Paramagnetic to ferromagnetic phase transition of Co doped Gd2O3 prepared by chemical route

Abstract Nanoparticles of Co-doped gadolinium oxide (Gd 1.90 Co 0.10 O 3−δ ) are prepared by co-precipitation method. To enhance the oxygen vacancy, the as prepared sample is sintered in vacuum at 700 °C for 6 h. The pure crystallographic phase as well as the complete substitution of Co-ions in the lattice of Gd 2 O 3 is confirmed by Rietveld analysis of the X-ray diffraction pattern. No impurity phase is formed in the doped sample of Gd 2 O 3 and this fact is also substantiated by the Raman Spectroscopy of the doped sample observed at room temperature. Magnetic measurements are carried out at different temperatures from 300 K down to 5 K by using a superconducting quantum interference device (SQUID) Magnetometer. The sample exhibit paramagnetic behavior down to 20 K but a feeble nonlinearity in the magnetization vs. field curve recorded at ∼20 K indicates the presence of very weak magnetic ordering in the sample. A clear hysteresis loop with high value of magnetization (∼103.56 emu/gm) is observed at 5 K with maximum applied field of 5 T. The lack of saturation in the hysteresis loop at and below ∼20 K indicates the coexistence of paramagnetic (PM) and ferromagnetic (FM) phase, which is confirmed by the good fitting of the M–T curve below ∼30 K by 3D spin wave and Curie–Weiss model. The observed magnetic phase transition is attributed to the substitution of Co-ions in Gd 2 O 3 lattice and is analyzed by oxygen vacancy mediated bound magnetic polaron model.