Deposition of La-Mn-O and Nd-Mn-O based thin films and study of their electrical transport and magnetic properties

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In the present thesis, the structural, electrical and magnetic properties of Nd0.7Sr0.3MnO3 (NSMO) and Nd0.8Na0.2MnO3 (NNMO) films as well as bilayers of NSMO/NNMO and La0.7Sr0.3MnO3/LaFeO3 (LSMO/LFO) are presented. Single phase cylindrical targets of NSMO and NNMO by solid state route and, LSMO and LFO by sol-gel route were prepared. Several NSMO films were grown by choosing different substrates and by varying the parameters such as post-annealing temperature and film thickness. NSMO films of 120 nm thickness grown on 001-Al2O3 are found to be in polycrystalline form. They all exhibit ferromagnetic transition and the TC value is found to increase with postannealing temperature. Similar polycrystalline behavior is observed on films grown on 001-MgO substrate. However NSMO films grown on 001-LaAlO3 substrate are found to be in single crystal form with epitaxial like growth. The ferromagnetic TC and metal-insulator transition temperature (TMI) are found to increase with film thickness due to the relaxation of lattice strain. These films exhibit a maximum negative magneto-resistance of 96% for an applied field of 5T.
Supervisor: S. Ravi