# US 5,703,740 A · Toroidal thin film head

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- Number: US 5,703,740 A
- Document ID: US5703740A
- Status: Granted
- Kind: A
- Application number: 08/727,694
- Filed: 1996-10-07
- Granted: 1997-12-30
- Earliest claimed: 1996-10-07
- Assignees: Velocidata, Inc.
- Inventors: Uri Cohen; Dennis R. Hollars
- Web page: https://patentgrep.com/patent/US5703740A

## CPC

- G11B 5/3123: {by using special coil configurations or conductors}
- G11B 5/3113: {for improving the magnetic domain structure or avoiding the formation or displacement of undesirable magnetic domains}
- G11B 5/313: {Disposition of layers}
- G11B 5/3163: {Fabrication methods or processes specially adapted for a particular head structure, e.g. using base layers for electroplating, using functional layers for masking, using energy or particle beams for shaping the structure or modifying the properties of the basic layers}
- G11B 5/3183: {intersecting the gap plane, e.g. "horizontal head structure"}
- G11B 5/3967: {Composite structural arrangements of transducers, e.g. inductive write and magnetoresistive read (G11B5/3906 takes precedence)}
- G11B 5/17: Construction or disposition of windings
- G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R)

## Abstract

A low-noise toroidal thin film head ("TFH") device has low coil resistance and inductance, especially suitable for very high magnetic recording areal densities and channel frequencies. The length of a toroidal coil turn is only about 20-30% that of the length of an average turn in the conventional planar spiral coil design. This allows either reduction of the device thermal noise (by about 6 dB) and/or increase of the device operational frequency bandwidth (by a factor of 3-5). The toroidal coil coupling efficiency between each turn and the magnetic core is practically 100%, thereby improving the write and read-back efficiencies. In one embodiment a non-via large back-closure contact area is provided between the bottom and top magnetic poles along their entire back-side width, and all other open branches and loose ends in the magnetic circuit are eliminated. The magnetic core has a gradual, smooth toroidal (or a horse-shoe) shape with no loose ends, nooks, crevices, or sharp corners. The larger back-closure contact area decreases the magnetic core reluctance and improves the device efficiency. Utilization of a soft non-magnetic seed-layer, such as gold, eliminates interference noise due to the conventional magnetic (NiFe) seed-layer. Slight mechanical texturing (scratching) of the seed-layer along the intended easy axis helps to define and induce strong magnetic uniaxial anisotropy in the plated magnetic poles. All these features facilitate significant reduction of Barkhausen and other sources of device noise. Embodiments include conventional TFH's, Planar TFH's, Pinched-Gap TFH's, and various versions of Magnetoresistive (MR) TFH's.

## Claims

### Claim 1

A toroidal thin film head (TFH) device comprising:
a substrate;
a bottom magnetic pole disposed on said substrate and including a bottom yoke-arm and a bottom pole-tip portion, said bottom yoke-arm having an elongated first back portion of a predetermined length and width, and a transitioning front portion, said first back portion having a first back-end;
a non-magnetic gap layer formed over at least said bottom pole-tip of said bottom magnetic pole;
a top magnetic pole disposed over said gap layer and overlaying said bottom magnetic pole, said top magnetic pole including a top yoke-arm of substantially the same shape and dimensions as said bottom yoke-arm and a top pole-tip portion, said top yoke-arm having an elongated second back portion of a predetermined length and width, and a transitioning front portion, said second back portion having a second back-end;
said first back portion of said bottom yoke-arm and said second back portion of said top yoke-arm being magnetically connected to each other at a back-closure region extending along substantially the entire width of said first and second back-ends such that said bottom magnetic pole and said top magnetic pole combine to form a magnetic core; and
a toroidal solenoid coil winding comprising at least one turn wrapped around at least one of said magnetic poles, for each of said at least one magnetic pole said solenoid coil winding comprising:
a first set of electrically conductive strips disposed below, and being insulated from, said magnetic pole;
a second set of electrically conductive strips disposed above, and being insulated from, said magnetic pole; and
said first set of electrically conductive strips and said second set of electrically conductive strips being joined along the sides of said magnetic pole in a manner to form a solenoid coil wrapped around said magnetic pole.

