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Structural and Electric Transport Properties of Lanthanum Based Manganites and Barium Based Ruthenates

Mazaheri, Mojtaba | 2010

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 41114 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Akhavan, Mohammad
  7. Abstract:
  8. The goal of this thesis is to understand the physical properties of lanthanum based manganites and barium based ruthenates. In order to obtain negative colossal magnetoresistance in manganites and fabrication of barium ruthenate in ordinary condition, the effects of variables such as ionic radii, chemical composition, temperature, magnetic field and processing in manganites and ruthenates systems are investigated. In the first part, the effects of potassium doping on structure, metalinsulator transition and magnetoresistance in )La1-yKy)0.7 Ca0.3 MnO3 and)La1-yKy)0.7 Ba0.3 MnO3 manganites systems are studied. Polycrystalline samples of manganites are synthesized by the sol‐gel method. In the second part, the polycrystalline samples of hexagonal 4H BaRu1-xMnxO3 are synthesized by the solid‐state reaction method for the first time. The samples have been characterized by X‐ray diffraction and atomic force microscopy. The results show that the samples have single phase, and a structural transition occurs in the LKCMO samples. The electrical and magnetic transport properties are measured in the temperature range 10‐300 K in the presence of the magnetic field up to 15 kOe. Noticeable magnetoresistance is observed for the manganite samples at room temperature and increases at low temperature, which is not observed in single crystals
  9. Keywords:
  10. Ruthenates ; Electrical Transport Properties ; Magnetic Resistance ; Manganite

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