Abstract

Epitaxial thin film fabrication of iron oxides including magnetite Fe₃O₄ and epsilon-ferrite ε-Fe₂O₃ with the potential for advancing electromagnetic devices has been investigated, which led to the first ever ε-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 P_Ar heavily influenced their magnetic and transport properties. High P_Ar=15m Torr caused a high magnetization of 6.52 kG for the Ge added sample and the clear Verwey transition at 122K for the non Ge addition case. Conversion electron Mössbauer spectroscopy (CEMS) measurements revealed that low P_Ar< 10m Torr 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 α-Fe₂O₃ (001)/SrTiO3 (111) epilayer synthesis, bilayer microstructure composed of an approximately 5nm thick initially grown ε-Fe₂O₃ (001) epilayer and subsequently grown ε-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 ε-Fe₂O₃ layer, 4-resistive-state multiferroic tunnel junction (MFTJ) is considered.