WO2010062300A2

WO2010062300A2 - Hard disk drive device read-write head with digital and analog modes of operation and use thereof

Info

Publication number: WO2010062300A2
Application number: PCT/US2009/005574
Authority: WO
Inventors: Nick Pileggi; William Pippin; Mike Sunners
Original assignee: Micromem Technologies, Inc.
Priority date: 2008-11-03
Filing date: 2009-10-13
Publication date: 2010-06-03
Also published as: WO2010062300A3

Abstract

The invention relates generally to hard disk devices, and more particularly, to hard disk devices using read-write components having electromagnetic elements. The invention can be utilized in any application requiring high sensitivity such as ionic particulate flow detection, and weak magnetic planar flux variation and transition detection. The invention combines both Hall Effect sensors and inductive effects to help increase precision of sensitivity, and increase flux noise rejection. Additionally, to acting as a sense element, the invention has the ability to generate a localized electromagnetic flux.

Description

HARD DISK DRIVE DEVICE READ-WRITE HEAD WITH DIGITAL AND ANALOG MODES OF OPERATION AND USE THEREOF

FIELD OF THE INVENTION

[0001] The invention encompasses embodiments relating generally to hard disk devices, and more particularly, to hard disk devices using read-write components having electromagnetic elements. The invention further encompasses methods useful in the measurement, detection, and filtering of weak magnetic flux signals local to the surface of the centrally located flux concentrator. Such signals would be likened to those generated by ionic flow, minerals acting in a magnetic field, or magnetic fields substantially weaker than those of the earth's magnetic flux baseline.

BACKGROUND OF THE INVENTION

[0002] Hard disk drives ("HDDs") remain a dominant form of storage technology and operate by taking advantage of magnetic fringe and boundary effects. An HDD involves read- write heads positioned in close proximity above rotating platters coated with ferromagnetic material to detect and modify data on the magnetic media surfaces. Current HDD technology uses Hall Effect sensors or Giant Magneto-Resistive ("GMR") sensors to implement the read portion of the read- write heads and a separate inductive component to implement the write portion of the read- write heads. A main reason for using separate read and write portions in current HDD technology is the level of magnetic flux that must be generated by the write head in order to switch the data storage area on the magnetic media surfaces from N (north) to S (south) and S to N. Separation of the read and write portions, however, makes current read- write heads costly to produce. Moreover, such compositions cannot adequately meet data density increases driven by the current demands for storage capacity without sacrificing reliability and costs. In addition, data density is further limited by the amorphous nature of the magnetic material sputtered on the platters.

[0003] As densities approach 1 Gbit/in² and beyond, GMR sensors for read-write heads will need to be thin enough to fit within the required read space created by necessary magnetic shield structures, yet sensitive enough to detect the magnetic fields from the stored data bits, and still yet structured in a manner to diminish the device's overall susceptibility to environmental noise that accompanies increases in device sensitivity. Density increases trigger similar restrictions for read-write heads using Hall Effect sensors for their read portions. Moreover, the size at which the inductive write component can be developed is approaching a finite limit due to the minimum amount of flux density necessary to switch the polarity of a stored data bit. As described above, the requisite magnetic flux density to be localized onto a single magnetic storage bit without affecting surrounding data also serves as a main reason for separating the write component from the read component in current HDD technology. Thus, current HDD technology requires a separate ferromagnetic structure with a wire loop of a certain size to provide the necessary inductance. ^v

[0004] Furthermore, the material aspects of the magnetic media surfaces themselves must be advanced in order to produce a more regular geometry of the magnetically sensitive molecules. Accordingly, there is a need for hard disk devices using a more regular and thus smaller magnetically responsive media, and having a read-write device that can accommodate rapid data density increases and yet prove both reliable and cost effective.

[0005] The means necessary to implement an HDD substantially require digital behavior. This involves arbitrary single bit comparison against the input flux as detected by the incorporated Hall Effect sensors. The invention is not limited to digital behavior and can provide substantial analog data as well. This feature allows for the invention to behave as a highly sensitive analog flux detector as well as a binary bit sensor for use in HDD. Due to the inductor local to the Hall Effect sensors, DC and AC electrical means are effective at providing noise rejection, signal filtering for rejection or acceptance, as well as for the generation of flux at the surface of the local concentrator. This element may also be used to implement magnetic field based reception and transmittal of data signals both analog and digital in nature.

SUMMARY

[0006] One embodiment of the invention encompasses a hard disk device comprising (i) a media material; and (ii) an integrated read-write device including (a) a substrate, (b) a plurality of Hall Effect sensors formed on the substrate, and (c) a flux concentrator formed above the plurality of Hall Effect sensors, wherein the flux concentrator has a post formed between the pluralities of Hall Effect sensors.

