WO2000052686A1

WO2000052686A1 - Method and apparatus for reading recorded magnetic media using an array of reading elements

Info

Publication number: WO2000052686A1
Application number: PCT/US2000/005739
Authority: WO
Inventors: Christian P. Marlowe
Original assignee: Quetico Technologies, Inc.
Priority date: 1999-03-05
Filing date: 2000-03-02
Publication date: 2000-09-08
Also published as: AU3866700A

Abstract

A reader head is provided that includes a plurality of Hall elements (502-506) mounted thereon. The Hall elements (502-506) are configured to simultaneously sense a plurality of magnetic fluctuations (508) in a predefined area of a magnetic media. The magnetic fluctuations (508) define binary data recorded on the magnetic media. With the plurality of Hall elements (502-506), the reader can sense a plurality of individual flux reversal characteristics in the magnetic media to more sensitively detect magnetic fluctuations located within the predetermined area. As a result, the data can be more easily read with less error.

Description

Method And Apparatus For Reading Recorded Magnetic Media Using An Array Of Reading Elements

Background

The invention relates generally to reader heads for reading magnetic media and, more particularly, to a novel reader head employing a plurality of magnetic reader elements.

The invention pertains to the use of magneto-responsive materials traditionally know as either "Hall Effect" and/or "magneto-resistive" to read recorded information from a magnetic disk, tape or other magnetic storage medium.

Conventional magneto-resistive (MR)and giant magneto-resistive (GMR) read elements are designed and constructed such that the active, portion of the element is at the edge of the read element's respective substrate. This construction requires extensive and expensive edge finishing for the element to operate properly. Further, the conventional MR and GMR read elements are designed to operate as simple single switches which produce only a bi-polar output responsive to the presence of either positive or negative flux reversals. These flux reversals have multiple characteristics aside from either the positive or negative flux reversals, such as positive to neutral, neutral to negative, positive to positive and so on.

Variations on the conventional MR and GMR head designs have been attempted which have been intended to reproduce the traditional geometry in a "planar" orientation. This reduces the cost to produce a reader head. However, these variations have met with little success and have found little or no commercial application. Also, these attempts have not addressed the multiple characteristics of magnetic flux reversals.

Therefore, there exists a need for a reader head that can sense a variety of flux reversals in magnetic recorded media. As will be seen, the invention does this in a simple and elegant manner. Summary of the Invention

A magneto resistive (MR) reader head has a plurality of sensing elements mounted thereon is provided for reading magnetic fluctuations in magnetic media. The sensing elements may include Hall elements that are configured to simultaneously sense a plurality magnetic fluctuations in a predefined area of magnetic media. The magnetic fluctuations define binary data that is recorded by inducing magnetic fields onto the media. With a plurality of sensing elements, the MR reader can sense a plurality of individual flux reversal characteristics in the magnetic media to more sensitively detect magnetic fluctuations located within the predetermined area of the recorded media. As a result, the data can be more easily read by the reader head with less error.

Brief Description of the Drawings

Figure 1 is a block diagram illustrating the general spatial relationship between a reader head and a magnetic recording disk;

Figure 2 is a block diagram illustrating a single magneto resistive element used in an MR head;

Figure 3 is a block diagram of a sensing element according to the invention;

Figure 4 is a block diagram of an array of sensing elements according to the invention;

Figure 5 is a block diagram of the array of Figure 4 connected to a Mixed Signal Transceiver according to the invention;

Figure 6 is a block diagram illustrating an array of sensing elements according to the invention;

Figure 7 is a graphical diagram illustrating the neutral to positive flux reversal transition of a single sensor element;

Figure 8 is a graphical diagram illustrating the negative to positive flux reversal transition of a single sensor element; Figure 9 is a graphical diagram illustrating the positive to positive flux reversal transition of a single sensor element;

Figure 10 is a graphical diagram illustrating the neutral to negative flux reversal transition of a single sensor element;

Figure 11 is a graphical diagram illustrating the positive to negative flux reversal transition of a single sensor element;

Figure 12 is a graphical diagram illustrating the negative to negative flux reversal transition of a single sensor element;

Figure 13 is a graphical diagram illustrating the neutral to neutral flux reversal transition of a single sensor element;

Figure 14 is a graphical diagram illustrating a combination of three individual sensor's outputs;

Figure 15 is a graphical diagram illustrating a combination of five individual sensor's outputs;

Figure 16 is a block diagram of a system for reading a magnetic disk according to the invention; and

Figure 17 is a block diagram of a multi-sensing element device according to the invention.