### Claim 2 (depends on 1)

A toroidal TFH device according to claim 1 wherein each of said first set and said second set of electrically conductive strips includes enlarged terminal contact pads disposed along the sides of said magnetic pole or segment of said magnetic core, said first set of conductive strips and said second set of conductive strips being joined at said terminal contact pads in a manner such as to form a solenoid coil wrapped around said magnetic pole or magnetic segment of said magnetic core.

### Claim 3 (depends on 1)

A toroidal magnetoresistive (MR) TFH device comprising an inductive toroidal element, such as described in claim 1, and an MR read element.

### Claim 4 (depends on 3)

The toroidal MR TFH device of claim 3 wherein said inductive toroidal element comprises at least one solenoid turn wrapped around at least one of said magnetic poles.

### Claim 5 (depends on 4)

The toroidal MR TFH device of claim 4 wherein said solenoid coil comprises a single turn.

### Claim 6 (depends on 4)

The toroidal MR TFH device of claim 4 wherein said solenoid coil comprises a selected number of turns to enable said inductive toroidal element to read information stored on a magnetic media moving relative to said inductive toroidal element, said solenoid coil having low electrical inductance and resistance.

### Claim 7 (depends on 6)

The toroidal MR TFH device of claim 6 wherein said inductive toroidal element is capable of reading servo data and/or data tracks.

### Claim 8 (depends on 7)

The toroidal MR TFH device of claim 7 wherein said inductive toroidal element is capable of reading servo data.

### Claim 9 (depends on 7)

The toroidal MR TFH device of claim 7 wherein said inductive toroidal element is capable of reading data tracks.

### Claim 10 (depends on 7)

The toroidal MR TFH device of claim 7 wherein said MR element is capable of reading data stored in small radii tracks and said inductive toroidal element is capable of reading data stored in large radii tracks.

### Claim 11 (depends on 13)

The toroidal MR TFH device of claim 13 wherein said bottom magnetic pole of said inductive toroidal element also functions as a top magnetic shield for the MR element.

### Claim 12 (depends on 11)

The toroidal MR TFH device of claim 11 wherein said MR element comprises a shorter bottom shield than said top shield.

### Claim 13 (depends on 12)

The toroidal MR TFH device of claim 12 wherein said toroidal solenoid coil comprises multiple turns wrapped around both of said top and said bottom magnetic poles.

### Claim 14 (depends on 12)

The toroidal MR TFH device of claim 12 wherein said toroidal solenoid coil comprises at least one turn wrapped around said bottom magnetic pole.

### Claim 15 (depends on 14)

The toroidal MR TFH device of claim 14 wherein said toroidal solenoid coil comprises a single turn.

### Claim 16 (depends on 15)

The toroidal MR TFM device of claim 15 wherein the width of said single turn occupies most of the space between said pole-tips and said back-closure.

### Claim 17 (depends on 12)

The toroidal MR TFH device of claim 12 wherein said bottom magnetic pole of said inductive toroidal element is partially etched in said pole-tip region in a manner such as to form an elevation in said bottom magnetic pole, said elevation being aligned under said top pole-tip and having a width essentially equal to the width of said top pole-tip.

### Claim 18 (depends on 11)

The toroidal MR TFH device of claim 11 wherein said toroidal solenoid coil comprises at least one turn wrapped around said top magnetic pole.

### Claim 19 (depends on 18)

The toroidal MR TFH device of claim 18 wherein said toroidal solenoid coil comprises a single turn.

### Claim 20 (depends on 19)

The toroidal MR TFH device of claim 19 wherein the width of said single turn occupies most of the space between said pole-tips and said back-closure.

### Claim 21 (depends on 11)

The toroidal MR TFH device of claim 11 wherein said bottom magnetic pole of said inductive toroidal element is partially etched in said pole-tip region in a manner such as to form an elevation in said bottom magnetic pole, said elevation being aligned under said top pole-tip and having a width essentially equal to the width of said top pole-tip.

### Claim 22 (depends on 21)

The toroidal MR TFH device of claim 21 wherein the depth of said elevation in said bottom magnetic pole is between 0.5 .mu.m and 1.5 .mu.m.

### Claim 23 (depends on 20)

The toroidal MR TFH device of claim 20 wherein said inductive toroidal write element comprises pole-tips having a pinched-gap configuration.

### Claim 24 (depends on 13)

The toroidal MR TFH device of claim 13 wherein said bottom magnetic pole of said inductive toroidal element is separate from a top magnetic shield of said MR element.

