First-principles Study Of Low-dimensional Quantum Magnetism

As one of the most basic materials,magnetic materials play an irreplaceable role in magnetoelectric functional devices.However,with the development of sci-ence and technology,the traditional magnetic materials can not satisfy the needs for high density,high speed,low power consumption and small size functional de-vices.In particularly,the traditional three-dimensional(3D)materials exist many suspended bonds and have a poverty property in a small scale nanometers.Then people gradually transfer their attention to the low-dimension high-performance materials.Since the first discovery of true two-dimensional(2D)magnetic ma-terials,wide varieties of related magnetic properties have been demonstrated in a number of low-dimensional systems.It provides a new opportunity for the efficient manipulation of spin-based devices in the future.A large number of 2D materials have been studied,which have made great contributions to the preparation of high-performance devices.The research on layered multiferroic materials also provides a new platform and opportunity for the basic physics research of strongly magneto-electric coupling materials.However,most of the low-dimensional materials can only work at low temperatures,which hinders the application of low-dimensional magnetic materials.Based on First-Principles calculation,we devoted to explore the multifunctional low-dimensional magnetic materials with multi-field control at room temperature.In the first part,we mainly focused on the anomalous magnetism in transi-tion metal compounds Se VX(X=Se,S,Te,Fe,Mn,Cr,Co).(1)We systematically explored the effects of the different phase structures on the different electronic structure in the same compound Se VS,Se VTe,Se VFe,and Se VMn.(2)We found the half-metallic ferromagnetism and antiferromagnetism in the 2H phase Sev Cr structure,when the 3D orbital of the Cr atoms have spin flip.These abnormal metallic magnetism and spin polarization flipping phenomena provide theoretical support for the development of spin filters.In the second part,we detailly investigated interfacial effects of magnetic het-erostructures,such as:(1)the exchange bias effect in the Ni Fe₂O₄/Ni O(NFO/NO)heterostructure caused by the exchange interaction between Fe atoms at the inter-face?(2)the Rashba spin-orbit coupling at Fe/Pb Zr_xTi_1-xO₃(Fe/PZT)interface?and(3)the interfacial exchange interaction at the interface of Bi₂Te₃/Cr Sb het-erostructure by introducing magnetism into topological insulators.The studies of these interfacial magnetism opens a new way for achieving high performance and small size devices available at room temperature.