MAGNETIC DISK DEVICE

According to one embodiment, a magnetic disk device includes a rotatable magnetic disk and a magnetic head including a recording head portion that records data on the magnetic disk. The recording head portion includes a main magnetic pole that applies a recording magnetic field to the magnetic disk, a first yoke provided on a first side of the main magnetic pole and a second yoke provided on a second side of the main magnetic pole, which is opposite to the first side. The magnetic head includes a first heater provided to oppose a side of the first yoke, opposite to the main magnetic pole and a second heater provided to oppose a side of the second yoke, opposite from the main magnetic pole.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2021-107222, filed Jun. 29, 2021, the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a magnetic disk device.

BACKGROUND

As a magnetic recording and reproducing device, for example, a magnetic disk device comprises a rotatable disk-shaped recording medium, a magnetic head for recording/reproducing data on a magnetic recording layer of the recording medium and a head actuator that positions the magnetic head at a desired radial position on the recording medium. The magnetic head includes a slider, a reproducing element and a recording element provided on the slider. In order to improve the recording density, a magnetic head having an assist function, for example, a heater, have been proposed. Here, by heating the magnetic head with the heater, the reproducing element and/or recording element are expanded to the recording medium side, so as to control the distance between the reproducing and/or recording element and the surface of the recording medium.

However, it takes a certain amount of time until the temperature of the magnetic head, especially the recording element section and the entire head, to saturate. For example, a certain amount of time is required from the time when the heater is started to be energized for the recording element to expand and protrude to the desired position. On the other hand, it is required for the magnetic disk drives to record data at high speed by shortening the time from the start to the end of writing. In order to shorten the time to start writing, it is necessary to shorten the above-described protruding time. Therefore, in order to achieve high-speed processing in a magnetic disk device, the protruding time needs to be shortened.

DETAILED DESCRIPTION

Various embodiments will be described hereinafter with reference to the accompanying drawings. In general, according to one embodiment, a magnetic disk device comprises a rotatable magnetic disk and a magnetic head including a recording head portion that records data on the magnetic disk. The recording head portion comprises a main magnetic pole that applies a recording magnetic field to the magnetic disk, a first yoke provided on a first side of the main magnetic pole and a second yoke provided on a second side of the main magnetic pole, which is opposite to the first side. The magnetic head includes a first heater provided to oppose a side of the first yoke, opposite to the main magnetic pole and a second heater provided to oppose a side of the second yoke, opposite from the main magnetic pole.

First Embodiment

As an example of the magnetic disk devices, a hard disk drive (HDD) according to the first embodiment will be described in detail.FIG.1is a block diagram schematically showing the HDD of the first embodiment, andFIG.2is a cross-sectional view showing a head portion of a magnetic head in the flying state and a magnetic disk.

As shown inFIG.1, the HDD10comprises a rectangular-shaped housing11, magnetic disks12as a recording medium installed in the housing11, a spindle motor14that supports and rotates the magnetic disks12, and magnetic heads16that each record (writes) and reproduce (reads) data with respect to the respective magnetic disk12. The HDD10comprises a head actuator18that moves and positions the respective magnetic head16on an arbitrary track on the respective magnetic disk12. The head actuator18includes a carriage assembly20that supports the magnetic heads16movably and a voice coil motor (VON)22that pivots the carriage assembly20.

The HDD10comprises a head amplifier IC30that drives the magnetic heads16, a main controller40and a driver IC48. The head amplifier IC30is, for example, provided on the carriage assembly20and is electrically connected to the magnetic heads16. The head amplifier IC30comprises a recording current supply circuit32that supplies a recording current to the recording coils of the magnetic heads16, a heater voltage supply circuit34that supplies drive power to a thermal actuator (to be referred to as “heater” hereinafter) of the magnetic heads16, which will be described later and an amplifier (not shown) that amplifies the signal read by the magnetic heads16, and the like.

The main controller40and the driver IC48are, for example, installed on a control circuit board (not shown) provided on a rear surface side of the housing11. The main controller40comprises an R/W channel42, a hard disk controller (HDC)44, a microprocessor (MPU)46, a memory47and the like. The main controller40is electrically connected to the magnetic head16via the head amplifier IC30. The main controller40is electrically connected to the VCM22and the spindle motor14via the driver IC48. Note that the HOC44is connectable to a host computer45.

