# US 9,040,179 B2 · Magnetic recording medium and magnetic recording and reproducing apparatus

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- Number: US 9,040,179 B2
- Document ID: US9040179B2
- Status: Granted
- Kind: B2
- Application number: 13/502,494
- Filed: 2010-10-18
- Published: 2012-08-09
- Granted: 2015-05-26
- Earliest claimed: 2009-10-19
- Assignees: Showa Denko K.K.
- Applicants: Takashi Tanaka
- Inventors: Takashi Tanaka
- Web page: https://patentgrep.com/patent/US9040179B2

## CPC

- G11B 5/667: including a soft magnetic layer
- G11B 5/73911: {Inorganic substrates}
- G11B 5/73919: {Aluminium or titanium elemental or alloy substrates}
- G11B 5/73921: {Glass or ceramic substrates}
- G11B 5/73923: {Organic polymer substrates}
- 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 perpendicular magnetic recording medium of the present invention comprises a non-magnetic substrate, and at least a backing layer, an under layer, an intermediate layer and a perpendicular magnetic recording layer, which are sequentially laminated on the non-magnetic substrate, wherein the backing layer is formed of a soft magnetic film having an amorphous structure, the under layer contains a NiW alloy containing any one or both of Co and Fe, the W content of the NiW alloy is within a range from 3 to 10 atom %, the total of the Co and Fe contents of the NiW alloy is 5 atom % or more and less than 40 atom %, the saturation magnetic flux density Bs of the NiW alloy is 280 emu/cm3 or more, the thickness of the under layer is within a range from 2 to 20 nm, and the intermediate layer contains Ru or a Ru alloy.

## Claims

### Claim 1

A perpendicular magnetic recording medium comprising a non-magnetic substrate, and at least a backing layer, an under layer, an intermediate layer and a perpendicular magnetic recording layer, which are sequentially laminated on the non-magnetic substrate, wherein
the backing layer is formed of a soft magnetic film having an amorphous structure,
the under layer contains a NiW alloy containing any one or both of Co and Fe,
the W content of the NiW alloy is within a range from 3 to 10 atom %,
the total of the Co and Fe contents of the NiW alloy is 20 atom % or more and less than 40 atom %,
the saturation magnetic flux density Bs of the NiW alloy is 280 emu/cm3 or more,
the thickness of the under layer is within a range from 10 to 20 nm, the under layer directly has contact with the backing layer, and
the intermediate layer contains Ru or a Ru alloy.

### Claim 2 (depends on 1)

The perpendicular magnetic recording medium according to claim 1, wherein the soft magnetic film contains a CoFe alloy.

### Claim 3 (depends on 2)

The perpendicular magnetic recording medium according to claim 2, wherein the Fe content of the CoFe alloy is within a range from 5 to 60 atom %.

### Claim 4 (depends on 1)

A magnetic recording/reproducing apparatus comprising the perpendicular magnetic recording medium according to claim 1, and a magnetic monopole head that performs writing of information to the perpendicular magnetic recording medium.

### Claim 5 (depends on 2)

A magnetic recording/reproducing apparatus comprising the perpendicular magnetic recording medium according to claim 2, and a magnetic monopole head that performs writing of information to the perpendicular magnetic recording medium.

### Claim 6 (depends on 3)

A magnetic recording/reproducing apparatus comprising the perpendicular magnetic recording medium according to claim 3, and a magnetic monopole head that performs writing of information to the perpendicular magnetic recording medium.

### Claim 7 (depends on 1)

The perpendicular magnetic recording medium according to claim 1, wherein the under layer contains the NiW alloy containing both of Co and Fe.