# US 10,319,398 B2 · Tapered junction shield for self-compensation of asymmetry with increasing aspect ratio for tunneling magneto-resistance (TMR) type read head

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- Number: US 10,319,398 B2
- Document ID: US10319398B2
- Status: Granted
- Kind: B2
- Application number: 15/686,497
- Filed: 2017-08-25
- Published: 2019-02-28
- Granted: 2019-06-11
- Earliest claimed: 2017-08-25
- Assignees: Headway Technologies, Inc.
- Applicants: Headway Technologies, Inc.
- Inventors: Urmimala Roy; Yan Wu
- Web page: https://patentgrep.com/patent/US10319398B2

## CPC

- G11B 5/3912: {Arrangements in which the active read-out elements are transducing in association with active magnetic shields, e.g. magnetically coupled shields (G11B5/3916 takes precedence)}
- G11B 5/3169: {Working or finishing the interfacing surface of heads, e.g. lapping of heads}
- G11B 5/3909: {Arrangements using a magnetic tunnel junction}
- G11B 5/3932: {Magnetic biasing films}
- G11B 5/398: {Specially shaped layers}
- G11B 2005/3996: {large or giant magnetoresistive effects [GMR], e.g. as generated in spin-valve [SV] devices}
- Y10T 29/49048: Machining magnetic material [e.g., grinding, etching, polishing]
- 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)
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

A junction shield (JS) structure is disclosed for providing longitudinal bias to a free layer (FL) having a width (FLW) and magnetization in a cross-track direction between sidewalls in a sensor. The sensor is formed between bottom and top shields and has sidewalls extending from a front side at an air bearing surface (ABS) to a backside that is a stripe height (SH) from the ABS. The JS structure has a lower layer (JS1) with a magnetization parallel to that of the FL, and a tapered top surface such that JS1 has decreasing thickness with increasing height from the ABS. As aspect ratio or AR (SH/FLW) increases above 1, longitudinal bias increases proportionally to slow an increase in asymmetry as AR increases, and without introducing a loss in amplitude for a reader with low AR. The JS1 layer may be antiferromagnetically coupled to an upper JS layer for stabilization.

## Claims

### Claim 1

A read head, comprising:
(a) a tunneling magnetoresistive (TMR) sensor structure that has a bottom surface formed on a bottom shield, a top surface contacting a top shield, and two sidewalls connecting the top and bottom surfaces, and comprising a free layer (FL) having a FL width (FLW) and a magnetization in a cross-track direction between the sidewalls, and a stripe height (SH) between a FL front side at an air bearing surface (ABS) and a FL backside; and
(b) a junction shield (JS) structure formed adjacent to each of the two sidewalls, wherein each JS structure provides a longitudinal bias to the FL magnetization, comprising:
a first JS layer with a bottom surface aligned orthogonal to the ABS, and a tapered top surface formed at a taper angle with respect to a first plane that is aligned orthogonal to the ABS and parallel to the first JS layer bottom surface, wherein a thickness of the first JS layer decreases with increasing height from the ABS such that there is a first thickness (t1) at the ABS that is greater than a second thickness (t2) at a backside of the first JS layer, and a first magnetization (of magnitude JS1) therein is parallel to the FL magnetization;
a first antiferromagnetic coupling (AFC) layer having a substantially uniform thickness on the first JS layer; and
a second JS layer formed on the first AFC layer, and having a substantially uniform thickness (t3) between a front side at the ABS and a backside thereof where t3<t2, and wherein a second magnetization (of magnitude JS2) is aligned anti-parallel to JS1 to provide a net longitudinal bias determined by the difference (JS1-JS2).

### Claim 2 (depends on 1)

The read head of claim 1 further comprised of an insulation layer formed between the lower JS layer and the bottom shield, and between the JS structure and the TMR sensor structure sidewalls.

### Claim 3 (depends on 1)

The read head of claim 1 wherein each JS structure further comprises
(a) a second AFC layer having a substantially uniform thickness on the second JS layer; and
(b) a third JS layer formed as the uppermost layer in each JS structure, the third JS layer has a substantially uniform thickness (t4) where t4<t2, and a third magnetization (of magnitude JS3) that is parallel to JS1.

### Claim 4 (depends on 3)

The read head of claim 3 wherein the first JS layer, second JS layer, and third JS layer are made of CoFe, NiFe, CoPt, CoCrPt, or FePt.

### Claim 5 (depends on 3)

The read head of claim 3 wherein each of the layers in each JS structure extends from the ABS to a first height that is greater than or equal to the stripe height (SH).

### Claim 6 (depends on 1)

The read head of claim 1 wherein the longitudinal bias applied to the free layer magnetization increases as the taper angle increases, for a given t2 and SH.

### Claim 7 (depends on 1)

The read head of claim 1 wherein increasing the taper angle provides a larger effective longitudinal bias for aspect ratios (ARs) having a (SH/FLW) greater than 1 thereby slowing the rate of increase in asymmetry compared with a junction shield structure having a uniform thickness in a first JS layer, and without introducing a loss in amplitude for low AR read heads.

### Claim 8 (depends on 1)

The read head of claim 1 wherein the TMR sensor structure further comprises a synthetic anti-parallel reference layer having an AP2/AFC layer/AP1 configuration wherein the AP2 layer has a magnetization that is pinned by an adjoining antiferromagnetic layer, the AP1 layer adjoins an opposite side of a tunnel barrier layer with respect to the FL, and has a magnetization that is aligned anti-parallel to that of the AP2 layer, and orthogonal to the FL magnetization in the absence of an externally applied magnetic field.