Doctor of Philosophy (PhD)
Physics and Astronomy
Correlated Electron Materials (CEMs) have attracted the attention of the materials community because the strong coupling between charge, lattice, orbital, and spin degrees of freedom produces exotic phenomena. Transition metal oxide series Srn+1RunO3n+1 (n = 1 to ∞) is a prototype of CEMs. The n = 2 member of this family Sr3Ru2O7 is the subject of this dissertation. It has a paramagnetic (PM) metallic ground state, which can be driven into an antiferromagnetic (AFM) insulator with a partial substitution of Ru by Mn. The focus of this research is to understand the role of chemical doping as the driving force for the structural, electrical and magnetic properties in Mn-doped Sr3Ru2O7. A key to achieving this goal is contained in the understanding of different magnetic ordering in the system. High quality single crystals Sr3(Ru1-xMnx)2O7 (0 ≤ x ≤ 0.7) have been grown by the floating zone technique in an image furnace. A phase diagram of Sr3(Ru1-xMnx)2O7 is presented, which is divided into five different regions. The structural, electrical and magnetic properties of Sr3(Ru1-xMnx)2O7 reveal a turning point around x = 0.2. Two characteristic temperatures TMIT and TM are determined from electrical and magnetic properties measurements, where TMIT represents the temperature of a metallic-to-insulating crossover while TM corresponds to a peak in magnetic susceptibility. TMIT monotonically increases with increasing x while TM shows a cusp at x = 0.16 (TMIT > TM) and the difference between TMIT and TM becomes much larger above x = 0.2. Elastic neutron scattering experiment on x = 0.16 crystal confirms a long-range AFM ordering below its TM and suggests short-range magnetic correlations between TMIT and TM.
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Hu, Biao, "Evolution of structural and physical properties of transition metal oxide Sr₃(Ru₁₋xMnx)₂O₇ (0 <̲ x>̲ 0.7) with Mn concentration" (2011). LSU Doctoral Dissertations. 3909.