  Epitaxial thin film fabrication of iron oxides including magnetite Fe3O4 and
epsilon-ferrite epsilon-Fe2O3 with the potential for advancing electromagnetic
devices has been investigated, which led to the first ever epsilon-ferrite
epitaxial layer being synthesized in the conventional sputtering process.
Concerning Fe3O4 (100) / MgO (100) films, a cube-on-cube epitaxial relationship
and sharp rocking curves with FWHM of 50 - 350 arcsec were confirmed regardless
of the small amount of Ge additions. Sputtering Ar gas pressure PAr heavily
influenced their magnetic and transport properties. High PAr = 15 mTorr caused
a high magnetization of 6.52 kG for the Ge added sample and the clear Verwey
transition at 122 K for the non Ge addition case. Conversion electron Mossbauer
spectroscopy (CEMS) measurements revealed that low PAr < 10 mTorr causes Fe/O
off-stoichiometry on the oxidizing side for the non Ge addition case and the
reductive side for the Ge addition case, respectively. Regarding the
epsilon-Fe2O3 (001) / SrTiO3(111) epilayer synthesis, bilayer microstructure
composed of an approximately 5nm thick initially grown epsilon-Fe2O3 (001)
epilayer and subsequently grown e-Fe2O3 (001) epilayer was confirmed from
cross-sectional TEM observations. The coexistence of magnetically hard and soft
phases was confirmed from the magnetization measurements. As a possible
application of the single nm thick epsilon-Fe2O3 layer, 4-resistive-state
multiferroic tunnel junction (MFTJ) is considered.
