Patterned perpendicular magnetic recording medium with data islands having a flux channeling layer below the recording layer
A patterned perpendicular magnetic recording medium, such as a disk for use in hard disk drives, has a flux channeling layer (FCL) located below the recording layer (RL) in each of the discrete data islands. The disk includes a substrate, a soft underlayer (SUL) of soft magnetically permeable material on the substrate, and a nonmagnetic exchange break layer (EBL) on the SUL. A nonmagnetic separation layer (SL) is located between the FCL and the RL in the islands. The FCL has an anisotropy field substantially lower than the anisotropy field of the RL, and a magnetization equal to or higher than the magnetization of the RL. The FCL is saturated at a much lower field than the RL and thus channels the magnetic flux from the write head through the island positions. The dipolar fields from the RL above the FCL polarize the magnetization of the FCL parallel to the magnetization direction of the RL in the absence of an external field, to thereby enhance the readback signal.
1. A patterned perpendicular magnetic recording medium comprising:
a substrate having a substantially planar surface;
a soft underlayer (SUL) of soft magnetically permeable material on the substrate surface and having a planar surface;
an exchange break layer (EBL) of nonmagnetic material comprising a base layer of EBL material covering the entire planar surface of the SUL and a plurality of pillars of EBL material extending from the base layer of EBL material; and
a plurality of discrete islands, each island located on a pillar of EBL material and comprising a flux channeling layer (FCL) on the EBL material of the pillar and prevented from exchange coupling with the SUL by the EBL material, a perpendicular magnetic recording layer (RL), and a nonmagnetic separation layer (SL) on the FCL between the FCL and the RL for preventing magnetic exchange coupling between the FCL and the RL, the FCL formed of a soft magnetic material having an anisotropy field lower than the anisotropy field of the RL and a magnetization higher than the magnetization of the material of the RL, the RL and FCL having parallel magnetizations perpendicular to the substrate surface.
2. The medium of claim 1 wherein the FCL comprises a material selected from Co, Fe, Ni, and an alloy comprising two or more of Co, Fe and Ni.
3. The medium of claim 1 wherein the EBL is formed of a material selected from the group consisting of Si, Ge, SiGe alloys, Ta, Cr, Ru, W, Zr, Nb, Mo, V, Al, CrTi, NiP, CNx, CHx, C, and oxides, nitrides and carbides of an element selected from the group consisting of Si, Al, Zr, Ti, and B.
4. The medium of claim 1 wherein the SUL is formed of a material selected from the group consisting of alloys of CoFe, CoNiFe, NiFe, FeCoB, CoCuFe, FeAlSi, FeTaN, FeN, FeTaC, CoTaZr and CoZrNb.
5. The medium of claim 1 wherein the SUL is a lamination of multiple magnetically permeable films separated by nonmagnetic films.
6. The medium of claim 5 wherein the nonmagnetic films in the lamination provide antiferromagnetic coupling of the magnetically permeable films in the lamination.
7. The medium of claim 1 wherein the SL is formed of a material selected from Ta, Cr, Au, Cu, Si, Pd, Pt and a RuCr alloy.
8. The medium of claim 1 wherein the RL is selected from a chemically-ordered alloy selected from alloys of FePt, CoPt, FePd, CoPd, CoPt 3 and CoPd 3 ; a chemically-ordered L1 0 or L1 1 phase alloy selected from FePt—X and CoPt—X, where the element X is selected from the group consisting of Ni, Au, Cu, Pd and Ag; and a multilayer selected from the group consisting of Co/Pt, Co/Pd, Co/Ni, Fe/Pt and Fe/Pd multilayers.
9. The medium of claim 1 wherein the RL is a multilayer selected from the group consisting of Co/Pt, Co/Pd, Co/Ni, Fe/Pt and Fe/Pd multilayers.
10. The medium of claim 9 wherein the SL is selected from a Ta/Pd bilayer, a Ta/Pt bilayer, a Si/Au/Pd trilayer and a Si/Au/Pt trilayer.
11. A magnetic recording disk drive comprising:
a magnetic recording disk comprising:
a substrate having a substantially planar surface;
a soft underlayer (SUL) of soft magnetically permeable material on the substrate surface and having a planar surface;
an exchange break layer (EBL) of nonmagnetic material comprising a base layer of EBL material covering the entire planar surface of the SUL and a plurality of pillars of EBL material extending from the base layer of EBL material; and
a plurality of discrete islands, each island located on a pillar of EBL material and comprising a flux channeling layer (FCL) on the EBL material of the pillar and prevented from exchange coupling with the SUL by the EBL material, a perpendicular magnetic recording layer (RL), and a nonmagnetic separation layer (SL) on the FCL between the FCL and the RL for preventing magnetic exchange coupling between the FCL and the RL, the FCL formed of a soft magnetic material having an anisotropy field lower than the anisotropy field of the RL and a magnetization higher than the magnetization of the material of the RL, the RL and FCL having parallel magnetizations perpendicular to the substrate surface;
a write head for switching the magnetization of the RL in the data islands; and
a read head for reading the magnetized RL in the data islands.