[0007] Another embodiment of the invention encompasses a method of determining a magnetic polarity of a bit on a hard disk device, comprising the steps of passing current through an induction coil to produce a magnetic field within a flux concentrator, the magnetic field magnetizing a media material to store a magnetic bit on the media material; and sensing the magnetic bit on the media material using a plurality of Hall Effect sensors, wherein the flux concentrator has a post formed between the plurality of Hall Effect sensors.

[0008] Another embodiment of the invention encompasses a method of determining a magnetic flux density, comprising the step of measuring the planar flux density on the surface of the flux concentrator as it affects the Hall Effect sensors. Further, by applying a DC electrical signal to the localized inductor, weak signals or those defined as noise can be electrically coupled in such a manner as to reduce their effect on the Hall Effect sensors. Similarly, applying an AC current to the localized inductor can allow for signal filtering at a particular frequency and a known pattern/signature and, in turn, allow for rejection or acceptance thereof. In addition, flux induced voltage at the localized coil terminal can be used as another source of data provided to the Hall Effect sensors.

[0009] Another embodiment of the invention encompasses a method of determining the magnitude of analog signals of similar flux magnitude as that experienced by the HDD embodiment. This embodiment is substantially similar to the HDD embodiment in that the HDD embodiment is an electrical subset of the complexity and sensitivity necessary to electrically represent the analog flux present at the surface of the flux concentrator. This embodiment has the ability to quantify the flux signal in a scalar fashion of higher precision than that of an HDD that simply qualifies the flux as either a north or south magnetically flowing signal.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figures IA and IB are diagrams of a read-write head 100 of an HDD in accordance with an embodiment of the invention. Figure IA is a top view of the embodiment and Figure IB is a substrate layer side view of the embodiment. [0011] Figure 2 illustrates various views of a flux concentrator 200 of a read-write head in accordance with an embodiment of the invention.

[0012] Figure 3 is a diagram of a Hall Effect sensor layer arrangement 300 on a read-write head in accordance with an embodiment of the invention.

[0013] Figure 4 depicts a secondary inductor in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0014] Figures IA and IB are diagrams of a read-write head 100 of a HDD in accordance with an embodiment of the invention. Read- write head 100 comprises a substrate 113 on which a flux concentrator 101, an integrated induction coil 107 and several Hall Effect or Hall Cross sensors 112 are formed. In one embodiment of the invention, substrate 113 may be manufactured from semiconductor material.

[0015] Each component of read- write head 100 is provided in detail below. Each of the Hall Cross sensors consists of an n-doped or equivalent layered region 112 in the form of two intersecting rectangles with the length to width ratio of greater than 2.5. The opposing ends 102 and 103 of one rectangle are electrically coupled to an externally provided drive current source as depicted in Figure IA. The opposing ends 109 and 110 of the other rectangle are electrically coupled to an external differential measuring circuit. The differential output is substantially related to the magnetic flux incident perpendicular to the surface of the Hall n-doped region 112. Each Hall Cross sensor ("HCS") may also be surrounded by a p-doped material 104 when the substrate properties are such where a boundary is necessary to protect the external components from electrical effects due to substrate electrical boundary issues. Not all embodiments require this feature and the decision to use it is predicated upon substrate properties. The integrated inductor ("II") 107 is electrically coupled to either an external drive circuit and / or an external differential measuring circuit via electrical pads 105 and 106 which are serially connected to the ends of the inductor 107 portion looping the center post 108 of the flux concentrator ("FC") 101. The flux concentrator is comprised of a body 101, a centrally located post 108 perpendicular to the base plane of the body 101, and flux point concentration elements 111. The flux concentrator body can assume any geometric shape that is useful to the intended application. In this embodiment, the geometry, from a top down view is described as a rectangle deposition that is substantially longer than it is wide; in Figure IA, the top of the FC is shown at the top of the drawing and the bottom of the FC is shown at the bottom of the drawing. Intersecting the central rectangle are two crosses substantially similar in base design to the Hall element 112 except that the externally located transverse arms terminate at a point (see 111) with the width of each of the transverse arms uniformly arching to an end of the main rectangle portion of the body and to the center of the body element. The result is to generate four sharp points (see 111) that will substantially concentrate flux in close proximity to and slightly above the HCS elements. To further the directing of the flux to impinge upon the center of the HCS elements, the ends of said points are thickened by the addition of material 111 to reduce the distance between the planar base of the flux concentrator and the HCS planar location. The centrally located post 108 extends from the layer base of element 101 to the layer at which the HCS elements reside. This portion of the flux concentrator is solely responsible for coupling the magnetic and electromagnetic flux affecting the flux concentrator as a whole to the integrated inductor via inductive loop 107. Additionally, electromagnetic flux generated by the integrated inductor via loop 107 is in turn coupled to the flux concentrator via post 108. As depicted in the side view of Figure IB, in this embodiment, the surface layer of the flux concentrator opposite the base layer of the HCS layer is substantially conical in its geometry above the intersection of the two transverse arms of the flux concentrator. With the exception of the HCS focusing points concluding at element 11 1, all surfaces may use smooth (i.e. cylindrical) surface transitions to eliminate all sharp angles for maximum flux concentration at said elements 111. Failure to do so may cause flux leakage points which will reduce the flux concentration effects at the HCS elements located in close proximity to element 111. The flux concentrator is comprised of substantially magnetically permeative materials. In one embodiment, perm-alloy, a metallic compound consisting of aluminum and nickel, is epitaxially deposited onto the said substrate 113 to provide the geometric shape defined. In another embodiment, FePt can be used as a suitable magnetically permeative material.

