Study of phase transition in doped NdNiO₃

Kumawat, Reshma (2022) Study of phase transition in doped NdNiO₃. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS dissertation of Reshma Kumawat (17MS074)) 17MS074_Thesis_file.pdf - Submitted Version Restricted to Repository staff only Download (8MB)

Abstract

Rare earth perovskite nickelates with chemical formula RNiO₃ (where, R is a rare earth element e.g., Nd, Y, Sm, Pr, La etc.) gain tremendous attention in the scientific community due to their electronic (metal-to-insulator; MIT) as well as magnetic (paramagnetic to E’-antiferromagnetic) phase transitions as a function of temperature, pressure, chemical doping etc. Moreover, in several RNiO₃ systems, the MIT also accompanies a sharp firstorder structural transition from high temperature orthorhombic (Pbnm) to low temperature monoclinic (P2₁/n) phases. However, the transition temperature can be engineered with the size of rare-earth ions. In the RNiO₃ family, Neodymium nickelate, NdNiO₃ snatches more attraction due to occurrence of MIT and magnetic transition at the same temperature around 200K (in bulk form). In this project we have carried out controlled doping of vanadium in NdNiO₃ (NNO) to observes the changes in TMIT . NdNi1−xVxO₃ (0 ≤x ≤ 0.1) nanostructures have been successfully synthesized by the solid-state method. Due to the varying valency of vanadium from +2 to +5, we were able to dope both hole (V+2) and electron (V+4) at the Ni side (+3 in NNO). XRD data confirmed the formation of phase-pure as well as V doped NdNiO3 with orthorhombic (Pbnm) space group. We have observed systematic changes in Ni-O bond length and Ni-O-Ni bond angle in NdNi1−xVxO₃ from the Rietveld refined XRD data using GSAS program. TMIT is observed to be increased and decreased with electron and hole doping, respectively using temperature dependent Raman spectroscopy and resistivity measurements. Temperature dependent Raman and Photoluminescence (PL) studies shows a continuous second-order MIT from 105 to 142K unlike sharp first-order transition in bulk NNO.

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