# US 9,520,148 B1 · Reset of magnetic domains in write head via external field

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- Number: US 9,520,148 B1
- Document ID: US9520148B1
- Status: Granted
- Kind: B1
- Application number: 14/976,286
- Filed: 2015-12-21
- Granted: 2016-12-13
- Earliest claimed: 2015-12-21
- Assignees: Seagate Technology LLC
- Applicants: Seagate Technology LLC
- Inventors: Yanzhang Liu; Kirill Rivkin; Lei Lu; Huaqing Yin
- Web page: https://patentgrep.com/patent/US9520148B1

## CPC

- G11B 5/465: Arrangements for demagnetisation of heads
- H01F 13/006: {Methods and devices for demagnetising of magnetic bodies, e.g. workpieces, sheet material (for erasing of information on magnetic record carriers G11B5/00)}
- 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)
- H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES

## Abstract

Methods of removing a magnetic domain from a slider structure, such as a shield in a write head, in a data storage assembly. The method comprises passing the slider structure in close proximity to a decaying magnetic field of at least 100 Oe and no more than 1500 Oe originating from within the storage assembly. In some implementations the decaying magnetic field has an oscillating polarity.

## Claims

### Claim 1

A method of removing a magnetic domain from a slider structure in a data storage assembly, the method comprising:
passing the slider structure in close proximity to a non-randomly decaying magnetic field of at least 100 Oe and no more than 1500 Oe originating from within the storage assembly.

### Claim 2 (depends on 1)

The method of claim 1 comprising passing the slider structure in close proximity to a decaying magnetic field of at least 200 Oe and no more than 1500 Oe originating from within the data storage assembly.

### Claim 3 (depends on 1)

The method of claim 1, wherein the decaying magnetic field decays in a step-wise manner.

### Claim 4 (depends on 3)

The method of claim 3, wherein the decaying magnetic field is a decaying oscillating polarity magnetic field.

### Claim 5 (depends on 4)

The method of claim 4, wherein a duration at a stepped peak is at least 0.25 second.

### Claim 6 (depends on 4)

The method of claim 4, wherein the decaying oscillating polarity magnetic field decays linearly or exponentially.

### Claim 7 (depends on 6)

The method of claim 6, wherein the decaying oscillating polarity magnetic field decreases by at least 50 Oe between adjacent peaks.

### Claim 8 (depends on 4)

The method of claim 4, wherein the decaying oscillating polarity magnetic field comprises at least two superimposed magnetic fields.

### Claim 9 (depends on 1)

The method of claim 1, wherein the slider structure is exposed to the decaying magnetic field at least 10 seconds and no more than 1 minute.

### Claim 10

A method of removing a magnetic domain from a shield of a write head, the method comprising:
exposing the write head to a magnetic field oscillating between at least +100 Oe and −100 Oe and no more than +1500 Oe and −1500 Oe.

### Claim 11 (depends on 10)

The method of claim 10, wherein the oscillating magnetic field decays over time.

### Claim 12 (depends on 11)

The method of claim 11, wherein the decaying oscillating magnetic field decreases by at least 50 Oe between adjacent peaks.

### Claim 13 (depends on 11)

The method of claim 11, wherein the write sensor is exposed to the oscillating magnetic field at least 10 seconds and no more than 1 minute.

### Claim 14

The method of claim Ti, wherein the magnetic field oscillates smoothly.

### Claim 15 (depends on 11)

The method of claim 11, wherein the magnetic field oscillates step-wise.

### Claim 16 (depends on 15)

The method of claim 15, wherein a frequency of adjacent step peaks is at least 0.5 second.

### Claim 17 (depends on 11)

The method of claim 11, wherein the write sensor is in a data storage assembly and the magnetic field originates from within the data storage assembly.

### Claim 18

A magnetic data storage assembly comprising:
an enclosure;
a slider in the enclosure, the slider comprising a write head; and
a magnetic field source in the enclosure, the source configured to provide a decaying magnetic field oscillating between at least +100 Oe and −100 Oe and no more than +1500 Oe and −1500 Oe.

### Claim 19 (depends on 18)

The assembly of claim 18, wherein the magnetic field source is present on the slider.

### Claim 20 (depends on 18)

The assembly of claim 18, wherein the magnetic field source is a permanent magnet.