[0016] The structure of read-write head 100 allows it to measure both the Hall Effect value of a local magnetic field and/or the inductive value of a local magnetic field. Both values will in essence be reading the same geometric point in space, i.e., a particular magnetic stored bit in the case of a digitally behaving HDD, or geometrically close magnetic flux line in the case of an analog responding sensor. In addition, the structure of read-write head 100 allows a magnetic field to be created from an electric field generated by induction coil 107. Thus, depending on whether the HDD is in read mode or write mode, read- write head 100 can both read and write a magnetic flux value located in a particular geometric location. The combination of both read and write elements into a single unit allows read-write head 100 to be physically small enough to support current data density demands. Yet such a composition allows read- write head 100 to overcome noise attendant from increased read sensitivity and to generate a magnetic write field of sufficient magnitude to write a data bit at room temperature. Such a composition is also cost effective to implement as it requires fewer steps to manufacture.

[0017] Figure 2 is a diagram illustrating various views of a flux concentrator 200 of a read- write head in accordance with some embodiments. Flux concentrator 200 is comprised of ferrous or other magnetically permeable materials to help focus and/or average the magnetic flux fields affecting the read- write device onto the Hall Effect sensors 112 formed on the substrate 113. Doing so allows the Hall Effect sensors 112 to achieve more stable readings. According to one embodiment of the invention, flux concentrator 200 takes the form of a modified H-Bridge structure. According to other embodiments of the invention, flux concentrator 200 takes the form of other geometrical shapes. In one embodiment, flux concentrator 200 has a three dimensional shape consisting of a flat top surface parallel to the top surfaces of Hall Effect sensors 112. Such a shape is designed to concentrate magnetic flux incidental on the flat surface of the flux concentrator 200 onto each Hall Effect sensor 112. Flux concentrator 200 may also comprise a cylindrical post 204 located proximate a middle body section perpendicular to the flat surface. In another embodiment, flux concentrator 200 comprises a set of tapered edges 202, each tapered edge 202 corresponding to each Hall Effect sensor 112 to concentrate magnetic flux onto the Hall Effect sensor 112. Tapered edges 202 may alternatively be sharp edges. In another embodiment, flux concentrator 200 has three-dimensional top surfaces that draw to a point opposite the cylindrical post 204. Such a shape is designed to concentrate magnetic flux located at that point (Figure IA). [0018] Figure 3 is a diagram of a Hall Effect sensor arrangement 300 on a read-write head in accordance with an embodiment of the invention. According to one embodiment, Hall Effect sensor arrangement 300 comprises four Hall Effect sensors 302 arranged in a grid-like manner. The additional Hall Effect sensors 302 increase sensitivity of the read-write head. According to other embodiments, Hall sensor arrangement 300 comprises other numbers of Hall Effect sensors 302, such as multiples of two, with half of the Hall Effect sensors 302 dedicated to the north polarized magnetic fields and half of the Hall Effect sensors 302 dedicated to the south polarized magnetic fields. As shown in Figure 3, a drive current is supplied to each of the Hall Effect sensors 302 so that the source of electrons can be near the center of the north and south magnetic fields.

[0019] A flux concentrator 200 (not shown in Figure 3) is arranged above and among the four Hall Effect sensors 302 so that concentrator base post 304 of the flux concentrator 200 is formed near the center of the four Hall Effect sensors 302. An induction coil 306 of electrically conductive material is provided in proximity to the concentrator base post 304. During write mode, current through the induction coil 306 produces a magnetic field within the flux concentrator, which in turn magnetizes the bit regions of the underlying magnetic media surface. According to one embodiment of the invention, this ability to induce magnetization in the flux concentrator 200 also allows for self-calibration of the Hall Effect sensors 302. Furthermore, the flux concentrator and coil combination may serve as electromagnetic sensors during write mode. For example, during write mode, such an arrangement allows for detection of a stored magnetic bit on the underlying magnetic media surface by measuring the inductive effects of the magnetic field on induction coil 306. According to one embodiment of the invention, the induction coil 306 is perpendicular to the sense plane of the flux concentrator.

