Study On Preparation Of Co-based Half-mentalic Magnetic Thin Films And The Magnetic Properties Of The Monolayer Thin Film

Half-mentalic materials have the properties of metals and semiconductors on different spinbands.The Heusler alloy in the half-metalic material has a very high total magnetic moment,utilizing its half-metal properties,high total magnetic moment and high spin polarization,etc.Special alloy films can be prepared and functional materials and devices with superior performance can be developed.In this study,by experiments and spin wave theory,combined with the research status so far,we studied the films of two-component alloys of Co₂MnSi and CoTiSb,summarized the results of the study,designed the films with special shapes and measuring methods,and discussed their properties.At the same time,using spin wave theory to discuss the alloy at zero temperature conditions,the system parameters on the magnetic properties and states.The study is divided into the following five chapters.The first chapter introduces the research content of spintronics,briefly describes the classification and characteristics of magnetoresistance effects.According to the deficiencies in the research,the introduction of half--metallic ferromagnetic materials and Heusler alloys,select Co₂MnSi and CoTiSb as the research components,To summarize the research progress in both physical properties and preparation,the Heisenberg model was used to study the magnetic properties and phases of the ground state.The second chapter introduces the specific experimental scheme for the preparation of alloy targets and thin films,discusses the experimental methods and operation flow,compares the experimental results of different preparation methods in the current research status,and analyzes the effects of experimental operations and instrument parameters on the preparation of thin films.Parameters include:pulsed laser energy E,pulse frequency F,deposition chamber pressure P,substrate temperature T,substrate material and deposition time.The specific methods of Heisenberg model and spin wave theory for theoretical research are also introduced.In the third chapter,Co₂MnSi alloy films were prepared by PLD.The X-ray diffraction patterns of the prepared samples were measured and analyzed.The surface morphologies measured by scanning electron microscopy and the composition of the films measured by X-ray energy dispersive spectroscopy were used to determine the structure of the films.Analyze the effect of changes in experimental parameters on the structure of the film sample,and draw the results:1 set the appropriate laser energy,can produce a structure and the block material in line with the film;2 Frequency affects the flatness,density and film thickness of the film surface;3 Pressure in the deposition chamber affects the structure of the film and the thickness of the film at different deposition times.According to the research results and research status,a special geometrical alloy thin film and magnetoresistance measurement method was designed and the magnetoresistive properties of the film were discussed.In the fourth chapter,CoTiSb alloy thin films were prepared by PLD.The X-ray diffraction patterns of the prepared samples were measured and analyzed.The surface morphology measured by scanning electron microscopy and the composition of the thin films measured by X-ray energy dispersive spectrometer were used to determine the structure of the films.The effect of experimental parameters on the results is similar to that of Co2MnSi alloy films.In Chapter 5,spin wave theory is used to study the ground state properties of an anisotropic two-dimensional frustration square lattice.The influence of the anisotropy of the system on the magnetic properties is discussed.Studies have shown that when the different anisotropic parameters and the second nearest neighbor exchange integration constants take different values,the system is in the superposition state of Neel state,collinear state,spin liquid state,or Neel and collinear states.