Synthesis, structural characterization, and studies of magnetic and dielectric properties of Gd3+ doped cerium oxide (Ce0.90Gd0.10O2−δ)

Abstract

To improve and modify the magneto-dielectric properties of cerium oxide, fractional incorporation of Gd3+ ions in place of Ce4+ in the pristine lattice was considered. Samples of Gd3+ substituted CeO2 (i.e., Ce0.90Gd0.10O2−δ, CGO) were synthesized by the solid state reaction method where the starting materials of CeO2 and Gd2O3 were heat treated at 800 °C for 10 h. X-ray diffractograms were recorded and analyzed by the Rietveld refinement method to confirm the formation of cubic structure as well as the proper and partial replacement of host cations of Ce4+ by strong magnetic impurity of Gd3+ ions. Transmission electron microscopy study of doped sample of Ce0.90Gd0.10O2−δ was carried to yield some important morphological behavior. The static magnetic measurements were performed by superconducting quantum interference device magnetometer. Interestingly nonlinearity due to onset of magnetic ordering was introduced which was clearly found in recorded magnetization (M) vs. field (H) curve below ~ 50 K. Analysis of magnetic behavior suggests the initiation of paramagnetic to ferromagnetic phase transition at low temperatures (below ~ 50 K). Hysteresis loops observed below ~ 50 K also suggest the onset of magnetic ordering in the doped sample, but saturation magnetization was not found owing to the fact that most of the host cations are in paramagnetic phase. The M–T curve is well fitted below ~ 50 K by a combined equation generated from 3D spin wave model and the Curie–Weiss law indicates the coexistence of paramagnetic (PM) and ferromagnetic (FM) phases in the sample. The onset of ferromagnetism in Ce0.90Gd0.10O2−δ was explained by oxygen vacancy mediated F-center exchange (FCE) coupling mechanism. Dielectric constant and ac conductivity increases with increase of temperature and frequency. The improved version of magnetic and electric properties of doped cerium oxide may be a potential candidate for dilute magnetic dielectric for applications in charge storage and sensor devices.