In the memory47of the main controller40, a heater power setting table (not shown) and the like, are stored. In the main controller40, for example, the MPU46adjusts the power supplied to the heater based on the heater power setting table.

As shown inFIGS.1and2, the magnetic disks12are each configured as a perpendicular magnetic recording medium. The magnetic disks12each include a substrate101formed, for example, into a discoidal shape with a diameter of 96 mm (about 3.5 inches) and made of a non-magnetic material. On each of the surfaces of the substrate101, a soft magnetic layer102made of a material that exhibits soft magnetic properties as a base layer, a perpendicular magnetic recording layer103having magnetic anisotropy in the perpendicular direction to the surface of the magnetic disk12as an upper layer, and a protective film104are stacked in order. The magnetic disks12are fit to the hub of the spindle motor14so as to be coaxial with each other. The magnetic disks12are rotated in the direction indicated by arrow B at a predetermined speed by the spindle motor14.

As shown inFIG.1, the carriage assembly20includes a bearing portion21rotatably supported by the housing11, and a plurality of suspensions26extending from the bearing section21. The magnetic heads16are supported on extending ends of the respective suspensions26. The magnetic heads16are electrically connected to the head amplifier IC30via respective wiring members (flexures) provided in the carriage assembly20.

The magnetic heads16each comprise a substantially rectangular disk-facing surface (air bearing surface (ABS))13that opposes the surface of the respective magnetic disk12. The Magnetic head16is maintained in a state where it flies a predetermined amount above the surface of the respective magnetic disk12by air flow generated between the disk surface and the ABS13by the rotation of the magnetic disk12. The direction of the air flow coincides with the rotational direction B of the magnetic disk12. As the magnetic disk12rotates, the magnetic head16travels in a direction opposite to the disk rotation direction B with respect to the magnetic disk12.

As shown inFIG.2, the head portion17includes a reproduction head (reproduction head portion)54and a recording head (recording head portion)54, formed by a thin-film process on a trailing edge located on the outflow side of the air flow, and is formed as a separate magnetic head. The reproduction head54and the recording head58are covered by a non-magnetic protective insulating film53, except for the portion exposed to the ABS13. The protective insulating film53constitutes an outline of the head portion17. Further, the head portion17includes a heater (first heater)76cand another heater (second heater)76d, which control the protrusion amount of the recording head58, and another heater (third heater)76b, which controls the protrusion amount of the reproduction head54. The heaters76cand76dare embedded in the protective insulating film53and are located in the vicinity of the recording head58. The heater76bis embedded in the protective insulating film53and is located in the vicinity of the reproduction head54. The detailed configuration of the heaters will be described later.

The longitudinal direction of the recording track formed on the perpendicular magnetic recording layer103of the magnetic disk12is defined as a down-track direction DT, and the width direction of the recording track orthogonal to the longitudinal direction is defined as a cross-track, direction.

The reproduction head54includes a magnetoresistive element55and a first magnetic shield film56and a second magnetic shield film57disposed respectively on a leading side and a trailing side of the magnetoresistive effect element55in the down track direction DT so as to interpose the magnetoresistive effect element55therebetween. The magnetoresistive element55, the first and second magnetic shielding films56and57are extend substantially perpendicularly to the ABS13.

The recording head58is provided on a trailing side (a first side) of the slider15with respect to the reproduction head54. The opposite side of the trailing side is a leading side (a second side). The recording head58includes a main magnetic pole60that generates a recording magnetic field in the perpendicular direction to the surface of the magnetic disk12, a trailing shield (a first yoke)6provided on the trailing side of the main magnetic pole60and opposing the main magnetic pole60with a wright gap.62, a leading shield (a second yoke)64opposing the leading side of the main magnetic pole60, and a pair of side shields (not shown) formed to be integrated with the leading shield and provided on respective sides both sides of the main magnetic pole60along the cross track direction. The main magnetic pole60and the trailing shield62constitute a first magnetic core which forms a magnetic path, and the main magnetic pole60and the leading shield64constitutes a second magnetic core that forms a magnetic path. The recording head58includes a first recording coil70wound on the first magnetic core and a second recording coil70wound on the second magnetic core.

