According to one embodiment, a magnetic recording medium includes: a substrate; and a magnetic recording layer structure formed above the substrate. The magnetic recording layer structure includes five or more magnetic recording layers and four or more nonmagnetic exchange coupling layers, where the magnetic recording layers and the nonmagnetic exchange coupling layers are arranged in an alternating pattern, and where the magnetic recording layers are separated from each other by least one of the nonmagnetic exchange coupling layers. The magnetic recording layer positioned closest to the substrate has each of the following: an average magnetic grain pitch of about 8.3 nm or less, a magnetic anisotropy field (H.sub.k) value of greater than or equal to about 20 kOe, and a thickness that is about 40% of a total thickness of the magnetic recording layer structure.

A magnetic recording medium includes a non-magnetic substrate, a soft magnetic underlayer, an orientation control layer, a perpendicular magnetic layer, and a protective layer arranged in this order. The perpendicular magnetic layer includes a first magnetic layer and a second magnetic layer from the non-magnetic substrate side in this order. The second magnetic layer contains a magnetic grain and provided farthest from the non-magnetic substrate. The first magnetic layer has a granular structure that contains an oxide in a grain boundary. The second magnetic layer has a granular structure that contains a carbide of an element contained in the magnetic grain in a grain boundary.

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 includes a non-magnetic substrate, a soft magnetic underlayer, an orientation control layer, a perpendicular magnetic layer, and a protective layer arranged in this order. The perpendicular magnetic layer includes a first magnetic layer and a second magnetic layer from the non-magnetic substrate side in this order. The second magnetic layer contains a magnetic grain and provided farthest from the non-magnetic substrate. The first magnetic layer has a granular structure that contains an oxide in a grain boundary. The second magnetic layer has a granular structure that contains a nitride of an element contained in the magnetic grain in a grain boundary.

A magnetic recording medium includes a substrate, an underlayer, and a magnetic layer that are arranged in this order. The magnetic layer has a granular structure including magnetic grains having a L1.sub.0 crystal structure, and grain boundary parts having a volume fraction in a range of 25 volume % to 50 volume %. The magnetic grains have a c-axis orientation with respect to the substrate. The grain boundary parts include a material having a lattice constant in a range of 0.30 nm to 0.36 nm, or in a range of 0.60 nm to 0.72 nm.

A magnetic recording medium is provided that includes a recording layer structure including a first magnetic recording layer, a second magnetic recording layer, a third magnetic recording layer, a fourth magnetic recording layer, and a plurality of nonmagnetic exchange coupling layers. The first magnetic recording layer is closest to a substrate and the fourth magnetic recording layer is farthest from the substrate. An amount of Co in the first magnetic recording layer is greater than or equal to the amount of Co in the second magnetic recording layer, the third magnetic recording layer, and the fourth magnetic recording layer.

The magnetic recording medium includes at least a nonmagnetic substrate and a magnetic recording layer, the magnetic recording layer consists of a first magnetic recording layer or a plurality of layers including at least the first magnetic recording layer and a second magnetic recording layer, the first magnetic recording layer has a granular structure including a first magnetic crystal grain and a first nonmagnetic crystal grain boundary, the first magnetic crystal grain consists of an ordered alloy having Fe, Pt and Rh, the first nonmagnetic crystal grain boundary consists of carbon, boron or a combination thereof, the second magnetic recording layer has a granular structure including a second magnetic crystal grain and a second nonmagnetic crystal grain boundary, the second magnetic crystal grain consists of an FePt ordered alloy or an ordered alloy having Fe, Pt and Rh, and the second nonmagnetic crystal grain boundary includes carbon.

An apparatus includes a first magnetic layer. A second magnetic layer overlies the first magnetic layer and is magnetically softer than the first magnetic layer. An exchange control layer is between the first magnetic layer and the second magnetic layer. The includes a higher Ms (saturation magnetization) than the first magnetic layer at room temperature.

A heat-assisted magnetic recording medium includes a substrate, an underlayer, and a magnetic layer including an alloy having a L1.sub.0 crystal structure and first and second layers, arranged in this order. Each of the first and second layers has a granular structure including C, SiO.sub.2, and BN at grain boundaries. Vol % of the grain boundaries in each of the first and second layers is 25 to 45 vol %. Vol % of C in the first layer is 5 to 22 vol %, and a volume ratio of SiO.sub.2 with respect to BN in each of the first and second layers is 0.25 to 3.5. Vol % of SiO.sub.2 in the second layer is greater than that of the first layer by 5 vol % or more. Vol % of BN in the second layer is smaller than that in the first layer by 2 vol % or more.

A heat-assisted magnetic recording medium includes a substrate, an underlayer, and a magnetic layer including an alloy having a L1.sub.0 crystal structure and first and second layers, arranged in this order. Each of the first and second layers has a granular structure including C, SiO.sub.2, and BN at grain boundaries. Vol % of the grain boundaries in each of the first and second layers is 25 to 45 vol %. Vol % of C in the first layer is 5 to 22 vol %, and a volume ratio of SiO.sub.2 with respect to BN in each of the first and second layers is 0.25 to 3.5. Vol % of SiO.sub.2 in the second layer is greater than that of the first layer by 5 vol % or more. Vol % of BN in the second layer is smaller than that in the first layer by 2 vol % or more.