Room temperature ferromagnetism of nanocrystalline Nd 1.90 Ni 0.10 O 3−δ

Nanocrystalline sample of Ni2+ doped neodymium oxide (Nd1.90Ni0.10O3−δ, NNO) is synthesized by co-precipitation method. Analysis of X-ray diffraction (XRD) pattern by Rietveld refinement method confirms the desired phase of NNO and complete substitution of Ni2+ ions in the Nd2O3 lattice. Analyses of transmission electron microscopy (TEM) and Raman spectroscopy of NNO recorded at room temperature (RT) also substantiate this fact. Besides, no traces of impurities are found in the analyses of XRD, TEM and Raman data. Room temperature hysteresis loop of NNO suggests the presence of weak ferromagnetism (FM) in low field region (~ 600 mT), but in high field region paramagnetism of the host is more prominent. Magnetization vs. temperature (M–T) curve in the entire temperature range (300–5 K) is analyzed successfully by a combined equation generated from three-dimensional (3D) spin wave model and Curie–Weiss law, which suggests the presence of mixed paramagnetic phase together with ferromagnetic phase in the doped sample. The onset of magnetic ordering is analyzed by oxygen vacancy mediated F-center exchange (FCE) coupling mechanism.