Magnetic Properties of Co-doped Bismuth Oxide (δ-Bi2O3) at Low Temperature

The (Bi2O3)(1-x-y)(Gd2O3)(x)(Lu2O3)(y) material compounds were prepared by using the solid-state reaction technique under normal air conditions. The heat treatments of the ternary samples were performed firstly at 800 A degrees C for 48 h and then at 750 A degrees C for 100 h. The structural, morphological, and magnetic properties of the materials were characterized by X-ray powder diffraction (XRD), scanning electron microscope, and a Quantum Design PPMS-9T system, respectively. From the XRD results, it was found that the phases of all of the samples consisted of the fluorite-type face-centered cubic delta-Bi2O3 phase. It was observed that the microstructure of the samples is uniformly distributed on the samples' surface. The temperature dependence of magnetization (M-T) measurements showed that the magnetization rose sharply at the critical temperature. The calculated critical temperature values vary from 22.19 to 56.61 K for the samples. All of the samples displayed the paramagnetic behavior. The paramagnetic behavior started from 300 K to very low temperature which varied from 22.19 to 56.61 K. The coercive rise on the magnetization below 22.19 K or 56.61 K with decreasing temperature causes a phase transformation in the delta-Bi2O3 system. This sudden increment was considered as a ferromagnetic or ferrimagnetic phase transition.