# US 7,608,348 B2 · Magnetic medium for storing information > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,608,348 B2 - Document ID: US7608348B2 - Status: Granted - Kind: B2 - Application number: 11/108,942 - Filed: 2005-04-18 - Published: 2006-03-30 - Granted: 2009-10-27 - Earliest claimed: 2004-05-10 - Assignees: Leibniz-Institut Fuer Festkoerper-Und Werkstoffforschung Dresden E.V. - Inventors: Sebastian Faehler - Web page: https://patentgrep.com/patent/US7608348B2 ## CPC - G11B 5/672: {having different compositions in a plurality of magnetic layers, e.g. layer compositions having differing elemental components or differing proportions of elements} - 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 Magnetic medium for storing information, includes at least two materials A and B which are connected with one another, material A being a hard magnetic material, wherein material B is a material which exhibits metamagnetic behavior in a magnetic field, the metamagnetic behavior of the material being such that, even after passing repeatedly through an external magnetic field from 0 to 10 tesla at least at a magnetic field strength below 3 tesla, an increase in the magnetization occurs as a function of the magnetic field, the increase being superproportional and having a positive curvature. ## Claims ### Claim 1 A magnetic medium for storing information, comprising: at least two materials A and B connected with one another; said material A being a hard magnetic material, said material Λ having a first coercivity Hc and a first remenence at a given temperature when independently situated; said material B being a material which exhibits metamagnetic behavior in a magnetic field at said given temperature, the metamagnetic behavior of the material B being such that, even after passing repeatedly through an external magnetic field from 0 to 10 Tesla at least at a magnetic field strength below 3 Tesla, an increase in magnetization occurs as a function of the magnetic field, the increase being superproportional and having a positive curvature and occurring at a transition field Ho which is less than Hc at said given temperature; said increase in magnetization of said material B at said transition field level Ho being sufficient to produce domain walls in said material B to function as nucleation cells in said material A at said given temperature so as to reduce a switching field of material A to about said transition field Ho so as to permit writing to material A at said given temperature while said writing remains stable at said given temperature. ### Claim 2 (depends on 1) The magnetic medium of claim 1, wherein said material B has a first or second-order phase transition induced by a magnetic field. ### Claim 3 (depends on 1) The magnetic medium of claim 1, wherein said material B has at least one phase transition in the temperature range from 250° K to 400° K, which involves a change in the magnetic order and transition temperature of which can be changed by an external magnetic field by at least 1° K/Tesla. ### Claim 4 (depends on 1) The magnetic medium of claim 1, wherein at least 20 atom percent of said material B comprises elements, which have magnetic orders at least at one temperature in the range from 1° K to 350° K. ### Claim 5 (depends on 1) The magnetic medium of claim 1, wherein said material B is based on Heusler alloys, manganates, or lanthanates. ### Claim 6 (depends on 1) The magnetic medium of claim 1, wherein said material B is based on the YCo2, with a variation in the composition of up to 10 atom percent. ### Claim 7 (depends on 1) The magnetic medium of claim 1, wherein said material B is based on the Gd5(SixGe1-x)4 with x>0.8, with a variation in the composition of up to 10 atom percent. ### Claim 8 (depends on 1) The magnetic medium of claim 1, wherein said material B is based on the Hf1-xTaxFe2 with x<0.2, with a variation in the composition of up to 10 atom percent. ### Claim 9 (depends on 1) The magnetic medium of claim 1, wherein said material B is based on the Ni2MnGa, with a variation in the composition of up to 10 atom percent. ### Claim 10 (depends on 1) The magnetic medium of claim 1, wherein said material B comprises alloys of elements which have no ferrimagnetic or ferromagnetic order/orders above 350° K, said alloys being present in quantities of not more than 30 atom percent. ### Claim 11 (depends on 1) The magnetic medium of claim 1, wherein said material B has alloys of elements which have magnetic orders at least at one temperature in the range from 1° K to 350° K, said alloys being present in quantities of not more than 20 atom percent. ### Claim 12 (depends on 11) The magnetic medium of claim 11, wherein said material B comprises alloys made of elements from the group comprising Fe, Co, Ni, Cr, Mn or from the rare earth group of elements. ### Claim 13 (depends on 1) The magnetic medium of claim 1, wherein said material A is ferrimagnetic or ferromagnetic in the temperature range from at least 250° K to 320° K and has an anisotropy field strength of at least 1.5 Tesla. ### Claim 14 (depends on 1) The magnetic medium of claim 1, wherein said material A comprises the elements Fe, Co, Ni, or Cr, the proportion of these elements combined being at least 20 atom percent. ### Claim 15 (depends on 1) The magnetic medium of claim 1, wherein said material A is formed as a monolayer or as a laminar composite. ### Claim 16 (depends on 15) The magnetic medium of claim 15, wherein at least 90 atom percent of said material A is consists of at least one of FePt, CoPt, FePd, MnAl, CrPt3, Co3Pt, Sm2Co7, Sm1Co5, Sm1Co7, Sm2Co17, Sm2Fe17N3, or Nd2Fe14B. ### Claim 17 (depends on 15) The magnetic medium of claim 15, wherein the laminar composite of said material A includes at least one of Co/Pd, Co/Pt, Fe/Pt, or Fe/Pd, the laminar structure having a periodicity of less than 3 nm. ### Claim 18 (depends on 1) The magnetic medium of claim 1, wherein said material A comprises alloys of elements, which do not have any ferromagnetic or ferrimagnetic orders above 350° K, said alloys being present in quantities of not more than 30 atom percent. ### Claim 19 (depends on 18) The magnetic medium of claim 18, wherein said material A comprises alloys of elements from the group comprising Pt, Cr, Zr, Ta, O, B, C, P, or N. ### Claim 20 (depends on 1) The magnetic medium of claim 1, wherein said material A comprises alloys of elements from the group comprising Fe, Co, Ni, Cr, Mn or from the rare earth group of elements, said alloys being present in quantities of not more than 30 atom percent. ### Claim 21 (depends on 1) The magnetic medium of claim 1, wherein said material Λ is in the form of a granular layer, this microstructure having arisen during layer growth, as well as during the subsequent structuring methods. ### Claim 22 (depends on 1) The magnetic medium of claim 1, wherein said material A is not textured. ### Claim 23 (depends on 1) The magnetic medium of claim 1, wherein said material A has a texture in which the minor magnetic axis is oriented in the direction of application. ### Claim 24 (depends on 1) The magnetic medium of claim 1, wherein said materials A and B are in the form of coherent monolayers or multilayers. ### Claim 25 (depends on 1) The magnetic medium of claim 1, wherein said materials A and B are present in the form of granular monolayers or multilayers in which said materials Λ and B are also present side by side in the plane of the layer. ### Claim 26 (depends on 1) The magnetic medium of claim 1, wherein said materials A and B are coupled with one another by means of exchange coupling. ### Claim 27 (depends on 1) The magnetic medium of claim 1, wherein said materials A and B are coupled with one another by means of magnetostatic interaction. ### Claim 28 (depends on 1) The magnetic medium of claim 1, wherein for coupling between said material A and said material B, one or more additional materials are present. ### Claim 29 (depends on 1) The magnetic medium of claim 1, wherein said materials A and B are connected with or covered by other functional materials, conventional for magnetic storage media including and at least one of the group consisting of soft magnetic base layers, seed layers, and corrosion-protection layers.