The main magnetic pole60is formed from a soft magnetic material having high magnetic permeability and high saturation flux density, and extends substantially perpendicular to the ABS13. A distal end portion60aof the main magnetic pole60on the ABS13side is tapered down toward the ABS13and formed into a columnar shape having a width less relative to those of other parts.

The trailing shield62is formed of a soft magnetic material and is provided to efficiently close the magnetic path via the soft magnetic layer102of the magnetic disk12directly under the main magnetic pole60. The trailing shield62is formed into a substantially L-shape, and a distal end portion thereof62ais formed into a slender rectangular shape.

The trailing shield62includes a first connection portion50connected to the main magnetic pole60. The first connection portion50is magnetically connected to an upper portion of the main magnetic pole60, that is, a portion of the main magnetic pole60, which is away from the ABS13, via a non-conductive material52. The first recording coil70is wound around, for example, the first connection portion50in the first magnetic core. When writing a signal to the magnetic disk12, a recording current is applied to the first recording coil70, and thus the first recording coil70excites the main magnetic pole60to make magnetic flux flow to the main magnetic pole60.

The leading shield64, formed of a soft magnetic material, is provided on the leading side of the main magnetic pole60, to oppose the main magnetic pole60. The leading shield64is formed into substantially an L-shape, and the leading portion64aon the ABS13side formed into a slender rectangular shape.

Further, the leading shield64includes a second connection portion68bonded to the main magnetic pole60at a position separated from the ABS13. The second connection68is formed, for example, of a soft magnetic material, and is magnetically connected to the upper portion of the main magnetic pole60, that is, the portion of the main magnetic pole60, which is away from the ABS13, via the non-conductive material69. Thus, the second connection68forms a magnetic circuit together with the main magnetic pole60and the leading shield64. The second recording coil72of the recording head58is, for example, wound around the second connection68. The second recording coil72of the recording head58, for example, is arranged to be wound around the second connection63so as to apply a magnetic field to the magnetic circuit.

The configurations of the heaters will now described.

As shown inFIG.2, the heater76cand the heater76dare arranged so as to interpose the recording head58therebetween. In more detail, the heater76c, the trailing shield62, the main magnetic pole60, the leading shield64and the heater76dare arranged in this order from the trailing side. In other words, the recording head58includes a trailing shield62provided on the trailing side of the main magnetic pole60and a leading shield64provided on the leading side opposite to the trailing side. The magnetic head16includes the heater76cprovided on a side of the trailing shield62, which is opposite to the main magnetic pole60, and the heater76dprovided on a side of the leading shield64, which is opposite to the main magnetic pole60. A lower end of each of the heaters76cand76dextends to the vicinity of the ABS13without being exposed to the ABS13and an upper end of each of the heaters76cand76dis placed at a height that substantially coincides with the upper end of the recording head58.

FIG.3is a side view showing an example of the shape of the heater76c.

As shown inFIG.3, the heater (first heater)76ccomprises a plurality of such configurations in each of which one right-angle and U-shaped end thereof is connected to an adjacent right-angle and U-shaped end. In other words, it is shaped such that rectangular notches are provided at predetermined intervals in the longitudinal direction of the rectangular material. The notches each have a rectangular shape elongated in the short side direction of the material, and the notches are alternately provided.

With this structure, the heater76cincludes a plurality of vertical portion each extending perpendicular to the ABS13, and the vertical portions are arranged in the track width direction so as to be spaced apart from each other. The vertical portions located at both ends in the track width direction extend upward beyond the upper end of the trailing shield62, and the upper ends of the vertical portions are substantially alignment with the upper end of the recording head58. Those vertical portions in the middle section along the track width direction are located to oppose the trailing shield62, extend upward beyond the upper end of the trailing shield62, and the upper ends of the vertical portions are substantially alignment with the upper end of the recording head58. The lower side of the heater76cis not exposed to the ABS13, but extends to the vicinity of the ABS13.

Note that the heater (second heater)76dhas a shape similar to that of the heater76c.

Next, an example of connection between the heater76b, heater76cand heater76d, and the heater voltage supply circuit34of the head amplifier IC30will be described with reference toFIGS.4to6.

