| Due to the strong correlation coupling of spin,charge,lattice and orbital multiple degrees of freedom,transition metal oxides exhibit lots of novel physical phenomena,such as colossal magnetoresistance effect,multiferrous,superconductivity,charge-spin-orbital orderings,metal-insulator transitions etc.Combining different transition metal oxides to form heterostructures allows a full utilization of interlayer coupling and interfacial reconstruction,presenting a approach of tuning the above phenomena and inducing more unforeseen effects that are important for new conceptual physics and application.Therefore,how to choose appropriate oxide materials and design functional heterointerfaces to explore or control the new unexpected phenomena is the focus of the current oxide heterostructures.And it is also the main research content of this article.In this paper,three different types of heterointerfaces,perovskite/perovskite,perovskite/brownmilleriteand perovskite/Na Cl structure,were designed and fabricated to explore novel physical effects.The main research results are as follows:1. The spin reorientation induced by the interface effect of La1-xSrxCo O3/La2/3Sr1/3Mn O3/La1-xSrxCo O3?perovskite/perovskite-typed interfaces?heterostructures on LaAlO3?001?substrate has been investigated,i.e.the easy magnetic axis of La2/3Sr1/3Mn O3?LSMO?is rotated from the initially perpendicularly aligned towards the in-plane direction,though the film is in a highly compressive state.The anisotropy constant can be tuned in a wide range by incorporating different Sr erg/cm3 for x=0,which is in sharp contrast to the KA?+1.5×105 erg/cm3 of the bare LSMO/LaAlO3 layer.As evidenced by the analysis of scanning transmission electron microscope?STEM?,X-ray absorption spectroscopy?XAS?and the results of density functional theory calculations?DFT?,the La1-xSrxCo O3/LSMO interface induced the off-center displacement of the Mn ions in Mn O6,which has caused an orbital reconstruction at interfaces,resulting in the anomalous spin orientation against magnetoelastic coupling.2. The perpendicular magnetic anisotropy induced by the interface effect of SrxCoSrxCo O2.5+??perovskite/brownmillerite-type interfaces?heterostructures on Sr Ti O3?001?substrate has been investigated,i.e.instead of lying in film plane,the magnetic moment of the tensilely strained LSMO aligns perpendicularly to the film.The most remarkable observation is the enhancement of the perpendicular anisotropy with the increase of the Sr content inSrxCo O2.5+?.The maximal anisotropy constant is?4.3×106 erg/cm3,gained when x=0.5.This value is two orders of magnitude greater than that obtained by compressively straining prefers to crystalize in the brownmillerite phase when the content of Sr is high.The brownmillerite phase causes,as evidenced by the result of the x-ray linear dichroism,an orbital reconstruction of the Mn O6 octahedra,thus the reorientation of the preferred magnetic direction.3. Composing two-dimensional Electron Gases?2DEGs?with Sr Ti O3 and Na Cl-structured Eu O that owns a large saturation magnetization and a fairly high Curie temperature.We obtained the 2DEGs that show long-range magnetic order thus unusual behaviors marked by isotropic butterfly-shaped magnetoresistance and remarkable anomalous Hall effect.We found evidences for the presence of more conductive domain walls than elsewhere in the oxide layer where the 2DEG resides.More than that,a relation between interfacial magnetism and carrier density is established.On this basis,any intermediate magnetic states between short-range and long-range ordered states can be achieved.The present work provides guidance for the design of high-performance magnetic 2DEGs. |
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