Detailed Description of Preferred Embodiments

'The invention is directed to an apparatus for sensing magnetic fluctuations in magnetic recorded media. The invention may include a plurality of sensing elements such as Hall elements for sensing magnetic fluctuations on magnetic recorded media. However, it will be appreciated by those skilled in the art, that this is illustrative of only one utility of the invention, and that the invention has greater applicability and utility in many other applications where the sensing of magnetic fluctuations is involved. Equivalent structures embodying the invention could be configured for such applications without diverting from the spirit and scope of the invention as defined in the appended claims.

The invention includes a magneto resistive (MR) reader having a plurality of sensing elements mounted thereon. The MR head is configured to read magnetic fluctuations in magnetic media such as hard disk drives used in a computer. The sensing elements may include Hall elements that are configured to simultaneously sense a plurality magnetic fluctuations in a predefined area of magnetic media. The magnetic fluctuations define binary data that is recorded by inducing magnetic fields onto the media. With a plurality of sensing elements, the MR reader can sense a plurality of individual flux reversal characteristics in the magnetic media. This allows the reader head to more sensitively detect magnetic fluctuations located within a predetermined area of the recorded media. As a result, the data can be more easily read by the reader head with less error.

The general form to this "Parallel Element" is such that a series of "tiles" of magneto-responsive material is laid out such the generally planar portion of the magneto-responsive material is parallel and adjacent to the recorded media. These tiles are than combined electrically to produce an output signal pursuant to the requirements defined by magnetic recording system. Two configurations are herein described. A material that the tiles may be composed of is intimidide or intimidine. This material is very sensitive to magnetic fluctuations.

Referring to the Figure 1, the general spatial relationship between the basic components of the invention are shown in elevation. A reader head may be comprised fa substrate 100 that is configured to read a magnetic medium such as a magnetic disk 102. The disk includes predetermined areas 104 having individual magnetic flux orientations such as positive, negative, neutral and variations in between. The sensing element 106 is fabricated onto a dielectric substrate 100. The substrate is generally associated with an integral to a head assembly 108. This head assembly 108 is mounted relative to a recorded medium 102 at a height 110. The recorded medium 102 contains information generally configured as flux reversals 111. The dimension at which the head assembly is mounted relative to the media is generally considered the "fly height" delta H. In this figure the flux reversals 111 are shown generally perpendicular to the plane of the media, however, this invention may be adapted and applied to flux reversals oriented generally parallel to the plane of the media.

The general electrical configuration of the magneto-responsive element is shown in Figure 2. The magneto-responsive element 106 is driven by a bias current represented by Vcc and the ground symbol, wherein a sense voltage, indicated by Ns+ and Vs-, is detected when the magneto-responsive element encounters a Z-axis flux field which is generally into or out of the view and is herein represented by the duel arrow line segment noted "F".

Figure 3 illustrates a configuration for a single magneto-responsive flux sensing element, wherein the magneto-responsive material 106 is shaped generally into a "cross-like" geometry, where each leg 302,304 of the cross is specifically connected to either leads providing bias current, or leads detecting sense voltage. In this geometry, only the center section 306, shown cross-hatched, is responsive to the presence of magnetic flux. This configuration of crossing the legs 302,304 greatly optimizes the responsiveness of the sensing element 300.

Figure 4 illustrates a novel construction in geometry of the flux sensing element. A multi-cross configuration 400 of magneto-responsive material such that a single bias current is imposed from Vcc to ground wherein multiple flux sensing areas are generated with several crossing voltage sensing features. In this figure three crossing features are employed however, any number of crossing features, greater than one, can be employed in a similar construction depending upon the resolution desired by the sensor and the number of flux reversals to be resolved more or less simultaneously. In this arrangement, only the actual common crossing area 402,404,406 can sense the presence, or absence, of magnetic flux. This maximizes the sensitivity of the array of sensing elements.

