomparably larger than the number of free electrons that have an origin in the lattice defects of SnO2itself, the characteristics of ATO can be controlled by the amount of additive Sb2O5. It is also possible to adjust the resistance of the non-magnetic spacer layer by using this phenomenon.

Referring toFIG. 3, the etching rate against oxalic acid (10 wt %) is substantially equal to the etching rate of SnO2, and sufficient chemical resistance as compared with ZnO was confirmed.

The CPP element having ATO for first layer82allows first layer82to have a large thickness, as will be later described. This will contribute to preventing manufacturing defects, such as pinholes in first layer82and short-circuits between layers81,83.

The method of manufacturing the CPP element of the second embodiment is basically the same as that of manufacturing the CPP element in first embodiment. In order to form an ATO layer, sputtering is performed using an ATO target having an adjusted composition or a SnO2target with a Sb2O5chip adhered thereto. The annealing condition is similar to that in the first embodiment.

Instead of ATO, first layer82of non-magnetic spacer layer8may be made of a material that is made by doping F (fluorine) into SnO2. Such a composition may be called “FTO” (Fluorine doped Tin Oxide). The layer configuration of magnetic field detecting element2is similar to that shown in Table 2 except that first layer82is made of ATO. The CPP element in which FTO is used is also capable of achieving both a large MR ratio and sufficient chemical resistance.

Next, appropriate layer configurations were studied for the non-magnetic spacer layer of the CPP element described above, based on experiments. The CPP element was formed by the same method described above in each embodiment.

First, the MR ratio and the AR value were measured for cases in which ZnO, SnO2, and ATO are used as first layer82of non-magnetic spacer layer8. The case in which ZnO was used is a comparative example. In the case in which ATO was used, the amount of additive Sb was 5 mol %. The AR value refers to the product of element area A and element resistance R. Since a large AR value may cause an increase in element resistance due to shot noise, the AR value is preferably equal to or smaller than 0.3 (Ωl/μm2). Since a small AR value may cause an increase in spin torque which may affect the response of the free layer, the AR value is preferably equal to or larger than 0.1 (Ωl/μm2). In conclusion, a proper range of the AR value is equal to or larger than 0.1 (Ωl/μm2) and equal to or smaller than 0.3 (Ω/μm2). In particular, the AR value is preferably equal to or larger than 0.15 (Ω/μm2) and equal to or smaller than 0.2 (Ω/μm2). The thickness of first layer82was changed from 0.4 nm to 4.0 nm in increments of 0.4 nm. The layer configuration is shown in Table 3.

FIGS. 4A-4Dshow the results.FIGS. 4B and 4Care identical except for the proper range of the AR value. Referring first toFIG. 4A, the MR ratio is substantially the same for the case in which SnO2was used as first layer82and for the case in which ZnO was used as first layer82. However, a larger MR ratio is achieved for the case in which SnO2is used as first layer82in the range in which the first layer has a relatively large thickness. In particular, a MR ratio as large as approximately 14 was achieved in the thickness range between 1.5 and 2.0 nm. Referring toFIGS. 4B,4C, the AR value presents a generally similar tendency for the case in which ZnO was used as first layer82and for the case in which SnO2was used, although the range of allowable thickness for first layer82slightly expands as compared with the case in which ZnO was used as first layer82. In other words, SnO2has equivalent or better characteristics as the material for the non-magnetic spacer layer of the magnetic thin film, as compared with ZnO.

The MR ratio for the case in which ATO was used is smaller than the MR ratio for the case in which ZnO was used as first layer82when compared at the same thickness. On the other hand, the thickness of the first layer that corresponds to the proper range of the AR value is shifted to larger values, as compared with the case in which ZnO was used. This is because ATO has a large electric conductivity. However, referring toFIG. 4D, it will be understood that the MR ratio for the case in which ATO was used as first layer82is substantially same as the MR ratio for the case in which ZnO or SnO2was used as first layer82, when compared in the proper range of the AR value.

