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 (Néel 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.

稀土镍酸盐的金属-绝缘体转变（MIT）和磁性能的控制仍然是材料科学中的一个基本问题。在这里，我们报告了一种通过将晶体尺寸减小至纳米级来调节MIT以及NdNiO ₃磁性能的方法。通过简单的基于水溶液的化学方法在大气压下在氧气下合成了不同尺寸的NdNiO ₃纳米颗粒。X射线衍射研究表明NbNiO ₃与Pbnm的正交晶体形成空间群，氧空位的存在和更高的八面体变形。通过FESEM和TEM评估了形态和粒度分布。温度相关的电阻率测量结果表明，金属到绝缘体的转变取决于颗粒尺寸；粒径越小，MIT温度（T _MI）越高。对温度相关的磁化率的进一步研究表明，在低于T _MI的温度（Néel温度T _N）下，磁性相变具有明显的特征，这表明在我们的NdNiO ₃纳米粒子中存在二级磁性相变。我们将较高的T _MI归因于二级磁相变的起源主要是由于较高的NiO ₆八面体形变和纳米晶体NdNiO ₃的带宽变窄，导致在高于体温的温度下打开了电荷转移间隙。