The Structure And Physical Properties Of Epitaxial Perovskite Bilayers Under Multidimensional Cooperation Adjustment

The perovskite oxides heterostructures or multilayers have shown rich and fascinating physical properties due to the strong correlation among spin,charge,orbital and lattice degrees of freedom at the interface of different perovskite oxides.To understand the underlying physics and pursue effective regulation,have become the hot issues in physical and material science.The epitaxial strain,octahedral proximity effect,and interfacial exchange coupling have shown critical and effective regulation of the structural and physical properties for the perovskite oxides heterostructures and multilayers.On the other hand,the substrate-orientation change gives rise to the different octahedral distortion/rotation,causing the magnetic and electronic properties of epitaxial films show highly dependent on substrate orientation.Meanwhile,the substrate-orientation change also induces different oxygen deficiency,further affecting the physical properties for the perovskite films.However,the investigation is mainly focused on that how the relative thickness/ratio of the constituent layers and the lattice/symmetry mismatch affect the interfacial structure/interaction and then the physical properties of perovskite-type oxides heterostructures or multilayers.Thus,it is still an open issue that how the substrate orientation dependent multidimensional cooperation affect the structure and then the performance of perovskite oxides bilayers,which is important for theory research and industrial application.Herein,the multidimensional cooperation effects of the substrate-orientation dependent oxygen deficiency,lattice mismatch-induced strain,and interfacial effects on the structure and the magnetoelectric properties of the epitaxial perovskite bilayers have been systematically investigated,with the respects to widen the tunable routes of the structural and physical properties of the perovskite-type multifunctional devices and their future industrial application.The detailed researches and results as follows:In introduction chapter,from the basic physics of perovskite oxides,we summarize the influence of lattice and symmetry mismatch induced epitaxial strain and interfacial coupling on the structural and physical properties of the perovskite-type thin films or heterostructures,analyze the relationship between the charge transfer and the interfacial magnetic properties of perovskite heterostructures,and emphasize the importance of substrate-orientation regulation in this work.In chapter 2,the perovskite La0.8Ca0.2MnO3/Ba0.8Sr0.2TiO3 bilayers were grown on single-crystal substrates by the polymer-assisted deposition(PAD),and the effects of annealing temperature,substrate orientation,and oxygen deficiency on the magnetic and transport properties of the bilayers have been investigated.It is found that the metal-insulator/ferromagnetic-paramagnetic transition temperatures of the bilayers change with different annealing temperature and show high dependence on substrate orientation.Moreover,the substrate-orientation change induces oxygen deficiency,coming out the low-temperature anormal metal-insulator transition and simultaneous ferromagnetic transition in the bilayers,dominated by the substrate orientation,oxygen deficiency,and their strong correlation.In chapter 3,the orthorhombic La0.7Ca0.3MnO3/DyMnO3 bilayers were grown on cubic substrates by PAD,and the effects of orientation-dependent interfacial coupling,oxygen deficiency,and orbital reconstruction on the physical properties of the bilayers have been investigated.It is found that the magnetic and transport properties of the bilayers are largely reduced due to the octahedral proximity effect required interfacial coupling,orientation adjusted oxygen deficiency,and the large/extra tensile strain induced orbital reconstruction,with the adjustion through substrate orientation change.In chapter 4,the perovskite NdNiO3/LaMnO3 bilayers were grown on single-crystal substrates by PAD,and the effects of substrate-orientation change on the magnetic and transport properties of the bilayers have been investigated.It is found that an anomalous low-temperature insulator-metal transition is observed,and the transition temperature shows high dependence on substrate orientation,as the magnetic properties of the bilayers,which is resulted from the substrate-orientation adj usted charge transfer and interlayer exchange coupling.In chapter 5,the perovskite La2NiMnO6/LaMnO3 bilayers were grown on single-crystal substrates by PAD,and the effects of the interfacial interaction on the Ni/Mn ordering and the corresponding magnetic and transport properties of the bilayer have been investigated.It is found that the Ni/Mn ordering increases,but the bilayer still shows two near ferromagnetic transition,which can be attributed to the Mn4+-O2--Ni2+ ferromagnetic superexchange interaction and the Mn4+-O2--Mn3+ferromagnetic double exchange interaction respectively.This is onset for the future research on the substrate-orientation adjusted Ni/Mn ordering and physical properties.In chapter 6,we summarize the research results of the multidimensional cooperation effects of the substrate-orientation-dependent oxygen deficiency,lattice-mismatch strain and interfacial interaction on the structure and physical properties of perovskite-type oxides bilayers,and emphasize the relationship between the orientation-dependent interfacial behaviors and the physical properties of perovskite-type oxides heterostructures or multilayers.Meanwhile,we also show some directions of future researches with expectation for widening the path to tune the performances of perovskite oxides heterostructures,and realizing the industrial application of new perovskite multifunctional devices.