David Warren Douglass

US Patent:

58305882, Nov 3, 1998

Filed:

Mar 16, 1993

Appl. No.:

8/033257

Inventors:

David C. Douglass - Freehold NJ
Jean Pierre Bucher - Lausanne, CH
Louis Aub Bloomfield - Charlottesville VA

Assignee:

University of Virginia Patent Foundation - Charlottesville VA

International Classification:

G11B 566
B05D 212

US Classification:

428694B

Abstract:

The invention relates to a method of producing a magnetic material for use in an ultrahigh density magnetic recording medium and to the medium itself. The method general includes the steps of vaporing a ferromagnetic lanthanide rare earth, growing clusters of the ferromagnetic lanthanide rare earth at a temperature below the temperature at which the ferromagnetic lanthanide rare earth forms locked-moment clusters, filtering superparamagnetic clusters from locked-moment clusters, and collecting the locked-moment clusters. Preferably, the ferromagnetic lanthanide rare earth is a ytterbium rare earth. Advantageously lanthanide alloys, mixtures of lanthanide rare earths and alloys of a mixture of lanthanide rare earths can be used. The filtering employs a gradient magnetic field to separate superparamagnetic clusters from moment-locked clusters. The gradient field magnet separates the superparamagnetic clusters which deflect by a large amount from the locked-moment clusters which deflect by a small amount.