Epitaxial Single Crystalline Ferrite Films for High Frequency Applications

Abstract

AbstractThe successful growth of single crystal ferrites in thin film form is an important step towards their future incorporation into integrated circuits operating at microwave frequencies. We have successfully grown high quality single crystalline spinel ferrite thin films of (Mn, Zn)Fe2O4 and CoFe2O4 on (100) and (110) SrTiO3 and MgAl2O4 at low temperature. These ferrite films are buffered with spinel structure layers that are paramagnetic at room temperature. In contrast to ferrite films grown directly on the substrates, ferrite films grown on buffered substrates exhibit excellent crystallinity and bulk saturation magnetization values, thus indicating the importance of lattice match and structural similarity between the film and the immediately underlying layer. X-ray, RBS, AFM and TEM analysis provide a consistent picture of the structural properties of these ferrite films. We then use this technique to grow exchange-coupled bilayers of single crystalline CoFe2O4 and (Mn, Zn)Fe2O4. In these bilayers, we observe strong exchange coupling across the interface that is similar in strength to the exchange coupling in the individual layers.