Growth and properties of stable self-biasing double layer epitaxial garnet films

One of the most important problems in maintaining self-sustained bubble domains in the top layer of double-layer epitaxial garnet films is stability of the magnetic saturation in the bottom layer, Because the stability depends on the nucleation field of the bottom layer, it is desirable to minimize any defects in the bottom layer. For this purpose double-layer epitaxial films were cut by a chemical etching technique to prevent any bad effect due to defects or magnetic spin disorder in the film edges. This method caused a drastic effect on the stability of the magnetic saturation in the bottom layers showing a high yield of more than 95 %. The second problem is the temperature sensitivity of the self-sustained bubbles which proved to depend on the temperature sensitivity of the characteristic length of the top layer. In the best result less than 3 %/°C was obtained so far. The self-biasing effect in the double layer epitaxial garnet films is discussed with respect to the wall energies and anisotropy fields of the various top and bottom layer films. The maximum effective field of 30 Oe was obtained in a (YSm)3GaIG/(EuEr)3GaIG system and 6 μm-diameter bubbles were driven by a conventional T-bar circuit.