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.

A heat-assisted magnetic recording (HAMR) disk has multiple independent data layers, each data layer being a continuous non-patterned layer of magnetizable material. Each data layer can store data independent and not related to the data stored in the other data layers. The data layers are separated by a nonmagnetic spacer layer (SL) and each data layer is formed of high-anisotropy (K.sub.u) material so that the coercivities of lower and upper data layers (RL1 and RL2) are greater than the magnetic write field. At a high laser power both RL1 and RL2 are heated to above their respective Curie temperatures and data is recorded in both RL1 and RL2. At low laser power only upper RL2 is heated to above its Curie temperature and data is recorded only in RL2. The SL prevents lower RL1 from being heated to above its Curie temperature at low laser power.

A laminating structure includes a first magnetic layer, a second magnetic layer, a first spacer disposed between the first and second magnetic layers and a second spacer disposed on the second magnetic layer.

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.

A laminating structure includes a first magnetic layer, a second magnetic layer, a first spacer disposed between the first and second magnetic layers and a second spacer disposed on the second magnetic layer.

A magnetic data storage medium capable of storing data bits may be configured at least with a magnetic underlayer structure and a recording structure. The recording structure can have at least a first magnetic layer and a second magnetic layer with the first magnetic layer decoupled by being constructed of an alloy of cobalt, platinum, and a platinum group metal element.

A perpendicular magnetic recording medium adapted for high recording density and high data recording rate comprises a non-magnetic substrate having at least one surface with a layer stack formed thereon, the layer stack including a perpendicular recording layer containing a plurality of columnar-shaped magnetic grains extending perpendicularly to the substrate surface for a length, with a first end distal the surface and a second end proximal the surface, wherein each of the magnetic grains has: (1) a gradient of perpendicular magnetic coercivity H.sub.k extending along its length between the first end and second ends; and (2) predetermined local exchange coupling strengths along the length.

There is provided a magnetic recording medium including a surface having a longitudinal direction and a lateral direction. An arithmetic average roughness Ra, a ratio PSD.sub.MD,short/PSD.sub.TD,short, and a ratio PSD.sub.MD,long/PSD.sub.TD,long on the surface satisfy Ra3.0 nm, PSD.sub.MD,short/PSD.sub.TD,short0.65, and 1.3PSD.sub.MD,long/PSD.sub.TD,long2.3, in which PSD.sub.MD,short is an average value of PSD values in a range from 0.15 m to 0.4 m in the longitudinal direction of the surface, PSD.sub.TD,short is an average value of PSD values in a range from 0.15 m to 0.4 m in the lateral direction of the surface, PSD.sub.MD,long is an average value of PSD values in a range from 0.4 m to 5.0 m in the longitudinal direction of the surface, and PSD.sub.TD,long is an average value of PSD values in a range from 0.4 m to 5.0 m in the lateral direction of the surface.

According to one embodiment, a perpendicular magnetic recording medium includes an underlying layer with convexes arranged with 1 to 20 nm intervals, and a multilayered amorphous magnetic recording layer formed on the underlying layer. The multilayered amorphous magnetic recording layer includes a first amorphous magnetic recording layer with a plurality of magnetic grains each formed on a corresponding convex to be widened toward its tip and being separated from each other at least in the convex side, a nonmagnetic protective layer covering at least a part of a sidewall of the magnetic particle, and a second amorphous magnetic recording layer formed on the nonmagnetic protective layer.