In this invention, it is intended to sample, more or less simultaneously each flux reversal several times by each independent' legs, 408-414, that cross to form the sensors 402,404,406. This is accomplished by the introduction of relative motion between the sensor and the magnetic flux reversals existing on the magnetic media. This is illustrated in Figure 5. Referring to Figure 5, an array of sensing elements 500 is illustrated, the elements 502-506 are the result of crossing legs 510-516. The sensing elements are passed over flux reversals 508 that exist on the magnetic media, not shown. The use of regressive analog delay lines 518-522 allows associated signals to be combined more or less simultaneously in mixed signal transducer 524. The mixed signal transducer is can be configured to mix and combine the signals using methods well known in the art. In the case of the configuration of Figure 5, which has three sensing features, this delay would be no greater than approximately 1/3 the length of the flux reversal or 33.3 percent of the electric signal produced by the interaction of the flux reversal with the flux sensing feature. Were 5 sensing features employed, this delay would be no greater than approximately 1/5 the length of the flux reversal or 20 percent of the electric signal produced by the interaction of the flux reversal with the flux sensing feature and so on. Figure 5 schematically indicates the use of delay lines 518-522 and a signal processor shown as mixed signal transducer 524, configured to perform oversampling operations relative to a Phase Locked Loop "PLL" to cause the electric signal generated by the flux sensing portion of the magneto-responsive material for each flux reversal to be combined in a fashion to allow for resolving important characteristics of each individual flux reversal. The important characteristics of each individual flux reversal include, but are not . limited to, polarity, period and amplitude. Figure 5 further indicates the output of a usable signal 526 to be delivered to whatever processing device is employed for such purpose to make use of such signal.

Figures 4 and 5 may be dependent upon the use of a delay line for adequate resolution of the flux reversal into a usable digital signal. This is initially important in that the entire sensing structure can be fabricated on a single layer, which has substantial cost benefits relative to the current art. However, as the demand for more tightly packed sensing arrays becomes required, the crossing sensing elements can be produced in an overlapping fashion, as indicated in a section view provided as Figure 6. In this figure, magneto-responsive sensing elements 602,604,606 are fabricated in an overlapping configuration, (non-conductive/non-magnetic separating agent not shown)whereby each sensing element simultaneously senses each flux reversal 608 progressively, with the same percentage offsets as indicated previously. Each sensing element is active concurrently mooting the need for delay lines prior to signal combination for useful output. Further, in Figure 6 the lines for voltage sensing as indicated as Vs+ and Vs- for each sensing element may be alternately into and out of the plane of the figure, or parallel to the motion of the flux reversals as required.

Although this arrangement of magneto-responsive sensor elements in Figure 6 is capable of resolving analog signals recorded to magnetic media, the primary initial application of this invention is to resolve binary flux reversals. In general, binary signals mean that a "positive" flux reversal would be considered a "one" and a "negative" flux reversal would be considered a "zero". It is to be understood that in this configuration the flux reversals are generally perpendicular to the plane of the media, however, this method of reading and resolving magnetic signals can be applied to magnetic flux reversals which are generally parallel to the plane of the media. The use of this sensor tile to resolve the generally perpendicular flux reversals is treated herebelow.

It is to be understood that the individual magneto-responsive sensing elements or tiles are "gross" analog sensors. By the use of the term gross, it is to be understood that the tiles, which generally are either of a similar cross sectional area or are smaller than the cross sectional area of the flux reversals to be resolved. As such, each individual tile is not capable of precisely resolving each individual flux reversal with certainty thus the requirement for more than one sensor tile to observe the flux characteristics of each flux reversal at slightly different positions as previously indicated.

Further, it is to be understood that the portion of the flux reversal where the most information about same is available is the leading edge transition of the flux reversal to be resolved relative to the previous flux reversal. For instance in a binary recording scheme, assuming that the magneto-responsive material chosen for the sensors is capable of producing both positive and negative transition voltages, there are seven possible flux transitions. These seven transitions are indicated by Figure 7 through Figure 13. Further, the seven transitions assume that the unrecorded magnetic media may have a neutral flux state, where there exist neither positive or negative flux reversals. These transitions are listed in tabular form below:

Figures 14 and 15 shows the relative instances of sampling available by this system for three and five sensor tiles respectively. This is for reference however, as each flux reversal may be sampled several times by this system to allow for either redundancy or the resolution of analog information from the flux reversals.

