Provided is a perpendicular magnetic recording medium that exhibits improved thermal stability and achieves reduction in switching magnetic field by providing a cap layer having characteristics (characteristics contributing to reducing switching magnetic field of the perpendicular magnetic recording medium as well as to improving thermal stability thereof) superior to existing cap layers.

A perpendicular magnetic recording layer (24) has a granular structure which comprises Co- Pt-alloy magnetic crystal grains (24A) and a non-magnetic grain boundary oxide (24B). A cap layer (26) has a granular structure which comprises Co-Pt-alloy magnetic crystal grains (26A) and a magnetic grain boundary oxide (26B). The Co- Pt -alloy magnetic crystal grains (26A) in the cap layer (26) contain 65-90 at % of Co and 10-35 at % of Pt. The magnetic grain boundary oxide (26B) is included in a volume fraction of 5-40 vol % with respect to the total volume of the cap layer (26).

A sputtering target according to the present invention contains Co and one or more metals selected from the group consisting of Cr and Ru, as metal components, wherein a molar ratio of the content of the one or more metals to the content of Co is ½ or more, and wherein the sputtering target contains Nb.sub.2O.sub.5 as a metal oxide component.

A magnetic stack includes a substrate and a soft magnetic underlayer deposited on a top surface of the substrate. A heat sink layer is disposed on top of the soft magnetic underlayer, and an interlayer is deposited on top of the heat sink layer. A non-magnetic seed layer is deposited on top of the interlayer. A magnetic recording structure which includes more than one magnetic recording layer is deposited on the top surface of the non-magnetic seed layer.

A heat-assisted magnetic recording (HAMR) medium has a multilayered underlayer between the heat-sink layer and the recording layer. One embodiment of the underlayer is a multilayer of a thermal barrier layer consisting essentially of MgO and TiO, and a seed layer containing MgO and nitrogen (N) directly on the thermal barrier layer, with the recording layer on and in contact with the seed layer. The interface between the thermal barrier layer and the seed layer contains Ti and N, some of which may be present as TiN to act as a diffusion barrier to prevent diffusion of the Ti into the recording layer. The Ti-containing thermal barrier layer has a higher thermal resistivity than the conventional MgO thermal barrier/seed layer and thus allows for reduced laser power to the recording layer while still achieving a high thermal gradient at the recording layer.

To provide a magnetic recording tape and the like that have excellent magnetic properties and exhibit a favorable SNR. There are provided a magnetic recording tape and the like including at least: a base layer that includes a long film having flexibility; and a magnetic layer formed on a side of one main surface of the base layer, in which an under layer and a seed layer are provided in the stated order from a side of the magnetic layer toward a side of the base layer between the magnetic layer and the base layer, the underlayer contains at least Co and Cr, and has an average atomic number ratio represented by the following formula (1): Co.sub.(100-y)Cr.sub.y (where y is within a range of 37≤y≤45.), and the seed layer formed directly on the base layer has a film thickness of 5 nm or more and 30 nm or less, and contains Ti and O and has an average atomic number ratio represented by the following formula (2): Ti.sub.(100-x)O.sub.x (where x≤10.) or contains Ti—Cr—O and has an average atomic number ratio represented by the following formula (3): (TiCr).sub.(100-x)O.sub.x (where x≤10.).

A magnetic recording medium according to one 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 heat-assisted magnetic recording (HAMR) disk has a magnetic recording layer (typically a FePt chemically-ordered alloy), a seed-thermal barrier layer (typically MgO) below the recording layer, a heat-sink layer, and an optical-coupling multilayer of alternating plasmonic and non-plasmonic materials between the heat-sink layer and the seed-thermal barrier layer. Unlike a heat sink layer, the multilayer has very low in-plane and out-of-plane thermal conductivity and thus does not function as a heat sink layer. The multilayer's low thermal conductivity allows the multilayer to also function as a thermal barrier. Due to the plasmonic materials in the multilayer it provides excellent optical coupling with the near-field transducer (NFT) of the HAMR disk drive.

A magnetic recording medium with a reduced average grain diameter and reduced grain diameter dispersion is provided. A magnetic recording medium having a magnetic property (magnetic anisotropy energy) applicable as a magnetic recording medium is provided. It is a magnetic recording medium containing a substrate, a grain diameter control layer, a first seed layer, a second seed layer, and a magnetic recording layer containing an ordered alloy in this order, in which the second seed layer is composed of crystal grains having TiN as a main component, and a grain boundary material having at least one or more selected from the group consisting of metal oxides and carbon as a main component.

A magnetic recording medium includes a layer structure including a magnetic layer, a base layer, and a back layer in this order, in which an average thickness t.sub.T is t.sub.T≤5.5 μm, a dimensional variation Δw in a width direction to tension change in a longitudinal direction is 660 ppm/N≤Δw, and a surface roughness R.sub.abe of the base layer on a side of the back layer is 4.2 nm≤R.sub.abe≤8.5 nm.

The invention provides a magnetic recording medium including a magnetic layer or a magnetic recording layer having a granular structure in which magnetic crystal grains are well separated from each other. The magnetic recording medium includes a substrate, a seed layer, and a magnetic recording layer, wherein the magnetic recording layer includes a first magnetic layer which is a continuous film consisting of an ordered alloy, and a second magnetic layer having a granular structure consisting of magnetic crystal grains consisting of an ordered alloy and a non-magnetic crystal grain boundary, and the seed layer consists of a material selected from the group consisting of an NaCl-type compound, a spinel-type compound, and a perovskite-type compound.