In the example of the connection shown inFIG.4, the heater voltage supply circuit34includes an amplifier341and an amplifier342, and, the amplifier341is connected to the heater76b, whereas the amplifier342is connected in parallel with the heater76cand the heater76d. To the amplifier341and the amplifier342, indicated power directed by the MPU46are input, respectively. The power is supplied from the amplifier341to the heater76bfor the heater76hto heat. The amplifier342supplies the power to the heater76cand the heater76dform these to heat.

In the example of the connection shown inFIG.5, the heater76cand the heater76dare connected in series to the amplifier342. When the heaters76cand76dare connected in series, the recording head542can be efficiently heated.

In the example of the connection shown inFIG.6, the heater voltage supply circuit34includes the amplifier341, the amplifier342and the amplifier343, and the amplifiers341,342and343are connected to the heater76b, the heater76cand the heater76d, respectively.

FIG.7is a diagram showing an example of protrusion of the head portion.

When recording data on a magnetic disk, the indicated voltage is applied to the heaters76cand76dbased on the instructions of the MPU46, and the recording head58is thermally expanded by the heat of the heaters76cand76d. In more detail, by applying voltage to the heaters76cand76d, the temperatures of the trailing shield62, the leading shield64, the first recording coil70and the second recording coil72are increased, to cause thermal expansion. Thus, the ABS13of the head portion17also expands toward the surface of the magnetic disk12, and thus the flying amount with respect to the surface of the magnetic disk, that is, the gap between the ABS13of the head17and the surface of the magnetic disk12can be adjusted.

The head portion of the magnetic head according to a comparative example will now be described.

FIG.8is a cross-sectional view of a head portion of a magnetic head according to the comparative example. As shown in the figure, in the head portion17according to the comparative example, only a single heater76ais provided as a heater to adjust the amount of protrusion of the recording head58. The heater76ais provided, for example, between the recording coils70and72and above the main magnetic pole6.

FIG.9is a diagram showing an example of the temperature distribution of the head portion when the heater76ais heated in the magnetic head of the comparative example. In the figure, the horizontal axis indicates the temperature, and the vertical axis indicates the height of the head portion17.

As shown inFIG.9, the temperature rises in the vicinity where the heater76ais located, but the heater76ais located above the trailing shield62, the leading shield64, the first recording coil70and the second recording coil72, and therefore the heat transfer of the heater76ais weakened. After the voltage is applied to the heater76a, when the first recording coil70and the second recording coil72are energized, the first recording coil70and the second recording coil72are heated, and therefore the temperature of the area where the first recording coil70and the second recording coil72are located increases. Thus, it can be understood that it takes time until the temperature becomes sufficiently high to form an appropriate gap.

FIG.10is a diagram showing an example of the temperature distribution during heating of the magnetic head according to the first embodiment. In the figure, the horizontal axis indicates the temperature and the vertical axis indicates the height of the head portion17.

As shown inFIG.10, in the magnetic head of the first embodiment, the entire recording head58is heated by the heater76cand the heater76d.

Therefore, as compared to the temperature distribution of the comparative example shown inFIG.9, it can be understood that the heat transfer of the heaters76cand76dis promoted, and the entire recording head58is heated. When the first recording coil70and the second recording coil72are energized, the first recording coil70and the second recording coil72are heated, but as compared to the temperature distribution inFIG.9, it can be understood that the change in temperature is less.

FIG.11is a diagram showing an example of comparison between the magnetic head of the first embodiment and the magnetic head of the comparison example in terms of the relationship between the time of heating and the average temperature. Here, the average temperature is the average of the temperatures of the main magnetic poles60, the trailing shield62and the leading shield64. A characteristic line g2indicated by a solid line illustrates the characteristics of the magnetic head of the embodiment, and a characteristic line g3indicated by a dashed line illustrates the characteristics of the magnetic head of the comparative example.

As shown inFIG.11, the average temperature of the characteristic line g2stabilizes earlier than that of the characteristic line g3. The time period from when the heaters are energized to the point when the temperature of the recording head58stabilizes is a time T1in this embodiment, whereas in the comparative example, it is a time T2(>T1). Since the recording of data is carried after the temperature of the recording head58stabilizes, it can be understood that the magnetic head of this embodiment can start data recording earlier than the magnetic head of the comparative example.

