Patent US 3,949,387

A beam addressable file using as a storage medium an amorphous magnetic composition having uniaxial anisotropy. The storage medium can be prepared in thin film or bulk form or as particles in a binder. The storage medium can be comprised of a single element or a multicomponent system where at least one of the components has an unpaired spin so that the composition has a net magnetic moment. The storage comosition exists in a microcrystalline structure (i.e., it has localized atomic ordering over a distance 25-100 angstroms) and also in a substantially amorphous structure (i.e., when the composition has localized atomic ordering only over distances less than 25 angstroms). Binary and ternary compositions, either alloys or compounds, are suitable. particularly good examples are combinations of rare earth elements and transition metal elements. The magnetic properties of these amorphous magnetic compositions are easily changed during fabrication or after fabrication, and the compositions can be doped readily without adversely affecting magnetic properties. Either electron beams or light beams can be used to write information into the storage medium and optical readout is generally preferred. Curie point writing or compensation point writing is used.