# US 10,311,908 B2 · Magnetic recording medium

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- Number: US 10,311,908 B2
- Document ID: US10311908B2
- Status: Granted
- Kind: B2
- Application number: 14/879,976
- Filed: 2015-10-09
- Published: 2016-04-07
- Granted: 2019-06-04
- Earliest claimed: 2013-05-01
- Assignees: Sony Corporation
- Applicants: Sony Corporation
- Inventors: Takashi Aizawa
- Web page: https://patentgrep.com/patent/US10311908B2

## CPC

- G11B 5/7369: {Two or more non-magnetic underlayers, e.g. seed layers or barrier layers}
- G11B 5/658: {containing oxygen, e.g. molecular oxygen or magnetic oxide}
- G11B 5/7379: {Seed layer, e.g. at least one non-magnetic layer is specifically adapted as a seed or seeding layer}
- 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 magnetic recording medium includes a flexible substrate, an amorphous seed layer, an under layer containing Ru, and a recording layer having a granular structure. The seed layer is provided between the substrate and the under layer. The under layer has a thickness in a range of 5 to 50 nm.

## Claims

### Claim 1

A magnetic tape comprising:
a flexible substrate;
an amorphous seed layer comprising an alloy comprising Ti and Cr;
an under layer containing Ru; and
a recording layer having a granular structure,
wherein the seed layer is provided between the substrate and the under layer, the under layer has a thickness in a range of 5 to 50 nm, and the substrate has a Young's modulus in a range of 6,250 to 16,000 N/mm2; and
wherein the magnetic tape has a crack-resistant load in a range of 200 to 500 g/12.75 mm.

### Claim 2 (depends on 1)

The magnetic tape of claim 1, wherein the seed layer reduces surface irregularities of the substrate.

### Claim 3 (depends on 1)

The magnetic tape of claim 1, wherein the substrate has a Young's modulus in a range of 6,250 to 7,000 N/mm2.

### Claim 4 (depends on 1)

The magnetic tape of claim 1, wherein the substrate has a thickness of 10.0 μm or less.

### Claim 5 (depends on 1)

The magnetic tape of claim 1, wherein the recording layer has a granular structure in which grains containing Co, Pt, and Cr are separated by oxides.

### Claim 6 (depends on 5)

The magnetic tape of claim 5, wherein the recording layer has an average composition represented by the following formula (1):
(CoxPtyCr100-x-y)100-z−(SiO2)z (1)
wherein, in the formula (1), x, y, and z satisfy 69≤x≤72, 12≤y≤16, 9≤z≤12, respectively.

### Claim 7 (depends on 1)

The magnetic tape of claim 1, wherein an amount of Ru in the under layer is at least about 10 at %.

### Claim 8 (depends on 1)

The magnetic tape of claim 1, wherein the seed layer comprises an amount of Ti in a range of 30 to less than 100 at % based on a total amount of Ti and Cr contained in the seed layer.

### Claim 9 (depends on 1)

The magnetic tape of claim 1 further comprising a soft magnetic lining layer.

### Claim 10 (depends on 1)

The magnetic tape of claim 1, wherein the surface recording density of the tape is at least 50 GB/in2.

### Claim 11 (depends on 1)

A data cartridge comprising the magnetic tape of claim 1.

### Claim 12 (depends on 11)

The data cartridge of claim 11, wherein the data cartridge has a capacity recording of at least 50 TB.