| Popis: |
Two experimental projects involving perovskite manganese oxide compounds are presented. The first involved dielectric and transport studies of the insulator-metal transition as a function of charge-carrier doping in La1-xCaxMnO3 (0 < x < 0.15) bulk samples. The results provide new insight into the role of competing magnetic, lattice and Coulomb energies in determining the insulator-metal transition near x=0.22. The second project involved the growth, structural characterization, and resistive anisotropy of a-axis oriented Nd0.2Sr0.8MnO3 thin films with thicknesses t in the range 10 nm< t < 150 nm. Thicker films develop regular crack arrays which are the origin of a highly anisotropic in-plane electrical resistance. These cracks form parallel to the crystallographic c-axis on films with tensile strain deposited on NdGaO3 (100) and La0.3Sr0.7Al0.65Ta0.35O3 (110) substrates. Films grown under compressive strain on LaAlO3 (110) substrates have no cracks. |
