Ys. Cho et al., ENHANCED MICROWAVE MAGNETIC PROPERTIES-IN NONSTOICHIOMETRIC YTTRIUM IRON GARNETS FOR HIGH-POWER APPLICATIONS, IEEE transactions on magnetics, 34(4), 1998, pp. 1387-1389
A nonstoichiometric 3 mol% Fe-deficient deficient yttrium iron garnet
composition (Y3Fe4.85O12) chemically-modified with Si and Mn was inves
tigated with regard to microstructure characteristics and microwave ma
gnetic properties for high power applications. The two additives, Si a
nd Mn were added to the garnet composition by a chemical method utiliz
ing a sol-gel reaction. The samples were sintered at 1500 degrees C fo
r 3 hrs in O-2. An increase;,in Si content tends to increase bulk dens
ity and to decrease grain size. An yttrium-rich second phase found in
pure Y3Fe4.85O12 was observed to disappear with a sufficient amount of
the additives. The improved microstructural characheristics were beli
eved to contribute to the enhanced microwave magnetic properties of th
e garnets. For example, spin wave line width, Delta H-k, which is a ke
y factor for this application, was found to increase from 3.1 Oe to 12
.6 Oe by adding 0.6 wt% SiO2 and 0.15 wt% MnO2, This can be attributed
to smaller grain size and elimination of the Y-rich phase.