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.

Provided herein is an apparatus including a top continuous layer and a bottom continuous layer under the top continuous layer. The top continuous layer and the bottom continuous layer are antiferromagnetically coupled. A number of granular columns are under the bottom continuous layer. The number of granular columns include at least a first granular layer under the bottom continuous layer and a second granular layer also under the first granular layer. The first granular layer and the second granular layer are separated by a non-magnetic spacer. The first granular layer and the second granular layer are ferromagnetically coupled. The first granular layer is antiferromagnetically coupled to the bottom continuous layer.

An apparatus is disclosed. The apparatus includes a storage layer, a first write layer, and a second write layer. The first write layer is disposed over the storage layer. The second write layer is disposed over the first write layer. The anisotropy field and magnetization associated with the second write layer at writing temperature is greater than anisotropy field and magnetization associated with the first write layer at the writing temperature.

Methods and media structures are provided for increasing writability and reducing unintentional erasure of perpendicular magnetic recording media. Variable permeability is controlled within a thin soft underlayer (SUL) structure, independent of bulk SUL material properties such as magnetic moment (B.sub.s) and magnetic anisotropy (Hk). Media with an improved combination of easier writability on the recorded track and difficult erasure off-track (between tracks and on neighboring tracks) is achieved, in part, by an unbalanced antiferromagnetically coupled (AFC) SUL structure. A permeability gradient is established within the soft underlayer with layers having different values of permeability and magnetic thickness (B.sub.s*t). In an aspect, a first SUL layer includes a high permeability region and an overlying low permeability region. A second layer antiferromagnetically couples the first layer to a low permeability third SUL layer. The present invention may be utilized with high density perpendicular recording media requiring carefully balanced magnetic properties.

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.

An apparatus may include a first magnetic layer, a first exchange break layer formed on the first magnetic layer, a second magnetic layer formed on the first exchange break layer, a second exchange break layer formed on the second magnetic layer, and a third magnetic layer formed on the second exchange break layer. The first magnetic layer has a first magnetic anisotropy energy, H.sub.k1, the second magnetic layer has a second magnetic anisotropy energy, H.sub.k2, and the third magnetic layer has a third magnetic anisotropy energy, H.sub.k3. In some embodiments, H.sub.k1H.sub.k2 is less than H.sub.k2H.sub.k3. In some embodiments, the apparatus may be a perpendicular magnetic recording medium.

A heat-assisted magnetic recording (HAMR) disk drive has a disk with at least two independent data layers (RL1 and RL2), each data layer storing an independent data stream. At a high laser power both RL1 and RL2 are heated to above their respective Curie temperatures and a first data stream is recorded in both RL1 and RL2. At a lower laser power only upper RL2 is heated to above its Curie temperature and a second data stream is recorded only in RL2. The data layers are separated by a nonmagnetic spacer layer (SL) that prevents lower RL1 from being heated to above its Curie temperature at low laser power. The first and second data streams are typically asynchronous. Recorded data is read back from both data streams simultaneously as a composite readback signal. A joint Viterbi detector detects the asynchronous data streams simultaneously from the composite readback signal.

According to one embodiment, a magnetic recording medium includes a first magnetic layer and a second magnetic layer. An easy magnetization axis of the first magnetic layer is aligned with a first direction. The first direction is from the first magnetic layer toward the second magnetic layer. The second magnetic layer has magnetic anisotropy in a plane perpendicular to the first direction. A second magnetization of the second magnetic layer is reverse orientation of a first magnetization of the first magnetic layer.

In one general embodiment, a magnetic medium includes a recording layer having at least three exchange control layers each having a magnetic moment less than 100 emu/cc, and four magnetic layers separated from one another by the exchange control layers. An uppermost of the magnetic layers is doped with oxygen. In another general embodiment, a magnetic medium includes a recording layer having at least three exchange control layers and four magnetic layers separated from one another by the exchange control layers. An uppermost of the magnetic layers has an oxygen content of greater than 0.5 vol %. An average pitch of magnetic grains in a lowermost of the magnetic layers is 9 nm or less. A lowermost of the magnetic layers has an oxide content of at least 20 vol %.

According to one embodiment, a magnetic recording medium includes a first magnetic region, a second magnetic region, and a third magnetic region. The second magnetic region is provided between the third magnetic region and the first magnetic region in a first direction from the third magnetic region to the first magnetic region. A first composition ratio of a first Pt atomic concentration in the first magnetic region to a first Co atomic concentration in the first magnetic region is higher than a second composition ratio of a second Pt atomic concentration in the second magnetic region to a second Co atomic concentration in the second magnetic region. A third composition ratio of a third Pt atom concentration in the third magnetic region to a third Co atom concentration in the third magnetic region is higher than the second composition ratio.