Preparation of heteroepitaxial SrRuO 3 thin film on Si substrate and microstructure of BaTiO 3 -NiFe 2 O 4 epitaxial com
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Preparation of heteroepitaxial SrRuO3 thin film on Si substrate and microstructure of BaTiO3-NiFe2O4 epitaxial composite thin film deposited on the SrRuO3 bottom electrode using PLD Naoki Wakiya1, Naonori Sakamoto1, Shigeki Sawamura1, Desheng Fu2, Kazuo Shinozaki3 and Hisao Suzuki2 1 Department of Materials Science and Chemical Engineering, Shizuoka University, 3-5-1 Johoku, Naka-ku, Hamamatsu 432-8561, Japan 2 Graduate School of Science and Technology, Shizuoka University, 3-5-1 Johoku, Naka-ku, Hamamatsu 432-8561, Japan 3 Department of Metallurgy and Ceramics Science, 2-12-1, O-okayama, Meguro-ku, Tokyo 1528550, Japan ABSTRACT A “0-0 type” multiferroic BaTiO3-NiFe2O4 (BT-NF) composite thin film was prepared on SrRuO3/(La,Sr)MnO3/CeO2/YSZ/Si(001) substrate using pulsed laser deposition (PLD). Epitaxial growth of the film was confirmed using x-ray pole figure measurements. Crosssectional TEM observations revealed that the crystal structure and morphology of the BT-NF composite thin film depends on the oxygen pressure during deposition. The film deposited at 1.0×10-2 Torr has smaller grains than that deposited at 1.0×10-1 Torr. The magnetic and ferroelectric properties of BT-NF composite thin film were correlated with the microstructure that was controlled by oxygen pressure during deposition. The film deposited at 1.0×10-2 Torr had paramagnetic properties with less polarization than the film deposited at 1.0×10-1 Torr. INTRODUCTION Multiferroic materials, which can be applied as novel memories and sensors, are categorizable into two groups. Those consisting of TbMnO31), DyMnO32), TbMn2O53), BiFeO34) or Ba0.5Sr1.5Zn2Fe12O225) show both ferroelectricity and either ferromagnetism or antiferromagnetism simultaneously. However, the transition temperature of these substances lay in the ultralow temperature region except for BiFeO3. Materials of the second group include composites such as BaTiO3(BT)-Ni(Co,Mn)Fe2O46), Pb(Zr,Ti)O3 (PZT)- Tb1-XDyXFe2 (TerfenolD)7), and BaTiO3-LaMnO38). In this second group, the combination of ferroelectric and ferromagnetic materials with high transition temperature is useful. The multiferroic composites can be further classified into the following three groups: (a) 2-2 type, (b) 1-3 type, and (c) 3-3 type. The 2-2 type is a stacked structure. The 1-3 type has a characteristic structure in which ferromagnetic (ferroelectric) nanopillars are embedded in the ferroelectric (ferromagnetic) matrix. The 3-3 type is a three-dimensionally mixed composite of ferroelectric and ferromagnetic materials. Regarding processing, the 2-2 type is prepared using both vapor phase deposition and chemical solution deposition; stacked thin films consisting of ferroelectric and ferromagnetic layers are prepared. The 3-3 type is prepared using sol–gel processing using a precursor containing ferroelectric and ferromagnetic sol. The 1-3 type is prepared using vapor phase deposition. Zheng et al. first prepared this type using pulsed laser deposition (PLD) and a composite ceramic target. The product was a BaTiO3-CoFe2O4
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