BISUBSTITUTED IRON-GARNET FILMS WITH FINE GRAINS PREPARED BY PYROLYSIS

Polycrystalline films of Y3-xBi(x)Fe5-yAl(y)O12 (x = 0.5-2.0, y = 0-1.2) were prepared on glass substrates by pyrolysis combined with spin-coating techniques. SEM and TEM studies revealed that the grain size increases with x but decreases with y. This means that enhancing the magneto-optical effect by increasing x results in large grain size, which causes a strong media noise due to light scattering at grain boundaries. To solve this problem we have made double-layer films. An underlayer of polycrystalline film low in x, hence small in grain size, was first made by a conventional pyrolysis process. On this an upper layer high in x was made. The upper layer was crystallized at a temperature approximately 50-degrees-C lower and was ten times smaller in grain size than the single-layer film with an equal x. Furthermore, the upper layer crystallized at the lower temperature (590-degrees-C) was exceedingly homogeneous.