The Nonlinear Optical And High Magnetic Optical Study Of Complex Oxides

Optics is an important part of physics.With the development of high magnetic field technology,the magneto-optical technology has discovered many new physical phenomena in materials and answered many physical questions.For example,the mechanism of the insulator to metal transition induced by high magnetic field.In addition,nonlinear optics,especially the second harmonic generation(SHG),are widely used to explore the lattice,ferroelectric,and ferromagnetic structures of materials.In this thesis,we introduce the application of magneto-optical spectra and nonlinear optics in exploring the physical properties of materials.The details are as follows:First,in the introduction,we give a general introduction to the magneto-optical and nonlinear optics.The second section introduces the international development and research status of high magneto-optical experiments.The third section introduces the principles of nonlinear optics,and its application in materials.The fourth section mainly introduces the research motivation and content of this thesis.The second chapter introduces the SHG optical system in our laboratory.The first section mainly introduces the construction of the SHG optical system and the use of lasers,photomultiplier tubes,and Lock-in amplifier.The second section briefly introduces the Labview data acquisition system based on this optical system.The third section introduces the Matlab data simulation system based on this optical system.Through this simulation system we can simulate the SHG polarization diagram of different samples.Section 4 introduces the relevant cooperation based on these systems.For example,we have explored the structure of WSe2 and characterized the ferroelectric phase transition of thin film materials.The third chapter mainly introduce that we have studied the metal to insulate transition of double-layer ruthenium oxide CRMO single crystal by high magnetic-optical measurement.Through the study of fine characteristics of magnetic spectroscopy,it was found that the 4d orbit of Ru ions in CRMO is in the antiferromagnetic/rail order(AFM/FO)structure at low temperature,and there is phase separation near the critical point of the metal to insulator transition.The fourth chapter mainly introduces the polarization rectification effect at the Ti/fatigue SrTiO3 heterojunction interface detect by the second harmonic technology.In addition,it is found that this fatigued SrTiO3 is in the preferroelectric state through Raman and dielectric measurement methods.We introduced an appropriate amount of oxygen vacancies at the Ti/SrTiO3 interface by repeatedly applying electric voltage.These oxygen vacancies and the electrons around them form "polarons".We used the technique of SHG to measure the polarization at different voltages and verified the polarization rectification effect of this "polaron".In addition,through different measurement methods such as Raman and dielectric without electric field,it was found that this fatigued SrTiO3 exhibited the preferroelectric effect.These findings not only provide a way to further study the ferroelectric state of perovskite oxides,but also propose a new type of polarized rectifier,which may become the basis of future electronic devices.The fifth chapter mainly introduces the nonlinear optical effects in MOF materials.MOF has become a highly adjustable platform due to its unique structural advantages such as skeleton structure.In recent years,MOF becomes one of the most promising solid nonlinear materials due to its excellent nonlinear optical properties.In order to synthesize MOF materials with better nonlinear performance,we designed the MOF-1 with new ligand structure.This experiment is still in progress.The sixth chapter is a summary of work and prospects.High magneto-optics play an important role in the characterization of materials.Many physical phenomena have been discovered and many physical problems is clearly under the high magnetic optical measurement.With the development of high magnetic field technology,we will improve the measurement range and accuracy of spectroscopy technology under high magnetic field.Nonlinear optics,especially the second harmonic generation technology,have the advantages of being sensitive to crystal symmetry,non-contact,and easy to operate.It has been more and more widely used to characterize the physical properties of new materials.However,the optical research on materials in our laboratory is still in the initial development stage,and there are still some problems and technologies that require in-depth research.