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| Author(s): |
Leandro Marcos Salgado Alves
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Lorena. |
| Institution: | Universidade de São Paulo (USP). Escola de Engenharia de Lorena (EEL/ASDI) |
| Defense date: | 2014-05-09 |
| Examining board members: |
Carlos Alberto Moreira dos Santos;
José Albino Oliveira de Aguiar;
Durval Rodrigues Junior;
Maria José Ramos Sandim;
Robson Ricardo da Silva
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| Advisor: | Carlos Alberto Moreira dos Santos |
| Abstract | |
This work presents the study of physical properties in polycrystalline samples of KxMoO2-?, and MoOy. We present results of X-ray and Neutrons diffraction patterns, density of states calculations by density functional theory, photoemission spectroscopy, electrical resistivity, magnetization, specific heat, and thermal expansion measurements. X-ray and neutrons diffraction results as well as calculations of the structure and diffractograms carried out by simulations using GSAS shown which the samples are high quality. Photoemission spectroscopy measurements shown the existence of Mo3+/Mo4+ in high fraction for KxMoO2-? and MoOy which are responsible to electrical anomalous behavior described by powder law predicted in the Luttinger Liquid theory. The observation of anomalous is related to Mo3+ ions in the samples. Magnetization and electrical resistivity confirm the existence of superconductivity in K-Mo-O system. It was observed that the critical temperature (TC) is a function of the starting composition of K and the higher TC found out and reported for this system (TC ~9.5 K). Magnetization measurements also have shown the coexistence of superconductivity and magnetism in KxMoO2-?. It was observed a Bose metal-insulator transition in K0.05MoO2-? which further evidence of the formation of Cooper pairs in the system. Finally, specific heat measurements, thermal expansion and electrical resistivity evidenced the existence of first order phase transition in high temperatures (between 250 and 270 K) in KxMoO2-? and MoOy polycrystalline as well as MoO2 single crystal. This transition is discussed looking for Mo atoms moving in the one-dimensional links Mo-Mo and of the distortions of MoO6 octahedra in the crystalline structure. (AU) | |
| FAPESP's process: | 10/06637-2 - Crystalline structure and physical properties of the anomalous conductor KxMoO2-d |
| Grantee: | Leandro Marcos Salgado Alves |
| Support Opportunities: | Scholarships in Brazil - Doctorate |