Radial magnetic field reset system for producing single domain soft magnetic underlayer on perpendicular magnetic recording medium
View Patent ↗A radial magnetic field reset apparatus including a housing having a cavity with a soft magnet rod disposed at its center and a permanent magnet disposed around the cavity. The cavity and thickness of the soft magnet rod are sized to permit a cassette of disks to be inserted into the housing with the soft magnet rod disposed within the inner diameter holes of the disks contained in the cassette. The soft magnet rod at the center of the housing attracts the magnetic field generated by the permanent magnet, which results in a substantially uniform, radial magnetic field inside the housing.
1. A method, comprising:
generating a substantially radial magnetic field over a plurality of disks with respect to a center of each of the plurality of disks, each of the plurality of disks comprising a soft magnetic underlayer (SUL) structure; and
concurrently inducing a substantially single domain state in the SUL structure of each of the plurality of disks using the substantially radial magnetic field, wherein generating the substantially radial magnetic field over the plurality of disks comprises:
providing a soft magnet rod within respective inner diameter holes of the plurality of disks; and
providing a permanent magnet outside of respective outer diameters of the plurality of disks to generate a magnetic field, wherein the soft magnetic rod attracts the magnetic field from the permanent magnet to generate the substantially radial magnetic field over the plurality of disks.
2. The method of claim 1 , wherein each of the plurality of disks further comprises a hard magnetic pinning layer and wherein the SUL structure comprises a soft ferromagnetic film.
3. The method of claim 2 , wherein the substantially radial magnetic field has a strength in approximately a range of 1000 Oe to 6000 Oe.
4. The method of claim 2 , wherein inducing the substantially single domain state in the SUL structure of the plurality of disks comprises:
aligning the hard magnetic pinning layer of each of the plurality of disks in a substantially uniform radial direction using the substantially radial magnetic field; and
providing a bias field to the SUL structure of each of the plurality of disks using the aligned hard magnetic pinning layer to induce the substantially single domain state in the soft ferromagnetic film.
5. The method of claim 1 , wherein the substantially radial magnetic field has a strength greater than approximately 500 Oe.
6. The method of claim 1 , wherein the substantially radial magnetic field has a strength of approximately 1500 Oe or greater.
7. The method of claim 1 , further comprising providing the plurality of disks in a completed fabrication state prior to inducing the substantially single domain state in the SUL structure of each of the plurality of disks using the substantially radial magnetic field.
8. The method of claim 1 , wherein the substantially radial magnetic field extends along a direction perpendicular to a diameter of each of the plurality of disks for a distance greater than a combined thickness of all of the plurality of disks.
9. A method, comprising:
disposing a soft magnet rod within an inner diameter hole of a magnetic recording disk comprising a soft magnetic underlayer (SUL) structure;
disposing a permanent magnet outside of an outer diameter edge of the disk;
generating a substantially radial magnetic field over the magnetic recording disk, with respect to a center of the magnetic recording disk, using the soft magnet rod and the permanent magnet; and
inducing a substantially single domain state in the SUL structure of the magnetic recording disk using the substantially radial magnetic field.
10. The method of claim 9 , wherein the soft magnet rod is maintained out of physical contact with the magnetic recording disk.
11. The method of claim 9 , wherein the substantially radial magnetic field has a strength greater than approximately 500 Oe.
12. The method of claim 10 , wherein the substantially radial magnetic field has a strength of approximately 1500 Oe or greater.
13. The method of claim 9 , further providing the magnetic recording disk in a completed fabrication state prior to disposing the soft magnet rod within the inner diameter hole of the magnetic recording disk.
14. A method, comprising:
disposing a soft magnet rod within an inner diameter hole of a magnetic recording disk comprising a soft magnetic underlayer (SUL) structure;
disposing a permanent magnet outside of an outer diameter edge of the disk;
generating a substantially radial magnetic field over the magnetic recording disk, with respect to a center of the magnetic recording disk, using the soft magnet rod and the permanent magnet; and
inducing a substantially single domain state in the SUL structure of the magnetic recording disk using the substantially radial magnetic field, wherein the magnetic recording disk further comprises a hard magnetic pinning layer and wherein the SUL structure comprises a soft ferromagnetic film.
15. The method of claim 14 , wherein inducing the substantially single domain state in the SUL structure comprises:
aligning the hard magnetic pinning layer in a substantially uniform radial direction using the substantially radial magnetic field; and
providing a bias field to the SUL using the aligned hard magnetic pinning layer to induce the substantially single domain state in soft ferromagnetic film.
16. The method of claim 14 , wherein the substantially radial magnetic field has a strength in approximately a range of 1000 Oe to 6000 Oe.