# US 5,352,501 A · Longitudinal magnetic recording medium comprising a circumterentially textured disk substrate, chromium primer layer and a cobalt chromium magnetic alloy layer having a segregation structure > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,352,501 A - Document ID: US5352501A - Status: Granted - Kind: A - Application number: 07/631,904 - Filed: 1990-12-21 - Granted: 1994-10-04 - Earliest claimed: 1989-12-27 - Assignees: Mitsubishi Kasei Corporation - Inventors: Yukihiro Miyamoto; Fumiaki Yokoyama - Web page: https://patentgrep.com/patent/US5352501A ## 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 5/73913: {Composites or coated substrates} - G11B 5/73917: {Metallic substrates, i.e. elemental metal or metal alloy substrates} - G11B 5/73919: {Aluminium or titanium elemental or alloy substrates} - G11B 5/73921: {Glass or ceramic substrates} - G11B 5/73923: {Organic polymer substrates} - Y10S 428/90: Magnetic feature - Y10S 428/928: Magnetic property - Y10T 428/12465: having magnetic properties, or preformed fiber orientation coordinate with shape - Y10T 428/1275: Next to Group VIII or IB metal-base component - Y10T 428/12854: Next to Co-, Fe-, or Ni-base component - Y10T 428/12944: Ni-base component - Y10T 428/265: 1 mil or less - Y10T 428/31: Surface property or characteristic of web, sheet or block - 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 A longitudinal magnetic recording medium comprising a non-magnetic substrate having a texture with a arithmetric average roughness Ra in a circumferential direction of at least 20 .ANG. and a magnetic alloy layer comprising cobalt and chromium as the main components, formed on the substrate, wherein the magnetic alloy layer has (i) a feature that when the orientation degree of the hcp crystal structure is represented by the diffraction ray intensity of electron diffraction by transmission electron diffractiometry, the intensity ratio of the electron diffraction ring in the Co (002) plane between the circumferential direction and the radial direction of the substrate is at least 3, and (ii) a segregation structure having low chromium concentration regions surrounded by high chromium concentration regions, the diameters of the defined low chromium concentration regions being within a range of from 80 to 500 .ANG., and the number of the surrounded low chromium concentration regions being from 600 to 1,500 regions/.mu.m.sup.2. ## Claims ### Claim 1 A longitudinal magnetic recording medium comprising a non-magnetic substrate in the form of a disk having a texture provided in a circumferential direction of the medium, with an arithmetric average roughness Ra measured in a radial direction of at least 20 angstroms, a non-magnetic chromium primer layer and a magnetic alloy layer comprising cobalt and chromium as the main components, formed on the substrate, wherein the magnetic alloy layer has (i) a feature that when an orientation degree of a hcp crystal structure is represented by diffraction ray intensity of electron diffraction by transmission electron diffractiometry, the intensity ratio of the electron diffraction ring in a Co (002) plane between the circumferential direction and the radial direction of the substrate is at least 3, and (ii) a segregation structure having cobalt chromium regions with a lower chromium concentration and a higher intensity of magnetization than surrounding cobalt chromium regions, diameters of the surrounded cobalt chromium regions being within a range of from 80 to 500 angstroms, and a number of the surrounded cobalt chromium regions being from 600 to 1,500 regions/.mu.m.sup.2. ### Claim 2 (depends on 1) The longitudinal magnetic recording medium according to claim 1, wherein the non-magnetic substrate has a texture with a arithmetric average roughness Ra in a radial direction of from 30 to 300 .ANG.. ### Claim 3 (depends on 1) The longitudinal magnetic recording medium according to claim 1, wherein the non-magnetic substrate has a texture with a arithmetric average roughness Ra in a radial direction of from 50 to 300 .ANG.. ### Claim 4 (depends on 1) The longitudinal magnetic recording medium according to claim 1, wherein the orientation degree of the hcp crystal structure of the magnetic alloy layer is such that the intensity ratio of the electron diffraction ring in the Co (002) plane between the circumferential direction and the radial direction of the substrate is at least 5. ### Claim 5 (depends on 4) The longitudinal magnetic recording according to claim 4, wherein the intensity ratio is at least 7. ### Claim 6 (depends on 1) The longitudinal magnetic recording medium according to claim 1 wherein the cobalt chromium regions with a lower chromium concentration and the surrounding cobalt chromium regions have a difference in the chromium concentration of at least 5 atomic %. ### Claim 7 (depends on 1) The longitudinal magnetic recording medium according to claim 1 wherein the chromium concentration in the cobalt chromium regions with lower chromium concentration is at