Magnetophotoresistance in Pr1 xCaxMnO3 Thin Films

In this work, a colossal magnetoresistive CMR Pr1 amp; 8722;xCaxMnO3 PCMO man ganite thin amp; 64257;lms and polycrystalline samples were studied with the main focus on the properties of the insulator to metal Mott phase transition. The polycrystalline PCMO samples were fabricated with the solid state reaction method. The polycrystalline sam ples were further processed into the epitaxial thin amp; 64257;lms with the pulsed laser deposition method PLD . The structural and magnetic properties of the samples were systemat ically investigated and the thin amp; 64257;lms samples were further investigated with magneto transport measurement where the thin amp; 64257;lms response to illumination was also studied. After the successful synthesis of polycrystalline PCMO samples with varying x between 0.0 0.5, the magnetic characterization of the samples showed rich magnetic properties having the signatures of the magnetic phase coexistence of antiferromag netic AFM and ferromagnetic FM ordering and cluster glass behaviour. With the increased doping concentration from x 0.3 to 0.5, the AFM charge order CO phase started to form up being strongest on the sample x 0.5. This AFM CO phase could be melted with the high external magnetic amp; 64257;eld at temperatures below Neel s tempera ture TN inducing an irreversible amp; 64257;rst order metamagnetic AFM to FM phase transition. The strength of the AFM CO phase decreased with decreasing Ca concentration and increasing temperature. The polycrystalline PCMO samples with Ca concentrations of 0.3 0.5, showing metamagnetic behaviour, were selected for the fabrication of the thin amp; 64257;lm samples. The amp; 64257;lms were grown using two different in situ oxygen treatment temperatures at 500 amp; 9702;C and 700 amp; 9702;C in the PLD system. The amp; 64257;lms with x 0.4 and 0.5 showed weaker AFM CO phase with greatly reduced melting amp; 64257;elds when compared to polycrystalline samples. Also, the robustness of the AFM CO phase was further decreased in thin amp; 64257;lms with the lower oxygen treatment temperature of 500 amp; 9702;C. The magneto transport measurements made on the thin amp; 64257;lms showed that the melting of AFM CO phase was connected to CMR effect where the increasing magnetic amp; 64257;eld induced an insulator to metal phase transition, which reduces the resistivity of the amp; 64257;lm around nine orders of magnitude. The use of illumination during the magneto transport measurements showed a vari ety of intriguing phenomena including magnetophotoresistance. The illumination had a huge effect to the insulator to metal transition IMT reducing the transition magnetic amp; 64257;eld signi amp; 64257;cantly. Moreover, by magnetically biasing the thin amp; 64257;lms with the constant external magnetic amp; 64257;eld, the IMT could be induced by switching on the illuminatio