Abstract: A perpendicular magnetic recording medium according to which both the thermal stability of the magnetization is good and writing with a magnetic head is easy, and moreover the SNR is improved. In the case of a perpendicular magnetic recording medium comprising a nonmagnetic substrate (1), and at least a nonmagnetic underlayer (2), a magnetic recording layer (3), and a protective layer (4) formed in this order on the nonmagnetic substrate (1), the magnetic recording layer (3) comprises a low Ku region (31) layer having a perpendicular magnetic anisotropy constant (Ku value) of not more than 1×105 erg/cm3, and a high Ku region (32) layer having a Ku value of at least 1×106 erg/cm3. Moreover, the magnetic recording layer (3) is made to have therein nonmagnetic grain boundaries that contain a nonmagnetic oxide and magnetically isolate crystal grains, which are made of a ferromagnetic metal, from one another.

Abstract: There is provided a perpendicular magnetic recording medium according to which both the thermal stability of the magnetization is good and writing with a magnetic head is easy, and moreover the SNR is improved. In the case of a perpendicular magnetic recording medium comprising a nonmagnetic substrate 1, and at least a nonmagnetic underlayer 2, a magnetic recording layer 3 and a protective layer 4 formed in this order on the nonmagnetic substrate 1, the magnetic recording layer 3 comprises a low Ku region 31 layer having a perpendicular magnetic anisotropy constant (Ku value) of not more than 1×105 erg/cm3, and a high Ku region 32 layer having a Ku value of at least 1×106 erg/cm3. Moreover, the magnetic recording layer 3 is made to have therein nonmagnetic grain boundaries that contain a nonmagnetic oxide and magnetically isolate crystal grains, which are made of a ferromagnetic metal, from one another.

Abstract: The quantity of oxide contained in a magnetic layer is controlled to control the crystal grains and the segregation structure for ensuring low noise characteristic in a granular magnetic layer of a perpendicular magnetic recording medium. The granular magnetic layer consists of ferromagnetic crystal grains and a nonmagnetic grain boundary region mainly of an oxide surrounding the ferromagnetic crystal grains. The perpendicular magnetic recording medium has a nonmagnetic underlayer composed of a metal or alloy having hexagonal closest-packed crystal structure. The ferromagnetic crystal grain is composed of an alloy containing at least cobalt and platinum. The volume proportion of the nonmagnetic grain boundary region mainly of the oxide falls within a range of 15% to 40% of the volume of the total magnetic layer.

Abstract: A perpendicular magnetic recording medium, which includes a nonmagnetic substrate, and a soft magnetic layer, a first orientation control layer, a nonmagnetic intermediate layer, and a perpendicular magnetic recording layer formed sequentially on the nonmagnetic substrate. The perpendicular magnetic recording medium further includes a second orientation control layer provided between the first orientation control layer and the nonmagnetic intermediate layer. The nonmagnetic intermediate layer has hexagonal close-packed (hcp) structure. The first orientation control layer has a face-centered cubic (fcc) structure. The second orientation control layer includes Co and Cr, and has the hcp structure.

Abstract: A magnetic recording medium, and method of manufacturing the same, is provided with excellent recording performance by employing a granular magnetic layer having a specified composition. A magnetic recording medium according to the present invention comprises a nonmagnetic underlayer, a granular magnetic layer, a protective film, and a liquid lubrication layer sequentially laminated on a nonmagnetic substrate. The granular magnetic layer consists of ferromagnetic crystal grains containing cobalt and nonmagnetic grain boundary region surrounding the ferromagnetic crystal grains. The ferromagnetic crystal grains contain platinum in the range of 15 at % to 17 at %.

Abstract: An object of the present invention is to provide a plating method on a glass base plate. The method allows forming a plating film on a base plate composed of a glass material with excellent adhesivity and homogeneity by means of an electroless plating method even to a thickness of 1 ?m or more. Before forming a plating film by a step of electroless plating S6, a surface treatment process is conducted on a surface of the base plate composed of a glass material. The surface treatment process comprises at least a step of glass activation treatment S2 to increase quantity of silanol groups on the surface of the base plate at least by a factor of two using an aqueous solution of diluted acid, a step of silane coupling agent treatment S3, a step of palladium catalyst treatment S4, and a step of palladium bonding treatment S5.

Abstract: A perpendicular magnetic recording medium is disclosed in which a soft magnetic layer used as a low Ku layer can be stably produced with high performance. Thermal stabilization of magnetization, ease of writing by a magnetic head, and SNR also are improved. A method of manufacturing the medium is disclosed. The perpendicular magnetic recording medium includes at least a nonmagnetic underlayer, a magnetic recording layer, and a protective layer formed in this order on a nonmagnetic substrate. The magnetic recording layer includes a low Ku layer having a relatively small perpendicular magnetic anisotropy constant (Ku value), and a high Ku layer in which the Ku value is relatively large, and the low Ku layer includes a soft magnetic thin film including an iron group element-based microcrystal structure, in which a nitrogen element is added to a ferromagnetic material mainly containing one of metals of Co, Ni and Fe or an alloy of the metal.