most 25 atomic % and the chromium concentration in the surrounding cobalt chromium regions is at least 30 atomic %. ### Claim 8 (depends on 1) The longitudinal magnetic recording medium according to claim 1, wherein the number of surrounded cobalt chromium regions with lower chromium concentration is from 800 to 1500 regions/.mu.m.sup.2. ### Claim 9 (depends on 1) The longitudinal magnetic recording medium according to claim 1, wherein the chromium concentration in the magnetic alloy layer is at least 6 atomic % relative to cobalt. ### Claim 10 (depends on 1) The longitudinal magnetic recording medium according to claim 1, wherein the chromium concentration in the magnetic alloy layer is from 6 to 25 atomic % relative to cobalt. ### Claim 11 (depends on 1) The longitudinal magnetic recording medium according to claim 1, wherein the magnetic alloy layer contains additive elements selected from the group consisting of Ta, Nb, Pt, Pd, Ni, Zr, W, Mo and Hf. ### Claim 12 (depends on 11) The longitudinal magnetic recording medium according to claim 11, wherein the additive elements are less than 10 atomic % relative to cobalt and chromium. ### Claim 13 (depends on 1) The longitudinal magnetic recording medium according to claim 1, wherein the magnetic alloy layer is provided on the non-magnetic substrate having a texture with a non-magnetic primer layer having a thickness of from 500 to 2,000 .ANG. interposed therebetween. ### Claim 14 (depends on 1) The longitudinal magnetic recording medium according to claim 1, wherein the non-magnetic substrate having a texture is an aluminum alloy plate having a Ni-P layer formed by electroless plating. ### Claim 15 (depends on 1) The longitudinal magnetic recording medium according to claim 1, wherein the non-magnetic substrate having a texture is selected from the group consisting of a metal substrate, a glass substrate, a ceramic substrate and a resin substrate. ### Claim 16 (depends on 1) The longitudinal magnetic recording medium according to claim 1, wherein the magnetic alloy layer has a thickness of from 300 to 1,500 .ANG.. ### Claim 17 (depends on 1) The in-plane magnetic recording medium according to claim 1, wherein a protective layer and/or a lubricating layer is formed on the magnetic alloy layer. ### Claim 18 (depends on 1) The longitudinal magnetic recording medium of claim 1, wherein the magnetic alloy layer is formed by a sputtering method under such a condition that a bias potential is applied so that the non-magnetic substrate is relatively negative to a plasma potential. ### Claim 19 (depends on 18) The longitudinal magnetic recording medium of claim 18, wherein the magnetic alloy layer is formed on the non-magnetic substrate by layer-forming by a sputtering method under such a condition that a substrate potential is made relatively negative to a ground potential of a sputtering apparatus. ### Claim 20 (depends on 18) The longitudinal magnetic recording medium of claim 18, wherein the magnetic alloy layer is formed by conducting layer-forming by a sputtering method under such a condition that a plasma potential is made higher than a ground potential while maintaining the non-magnetic substrate at a level of the ground potential. ### Claim 21 (depends on 18) The longitudinal magnetic recording medium of claim 18, wherein the magnetic alloy layer is formed by providing an intermediate electrode in a vicinity of a target and conducting layer-forming under such a condition that a positive potential is applied to the intermediate electrode relative to a grounding portion of the non-magnetic substrate. ### Claim 22 A longitudinal magnetic recording medium comprising a non-magnetic substrate in the form of a disk having a texture provided in a circumferential direction of the medium with an arithmetric average roughness Ra measured in a radial direction of at least 20 .ANG. provided on an aluminum alloy plate having a Ni-P layer formed by electroless plating, and a magnetic alloy layer comprising cobalt and chromium as the main components, formed on the substrate with a non-magnetic chromium primer layer having a thickness of from 500 to 2,000 .ANG. interposed therebetween, wherein the magnetic alloy layer has (i) a feature that when an orientation degree of a hcp crystal structure is represented by diffraction ray intensity of electron diffraction by transmission electron diffractiometry, the intensity ratio of the electron diffraction ring in a Co (002) plane between the circumferential direction and the radial direction of the substrate is at least 3, and (ii) a segregation structure having cobalt chromium regions with a lower chromium concentration and a higher intensity of magnetization than surrounding cobalt chromium regions, diameters of the surrounded cobalt chromium regions being within a range of from 80 to 500 .ANG., and a number of the surrounded cobalt chromium regions being from 600 to 1,500 regions/.mu.m.sup.2, and a protecting layer is formed on the magnetic alloy layer, and a lubricating layer is formed further thereon.