研究目的
To explore the relationship between optical properties, oxygen vacancies and magnetism in SrTiO3.
研究成果
Oxygen vacancies in SrTiO3-δ affect optical and magnetic properties, inducing weak ferromagnetism and altering absorption. Theoretical calculations show that magnetism arises from spin-polarized Ti 3d states, with contributions from localized and itinerant electrons. The relationship between vacancies, strain, and charge states influences these properties, suggesting potential for magneto-optical applications.
研究不足
The study is limited by the surface sensitivity of XPS, which may not fully represent bulk properties. DFT calculations with GGA underestimate band gaps and may not accurately describe spin fluctuations in magnetic systems. The method for creating oxygen vacancies might not be fully controllable, and the samples are polycrystalline, which could affect anisotropy measurements.
1：Experimental Design and Method Selection:
The study involved preparing SrTiO3-δ samples with varying oxygen vacancy concentrations (δ=
2：00, 125, 250) using solid-state reaction and a getter material method. Theoretical calculations used the FP-LAPW method with GGA approximation. Sample Selection and Data Sources:
High-purity SrCO3 and TiO2 were used as precursors. Samples were characterized using XRD, EDXMA, XPS, FT-IR, UV-vis spectroscopy, and VSM magnetometry.
3：List of Experimental Equipment and Materials:
Equipment includes Siemens D5000 X-ray diffractometer, Omicron DAR 400 XPS system, Nicolet Protege 650 FT-IR spectrometer, JENWAY 6400 spectrophotometer, VSM magnetometer, and computational tools like WIEN2k. Materials include SrCO3, TiO2, metallic Ti, KBr, and alumina crucibles.
4：2k. Materials include SrCO3, TiO2, metallic Ti, KBr, and alumina crucibles. Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: Samples were synthesized by calcining at 800°C, sintering at 1300°C, and annealing with Ti getter in vacuum. Characterization involved XRD for structure, XPS for surface composition, FT-IR for transmission, UV-vis for absorption, and VSM for magnetism. Computational calculations were performed on supercells with oxygen vacancies.
5：Data Analysis Methods:
Data were analyzed using Fullprof for XRD, CasaXPS for XPS, and various software for optical and magnetic data fitting. Theoretical calculations used FP-LAPW with GGA for electronic structure and magnetism.
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X-ray diffractometer
Siemens D5000
Siemens
Used for X-ray diffraction to identify phase formation and structure of materials.
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XPS system
Omicron DAR 400
Omicron
Used for X-ray photoelectron spectroscopy to examine surface composition and chemical valence state.
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FT-IR spectrometer
Nicolet Protege 650
Nicolet
Used for Fourier Transform Infrared spectroscopy to record transmission spectra.
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Spectrophotometer
JENWAY 6400
JENWAY
Used for ultraviolet-visible absorption measurements.
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VSM magnetometer
Used for vibrating sample magnetometry to measure magnetization.
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EDXMA system
Oxford instrument
Used for energy-dispersive X-ray micro-analysis to analyze elements and microstructure.
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FESEM
Used for field emission scanning electron microscopy to analyze microstructure.
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Computational software
WIEN2k
Used for FP-LAPW calculations of electronic structure and magnetic properties.
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