Fei-Xiang Wu

Metal–insulator transition in SrIrO3 with strong spin–orbit interaction

The thickness-dependent metal-insulator transition is observed in meta-stable orthorhombic SrIrO3 thin films synthesized by pulsed laser deposition. SrIrO3 films with thicknesses less than 3 nm demonstrate insulating behaviour, whereas those thicker than 4 nm exhibit metallic conductivity at high temperature, and insulating-like behaviour at low temperature. Weak/Anderson localization is mainly responsible for the observed thickness-dependent metal-insulator transition in SrIrO3 films. Temperature-dependent resistance fitting shows that electrical-conductivity carriers are mainly scattered by the electron-boson interaction rather than the electron-electron interaction. Analysis of the magneto-conductance proves that the spin-orbit interaction plays a crucial role in the magneto-conductance property of SrIrO3.

Significant ferrimagnetism observed in Aurivillius Bi4Ti3O12 doped by antiferromagnetic LaFeO3

Highly crystalline quality c-axis epitaxial nLaFeO3–Bi4Ti3O12 (n=0.5,1.0,1.5) thin films were deposited on SrTiO3 (001) substrates by pulsed laser deposition. The x-ray diffraction and transmission electron microscopy characterizations confirm that there are designed even-odd number perovskite-block structures in n=0.5 and 1.5 films while it has even-even number ones in n=1.0 films. The remarkable physical property of n=0.5 and 1.5 samples is the presence of ferrimagnetism even up to room temperature. While it is antiferromagentic property in n=1.0 sample. The observed ferrimagentism is explained qualitatively by considering the crystal structure in nLaFeO3–Bi4Ti3O12.

Significant ferrimagnetisms observed in superlattice composed of antiferromagnetic LaFeO3 and YMnO3

A series of LaFeO3/YMnO3 superlattices with various thicknesses are synthesized epitaxially on (001) and (111) SrTiO3 substrates. X-ray diffraction, high-resolution cross-sectional transmission electron microscopy, and sub-nanometer-scale resolved electron energy loss spectroscopy characterizations prove that grown superlattices have designed layer-by-layer structures, and there is atomically sharp interface between two successive constituent layers. Temperature-dependent magnetization and magnetic hysteresis loop measurements substantiate that there is significant ferrimagnetism generated at LaFeO3/YMnO3 interfaces. The generated ferrimagnetism is discussed by considering the magnetic structures in each constituent layer.

Microstructure and ferromagnetic property in CaRuO3 thin films with pseudoheterostructure

CaRuO3 thin films were synthesized on SrTiO3 substrates by pulsed laser deposition. Detailed microstructure analysis by transmission electron microscopy revealed the pseudoheterostructure in CaRuO3 films. It consists of a coherently strained cubic CaRuO3 layer contacted with substrate, as well as a strained orthorhombic CaRuO3 layer. The orthorhombic CaRuO3 layer is composed of two types of domains. The ferromagnetic property of the pseudoheterostructure CaRuO3 was revealed by superconducting quantum interference device measurement. This is due to the cubic CaRuO3 layer, which is supported by first-principle calculations. The formation mechanism of pseudoheterostructure in ultrathin CaRuO3 thin films was proposed.

The Microstructural Characterization of Multiferroic LaFeO3-YMnO3 Multilayers Grown on (001)- and (111)-SrTiO3 Substrates by Transmission Electron Microscopy

The microstructure of multiferroic LaFeO3-YMnO3 (LFO-YMO) multilayers grown on (001)- and (111)-SrTiO3 substrates is characterized by the transmission electron microscopy (TEM). Detailed TEM characterization reveals that LFO-YMO multilayers grown on both substrates have clear layer-by-layer morphology and distinct chemical-composition layered structure. The most notable feature is that LFO-YMO multilayers grown on (001)-SrTiO3 substrate have three types of domains, while those on (111)-SrTiO3 have only one. The multi-/twin- domain structure can be qualitatively explained by the lattice mismatch in this system. The details of the domain structure of LFO-YMO multilayers are crucial to understanding their magnetic properties.