# US 5,344,706 A · Magnetic recording medium comprising an underlayer and a cobalt samarium amorphous magnetic layer having a SmCo.sub.5 crystalline interface with the underlayer

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- Number: US 5,344,706 A
- Document ID: US5344706A
- Status: Granted
- Kind: A
- Application number: 07/975,132
- Filed: 1992-11-12
- Granted: 1994-09-06
- Earliest claimed: 1991-10-01
- Assignees: Carnegie Mellon University
- Inventors: David N. Lambeth; E. M. T. Velu
- Web page: https://patentgrep.com/patent/US5344706A

## CPC

- G11B 5/656: {containing Co (containing inorganic, non-oxide compounds of Si, N, P, B, H or C G11B5/657; containing oxygen G11B5/658)}
- G11B 5/7373: {Non-magnetic single underlayer comprising chromium}
- G11B 5/7377: {Physical structure of underlayer, e.g. texture}
- Y10S 428/90: Magnetic feature
- Y10S 428/928: Magnetic property
- Y10T 428/12465: having magnetic properties, or preformed fiber orientation coordinate with shape
- Y10T 428/12826: Group VIB metal-base component
- Y10T 428/1284: W-base component
- Y10T 428/12854: Next to Co-, Fe-, or Ni-base component
- Y10T 428/12861: Group VIII or IB metal-base component
- Y10T 428/265: 1 mil or less
- 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)
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

The present invention pertains to a thin film media structure for low noise high density longitudinal magnetic recording. The thin film media structure is comprised of a substrate. The thin film media structure is also comprised of an underlayer in contact with the substrate. Additionally, the thin film media structure is comprised of a CoSm or a CoSmQ film in contact with the underlayer such that the underlayer is between the substrate and the CoSm or CoSmQ. In a preferred embodiment, the underlayer is made of Cr or W and there is additionally an overlayer in contact with the CoSm or CoSmQ film, an overcoat in contact with the overlayer and an organic lubricant disposed on the overcoat. The present invention also pertains to a low noise high coercivity media structure for longitudinal magnetic recording. The high coercivity media structure is comprised of a substrate. The high coercivity media structure is also comprised of a multi-magnetic layer comprised of at least two layers of an alloy of Co and Sm, or Co and Sm and Q with an intermediate layer therebetween, and an underlayer in contact with the substrate and between the substrate and one of the CoSm layers.

## Claims

### Claim 1

A thin film media structure having an in plane coercivity of at least 1650 oersteds for longitudinal magnetic recording comprising:
a substrate;
an underlayer in contact with the substrate, the underlayer being comprised of Cr, W or Mo of a predominantly <110> texture; and film comprised of an alloy of Co and Sm forming a fine grain or amorphous magnetic layer disposed on the underlayer and forming a SmCo.sub.5 crystalline interface with the underlayer such that the underlayer is between the substrate and the film, the film being less than 50 nm thick.

### Claim 2 (depends on 1)

A media structure as described in claim 1 wherein the underlayer is 10-5000 angstroms thick.

### Claim 3 (depends on 2)

A media structure as described in claim 2 wherein the CoSm alloy film is from 30 to less than 500 angstroms thick.

### Claim 4 (depends on 1)

A media structure as described in claim 1 including an overlayer in contact with the CoSm film such that the CoSm film is between the overlayer and the underlayer.

### Claim 5 (depends on 4)

A media structure as described in claim 4 including an overcoat in contact with the overlayer such that the overlayer is between the overcoat and the CoSm alloy film.

### Claim 6 (depends on 5)

A media structure as described in claim 5 wherein the overlayer is 10-500 angstroms thick and is comprised of Cr, W, Y or Pt.

### Claim 7 (depends on 6)

A media structure as described in claim 6 wherein the overcoat is 10-500 angstroms thick and is comprised of carbon, SiO.sub.2 or ZrO.sub.2.

### Claim 8 (depends on 1)

A media structure as described in claim 1 wherein the CoSm is of the form Co.sub.1-x Sm.sub.x where 0.005.ltoreq.x.ltoreq.0.30.

### Claim 9

A thin film media structure having an in plane coercivity of at least 1650 oersteds for longitudinal magnetic recording comprising:
a substrate;
an underlayer in contact with the substrate, the underlayer being comprised of Cr, W or Mo of a predominantly <110> texture; and
at least one layer of a film less than 50 nm thick comprised of an alloy of Co, Sm and Q having a fin grain or amorphous structure and forming a SmCo.sub.5 crystalline interface with the underlayer such that the underlayer is between the substrate and CoSmQ film, wherein Q is selected from the group consisting of Ta, Mo, Bi, Zr, B, Ni, Cr, Pt and combinations thereof.

### Claim 10 (depends on 9)

A media structure as described in claim 9 including an overlayer in contact with the CoSmQ film such that the CoSmQ film is between the overlayer and the underlayer and the overlayer is comprised of Cr, W, Y or Pt and is 10-500 angstroms thick.

### Claim 11 (depends on 10)

A media structure as described in claim 10 including an overcoat in contact with the overlayer such that the overlayer is between the overcoat and the CoSmQ alloy film.

### Claim 12 (depends on 9)

A media structure as described in claim 9 wherein the CoSmQ is of the form Co.sub.1-x-y Sm.sub.x Q.sub.y where 0.005.ltoreq.x.ltoreq.0.3 and 0.01.ltoreq.y.ltoreq.0.10.

### Claim 13 (depends on 9)

A media structure as described in claim 9 including an overcoat in contact with the CoSmQ alloy film.

### Claim 14 (depends on 1)

A media structure as described in claim 1 wherein there are multi-magnetic layers comprised of at least two said layers of CoSm film with an intermediate layer therebetween, said underlayer disposed between the substrate and one of the CoSm or layers.

### Claim 15 (depends on 9)

A media structure as described in claim 9 wherein there are multi-magnetic layers comprised of at least two said layers of CoSmQ film with an intermediate layer therebetween, said underlayer disposed between the substrate and one of the CoSmQ layers.

### Claim 16 (depends on 14, 15)

A high coercivity media structure as described in claims 14 or 15 including an overlayer in contact with the multi-magnetic layer such that the multi-magnetic layer is between the underlayer and overlayer and the overlayer and intermediate layer are comprised of Cr.