CPC Class G11B

A method and an apparatus (10) for making thin layers from particles, wherein the particles are deposited on a carrier fluid flowing by gravity along a ramp (12) leading to a dam (18). The particles are held back at the bottom of the ramp (12), thereby causing the particles to be piled up one against the other in a monolayer configuration.

Techniques for bonding substrates are disclosed. According to one aspect of the techniques, an index bonding is provided to ensure that non-flatness of substrates is compensated when two substrates are bonded together so as to minimize possible dynamic imbalance of a disc. According to another aspect of the techniques, a dynamic alternating electric field bonding is provided to eliminate bubbles from a type of glue used to bond two substrates, wherein a power source is used to generate a dynamic alternating electromagnetic field in accordance with the substrates and/or the characteristics of the glue.

An optical recording medium with a high productivity is provided which can certainly record/reproduce data even when a blue or blue-violet laser beam is used as an irradiation light. An optical recording medium has a substrate and a recording layer. The recording layer includes a recording portion and a coating portion. The recording portion and the coating portion are all made substantially from Bi and O. The ratio of the number of O atoms to the total number of Bi atoms and O atoms of the coating portion is less than that of the recording portion. The ratio of the number of O atoms of the recording portion is in the range of from 62% to 77%. The ratio of the number of O atoms to the total number of Bi atoms and O atoms of the coating portion is in the range of from 60% to 70%.

A magnetic disk for information storage that includes a substrate and an information layer for containing information. The information layer includes a upper (e.g., recording) and lower (e.g., stabilizing) layers. The information layer has a remanence-squareness-thickness-product (“Mrt”) that varies radially between first and second disk radii. At least one of the following conditions is true: (i) the information layer has a coercivity that is at least substantially constant between the first and second disk radii; (ii) the lower magnetic layer has a magnetic anisotropy energy of no more than about 1.5×106 erg/cm3; and (iii) the magnetic anisotropy energy of the upper magnetic layer is at least about 150% of the magnetic anisotropy energy of the lower magnetic layer.

A perpendicular magnetic recording medium includes a nonmagnetic substrate; a first underlayer provided on the nonmagnetic substrate; a first nonmagnetic intermediate layer provided on the first underlayer; a second underlayer provided on the first nonmagnetic intermediate layer; a second nonmagnetic intermediate layer provided on the second underlayer; and a magnetic recording layer provided on the second nonmagnetic intermediate layer, wherein the first underlayer comprises a soft magnetic material which has a face-centered cubic structure and which includes at least Ni and Fe, and wherein the second underlayer comprises a soft magnetic material which has a face-centered cubic structure and which includes at least Co. The orientation dispersion is reduced and crystal grain diameters are smaller in the magnetic recording layer, and the film thickness of nonmagnetic intermediate layers can be decreased so that performance improvements such as reduced noise, increased S/N ratio, and improved write-ability are achieved.