Abstract: A method is described for adjusting magnetic properties of iron-containing magnetic films. The coercivity of magneto-optic films such as bismuth garnet films is adjusted by an annealing method which comprises reduction with a reducing agent such as H.sub.2 followed by oxidation using an oxidizing agent such as O.sub.2 and/or O.sub.3 to adjust to required coercivity levels with the sequence of reduction followed by oxidation repeated one or more times to obtain required coercivity. It is also an aspect of the invention to precede the first reducing treatment with an oxygen annealing step to enhance uniformity of the switching field.

Abstract: A bistable single crystal magneto-optic film of preselected coercivity is described. The film is readily switchable and is characterized by a substantially square shaped hysteresis loop. The film properties are attributed to controlled introduction in the film of defects of predetermined size and distribution. Defects of from about 0.4 .mu.m to about 4.0 .mu.m present in numbers per cm.sup.2 of from about 10 to about 10.sup.6, with optimal distribution falling in the range of from about 100 to about 1000, are described. Also described are methods of achieving the required defect size and distribution utilizing procedures such as ion bombardment, particle abrasion/deposition, laser ablation or annealing of the film or substrate upon which the film is supported. Devices in which the films can be used to advantage, such as flaw detecting, imaging and microwave processing, are described.

Abstract: A method of forming an epitaxial layer of an oxidic high T.sub.c superconductor on a substantially lattice matched monocrystalline substrate is described. The film is formed by liquid phase epitaxy utilizing a melt containing a nutriment composed of oxides of each element of the oxidic superconductor and a non-oxidic flux for such oxides. The preferred flux is an alkali halide. The monocrystalline substrate on which the film is dsposited is introduced into the melt and an epitaxial layer of oxidic superconductor is formed on the substrate.