Magnetic properties of Co-doped bismuth oxide (δ-Bi2O3) at low temperature

Abstract

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 °C for 48 h and then at 750 °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 δ-Bi2O3 phase. It was observed that the microstructure of the samples is uniformly dis tributed 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 tem perature causes a phase transformation in the δ-Bi2O3 system. This sudden increment was considered as a ferromagnetic or ferrimagnetic phase transition