System and method for manipulating domain pinning and reversal in ferromagnetic materials
A method for manipulating domain pinning and reversal in a ferromagnetic material comprises applying an external magnetic field to a uniaxial ferromagnetic material comprising a plurality of magnetic domains, where each domain has an easy axis oriented along a predetermined direction. The external magnetic field is applied transverse to the predetermined direction and at a predetermined temperature. The strength of the magnetic field is varied at the predetermined temperature, thereby isothermally regulating pinning of the domains. A magnetic storage device for controlling domain dynamics includes a magnetic hard disk comprising a uniaxial ferromagnetic material, a magnetic recording head including a first magnet, and a second magnet. The ferromagnetic material includes a plurality of magnetic domains each having an easy axis oriented along a predetermined direction. The second magnet is positioned adjacent to the magnetic hard disk and is configured to apply a magnetic field transverse to the predetermined direction.
1. A method for manipulating domain pinning and reversal in a ferromagnetic material, the method comprising:
applying an external magnetic field to a uniaxial ferromagnetic material comprising a plurality of magnetic domains each having an easy axis oriented along a predetermined direction, the external magnetic field being applied transverse to the predetermined direction and at a predetermined temperature; and
varying a strength of the external magnetic field at the predetermined temperature, thereby isothermally regulating pinning of the magnetic domains,
wherein, below a value H max of the external magnetic field, increasing the strength of the external magnetic field comprises increasing a pinning force of the magnetic domains, and
wherein, above a value H max of the external magnetic field, increasing the strength of the external magnetic field comprises decreasing a pinning force of the magnetic domains.
2. The method of claim 1 , wherein applying the external magnetic field comprises generating a site-random magnetic field in the ferromagnetic material.
3. The method of claim 1 , wherein applying the external magnetic field comprises inducing quantum fluctuations in the ferromagnetic material.
4. The method of claim 1 wherein the strength of the external magnetic field is increased at the predetermined temperature.
5. The method of claim 1 , wherein the strength of the external magnetic field is increased to the value H max maximizing the pinning force.
6. The method of claim 1 wherein the strength of the external magnetic field is increased to a value approaching an anisotropy field of the ferromagnetic material.
7. The method of claim 1 wherein the predetermined temperature is at or about room temperature.
8. The method of claim 1 wherein the predetermined temperature is near the Curie point of the ferromagnetic material.
9. The method of claim 1 wherein the predetermined temperature is sufficiently far below the Curie point of the ferromagnetic material so as to be in a quantum mechanical regime.
10. The method of claim 1 wherein the ferromagnetic material comprises one or more metals selected from the group consisting of: transition metals and rare earth metals.
11. The method of claim 10 wherein the one or more metals are selected from the group consisting of: Ag, Au, Ce, Co, Cr, Dy, Er, Fe, Gd, Ho, Mn, Mo, Nb, Nd, Ni, Pd, Pt, Re, Rh, Ru, Sm, Ta and Y.
12. The method of claim 1 wherein the ferromagnetic material is a bulk ferromagnet.
13. The method of claim 1 wherein the ferromagnetic material is a thin-film ferromagnet.
14. The method of claim 13 wherein the thin-film ferromagnet is part of a magnetic hard disk.
15. The method of claim 14 wherein the predetermined direction is perpendicular to a surface of the magnetic hard disk.
16. The method of claim 14 wherein the predetermined direction is in a plane of a surface of the magnetic hard disk.
17. The method of claim 1 , wherein the uniaxial ferromagnetic material comprises random site disorder.