Electronic behavior of epitaxial thin films of doped rare-earth nickelates

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PhD; 2023; Physics

Rare-earth nickelates (RENiO3), a family of transition metal oxides, exhibit a complex phase diagram involving electronic, magnetic, and structural phase transitions. While LaNiO3 remains paramagnetic, metallic down to very low temperature, RENiO3 members with RE=Nd, Pr exhibit simultaneous metal-insulator transition (MIT), paramagnetic to antiferromagnetic transition, structural phase transition and a bond disproportionation (BD) transition as a function of temperature. The other members of the series such as EuNiO3, SmNiO3, etc. first undergo simultaneous MIT, BD, and structural phase transition and further becomes antiferromagnetic upon lowering the temperature. Understanding the origin of the MIT in this family remains a challenging problem and has attracted a lot of attention in recent times. The MIT temperature can be tuned by a variety of parameters such as chemical doping, pressure, epitaxial strain, light, etc. In this thesis, we have grown epitaxial thin films of doped rare-earth nickelates and investigated their electronic and magnetic behavior using several experimental techniques, including synchrotron-based measurements. In the first part, we have investigated Ca2+ (divalent) and Ce4+ (tetravalent) doped NdNiO3 thin films.