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Permanent Decoration of Magnetic Domain Walls

IP.com Disclosure Number: IPCOM000085377D
Original Publication Date: 1976-Mar-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 3 page(s) / 30K

Publishing Venue

IBM

Related People

Gambino, RJ: AUTHOR [+3]

Abstract

A method has been devised for the permanent high-resolution decoration of magnetic domain walls by a fixing technique utilizing conventional ferrofluids.

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Permanent Decoration of Magnetic Domain Walls

A method has been devised for the permanent high-resolution decoration of magnetic domain walls by a fixing technique utilizing conventional ferrofluids.

As seen in the figure, a neutral substrate 2 supports a 1 micron thick film 4 of magnetic material. The magnetic film 4 has alternating regions of magnetic domains 6 that are separated by walls or domains 8. If a ferrofluid 12 is deposited over the magnetic film 4, magnetic particles 10 in such ferrofluid will deposit out on high-field regions adjacent a wall 8.

A normal ferrofluid 12 comprises a liquid suspension of magnetic particles that are about 100-500 Angstroms diameter particles suspended in a liquid of water, ethylene-glycol or kerosene. The magnetic particles are usually Gamma - Fe(2)O(3) or Fe(3)O(4).

Surfactants are added to the suspension, which surfactant acts as a sheath around each magnetic particle 10. Consequently, the particles 10 remain separated in the absence of a strong magnetic field. In the vicinity of each domain wall 8 of the thin magnetic film 4 there is a strong magnetic field; the magnetic particles 10 adhere to the magnetic film 4 in these regions.

A method has been found in which the excess particles 10 that do not contribute to pattern formation are easily removed. The colloidal stability of the water base ferrofluid 12 is destroyed by the addition of isopropyl alcohol. The alcohol dissolves the surfactants on the surface of the magnetite particles 10. This causes flocculation of the colloid.

The magnetite particles 10 that are not tightly bound in pattern formation aggregate. The aggregates are large (1000 angstrom) clusters of particles that do not interact with the existing pattern, and due to their size can easily be flushed away. A gentle rinse in alcohol will wash away only those...