[0020] Additional benefits of the arrangement of the components of read- write head 100 include allowing for continued electrical inductive excitation of the flux concentrator 200 to create a threshold level of magnetic flux to be sensed by the Hall Effect sensors 302. Such an arrangement also allows for electrical inductive excitation of the flux concentrator for purposes of reflecting the magnetic flux levels as detected by the Hall Effect sensors 302. [0021] According to the embodiment depicted in Figure 4, a second inductor 116 is present. Electrical connections 114 serially connected with inductor 1 16 and serially terminated at terminal 115 provide for an electrical current path to either power the inductor 116 or for the electrical path to provide for an external signal representative of induced voltage present within inductor 116.

[0022] The foregoing description, for purposes of explanation, has been provided with reference to specific embodiments. The illustrative discussions above, however, are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.

Claims

CLAIMSWHAT IS CLAIMED IS:

1. A hard disk device comprising: a media material; an integrated read-write device comprising: a substrate; a plurality of Hall Effect sensors formed on the substrate; a flux concentrator formed above the plurality of Hall Effect sensors, the flux concentrator having a cylindrical post formed between the plurality of Hall Effect sensors.

2. The hard disk device of claim 1, wherein the flux concentrator further comprises a plurality of tapered edges, each tapered edge corresponding to each of the plurality of Hall Effect sensors to concentrate magnetic flux onto the Hall Effect sensors.

3. The hard disk device of claim 1 , wherein a top surface of the flux concentrator is of such shape as to facilitate optimal flux concentration or flux detection.

4. The hard disk device of claim 3, wherein the top surface is flat for generic sense applications.

5. The hard disk device of claim 3, wherein the top surface is tapered to a point where application requires more precise flux concentration or flux detection.

6. The hard disk device of claim 3, wherein the top surface has multiple tapered points where the application requires differentially variant flux boundary detection.

7. The hard disk device of claim 4, wherein the cylindrical post of the flux concentrator is located proximate a middle body section of the flux concentrator perpendicular to the top flat surface of the flux concentrator.

8. The hard disk device of claim 4, wherein the integrated read-write device further comprises an induction coil formed proximate to the flux concentrator wherein current through the induction coil produces a magnetic field within the flux concentrator, the magnetic field magnetizes the media material to store a magnetic bit on the media material.

9. The hard disk device of claim 8, wherein the induction coil is formed coupled to the post of the flux concentrator.

10. The hard disk device of claim 8, wherein the flux concentrator and the induction coil serve as an electromagnetic sensor to detect a stored magnetic bit or weak magnetic flux of similar amplitude on the media material.

11. The hard disk device of claim 1 , wherein the flux concentrator is comprised of a ferrous material.

12. A method of determining a magnetic polarity of a bit on a hard disk device comprising: passing current through an induction coil to produce a magnetic field within the flux concentrator of claim 3, the magnetic field magnetizing a media material in close proximity to the flux concentrator to store a magnetic bit on the media material; and sensing the magnetic bit on the media material in close proximity to the flux concentrator using a plurality of Hall Effect sensors, wherein the flux concentrator has a post formed between the plurality of Hall Effect sensors.

13. The method of claim 12, wherein each of the Hall Effect sensors comprises a drive current supplied by a source of electrons in geometric reverse parallel, and wherein the source of electrons is the geometric center of north and south magnetic fields.

14. A method of applying flux to exploit a Hall Effect sensor to assist with self-calibration related to the behavior of Hall Effect sensors comprising electrically exciting the flux concentrator of claim 3.

15. A method of creating a minimum flux level for concentrating of flux noise comprising providing a base level of DC flux at a Hall Effect sensor of claim 1.

16. A method of filtering magnetic flux based upon AC frequency coupling means comprising stimulating the flux concentrator of claim 3 with an AC current.

17. A method of producing a flux on an external surface of the flux concentrator of claim 3 comprising providing the flux concentrator with a DC and/or AC electrical excitation of an induction coil.

18. The hard disk drive of claim 8, wherein the integrated read-write device further comprises a second induction coil.

19. The hard disk drive of claim 18, wherein the induction coils can be electrically coupled to provide for differential AC and DC signal analysis.

20. The hard disk drive of claim 18, wherein one induction coil is utilized as a sense element and the second induction coil is used as an AC filtering element.

21. The hard disk drive of claim 18, wherein one induction coil is utilized as a sense element and the second induction coil is used as a DC filtering element.

22. The hard disk drive of claim 18, wherein the induction coils are used to induce an external flux on an external surface of the flux concentrator.