### Claim 25 (depends on 24)

The toroidal MR TFH device of claim 24 wherein said MR element comprises a shorter bottom shield than said top shield.

### Claim 26 (depends on 25)

The toroidal MR TFH device of claim 25 wherein said toroidal solenoid coil comprises multiple turns wrapped around both of said top and said bottom magnetic poles.

### Claim 27 (depends on 24)

The toroidal MR TFH device of claim 24 wherein said toroidal solenoid coil comprises at least one turn wrapped around at least one of said magnetic poles.

### Claim 28 (depends on 27)

The toroidal TFH device of claim 27 wherein said toroidal solenoid coil comprises a single turn wrapped around either said bottom magnetic pole or said top magnetic pole.

### Claim 29 (depends on 28)

The toroidal MR TFH device of claim 28 wherein the width of said single turn occupies most of the space between said pole-tips and said back-closure.

### Claim 30 (depends on 12)

The toroidal MR TFH device of claim 12 wherein said inductive toroidal element and said MR read element are disposed on a 30%, or smaller, form-factor slider.

### Claim 31 (depends on 1)

A toroidal TFH device for transferring information to and from a magnetic storage medium, said device comprising the inductive toroidal TFH write element of claim 1, and a read element comprising a TFH device.

### Claim 32 (depends on 31)

The toroidal TFH device of claim 31, wherein said read element comprises a magnetoresistive (MR) device.

### Claim 33 (depends on 32)

The toroidal TFH device of claim 32, wherein said read element and said write element are situated in tandem with each other.

### Claim 34 (depends on 32)

The toroidal TFH device of claim 32, wherein said read element and said write element are situated side-by-side on a rail of a slider.

### Claim 35 (depends on 32)

The toroidal TFH device of claim 32, wherein said read element and said write element are situated on different rails of a slider.

### Claim 36 (depends on 31)

The toroidal TFH device of claim 31, wherein the read element comprises an inductive toroidal TFH device.

### Claim 37 (depends on 36)

The toroidal TFH device of claim 36, wherein the read element and the write element are situated side-by-side on a rail of a slider.

### Claim 38 (depends on 36)

The toroidal TFH device of claim 36, wherein said read element and said write element are situated on different rails of a slider.

### Claim 39 (depends on 38)

The toroidal TFH device of claim 38, comprising at least one pair of an inductive toroidal write element and a read element placed side-by-side on a rail of said slider, each of said at least one pair being situated on a separate rail of said slider.

### Claim 40 (depends on 38)

The toroidal TFH device of claim 38 wherein said inductive toroidal write element comprises pole-tips having a pinched-gap configuration.

### Claim 41 (depends on 1)

The toroidal TFH device of claim 1 wherein said pole-tips comprise a pinched-gap configuration.

### Claim 42 (depends on 1)

A toroidal TFH device such as in claim 1 wherein said device is disposed on a 30%, or smaller, form-factor slider.

### Claim 43

A planar toroidal thin film head (TFH) magnetic transducing device comprising:
a substrate having a major flat surface;
a bottom magnetic layer segment positioned over said major flat surface of said substrate, said bottom magnetic layer segment having essentially a constant width and a length determined by first and second opposing edges;
a top magnetic layer disposed above said bottom magnetic layer segment, said top magnetic layer having the same approximate overall length as said bottom magnetic layer segment, wherein said top magnetic layer comprises two separate pole-piece segments;
a magnetic transducing gap raised over an insulative pedestal, said transducing gap separating said pole-piece segments of said top magnetic layer;
each of said two magnetic pole-piece segments comprising a first portion and a second portion;
said first portion of each of said pole-piece segments comprising a narrow pole-tip region adjacent to said magnetic transducing gap and a tapered region wherein the width of said tapered region forms a transition from the width of said second portion to the width of the narrow pole tip region;
said second portion of each of said pole-piece segments having a substantially constant width, which is essentially equal to the width of said bottom magnetic layer segment;
each of said second portions of said pole-piece segments forms a magnetic closure with one of said opposing edges of said bottom magnetic segment;
wherein said bottom magnetic layer segment and said magnetic pole-piece segments of said top magnetic layer comprise a magnetic core;
a toroidal solenoid coil winding comprising at least one turn wrapped around at least one of said magnetic segments of said magnetic core, said toroidal solenoid coil winding comprising:
a first set and a second set of electrically conductive strips;
said first set of electrically conductive strips being disposed below, and being insulated from, said magnetic segment of said magnetic core;
said second set of electrically conductive strips being disposed above, and being insulated from, said magnetic segment of said magnetic core;
said first set of electrically conductive strips and said second set of electrically conductive strips being joined along the sides of said magnetic segment of said magnetic core in a manner such as to form a toroidal coil wrapped around said magnetic segment of said magnetic core.