By the use of the sensor tile information described above, and by combining the information available from all sensor tiles using PLL and over-sampling methodology, both of which are well understood in their respective arts, each flux reversal can be easily resolved to determine its nature as either a one, zero or other analog data signal, as required.

Referring to Figure 16, a system for reading magnetic media according to the invention is illustrated. The system 1600 includes a substrate 1602 mounted on a reader arm 1604, which is mounted to a servo motor (not shown) configured to manipulate the arm. Sensing elements 1606-1610 are mounted on the substrate and positioned so as to sensitively read digital data from a magnetic media. The sensing elements are connected by signal lines 1612-1616 to mixed signal device (MSD) 1618 combines the signals from the sensing elements. A phased locked loop (not shown) may synchronize the signals into an output signal 1620 for transmission to a processor (not shown) for processing the data. The disk head may fly over a magnetic disk 1622 which is mounted on a shaft 1624 and driven by a motor 1626.

The invention is directed to an apparatus The invention is directed to an apparatus for sensing magnetic fluctuations in magnetic recorded media. The invention may include a plurality of sensing elements such as Hall elements for sensing magnetic fluctuations on magnetic recorded media. However, it will be appreciated by those skilled in the art, that this is illustrative of only one utility of the invention, and that the invention has greater applicability and utility in many other applications where the sensing of magnetic fluctuations is involved. Equivalent structures embodying the invention could be configured for such applications without diverting from the spirit and scope of the invention as defined in the appended claims.. Although this embodiment is described and illustrated in the context of a MR head for reading magnetic fluctuations on recorded magnetic media, the invention extends to other applications where sensitive detection of magnetic fluctuations is useful. Furthermore, while the foregoing description has been with reference to particular embodiments of the invention, it will be appreciated that these are only illustrative of the invention and that changes may be made to those embodiments without departing from the principles of the invention, the scope of which is defined by the appended claims.

Claims

1. A magneto resistive (MR) reader head for sensing a magnetic flux from a magnetic media, comprising:

a substrate; and

a plurality of Hall elements mounted on the substrate and configured to simultaneously sense a like plurality of magnetic flux reversals on a predefined area of the magnetic media.

2. The MR reader head according to Claim 1, wherein each of the plurality of elements are configured to sense individual flux reversal characteristics in the magnetic media.

3. The MR head of Claim 2, wherein the individual flux reversal characteristics include polarity, period and amplitude.

4.. The MR reader head according to Claim 1 , wherein the sensing sensitivity of the flux reversals is enhanced.

5. A magneto resistive (MR) reader head for sensing a magnetic flux from a magnetic media, comprising:

a substrate; and

an array of sensing elements mounted on the substrate and configured to simultaneously sense a plurality of magnetic flux reversals on a predefined area of the magnetic media.

6. The MR head of Claim 5, wherein the array of sensing elements comprises a plurality of cross-like geometrically coupled base structures, each base structure including a leg pair and having a Hall element disposed thereon at respective cross-sections of the leg pair.

7. The MR head of Claim 6, wherein each Hall element is spaced apart from an adjacent Hall element by a distance ΔT so that a like plurality of flux reversals can be sensed simultaneously to provide a resulting representative waveform that is indicative of the flux reversal characteristics sensed by each of the Hall elements in the sensing array.

8. The MR head of Claim 5, wherein the array of sensing elements comprises a plurality of adjacent horizontal base structures, each base structure having a Hall element disposed thereon.

9. The MR head of Claim 8, wherein each Hall element is spaced apart from an adjacent Hall element by a distance ΔT so that a like plurality of flux reversals can be sensed simultaneously to provide a resulting representative waveform that is indicative of the flux reversal characteristics sensed by each of the Hall elements in the sensing array.

10. The MR head of Claim 6, wherein the Hall element comprises Intimidide.

11. The MR head of Claim 6, wherein the Hall element comprises Intimidine.

12. A magneto resistive (MR) reader head for sensing a magnetic flux from a magnetic media, comprising:

a substrate;

a plurality of Hall elements mounted on the substrate and configured to simultaneously sense a like plurality of magnetic flux reversals on a predefined area of the magnetic media; and

a mixed signal transducer coupled to each of the plurality of Hall elements by a respective delay line, the transducer configured to operate on respective electrical signals provided by each Hall element via the respective delay lines to provide a resulting output signal.