Growth Of Oxide Thin Films And Heterostructures And Its Magneto-optical Study

Due to the strong interaction between the degrees of freedom,when the dimension of the material is reduced,rich and peculiar physical properties will appear.Double perovskite oxide Y2NiMnO6(YNMO)has attracted attention because of its special E*-type antiferromagnetic order and magnetically induced ferroelectricity,and its potential application value in devices.Rare earth iron garnet oxides,as high-temperature ferrimagnetic insulators,exhibits a large magneto-optical effect caused by strong spin-orbit coupling and a very narrow ferromagnetic resonance linewidth.It is an ideal material for studying ultrafast dynamics.The regulation of magnetic anisotropy in rare earth iron garnet oxide thin films makes it of great research value in the field of spintronics devices.The content of the thesis is divided into five chapters,we use pulsed laser deposition technology to grow YNMO films and Sm3Fe5O12(SmIG)films,and study the structure and magnetic control of double perovskite YNMO films by oxygen pressure and interface engineering.The regulation of ferrimagnetic SmIG thin-film magnetic anisotropy and the ultrafast dynamics research of the interface coupling of CoFe/SmIG heterostructure provide methods and directions for the preparation,application and scientific research of high-frequency devices in the future.The first chapter summarizes the basic knowledge of perovskite oxides and the research progress of double perovskite oxides,and introduces the research status of YNMO materials.Then introduce the research progress of rare earth iron garnet oxides,including the magnetic anisotropy control of rare earth garnet thin films and the research in the field of ultrafast spin dynamics.The second chapter introduces the growth methods of epitaxial thin films,physical property characterization methods and ultrafast magneto-optical Kerr effect system construction.Firstly,the principles,characteristics and growth factors of pulsed laser deposition technology(PLD)are introduced.Secondly,X-ray diffraction(XRD),reciprocal space mapping(RSM),Raman spectroscopy are introduced in the characterization of thin film structure.Superconducting quantum interference device(SQUID)and the magneto-optical Kerr effect system are introduced in the characterization of magnetic properties.In the element valence state analysis,X-ray photoelectron spectroscopy(XPS)is introduced.In the absorption rate and optical band gap acquisition,the ultraviolet-visible near-infrared absorption spectroscopy is introduced.Finally,the construction of the time-resolved magneto-optical Kerr effect system is introduced.In Chapter 3,we studied the growth of YNMO films and the manipulation of their structure and magnetic properties.The growth process of YNMO film and heterojunction is introduced,and the regulation of the structure and magnetic properties of the film is studied by changing the growth oxygen pressure and interface engineering(insertion of buffer layer).The growth oxygen pressure has a significant effect on the crystal structure.Under high oxygen pressure,the lattice constant is closer to the bulk;at the same time,under the action of the oxygen pressure and the buffer layer,the magnetism of the YNMO film is equivalent to that of the bulk.The fourth chapter introduces the magnetic anisotropy manipulation of SmIG thin film and the ultrafast dynamics of interfacial spin coupling of CoFe/SmIG heterojunction.In this chapter,we introduce the growth of SmIG thin films in detail and obtain high-quality epitaxial thin films.Secondly,by changing the crystal orientation of the substrate from(111)to(001),we find that the magnetic anisotropy of the film has achieved the switching from in-plane magnetic anisotropy to out-of-plane magnetic anisotropy,and it has universal application.This provides a way to obtain different magnetic anisotropy.Finally,using he self-built time-resolved magneto-optical Kerr effect(TR-MOKE)system,the effects of interfacial spin coupling and magnetic anisotropy switching on the optically excited spin waves of the CoFe/SmIG heterojunction are explored,and it is found that both the frequency of the spin precession and the effective damping factor can be manipulated by the magnetic anisotropy switching of the SmIG film in the CoFe/SmIG heterojunction.These findings provide ideas for spin manipulation in magnetic thin films and heterojunctions,and promote the research of high-frequency spintronics devices.Chapter 5 summarizes the work of this article and the next research plan.Firstly,the ultrafast magneto-optical research of YNMO film has not been studied yet,and the ultrafast dynamics process is not clear;secondly,YNMO,as a multiferroic material,is very valuable for studying the magneto-electric coupling of the film through optical means;The study of ultrafast magnetization dynamics of SmIG thin films deserves further advancement;finally,we grow Tm3Fe5O12 thin films,and the regulation of magnetic anisotropy and its ultrafast kinetics need in-depth research.