Abstract: A thick film bismuth doped rare earth iron garnet greater than 50 ?m in thickness with a growth-induced uniaxial anisotropy less than zero, such that all the magnetic domains in the film have their magnetization vectors in the plane of the film. A preferred embodiment comprises a film of composition Bi1.13Gd1.36Lu0.51Fe4.55Ga0.45O12. Films with such anisotropy solve the problem of devices and sensors that require a continuously varying Faraday rotation without the effective insertion losses that are inherent to discrete perpendicular domains. A similar effect can be achieved with a film of perpendicular domains by launching the light in the plane of the thick film in a non-waveguiding mode as opposed to the conventional perpendicular direction.

Abstract: In an arrangement substantially like an optical isolator, appropriate choice of the composition of the magneto-optic element can result in a variable optical attenuator. The composition is selected to vary in the direction of light propagation, and also is selected such that the magneto-optic element comprises a compensation wall. The compensation wall is movable in response to a change in the temperature of the magneto-optic element, whereby the attenuation of the device is changed.

Abstract: Garnet material according to a particular embodiment of the invention exhibits a substantially rectangular magnetization loop, with .vertline.H.sub.S .vertline.>.vertline.4.pi.M.sub.S .vertline.Oe and .vertline.4.pi.M.sub.s .vertline.<100 G over a predetermined operating range (e.g., -40.degree. to +80.degree. C.), where H.sub.S is the switching magnetic field of the loop, and 4.pi.M.sub.S is the saturation magnetization. The material exhibits improved latching behavior. In a further embodiment of the invention the composition of the garnet material is selected such that the material exhibits hard latching behavior (.vertline.H.sub.s .vertline.>500 Oe) at least at room temperature. Garnet materials according to the invention can advantageously be used in magneto-optic isolators and other magneto-optic devices. For instance, the material enables manufacture of isolators that do not contain a bias magnet.