Federated Physics Department of NJIT and Rutgers-Newark
Degree:
Doctor of Philosophy
Program:
Applied Physics
Document Type:
Dissertation
Advisory Committee:
Tyson, Trevor (Committee chair)
Ravindra, N. M. (Committee member)
Zhou, Tao (Committee member)
Liu, Zhenxian (Committee member)
Wu, Weida (Committee member)
Ahn, Ken Keunhyuk (Committee member)
Date:
2009-08
Keywords:
Manganese oxides
Raman
Rare-earth
Diffraction
Infrared
Magnetic
Availability:
Unrestricted
Abstract:
Rare-earth Manganese Oxides (RMnO3) exhibit two distinct structural phases: the orthorhombic structure and the hexagonal structure. The doped orthorhombic phase exhibits a metal to insulator transition, charge ordering and a strong response of electron transport properties to magnetic fields (colossal magneto-resistance). At low temperatures, this system may also exhibit a finite polarization which couples to external magnetic fields. The hexagonal phase is known to have a large spontaneous polarization at high temperatures which couples to the low temperature magnetic order. These materials are important from the basic point of view of understanding strong electronic correlations and spin-lattice coupling. From, a practical perspective, they hold promise to produce sensors and storage devices with extremely high sensitivity and high density. However, a detailed understanding of their properties is needed.
In this work, optical, transport and structural measurements, as a function of pressure and temperature, are conducted to explore the physical properties of these materials. Synchrotron based x-ray diffraction and infrared measurements, Raman measurement, laboratory based transport measurements and neutron scattering measurements were conducted on bulk polycrystalline, thin film and single crystal samples. The electronic, structural and magnetic properties are studied in detail. The results will be used to refine theoretical models of these materials.
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