If first layer82has a small thickness, then pin holes are more likely to occur due to variations in thickness during deposition. This may result in degradation in the reliability-related characteristics due to electromigration, which is observed in a magnetic thin film of a type in which electric resistance of non-magnetic spacer layer8is varied two-dimensionally in the film surface. Also, a short-circuit may occur between the second layers during lapping, which will cause noise and deterioration in the MR ratio. For these reasons, wide discretion for setting the thickness of the first film provides significant advantages, resulting in wide discretion for head design.

The proper range of the thickness of the first layer can be determined from the proper range of the AR value. When SnO2is used as first layer82, the thickness of 1.1 to 1.9 nm corresponds to the proper range of the AR value which is equal to or larger than 0.1 and equal to or smaller than 0.3. The thickness of 1.3 to 1.5 nm corresponds to the proper range of the AR value which is equal to or larger than 0.15 and equal to or smaller than 0.2. When ATO is used as first layer82, the thickness of 1.5 to 2.6 nm corresponds to the proper range of the AR value which is equal to or larger than 0.1 and equal to or smaller than 0.3. The thickness of 1.9 to 2.3 nm corresponds to the proper range of the AR value which is equal to or larger than 0.15 and equal to or smaller than 0.2. A sufficient MR ratio is achieved for any of these thickness ranges.

Next, using the amount of additive Sb as a parameter, the MR ratio was measured for the case in which ATO was used. The layer composition was similar to that shown in Table 3, and the thickness of the first layer was chosen to be 1.4 nm. The amount of additive Sb was chosen to be 0.1, 0.3, 1, 5, 10, 15, 20, 25 mol %. Referring toFIG. 5, although the influence of the amount of additive Sb on the MR ratio is limited, the MR ratio tends to be reduced when the amount exceeds 20 mol %. Accordingly, the amount of additive Sb is preferably more than 0 mol % and equal to or less than 20% mol.

Next, studies were made on the influence of the thickness of the second layer on the MR ratio. In the case in which SnO2was used as first layer82, the thickness of the first layer was chosen to be 1.4 nm, and Cu was used for the second layer. In the case in which ATO was used as first layer82, the thickness of the first layer was chosen to be 2.0 nm, and Cu was used for the second layer. In each case, the thickness of the second layer was chosen to be 0.2, 0.3, 0.7, 1.5, 2.0, 2.5 nm. Referring toFIG. 6, the MR ratio is sharply decreased when the thickness of Cu is small. This is probably because the function of Cu to prevent oxygen diffusion is degraded. The MR ratio is gradually decreased when the thickness of Cu is large. This is probably because information encoded in the spin state of conduction electrons is gradually lost in accordance with an increase in the thickness of the Cu layer. The range of desired thickness of the second layer for achieving a MR ratio of approximately 10 is 0.3-2.5 nm when SnO2was used as first layer82, and is 0.3-2.0 nm when ATO was used as first layer82.

Finally, chemical resistance of the element was investigated using ZnO, SnO2and ATO as first layer82of non-magnetic spacer layer8. The layer composition of the CPP element was the same as shown inFIG. 3. The thickness of the layer was chosen to be 1.4 nm in the case of the ZnO layer, 1.4 nm in the case of the SnO2layer, and 2.0 nm in the case of the ATO layer. CPP elements were formed in accordance with the manufacturing method described in the embodiment, and the air bearing surface was lapped while the elements were in the state of a bar. Although neutral slurry was used for lapping, it is thought that pH was gradually changed under the influence of the material that was lapped. After lapping, a DLC (Diamond like Carbon) layer was formed on the lapped surface. One hundred elements were manufactured for each case, and the resistance of the elements was measured.

If an element has large chemical resistance, then the first layer is less susceptible to corrosion and elusion even if the pH of the slurry is changed with the progression of lapping. Specifically, the elements have small variations in resistance because of the low etching rate against acid (oxalic acid). On the other hand, if elements have small chemical resistance, then the first layer is susceptible to corrosion and elusion, and this results in large variations in resistance. Therefore, it is possible to perform relative evaluation of the degree of chemical resistance of the elements by measuring variation in resistance of the elements.