Abstract: A perpendicular magnetic recording medium, which includes a nonmagnetic substrate, and a soft magnetic layer, a first orientation control layer, a nonmagnetic intermediate layer, and a perpendicular magnetic recording layer formed sequentially on the nonmagnetic substrate. The perpendicular magnetic recording medium further includes a second orientation control layer provided between the first orientation control layer and the nonmagnetic intermediate layer. The nonmagnetic intermediate layer has hexagonal close-packed (hcp) structure. The first orientation control layer has a face-centered cubic (fcc) structure. The second orientation control layer includes Co and Cr, and has the hcp structure.

Abstract: A perpendicular magnetic recording medium and method thereof, includes a nonmagnetic substrate; a soft magnetic under layer; an intermediate layer; a bilayer magnetic recording layer; a protective layer; and a liquid lubricant layer. According to a following order, the soft magnetic under layer, the intermediate layer, the bilayer magnetic recording layer, the protective layer, and the liquid lubricant layer are sequentially stacked on the nonmagnetic substrate. The bilayer magnetic recording layer includes a first magnetic layer including a CoCr alloy crystalline film, and a second magnetic layer including a rare earth-transition metal alloy noncrystalline film.

Abstract: A disk substrate for a perpendicular magnetic recording medium is, disclosed. The substrate exhibits sufficient productivity, serves the function of a soft magnetic backing layer of the perpendicular magnetic recording medium, and scarcely generates noise. A perpendicular magnetic recording medium using such a substrate also is disclosed. The disk substrate comprises at least a soft magnetic underlayer formed on a nonmagnetic base plate by means of an electroless plating method. The thermal expansion coefficient of the soft magnetic underlayer is larger than a thermal expansion coefficient of the nonmagnetic disk-shaped base plate. A saturation magnetostriction constant ?s satisfies a relation ?s??1×10?5.

Abstract: The quantity of oxide contained in a magnetic layer is controlled to control the crystal grains and the segregation structure for ensuring low noise characteristic in a granular magnetic layer of a perpendicular magnetic recording medium. The granular magnetic layer consists of ferromagnetic crystal grains and a nonmagnetic grain boundary region mainly of an oxide surrounding the ferromagnetic crystal grains. The perpendicular magnetic recording medium has a nonmagnetic underlayer composed of a metal or alloy having hexagonal closest-packed crystal structure. The ferromagnetic crystal grain is composed of an alloy containing at least cobalt and platinum. The volume proportion of the nonmagnetic grain boundary region mainly of the oxide falls within a range of 15% to 40% of the volume of the total magnetic layer.

Abstract: A perpendicular magnetic recording medium is disclosed in which a soft magnetic layer used as a low Ku layer can be stably produced with high performance. Thermal stabilization of magnetization, ease of writing by a magnetic head, and SNR also are improved. A method of manufacturing the medium is disclosed. The perpendicular magnetic recording medium includes at least a nonmagnetic underlayer, a magnetic recording layer, and a protective layer formed in this order on a nonmagnetic substrate. The magnetic recording layer includes a low Ku layer having a relatively small perpendicular magnetic anisotropy constant (Ku value), and a high Ku layer in which the Ku value is relatively large, and the low Ku layer includes a soft magnetic thin film including an iron group element-based microcrystal structure, in which a nitrogen element is added to a ferromagnetic material mainly containing one of metals of Co, Ni and Fe or an alloy of the metal.

Abstract: A manufacturing method for a magnetic recording medium is disclosed. By using the method, the anisotropic magnetic field (Hk) of an underlayer is improved, spike noise generated in the soft magnetic underlayer is suppressed, and the signal-to-noise ratio (SNR) is improved without employing a special layer configuration and without the need for complicated and expensive processing. A soft magnetic underlayer is formed by laminating a soft magnetic lower underlayer, a non-magnetic metal layer, and a soft magnetic upper underlayer in succession on a non-magnetic substrate. After forming the non-magnetic metal layer, its surface is exposed to a gas containing between 2 and 100 at % oxygen. A perpendicular magnetic recording layer is formed on the soft magnetic underlayer.