FIG.12is a diagram showing an example of a comparison between the magnetic head of the first embodiment and the magnetic head of the comparison example in terms of the relationship between the time of heating and the gap. Here, a gap D is the gap between the ABS13of the head portion17and the surface of the magnetic disk12(the flying amount). A characteristic line g4indicated by a solid line illustrates the characteristics of the magnetic head of the embodiment, and a characteristic line g5indicated by a dashed line illustrates the characteristics of the magnetic head of the comparative example.

As indicated by the characteristic line g4inFIG.12, when the heaters76cand76dare started to be energized, the head portion17gradually expands to reduce the gap D between the ABS13of the head portion17and the surface of the magnetic disk12. Here, assuming that the gap D1is a suitable distance for recording, the time until the gap becomes D1is a time required for protruding the ABS13, which is a protruding time T3.

As shown in the characteristic lines g4and g5, the protruding time at which the gap D1stabilizes is T3for the magnetic head of this embodiment, whereas it is T4(>T3) for the magnetic head of the comparative example, That is, it can be understood that the magnetic head of this embodiment reaches the gap D1faster than the magnetic head of the comparative example. Since data recording is carried out after the gap is stabilized, the magnetic head of this embodiment is able to record data faster than the magnetic head of the comparative example.

According to the HDD10of the first embodiment, which is configured as described above, the recording head5can be efficiently heated by the heaters76cand76dlocated in the vicinity of the recording head58. With this structure, in the HDD10, the time required for the magnetic head to protrude can be shortened, making it possible to start recording earlier. Thus, the performance of the data recording process of the HDD10can be improved.

Next, the magnetic head of an HDD of another embodiment will be described. In this embodiment, which will be provided below, the same parts as those in the first embodiment described above are denoted by the same reference symbols as those of the first embodiment, and the detailed description thereof may be omitted or simplified.

Second Embodiment

FIG.13is a cross-sectional view of a head portion of a magnetic head of an HDD and a magnetic disk in the second embodiment. The second embodiment is different from the first embodiment in the structure of the heaters. The structure of the HDD other than the heaters is the same as that of the HDD of the first embodiment. Therefore, the structure of the heaters will be explained in detail.

As shown inFIG.13, a heater (first heater)76cand another heater (second heaters)76dare provided on respective sides of the recording head58while interposing the recording head58from both sides. The heaters76cand76dare each shortened in the vertical direction shown in the figure (the direction perpendicular to the ABS13). Specifically, the lower end of the heater76cextends to the vicinity of the ABS13, and the upper end thereof is located at the same height as that of the upper end of the trailing shield62. As in the case of the heater76c, the lower end of the heater76dis not exposed to the ABS13, but extends to the vicinity of the ABS13, and the upper end thereof is located at the same height as that of the upper end of the leading shield64.

FIG.14is a side view showing an example of the shape of the heater76c, andFIG.15is a side view showing an example of the shape of the heater76d.

As shown inFIG.14, the heater (first heater)76cincludes a plurality of vertical portions each extending perpendicular to the ABS13, and arranged along the track width direction. The vertical portions located at both ends along the track width direction extend upward beyond the upper end of the trailing shield62, while those vertical portions located in the middle along the track width direction are located to oppose the trailing shield62and at the same height as that of the trailing shield62.

As shown inFIG.15, the heater (second heater)76dincludes a plurality of vertical portions each extending perpendicular to the ABS13, and arranged along the track width direction. The vertical portions located at both ends along the track width direction extend upward beyond the upper end of the leading shield64, while those vertical portions located in the middle along the track width direction are located to oppose the leading shield64and at the same height as that of the leading shield64.

As described above, the heaters76cand heater76dmay be configured according to the sizes of the trailing shield62and the leading shield64. With the above-described configuration, the recording head58can be thermally expanded more efficiently.

In the second embodiment as well, advantageous effect similar to those of the first embodiment described above can be obtained.

The recording head of the magnetic head of each of the embodiments can be applied to a type which does not comprise a leading shield and/or side shields. The material, shape, size, etc., of the elements which constitute the head portion of the magnetic head can be changed as needed. In the magnetic disk device, the number of magnetic disks and the number of magnetic heads can be increased or decreased as needed, and the size of the magnetic disks can be selected in various ways. The shapes of the first and second heaters are not limited to those of the embodiments described above, and can be changed in various ways as needed.