Multiferroic Properties Of Double Perovskite Rare Earth-Nickel-Manganese Oxides Super Lattices

Multiferroic materials have broad application prospects, thus becoming the hotspot in the current research field of functional materials. Perovskite oxides have very rich physical features, especially the potential multiferroic features. Such type of materials can be used to design and make four storage state memory device, adjustable microwave device and other new electronic spin devices. They are expected to become a key force in the innovation of information industry. The current research focus for perovskite multiferroic materials is searching a system with ferromagnetic order, large spontaneous polarization and high transition temperature that above room-temperature. First-principles study which based on density functional theory is an accurate and simple method. With the upgrading of the computing speed, first-principles study has become an important research method in the fields of physics, chemistry, biomedicine and materials science. It is helpful to use first-principles to investigate multiferroic properties of perovskite materials.This work studied multiferroic properties in double perovskite rare earthnickel-manganese oxides super lattice via first-principles method. Firstly, for Pr2NiMnO6/La2NiMnO6 ordered super lattice, we calculated six structures on account of the difference of B site ions arrangement and magnetic orders. The [111] FM order structure was found to satisfy the condition for the existence of spontaneous polarization. The octahedral rotation angles, displacements of A site ions and other structural information have been given after analyzing geometric structure carefully. Based on the modern polarization theory Berry Phase method, the spontaneous polarization was calculated. Secondly, for Er2NiMnO6/La2NiMnO6 ordered super lattice, we studied structural features and got a series of distortion parameters. And then combined with the indirect exchange interaction, the connection between structural distortion and electronic properties especially magnetic moment was illustrated. The relationship between the polarization and A site ionic radius was also investigated. Thirdly, we tried to regulate and control the polarization in the case of getting these multiferroic features of above-mentioned super lattices. The spontaneous polarizations of continuous structures were computed due to the difference of A site ionic radius. In order to enhance the polarization, the Coulomb interaction was brought in by building discontinuous structure. After analyzing structural features of upper and lower parts, the connection between distortion and B site ions arrangement was also explained. Some useful conclusions were obtained from structural design to theoretic calculation and analysis. These conclusions may provide a reference for the research about multiferroic materials in the future.