Recording disk with antiferromagnetically coupled multilayer ferromagnetic island disposed in trench between discrete tracks
View Patent ↗An apparatus having a write head for writing data on to a recording medium comprises a recording disk medium and one or more ferromagnetic islands. The recording disk medium has a data layer in discrete tracks with trenches between the discrete tracks, and a soft underlayer beneath the data layer and the trenches. The one or more ferromagnetic islands are disposed in the trenches between the discrete tracks in the recording disk medium and over the soft underlayer. The one or more ferromagnetic islands comprise a first layer having a first magnetization direction and a second layer having a second magnetization direction that is different than the first magnetization direction.
1. An apparatus having a write head for writing data on to a recording medium, comprising:
a recording disk medium having a data layer in discrete tracks with trenches between the discrete tracks, and a soft underlayer beneath the data layer and the trenches;
one or more ferromagnetic islands disposed in the trenches between the discrete tracks in the recording disk medium and over the soft underlayer, the one or more ferromagnetic islands comprise a first layer having a first magnetization direction and a second layer having a second magnetization direction that is different than the first magnetization direction.
2. The apparatus as defined in claim 1 wherein the recording disk medium is a perpendicular magnetic recording medium.
3. The apparatus as defined in claim 1 wherein the one or more ferromagnetic islands have a trapezoidal-shaped cross section.
4. The apparatus as defined in claim 1 wherein the width of the one or more ferromagnetic islands is between 10 percent and 45 percent of the track pitch, where track pitch is the distance from a first leading edge of one track to a second leading edge of an adjacent track.
5. The apparatus as defined in claim 1 wherein the height of the one or more islands is equal to the height of the data layer.
6. The apparatus as defined in claim 1 wherein the first and second layers are separated by a layer of Ruthenium.
7. The apparatus as defined in claim 6 wherein the first layer has a thickness that is about one half the thickness of the data layer.
8. The apparatus as defined in claim 6 wherein the second layer is formulated such that its magnetization times its thickness product is about equal to that of the first layer such that most of the remnant flux can circulate between the first and second layers thus avoiding demagnetization fields within the one or more ferromagnetic islands.
9. An apparatus having a write head for writing data on to a recording medium, comprising:
a recording disk medium having a data layer in discrete tracks with trenches between the discrete tracks, and a soft underlayer;
one or more ferromagnetic islands disposed in the trenches between the discrete tracks in the recording disk medium;
wherein the one or more ferromagnetic islands are comprised of multiple layers of a ferromagnetic material that are separated by an antiferromagnetic coupled layer such that flux is conducted in a Z-direction toward the soft underlayer.
10. The apparatus as defined in claim 9 wherein the one or more ferromagnetic islands is comprised of two layers of a ferromagnetic material separated by a layer of Ruthenium.
11. The apparatus as defined in claim 10 wherein a first ferromagnetic layer of the two layers of the ferromagnetic material has a thickness that is about one half the thickness of the data layer.
12. The apparatus as defined in claim 9 wherein a second layer of the ferromagnetic material is formulated such that its magnetization times its thickness product is about equal to that of a first layer of the ferromagnetic material such that most of the remnant flux can circulate between the first and second layers of the ferromagnetic material thus avoiding demagnetization fields within the one or more ferromagnetic islands.