Perpendicular magnetic recording disk with recording layer containing selected metal oxides and formed on a reduced-thickness exchange-break layer
View Patent ↗A perpendicular magnetic recording disk has a granular Co-based ferromagnetic alloy recording layer (RL) with oxides of a selected metal (Ta or Nb) and a reduced-thickness exchange-break layer (EBL) between the RL and the soft magnetic underlayer (SUL). A perpendicular magnetic recording system that includes the disk, the write head and the read head, has an improved ability to write to the RL because of the reduced-thickness EBL.
1. A perpendicular magnetic recording disk comprising:
a substrate;
an underlayer of magnetically permeable material on the substrate;
a granular perpendicular magnetic recording layer consisting essentially only of Co, Pt, Cr, Ta and oxygen, wherein the amount of Ta present in the recording layer is greater than about 2 atomic percent and less than about 5 atomic percent, the recording layer having a hexagonal-close-packed (hcp) crystalline structure with the c-axis oriented substantially perpendicular to the recording layer and inter-granular material comprising oxides of Ta;
an exchange-break layer between the underlayer and the recording layer for magnetically decoupling the recording layer and the underlayer, the exchange-break layer being a nonmagnetic hcp material selected from the group consisting of Ru and Ru-based alloys, the exchange-break layer having a thickness greater than 8 nm and less than 14 nm; and
a seed layer between the underlayer and the exchange-break layer for encouraging the hcp growth of the exchange-break layer, the seed layer comprising an alloy of Ni and an element selected from the group consisting of Fe, V and W, the exchange-break layer being directly on and in contact with the seed layer;
wherein the recording layer has a coercivity H c greater than about 5000 Oe and a nucleation field H n more negative than about −1500 Oe.
2. A perpendicular magnetic recording system comprising:
the disk of claim 1 ;
a write head for magnetizing regions in the recording layer of said disk; and
a read head for detecting the transitions between said magnetized regions.
3. The disk of claim 1 wherein the amount of oxygen present in the recording layer is greater than about 22 atomic percent and less than about 35 atomic percent.
4. The disk of claim 1 wherein the recording layer is an antiferromagnetically-coupled (AFC) recording layer comprising first and second granular ferromagnetic alloy layers separated by a nonmagnetic antiferromagnetically-coupling layer, each of said first and second layers consisting essentially only of Co, Pt, Cr, Ta and oxygen, wherein the amount of Ta present in each of said first and second layers is greater than about 2 atomic percent and less than about 5 atomic percent and each of said first and second layers has a hexagonal-close-packed (hcp) crystalline structure with the c-axis oriented substantially perpendicular to the layer and inter-granular material comprising oxides of Ta, said first layer being located between the exchange-break layer and said second layer, the AFC recording layer having a substantial net magnetic moment in the absence of an applied magnetic field.
5. The disk of claim 1 wherein the underlayer of magnetically permeable material 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.
6. The disk of claim 1 wherein the underlayer of magnetically permeable material is a lamination of multiple magnetically permeable films separated by nonmagnetic films.
7. The disk of claim 6 wherein the nonmagnetic films in the lamination provide antiferromagnetic coupling of the magnetically permeable films in the lamination.