Magnetic media with improved exchange coupling
View Patent ↗A magnetic recording medium includes a substrate, an underlayer, a lower magnetic layer formed on the underlayer, an intermediate layer, and an upper magnetic layer formed on the intermediate layer. The intermediate layer is typically Ru, and promotes anti ferromagnetic coupling between the upper and lower magnetic layers. The upper and lower magnetic layers are typically Co alloys. The lower magnetic layer has a high saturation magnetization Ms to promote high exchange coupling between the upper and lower magnetic layers. The dynamic coercivity of the lower magnetic layer is lower than the exchange field to ensure rapid switching of the lower magnetic layer.
1. A magnetic disk drive comprising:
a magnetic disk containing recorded dare;
a read-write head; and
a motor coupled to rotate said magnetic disk at a rotational velocity during ordinary operation of said disk drive;
said magnetic disk comprising:
a substrate;
a lower magnetic layer structure formed over the substrate;
an intermediate layer comprising Ru; and
an upper magnetic layer structure formed over the intermediate layer, said upper magnetic layer structure being antiferromagnetically coupled to the lower magnetic layer structure, wherein the relationship between the dynamic coercivity of the lower magnetic layer structure and the exchange field is such that after termination of application of a write magnetic field to the usable locations on the disk the portion of the lower magnetic layer structure at said locations achieve substantially their steady magnetization state within the time required for one revolution of said disk when said disk is being rotated at said rotational velocity.
2. Magnetic disk drive or claim 1 further comprising an underlayer formed between the substrate and the lower magnetic layer structure, and wherein at least one of said upper and lower magnetic layer structures comprises a plurality of layers.
3. A magnetic disk drive comprising:
a magnetic disk containing recorded data;
a read-write head; and
a motor coupled to rotate said magnetic disk at a rotational velocity during ordinary operation of said disk drive;
said magnetic disk comprising:
a substrate;
a lower magnetic layer structure formed over the substrate;
an intermediate layer comprising Ru; and
an upper magnetic layer structure formed over the intermediate layer, said upper magnetic layer structure being antiferromagnetically coupled to the lower magnetic layer structure, wherein the relationship between the dynamic coercivity of the lower magnetic layer structure and the exchange field is such that after termination of application of a write magnetic field to the usable locations on the disk the portion of the lower magnetic layer structure at said locations achieve more than 90% of their steady magnetization state within the time required for one revolution of said disk when said disk is being rotated at said rotational velocity.
4. Magnetic disk drive of claim 3 further comprising an underlayer formed between the substrate and the lower magnetic layer structure, and wherein at least one of said upper and lower magnetic layer structures comprise a plurality of layers.
5. Magnetic disk drive of claim 3 wherein the relationship between the dynamic coercivity of the lower magnetic layer structure and the exchange field is such that after termination of application of a write magnetic field to the usable locations on the disk the portion of the lower magnetic layer structure at said locations achieves more than 95% of their steady magnetization state within the time required for one revolution of said disk when said disk is being rotated at said rotational velocity.
6. Method for using a magnetic disk drive, said magnetic disk drive comprising a magnetic disk containing recorded data, a read-write head, and a motor coupled to rotate said magnetic disk at a rotational velocity during ordinary operation of said disk drive, said magnetic disk comprising a substrate, a lower magnetic layer structure formed over the substrate, an intermediate layer comprising Ru, and an upper magnetic layer structure formed over the intermediate layer, said upper magnetic layer structure being antiferromagnetically coupled to the lower magnetic layer structure, said method comprising:
rotating said magnetic disk;
recording data in said magnetic disk by applying a write magnetic field to locations on said magnetic disk; and
terminating application of said write magnetic field to said locations on said magnetic disk, wherein the relationship between the dynamic coercivity of the lower magnetic layer structure and the exchange field is such that after said termination the portion of the lower magnetic layer structure at said locations achieve substantially their steady magnetization state within the time required for one revolution of said disk when said disk is being rotated at said rotational velocity.
7. Method of claim 6 wherein said magnetic disk further comprises an underlayer formed between the substrate and the lower magnetic layer structure, and wherein at least one of said upper and lower magnetic layer structures comprises a plurality of layers.
8. Method for using a magnetic disk drive, said magnetic disk drive comprising a magnetic disk containing recorded data, a read-write head, and a motor coupled to rotate said magnetic disk at rotational velocity during ordinary operation of said disk drive, said magnetic disk comprising a substrate, a lower magnetic layer structure formed over the substrate, an intermediate layer comprising Ru, and an upper magnetic layer structure formed over the intermediate layer said upper magnetic layer structure being antiferromagnetically coupled to the lower magnetic layer structure, said method comprising:
rotating said magnetic disk;
recording data in said magnetic disk by applying a write magnetic field to locations on said magnetic disk; and
terminating application of said write magnetic field to said locations on said magnetic disk, wherein the relationship between the dynamic coercivity of the lower magnetic layer structure and the exchange field is such that after said termination the portion of the lower magnetic layer structure at said locations achieve more than 90% of their steady magnetization state within the time required for one revolution of said disk when said disk is being rotated at said rotational velocity.
9. Method of claim 8 wherein the relationship between the dynamic coercivity of the lower magnetic layer structure and the exchange field is such that after termination of application of a write magnetic field to the usable locations on the disk the portion of the lower magnetic layer structure at said locations achieves more than 95% of their steady magnetization state within the time required for one revolution of said disk when said disk is being rotated at said rotational velocity.
10. Method of claim 8 wherein said magnetic disk further comprises an underlayer formed between the substrate and the lower magnetic layer structure, and wherein at least one of said upper and lower magnetic layer structures comprises a plurality of layers.