Provided is a glass for a magnetic recording medium substrate or for a glass spacer for a magnetic recording/reproducing apparatus, in which the total content of Li.sub.2O, Na.sub.2O, K.sub.2O, B.sub.2O.sub.3, and ZnO (Li.sub.2O+Na.sub.2O+K.sub.2O+B.sub.2O.sub.3+ZnO) is in a range of 0 mol % or more and 3 mol % or less, the mole ratio of the total content of Al.sub.2O.sub.3 and MgO relative to the total content of SiO.sub.2 and CaO [(Al.sub.2O.sub.3+MgO)/(SiO.sub.2+CaO)] is in a range of 0.30 or more and 0.6 or less, the total content of SiO.sub.2 and Al.sub.2O.sub.3 (SiO.sub.2+Al.sub.2O.sub.3) is in a range of 64 mol % or more and 85 mol % or less, and the total content of SiO.sub.2, Al.sub.2O.sub.3, MgO, and CaO (SiO.sub.2+Al.sub.2O.sub.3+MgO+CaO) is in a range of 87 mol % or more and 98 mol % or less.

A heat-assisted magnetic recording (HAMR) media stack is provided in which Iridium (Ir)-based materials may be utilized as a secondary underlayer instead of a Magnesium Oxide (MgO) underlayer utilized in conventional media stacks. Such Ir-based materials may include, e.g., pure Ir, Ir-based alloys, Ir-based compounds, as well as a granular Ir layer with segregants. The use of Ir or Ir-based materials as an underlayer provide advantages over the use of MgO as an underlayer. For example, DC sputtering can be utilized to deposit the layers of the media stack, where the deposition rate of Ir is considerably higher than that of MgO resulting in higher manufacturing production yields. Further still, less particles are generated during Ir-based layer deposition processes, and Ir-based underlayer can act as a better heat sink. Further still, the morphology and structure of a recording layer deposited on an Ir-based layer can be better controlled.

The magnetic tape has one or more of each of an area A and an area B having different center line average surface roughness Ra measured on a surface of a magnetic layer in a region over a part of the magnetic tape in a longitudinal direction, with a ratio B.sub.Mag/A.sub.Mag of 1.20 to 10.00 and a ratio B.sub.Mag/B.sub.Back of equal to or greater than 2.0 in a case where extraction amounts per unit area of a component selected from the group consisting of fatty acid, fatty acid ester, and fatty acid amide extracted from a magnetic layer side of the area A and the area B are defined as A.sub.Mag and B.sub.Mag respectively, and an extraction amount per unit area of the above component extracted from a back coating layer side of the area B is defined as B.sub.Back.

The magnetic tape has one or more of each of an area A and an area B having different center line average surface roughness Ra measured on a surface of a magnetic layer in a region over a part of the magnetic tape in a longitudinal direction, with a ratio B.sub.Mag/A.sub.Mag of 1.20 to 10.00 and a ratio B.sub.Mag/B.sub.Back of equal to or greater than 2.0 in a case where extraction amounts per unit area of a component selected from the group consisting of fatty acid, fatty acid ester, and fatty acid amide extracted from a magnetic layer side of the area A and the area B are defined as A.sub.Mag and B.sub.Mag respectively, and an extraction amount per unit area of the above component extracted from a back coating layer side of the area B is defined as B.sub.Back.

A method for forming a magnetic recording medium according to one embodiment includes forming a magnetic layer above an underlayer. The magnetic layer includes a first magnetic material and particulates. A protective layer is formed above the magnetic layer, the protective layer including a second material. A method for forming a magnetic recording medium according to another embodiment includes forming a first nonmagnetic layer above a base film. The first nonmagnetic layer has first nonmagnetic particles. A second nonmagnetic layer is formed above the first nonmagnetic layer, the second nonmagnetic layer having second nonmagnetic particles. A magnetic layer is formed above the second nonmagnetic layer, the magnetic layer including a magnetic material.

A method for forming a magnetic recording medium according to one embodiment includes forming a magnetic layer above an underlayer. The magnetic layer includes a first magnetic material and particulates. A protective layer is formed above the magnetic layer, the protective layer including a second material. A method for forming a magnetic recording medium according to another embodiment includes forming a first nonmagnetic layer above a base film. The first nonmagnetic layer has first nonmagnetic particles. A second nonmagnetic layer is formed above the first nonmagnetic layer, the second nonmagnetic layer having second nonmagnetic particles. A magnetic layer is formed above the second nonmagnetic layer, the magnetic layer including a magnetic material.

A magnetic recording medium according to one embodiment includes an underlayer and a magnetic layer above the underlayer. The magnetic layer includes a first magnetic material and particulates. A protective layer is positioned above the magnetic layer, the protective layer including a second material. A magnetic recording medium according to another embodiment includes a base film and a first nonmagnetic layer above the base film. The first nonmagnetic layer has first nonmagnetic particles. A second nonmagnetic layer is positioned above the first nonmagnetic layer, the second nonmagnetic layer having second nonmagnetic particles. A magnetic layer is positioned above the second nonmagnetic layer, the magnetic layer including a magnetic material.

A magnetic device including: a magnetic reader; a magnetic writer; and a variable overcoat, the variable overcoat positioned over at least the magnetic reader and writer, the variable overcoat having an overcoat layer, the overcoat layer having a substantially constant thickness and material; and at least one disparate overcoat portion, the disparate overcoat portion having a different thickness, a different material, or both, than the overcoat layer.

A stack includes a substrate, a magnetic recording layer comprising FePtX disposed over the substrate, and a capping layer disposed on the magnetic recording layer. The capping layer comprises Co; at least one rare earth element; one or more elements selected from a group consisting of Fe and Pt; and an amorphizing agent comprising one to three elements selected from a group consisting of B, Zr, Ta, Cr, Nb, W, V, and Mo.

A stack includes a substrate, a magnetic recording layer comprising FePtX disposed over the substrate, and a capping layer disposed on the magnetic recording layer. The capping layer comprises Co; at least one rare earth element; one or more elements selected from a group consisting of Fe and Pt; and an amorphizing agent comprising one to three elements selected from a group consisting of B, Zr, Ta, Cr, Nb, W, V, and Mo.