Epitaxial SrRuO3 thin films were grown on both (100) and (111) SrTiO3 substrates with atomically flat surfaces that are required to grow high-quality films of materials under debate. The following notable differences were observed in the (111)-oriented SrRuO3 films: (1) slightly different growth mode, (2) approximately 10 K higher ferromagnetic transition temperature, and (3) better conducting behavior with higher relative resistivity ratio, than (100)c-oriented SrRuO3 films. Together with the reported results on SrRuO3 thin films grown on (110) SrTiO3 substrate, the different physical properties were discussed newly in terms of the Ru-Ru nearest neighbor distance instead of the famous tolerance factor.PACS75.70.Ak; 75.60.Ej; 81.15.Fg

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Unipolar resistive switching (URS) as well as bipolar resistive switching (BRS) behaviors in a Cu/TaOx/Pt structure were investigated. Upon increasing the compliance current (Ic), the current-voltage characteristics of the Cu/TaOx/Pt structure showed a URS behavior at Ic = 0.1 mA then experienced a non-reversible transition from the URS to a BRS mode at Ic = 10 mA. Through a detailed analysis of the electrical properties in each resistance state of URS and BRS, we revealed that the permanent transition from the URS to the BRS mode was induced by the formation of stronger Cu metal conductive filaments within the TaOx thin film. More interestingly, both URS and BRS modes were governed by the formation and rupture of conductive filaments, whereas the rupture of these filamentary paths in BRS was proposed due to both Joule heating and electric field effects.

Polycrystalline Ca 2 Fe 2Àx Al x O 5 (x = 0-1.4) samples were prepared by conventional solid-state reactions. Their crystalline/electronic structures and magnetic properties were characterized in detail. Powder X-ray diffraction analyses revealed that the samples crystallized in orthorhombic brownmillerite-type structures with the occurrence of the Pcmn-Ibm2 phase separation in the region between x = 0.4 and 0.6. The results obtained from analyzing Raman scattering and X-ray-absorption fine-structure spectra also indicated this phase separation. Although x in Ca 2 Fe 2Àx Al x O 5 varies in a wide range from 0 to 1.4, the +3 oxidation state of Fe remained almost unchanged. Magnetization measurements revealed that all Ca 2 Fe 2Àx Al x O 5 samples have weak ferromagnetic order, and both the saturation magnetization and coercive force are dependent on the temperature, x, and structure phases.