# US 5,710,384 A · Magneto-optical recording medium target and manufacture method of same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,710,384 A - Document ID: US5710384A - Status: Granted - Kind: A - Application number: 08/613,096 - Filed: 1996-03-08 - Granted: 1998-01-20 - Earliest claimed: 1995-03-08 - Assignees: Hitachi Metals, Ltd. - Inventors: Kaoru Masuda - Web page: https://patentgrep.com/patent/US5710384A ## CPC - C23C 14/3414: {Metallurgical or chemical aspects of target preparation, e.g. casting, powder metallurgy} - C22C 1/0441: {Alloys based on intermetallic compounds of the type rare earth - Co, Ni} - G11B 11/10582: {Record carriers characterised by the selection of the material or by the structure or form} - C23C: COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL (making metal-coated products by extrusion B21C23/22; covering with metal by connecting pre-existing layers to articles, see the relevant places, e.g. B21D39/00, B23K; metallising of glass C03C; metallising mortars, concrete, artificial stone, ceramics or natural stone C04B41/00; enamelling of, or applying a vitreous layer to, metals C23D; treating metal surfaces or coating of metals by electrolysis or electrophoresis C25D; single-crystal film growth C30B; by metallising textiles D06M11/83; decorating textiles by locally metallising D06Q1/04) - C22C: ALLOYS (treatment of alloys C21D, C22F) - 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 The invention provides a magneto-optical recording medium target and a manufacture method thereof which target can produce the leakage magnetic flux in sufficient density and has the high mechanical strength. The target is a sintered body containing 15 to 30 atomic % at least one rare earth metal and the balance at least one transition metal, in which alloy powder having such a composition is sintered so that the original morphology of the alloy powder essentially remains. Specifically, the target has a micro structure in which the alloy powder particles consisted of the rare earth metal and the transition metal are interconnected through grain boundary phases. The target is able to have the deflective strength not less than 50 MPa, the relative density not less than 99%, and the content of oxygen not more than 1000 ppm. Particulate micro structures preferably have a grain size d.ltoreq.250 .mu.m and a volume mean size d.sub.av of 50.ltoreq.d.sub.ad .ltoreq.120 .mu.m. The target can be manufactured by producing alloy powder having the above target composition and sintering the alloy powder at a temperature lower than the liquid phase occurring temperature by 30.degree. C. or more and under a high pressure not less than 90 MPa. ## Claims ### Claim 1 A target for a magneto-optical recording medium, having a target micro structure formed by sintering alloy powder composed essentially of intermetallic compound containing 15 to 30 atomic % of at least one rare earth metal and the balance of at least one transition metal so that original morphology of said alloy powder essentially remains. ### Claim 2 A target for a magneto-optical recording medium, said target being a sintered body containing 15 to 30 atomic % of at least one rare earth metal and the balance of at least one transition metal, said target being provided with a microstructure in which traces of the particle surfaces of alloy raw material powder consisting essentially of intermetallic compound and having said composition remain. ### Claim 3 A target for a magneto-optical recording medium, having particulate micro structures in which the original form of alloy powder consisting essentially of intermetallic compound and having a composition of 15 to 30 atomic % of at least one transition metal remains so that the particulate micro structures are interconnected through grain boundary phases to make a target micro structure, and deflective strength of said target being not less than 50 MPa. ### Claim 4 (depends on 3) A target for a magneto-optical recording medium according to claim 3, wherein, in a microstructure of said target, said particulate micro structures interconnected through the grain boundary phases among said intermetallic compound alloy powder particles have a substantial grain size not more than 350 .mu.m. ### Claim 5 (depends on 1, 2, 3) A target for a magneto-optical recording medium according to any of claims 1 to 3, wherein the grain size said particulate micro structures is not more than 250 .mu.m and the volume mean size d.sub.av of said particulate micro structures is in the range of 50.ltoreq.d.sub.av .ltoreq.120 .mu.m. ### Claim 6 (depends on 1, 2, 3) A target for a magneto-optical recording medium according to any of claims 1 to 3, wherein the density of said target is not less than 99% in relative density. ### Claim 7 (depends on 1, 2, 3) A target for a magneto-optical recording medium according to any of claims 1 to 3, wherein the oxygen content of said target is not more than 1000 ppm. ### Claim 8 (depends on 1, 2, 3) A target for a magneto-optical recording medium according to any of claims 1 to 3, wherein the deflective strength of said target is not less than 70 MPa. ### Claim 9 A manufacture method of a target for a magneto-optical recording medium, comprising the steps of producing alloy powder consisting essentially of intermetallic compound and having a target composition of 15 to 30 atomic % of at least one rare earth metal and the balance of at least one transition metal in advance, and then sintering said alloy powder at a temperature lower than the liquid phase occurring temperature of said target composition by 30.degree. C. or more and under a high pressure not less than 90 MPa.