Magnetic core with field confinement structure

• US 5,717,552 A
• Filed: 09/10/1996
• Issued: 02/10/1998
• Est. Priority Date: 09/10/1996
• Status: Expired due to Term

• Current Assignee: Ampex Corporation (Delta Information Systems, Inc.)
• Original Assignee: Ampex Corporation (Delta Information Systems, Inc.)
• Inventors: Varian, George R.
• Primary Examiner(s): Wolff, John H.
• Application Number:
  US08/709,800
• Time in Patent Office: 518 Days
• Field of Search: 360/125, 360/126, 360/128
• US Class Current: 360/125.01
• CPC Class Codes: G11B 2005/0002 Special dispositions or recording techniques
• CPC Class Codes: G11B 5/11 Shielding of head against electric or magnetic fields
• CPC Class Codes: G11B 5/313 Disposition of layers
• CPC Class Codes: G11B 5/3143 including additional layers for improving the electromagnetic transducing properties of the basic structure, e.g. for flux coupling, guiding or shielding G11B5/3116, G11B5/312 take precedence
• CPC Class Codes: G11B 5/39 using magneto-resistive devices or effects
• CPC Class Codes: H01F 27/36 Electric or magnetic shields or screens movable for varying inductance H01F21/10
• CPC Class Codes: H01F 27/363 made of electrically conductive material

Abstract

An improved, shielded magnetic core structure is disclosed that is particularly well suited for use in magnetic read and write heads adapted for narrow track, short wavelength magnetic recording systems, and for transformers of high performance, wide band application. The improved magnetic cores use novel field confinement structures to reduce or eliminate leakage magnetic paths which normally do not link the head gap or do not link the transformer windings. This shielding arrangement substantially improves the performance of such devices, as compared to conventional, unshielded heads and transformers. Embodiments involving toroidal cores, thin film heads, and MR heads are disclosed, along with high performance, wide band transformer structures.

Claims

1. A magnetic core defining a field path, said core being surrounded by a non-magnetic conductive shield, that acts to isolate said core, with the shield having at least one current interrupting cut region formed therein.

2. The magnetic core defined in claim 1, further including a gap formed in the magnetic core at a location that is exposed by an opening formed in said shield.

3. The magnetic core of claim 2 wherein said gap is located at a position near a magnetic recording medium.

4. The magnetic core of claim 3 wherein the magnetic recording medium associated with said gap is provided with a conductive backing that cooperates with the recording medium to provide an additional shielding function, and wherein a separation between the conductive backing and the rest of the core shield is provided to form a portion of the current interrupting cut in said shield.

5. The magnetic core of claim 2, further including at least one winding linking the magnetic core in proximity of said shield.

6. The magnetic core of claim 5 wherein a portion of said winding structure acts as a shield for said core.

7. The magnetic core of claim 2, further including magnetic field sensing means associated with the gap in said core.

8. The core of claim 7 wherein the field sensing element is an magneto-resistive element.

9. The magnetic core of claim 1, further including two or more windings wrapped around the core in proximity to said shield.

10. The magnetic core of claim 1, further including first and second winding means associated with the core to define a transformer structure wherein said core and said winding means are separated by said shield.

11. The core defined in claim 1 wherein a portion of said field path is comprised of a core formed of high permeability material.

12. The core of claim 11 further including a core of toroidal shape.

13. The core of claim 11 wherein the shield surrounds a substantial portion of the magnetic path of the device.

14. The core of claim 11 wherein the shield is comprised of a conductive material having a thickness in excess of the skin depth in the material at the operating frequency.

15. The core of claim 14 wherein the shield is comprised of copper having a thickness slightly in excess of ten micro meters.

16. The core of claim 11 comprised of two core portions adhered together about a non-magnetic gap structure, said core having a winding window formed therein through which at least one winding is wound.

17. The magnetic core of claim 16 wherein the shield is comprised of a first conductive layer deposited upon one side and the ends of the core and a second conductive layer deposited upon the other side and the ends of said core.

18. The magnetic core of claim 1 wherein the shield surrounds a substantial portion of a toroidal core and overlaps upon itself along the periphery of the toroid by an amount in excess of the dimension of the current interrupting cut.

19. The magnetic core of claim 1 wherein the shield surrounds a substantial portion of a toroidal core and abuts against itself along the periphery of the toroid with a separation sufficient to form the current interrupting cut.

20. The magnetic core of claim 1 wherein the core is of toroidal shape, and generally square cross-section, being covered with a thin shield of copper having four current interrupting cuts formed therein near that corners of the cross-section.