Abstract: A substrate for a perpendicular magnetic recording medium has a soft magnetic underlayer that functions as a soft magnetic backing layer of a perpendicular magnetic recording medium. The substrate for a perpendicular magnetic recording medium has a nonmagnetic base made of Al—Mg alloy or the like. The soft magnetic underlayer is formed of a Ni—P alloy containing phosphorus in a range of 0.5 wt % to 6 wt % formed by electroless plating on the nonmagnetic base. The substrate can also include a nonmagnetic underlayer formed by electroless plating on the base before electroless plating the soft magnetic underlayer. To form the perpendicular magnetic recording medium, the surface of the soft magnetic is textured using free abrasive grains. Thereafter, a nonmagnetic seed layer, a magnetic recording layer, and a protective layer can be formed by sputtering. A soft magnetic supplemental layer also can be formed on the soft magnetic underlayer before forming the seed layer.

Abstract: A high-recording-density magnetic recording medium and a method of its manufacture can achieve a high OR with only a small reduction in Hcr. The magnetic recording medium has a nonmagnetic substrate and a first seed layer, a second seed layer, a first underlayer, a second underlayer, and a magnetic recording layer formed on the substrate in this order. The first seed layer can be a single layer or a plurality of layers made of at least one material selected from the group consisting of Ni—Ti alloys, Cr—Al alloys, Cr—Ta alloys, and Cr—Ti alloys. The second seed layer can be a single layer or a plurality of layers made of at least one material selected from the group consisting of Ni—W alloys, Ni—Ru—W alloys, and Co—W alloys. The first underlayer can be a single layer or a plurality of layers made of a Cr—Ru alloy. The second underlayer can be a single layer or a plurality of layers made of a Cr alloy comprising Cr and at least one element selected from the group consisting of Mo, B, Ti, and W.

Abstract: A perpendicular magnetic recording medium has a magnetic recording layer and laminated magnetic layers composed of different materials. In a first magnetic layer of the magnetic recording layer, ferromagnetic grains are surrounded by a nonmagnetic grain boundary region composed principally of oxide and/or nitride. In a second magnetic layer of the magnetic recording layer, ferromagnetic grains are surrounded by a nonmagnetic grain boundary region composed principally of chromium. The recording medium has an intermediate layer composed of a material having hcp or fcc structure. Advantageously, a heating process is conducted after forming the first magnetic layer and before forming the second magnetic layer. The medium achieves improvement in electromagnetic conversion characteristics and simultaneously improvement in corrosion resistance to provide a perpendicular magnetic recording medium with high recording density and simultaneously high reliability.

Abstract: A magnetic recording medium exhibiting low noise and having a sufficiently high coercive force includes a magnetic layer having a granular structure including ferromagnetic crystal grains with a hexagonal closed packed structure and a nonmagnetic grain boundary region of mainly an oxide intervening between the crystal grains. An underlayer has a body-centered cubic lattice structure. A nonmagnetic intermediate layer with the hexagonal closest packed structure includes Ru, Os, and/or Re, which are provided between the magnetic layer and the underlayer. A degree of mismatching ?=|d1?d2|/d1 is at most 10%, for instance, in a range from 2.5% to 7.0%, where d1 is a spacing of lattice planes of the crystal grains in the magnetic layer and d2 is a spacing of the lattice planes of the crystal grains in the intermediate layer.

Abstract: A magnetic recording medium has a non-magnetic under-layer, a magnetic layer, a protective film and a liquid lubricant layer sequentially laminated on a non-magnetic substrate. The magnetic layer has a multi-layer structure laminated with two or more magnetic layer components, each of the magnetic layer components having ferromagnetic grains and non-magnetic grain boundaries surrounding the grain. The resulting magnetic recording medium has a granular magnetic layer exhibiting very high Hc accompanying high density of magnetic recording, while decreasing the amount of platinum needed for attaining the high Hc, and reducing media noise accompanying the high recording density.

Abstract: A magnetic recording medium for perpendicular magnetic recording system includes a nonmagnetic substrate and layers sequentially laminated on the substrate. The layers include a seed layer comprised of a metal or an alloy with a face centered cubic crystal structure, a nonmagnetic underlayer of a metal or an alloy with a hexagonal closest packed crystal structure, a magnetic layer having a granular structure including ferromagnetic crystalline grains with a hexagonal closest packed structure and nonmagnetic grain boundary region of mainly oxide surrounding the crystalline grains, a protective layer, and a liquid lubricant layer.

Abstract: A perpendicular magnetic recording medium has a granular magnetic layer and a nonmagnetic underlayer of a metal or an alloy having a hexagonal close packed (hcp) crystal structure. A seed layer of a metal or an alloy of a face-centered cubic (fcc) crystal structure is provided under the nonmagnetic underlayer. Such a perpendicular magnetic recording medium exhibits excellent magnetic characteristics even when the thickness of the underlayer or the total thickness of the underlayer and the seed layer is very thin. Excellent magnetic characteristics can be obtained even when of the substrate is not preheated. Accordingly, a nonmagnetic substrate, such as a plastic resin can be employed to reduce the manufacturing cost.