Investigation of metal-insulator transition temperature and magnetic properties of NdNiO₃ nanoparticles

Subir Roy, Rajesh Katoch, R. B. Gangineni, S. Angappane

Journal of Solid State Chemistry, 121865 (2020)

 The control of metal–insulator transition (MIT) and magnetic properties of rare-earth nickelates remains a fundamental problem in material science. Here, we report a possible way to tune the MIT as well as the magnetic properties of NdNiO₃ by reducing the crystalline size to the nanoscale. NdNiO₃ nanoparticles of different sizes have been synthesized by a simple aqueous solution-based chemical method in the atmospheric pressure under oxygen. The x-ray diffraction study shows the formation of orthorhombic nanocrystals of NdNiO₃ with Pbnm space group, presence of oxygen vacancies and higher octahedral distortion. The morphology and the particle size distribution have been evaluated by FESEM and TEM. The temperature dependent resistivity measurement shows the metal to insulator transition, which depends on the particle size; lower the particle size, higher the MIT temperature (T_MI).  Further study on the temperature dependent magnetic susceptibility shows the signature of magnetic phase transition at a temperature (Neel temperature T_N), lower than the T_MI, which indicates the existence of second order magnetic phase transition in our NdNiO₃ nanoparticles.  We have attributed the higher T_MI and the origin of second order magnetic phase transition predominantly to the higher NiO₆ octahedral distortion and the narrowing of bandwidth of the nanocrystalline NdNiO₃, which leads to the opening of the charge transfer gap at the temperature higher than the bulk.