FIG. 7shows variation (standard deviation) in element resistance of the elements that was measured in this way. InFIG. 7, the variation is normalized such that the variation in the case in which ZnO was used as first layer82is equal to 1. The variation in element resistance is the smallest when. SnO2was used as first layer82, and is substantially the same when ATO was used. On the other hand, considerably large variation was found when ZnO was used as first layer82. This result is consistent with the etching rate of each material shown inFIG. 3. The magneto resistance element in which SnO2or ATO is used as first layer82of non-magnetic spacer layer8is resistive against change in characteristics during manufacture, and is quite excellent from an industrial viewpoint.

Next, explanation will be made regarding a wafer for fabricating a thin-film magnetic head described above.FIG. 8is a schematic plan view of a wafer. Wafer100has layers which are deposited thereon to form at least the magnetic field detecting element. Wafer100is diced into bars101which serve as working units in the process of forming air bearing surface ABS. After lapping, bar101is diced into sliders210which include thin-film magnetic heads1. Dicing portions, not shown, are provided in wafer100in order to dice wafer100into bars101and into sliders210.

Referring toFIG. 9, slider210has a substantially hexahedral shape. One of the six surfaces of slider210forms air bearing surface ABS, which is positioned opposite to the hard disk.

Referring toFIG. 10, head gimbal assembly220has slider210and suspension221for resiliently supporting slider210. Suspension221has load beam222in the shape of a flat spring and made of, for example, stainless steel, flexure223that is attached to one end of load beam222, and base plate224provided on the other end of load beam222. Slider210is fixed to flexure223to provide slider210with an appropriate degree of freedom. The portion of flexure223to which slider210is attached has a gimbal section for maintaining slider210in a fixed orientation.

Slider210is arranged opposite to a hard disk, which is a rotationally-driven disc-shaped storage medium, in a hard disk drive. When the hard disk rotates in the z direction shown inFIG. 10, airflow which passes between the hard disk and slider210creates a dynamic lift, which is applied to slider210downward in the y direction. Slider210is configured to lift up from the surface of the hard disk due to this dynamic lift effect. Thin-film magnetic head1is formed in proximity to the trailing edge (the end portion at the lower left inFIG. 9) of slider210, which is on the outlet side of the airflow.

The arrangement in which a head gimbal assembly220is attached to arm230is called a head arm assembly221. Arm230moves slider210in transverse direction x with regard to the track of hard disk262. One end of arm230is attached to base plate224. Coil231, which constitutes a part of a voice coil motor, is attached to the other end of arm230. Bearing section233is provided in the intermediate portion of arm230. Arm230is rotatably held by shaft234which is attached to bearing section233. Arm230and the voice coil motor to drive arm230constitute an actuator.

Referring toFIG. 11andFIG. 12, a head stack assembly and a hard disk drive that incorporate the slider mentioned above will be explained next. The arrangement in which head gimbal assemblies220are attached to the respective arm of a carriage having a plurality of arms is called a head stack assembly.FIG. 11is a side view of a head stack assembly, andFIG. 12is a plan view of a hard disk drive. Head stack assembly250has carriage251provided with a plurality of arms252. Head gimbal assemblies220are attached to arms252such that head gimbal assemblies220are arranged apart from each other in the vertical direction. Coil253, which constitutes a part of the voice coil motor, is attached to carriage251on the side opposite to arms252. The voice coil motor has permanent magnets263which are arranged in positions that are opposite to each other and interpose coil253therebetween.

Referring toFIG. 12, head stack assembly250is installed in a hard disk drive. The hard disk drive has a plurality of hard disks which are connected to spindle motor261. Two sliders210are provided per each hard disk262at positions which are opposite to each other and interpose hard disk262therebetween. Head stack assembly250and the actuator, except for sliders210, work as a positioning device in the present invention. They carry sliders210and work to position sliders210relative to hard disks262. Sliders210are moved by the actuator in the transverse direction with regard to the tracks of hard disks262, and positioned relative to hard disks262. Thin-film magnetic head1that is included in slider210writes information to hard disk262by means of the write head portion, and reads information recorded in hard disk262by means of the read head portion.

Although certain preferred embodiments of the present invention have been shown and described in detail, it should be understood that various changes and modifications may be made without departing from the spirit or scope of the appended claims.