### Claim 44 (depends on 43)

A toroidal TFH device according to claim 43 wherein each of said first set and said second set of electrically conductive strips includes enlarged terminal contact pads disposed along the sides of said magnetic pole or segment of said magnetic core, said first set of conductive strips and said second set of conductive strips being joined at said terminal contact pads in a manner such as to form a solenoid coil wrapped around said magnetic pole or magnetic segment of said magnetic core.

### Claim 45 (depends on 44)

The planar toroidal TFH device of claim 44 wherein said pole-tips are formed as integral parts of said pole-pieces in a single magnetic layer.

### Claim 46 (depends on 44)

The planar toroidal TFH device of claim 44 wherein said pole-tips are formed as separate parts, in an additional magnetic layer on top of said magnetic pole-pieces.

### Claim 47 (depends on 44)

The planar toroidal TFH device of claim 44 wherein said second portion of each of said magnetic pole-piece segments comprises a tapered shape, said width of each of said magnetic closures is larger than any width of said first portion of said pole-piece segment.

### Claim 48

A planar toroidal thin film head (TFH) magnetic transducing device comprising:
a substrate having a major flat surface;
a bottom magnetic segment positioned over said major flat surface of said substrate, said bottom magnetic segment having essentially a constant width and a length determined by first and second opposing edges;
two magnetic pillars, each pillar having a top side, a bottom side, and a width essentially equal to the width of said bottom magnetic segment, wherein each of said magnetic pillars is disposed so as to rise above said bottom magnetic segment and wherein said bottom side of each of said magnetic pillars forms a bottom magnetic closure with one of said opposing edges of said bottom magnetic segment;
a top magnetic layer disposed above said bottom magnetic segment and said magnetic pillars, wherein said top magnetic layer comprises two pole-piece segments, each of said two magnetic pole-piece segments comprising a first portion and a second portion;
a magnetic transducing gap formed over an insulative pedestal, said magnetic transducing gap separating said two pole-piece segments of said top magnetic layer;
said first portion of each of said pole-piece segments comprises a pole-tip region adjacent to said magnetic transducing gap and a tapered region wherein the width of said tapered region forms a transition from said second portion to said pole tip region;
said second portion of each of said pole-piece segments having a substantially constant width, which is essentially equal to the width of said bottom magnetic layer segment;
each of said pole-piece segments forms an upper magnetic closure with the top side of one of said magnetic pillars;
a magnetic core comprising said bottom magnetic layer segment, said magnetic pillars, and said magnetic pole-piece segments of said top magnetic layer;
a toroidal solenoid coil winding comprising at least one turn wrapped around at least one of said magnetic segments of said magnetic core;
for each of said at least one magnetic segment said toroidal solenoid coil winding comprises a first set and a second set of electrically conductive strips;
said first set of electrically conductive strips being disposed below, and being insulated from, said magnetic segment of said magnetic core;
said second set of electrically conductive strips being disposed above, and being insulated from, said magnetic segment of said magnetic core;
said first set of electrically conductive strips and said second set of electrically conductive strips being joined along the sides of said magnetic segment of said magnetic core in a manner such as to form a solenoid coil wrapped around said magnetic segment of said magnetic core.

### Claim 49 (depends on 48)

A toroidal TFH device according to claim 48 wherein each of said first set and said second set of electrically conductive strips includes enlarged terminal contact pads disposed along the sides of said magnetic pole or segment of said magnetic core, said first set of conductive strips and said second set of conductive strips being joined at said terminal contact pads in a manner such as to form a solenoid coil wrapped around said magnetic pole or magnetic segment of said magnetic core.

### Claim 50 (depends on 44)

The planar toroidal TFH device of claim 44 wherein at least one turn of said toroidal solenoid coil is wrapped around at least one of said magnetic pillars.

### Claim 51 (depends on 43, 48)

A planar toroidal TFH device according to claims 43 or 48 wherein each of said magnetic closures has a width which is substantially equal to the width of said bottom magnetic layer segment.