Study On Interface Effect And Magnetic Coupling Performance Of SrRuO₃ Oxide

In recent years,due to the rich physical characteristics of transition metal oxide heterojunctions,such as magnetic proximity effect,exchange bias effect and other magnetic coupling properties,it has attracted extensive attention from scientists.The environment around the d-orbital electron ligands of transition group metal cations in the heterojunction film and the change of ion valence state significantly affect the electronic structure at the interface,the spatial distribution of charge and the reconstruction of the orbital.Therefore,the key issue of functional oxide heterojunction research is to realize new magnetic ordered phases and various magnetic coupling effects through coupling and competition among multiple degrees of freedom such as interface charge,lattice,orbit and spin.However,for the 3d-4d or3d-5d ABO₃ oxide interface,compared with the 3d-3d ion,the orbital energy separation is larger,and the orbital hybridization or orbital occupation is still unclear.The 4d transition metal oxide SrRuO₃?SRO?is a cruising ferromagnetic material.In the heterojunction composed of the 3d transition metal oxide,the 4d orbital electrons traveling at the interface interact with the 3d orbital electrons,making the heterojunction The interface exhibits rich and novel physical properties.However,the specific interaction mechanism of the interface is different from that of 3d orbital electrons.The current theory has great limitations,which has prompted many researchers to show a strong interest in the interface coupling of 3d/4d oxide heterojunction.In this paper,the magnetic coupling of the 3d/4d oxide heterojunction interface is studied,and the 4d transition metal oxide strontium ruthenate?SrRuO₃,SRO?and the 3d transition metal nickelate oxide?RNiO₃,R=La,Sm,Nd?are prepared.the 4d orbital electron interacts with the 3d orbital electron to generate charge transfer and orbital reconstruction,making the heterojunction interface exhibit unique magnetic coupling properties different from the 3d-3d heterojunction interface.The main content of the paper is as follows:?1?Single-layer thin films with different orientations of strontium ruthenate?SrRuO₃?and lanthanum nickelate?LaNiO₃,LNO?were prepared by pulsed laser deposition system.The electronic structure of the thin film was analyzed by X-ray photoelectron spectroscopy?XPS?.It was found that the magnetic properties,electrical properties and thermal properties of SRO films with different orientations are temperature dependent,and the magnetic properties,electrical properties and thermal properties are well coupled within the temperature range of Fermi liquid.?2?A series of superlattice samples consist of SrRuO₃ and LaNiO₃ are prepared by pulsed laser deposition system,and A high spin-state of SrRuO3 at the interface and a large magnetic coupling were observed in the SrRuO₃/LaNiO₃ superlattices.The results of X-ray linear dichroism show a preferential occupation of thed_3z2-r2orbitals compared to the single-layer film.Theoretical calculations show that enhanced densities of e_g of the SrRuO₃ below the Fermi level contributes to the magnetic moment of the system,and further reveals that the high spin state and interface magnetic coupling of SrRuO₃ originated from orbital reconstruction.Studies have shown that the orbital occupancy is strongly correlated with the magnetic properties at the interfaces,thus extending the concept of freedom in orbital modulation on magnetic coupling properties.?3?A series of superlattice samples consist of SrRuO₃/NdNiO₃ and SrRuO₃/SmNiO₃ were prepared by pulsed laser deposition system to further investigate the interface magnetic coupling effect of SrRuO₃/nickelate.The magnetic properties of the SrRuO₃/Nd?Sm?NiO₃ superlattice thin film can be adjusted by adjusting the A site of nickelate.The exchange bias fields of²08 Oe and³75 Oe were found in the hysteresis loop,respectively.The magnetization curve of ZFC-FC shows that the thin film exhibits spin-glass-like behavior at low temperature.