Permanent magnet shaped to provide uniform biasing of a magnetoresistive reproduce head

• US 4,987,508 A
• Filed: 12/23/1988
• Issued: 01/22/1991
• Est. Priority Date: 12/23/1988
• Status: Expired due to Term

• Current Assignee: Eastman Kodak Company
• Original Assignee: Eastman Kodak Company
• Inventors: Smith, Neil
• Primary Examiner(s): Tupper, Robert S.
• Application Number:
  US07/288,926
• Time in Patent Office: 760 Days
• Field of Search: 360/113, 338/32 R, 335/297, 335/302
• US Class Current: 360/327.23
• CPC Class Codes: G11B 5/3903 using magnetic thin film layers or their effects, the films being part of integrated structures
• CPC Class Codes: H01F 7/02 Permanent magnets [PM]

Abstract

The invention teaches modifying the shape of a bar magnet which is uniformly magnetized either in the direction of its height or width to increase the volume of magnetic material at each end of the magnet. This results in increased magnetic field contribution from the magnet ends which modifies the field direction at the magnet faces so that the field lines converge rather than diverge just as they enter and leave the central portion of the magnet. Further along the field direction, the field lines change from being convergent to again being divergent, as is the usual case for a conventional bar magnet. Because of this transition there is an extended region over which the field lines are effectively straight and parallel, i.e. the field is uniform. This uniformity has been attained without increasing the length of the magnet, and a bar magnet so modified according to the teaching of the invention is suitable for the uniform biasing of MR elements in a single track or in a multitrack head.

Claims

1. A magnet for biasing a magnetoresistive element utilized in a magnetoresistive head, said magnet comprising:

a. magnetic material in the shape of a rectangular parallelepiped bar having mutually orthogonal length, height, and width dimensions, wherein the longest dimension of said magnet is designated as "length" and the two mutually orthogonal shorter dimensions are designated as "height" and "width",

b. magnetization means for uniformly magnetizing said bar along said height dimension, whereby magnetic charges are generated on first and second surfaces of said bar perpendicular to the direction of said magnetization, and

c. means for modifying the distribution of said charges at the longitudinal end regions of said bar, whereby the external field of said magnet has an extended region of uniform field for biasing said magnetoresistive element utilized in said magnetoresistive head.

2. The magnet of claim 1 wherein said magnetization means is means for permanently magnetizing said magnetic material.

3. The magnet of claim 2 wherein said means for modifying the distribution of said charge at the longitudinal end regions of said bar is means for extending the width of said bar at said longitudinal end regions.

4. A magnet for biasing a magnetoresistive element utilized in a magnetoresistive head, said magnet comprising:

a. magnetic material in the shape of a rectangular parallelepiped bar having mutually orthogonal length, height, and width dimensions, wherein the longest dimension of said magnet is designated as "length" and the two mutually orthogonal shorter dimensions are designated as "height" and "width",

b. magnetization means for uniformly magnetizing said bar along said width dimension, whereby magnetic charges are generated on first and second surfaces of said bar perpendicular to the direction of said magnetization, and

c. means for modifying the distribution of said charges at the longitudinal end regions of said bar, whereby the external field of said magnet has an extended region of uniform field for biasing said magnetoresistive element utilized in said magnetoresistive head.

5. The magnet of claim 4 wherein said magnetization means is means for permanently magnetizing said magnetic material.

6. The magnet of claim 5 wherein said means for modifying the distribution of said charge at the longitudinal end regions of said bar, is means for extending the width of said magnetized bar at said longitudinal end regions.

7. A magnet for biasing a magnetoresistive element utilized in a magnetoresistive reproduce head, said magnet comprising:

a. a permanent magnetic material having a "C" shaped structure of rectangular cross-section, wherein the longest dimension of said magnet is designated as "length" and the two mutually orthogonal shorter dimensions are designated as "height" and "width",

b. uniform magnetization in said "C" shaped structure wherein said magnetization lies in the width direction of said cross section to provide an extended region of uniform field proximate said magnet, said extended region lying along said width direction, and said magnetoresistive element further being located in said extended region whereby said magnetoresistive element utilized in said magnetoresistive head is biased.

8. A magnet for biasing a magnetoresistive element utilized in a magnetoresistive reproduce head, said magnet comprising:

a. a permanent magnetic material having a "C" shaped structure of rectangular cross-section, wherein the longest dimension of said magnet is designated as "length" and the two mutually orthogonal shorter dimensions are designated as "height" and "width",

b. uniform magnetization in said "C" shaped structure wherein said magnetization lies in the height direction of said cross section to provide an extended region of uniform field proximate said magnet, said extended region lying along said width direction, and said magnetoresistive element further being located in said extended region whereby said magnetoresistive element head is biased.

9. A magnetoresistive head for reproducing signal recorded on a magnetic medium, said head comprising:

a. a non magnetic substrate,

b. magnetoresistive means having a hard magnetic axis, said magnetoresistive means being deposited on said substrate,

c. permanent magnet means for biasing said magnetoresistive means along said hard magnetic axis, said permanent magnet means further comprising,

1. permanent magnetic material having a "C" shaped structure of rectangular cross section, wherein the longest dimension of said permanent magnetic material is designated as "length" and having two mutually orthogonal shorter dimensions designated as "height" and "width", said cross section further comprising the height and width dimensions of said "C" shaped structure,

2. uniform magnetization of said "C" shaped structure, said magnetization lying along said height dimension of said "C" shaped structure, wherein said permanent magnetic material provides an extended region of uniform field proximate said permanent magnetic material, said extended region lying along said height direction, and said magnetoresistive element further being located in said extended region whereby said permanent magnetic material coacts with said magnetoresistive means to uniformly bias said magnetoresistive means along said hard magnetic axis.

10. The magnetoresistive head of claim 9 wherein said permanent magnet means is a deposited permanent magnet.

11. The magnetoresistive head of claim 9 wherein said magnetoresistive means comprises a plurality of magnetoresistive elements configured in a multitrack magnetoresistive reproduce head.

12. The magnetoresistive had for reproducing signal recorded on a magnetic medium, said head comprising:

a. a non magnetic substrate,

b. magnetoresistive means having a hard magnetic axis, said magnetoresistive means being deposited on said substrate,

c. permanent magnet means for biasing said magnetoresistive means along said hard magnetic axis, said permanent magnet means further comprising,

1. permanent magnetic material having a "C" shaped structure of rectangular cross section, wherein the longest dimension of said permanent magnetic material is designated as "length" and having two mutually orthogonal shorter dimensions designated as "height" and "width", said cross section further comprising the height and width dimensions of said "C" shaped structure,

2. uniform magnetization of said "C" shaped structure, said magnetization lying along said width dimension of said "C" shaped structure, wherein said permanent magnetic material provides an extended region of uniform field proximate said permanent magnetic material, said extended region lying along said width direction, and said magnetoresistive element further being located in said extended region whereby said permanent magnetic material coacts with said magnetoresistive means to uniformly bias said magnetoresistive means along said hard magnetic axis.

13. The magnetoresistive head of claim 12 wherein said permanent magnet means is a deposited permanent magnet.

14. The magnetoresistive head of claim 12 wherein said magnetoresistive means comprises a plurality of magnetoresistive elements configured in a multitrack magnetoresistive reproduce head.