Manufacture of magnetic materials which exhibit exchange anisotropy

US3961990A · kind A · utility

Assignee

• BASF SE

Inventors

• Eberhard Koester · Bischofswerda, DE
• Gerd Wunsch · Speyer, DE
• Paul Deigner · Bad Dürkheim, DE
• Karl Uhl
• Werner Stumpfi
• Werner Steck · Ludwigshafen, DE

Key dates

• Filing date: Dec 23, 1974
• Grant date: Jun 8, 1976
• Expiry date: Dec 23, 1994

Classification

• Technology area (CPC H): Electricity
• CPC primary: H01F1/12
• WIPO field: Electrical machinery, apparatus, energy
• WIPO sector: Electrical engineering

Abstract

A process for the manufacture of magnetic materials containing a phase A with a ferromagnetic spin system, of composition Co.sub.x Ni.sub.1.sub.-x and a phase B with an antiferromagnetic spin system of composition (CoO).sub.x (NiO).sub.1.sub.-x , with values of x from 0.05 to 0.96, the phases A and B showing exchange interaction. The materials are manufactured by surface oxidation of starting materials having a ferromagnetic layer, at least on the surface but optionally extending deeper, of composition A, to produce the antiferromagnetic phase B, nitrous oxide being used as the oxidant. Magnetic materials thus obtained have an asymmetrical hysteresis loop, which manifests itself at different temperatures, namely the particular Neel temperature of the phase B, which depends on the composition of the phases which varies in accordance with the values of x.