Oxygen vacancy and Ce3+ ion dependent magnetism of monocrystal CeO2 nanopoles synthesized by a facile hydrothermal method

Monocrystal CeO2 nanopoles of 15–25 nm in diameter and 300–900 nm or more in length were synthesized within 100 h using hydrothermal method with CeCl3·7H2O as cerium source, NaOH as mineralizer, and ethylenediamine as complexant. The results of XRD and SADE analysis indicate that the as-synthesized CeO2 samples have the fluorite structure. The band gaps of CeO2 samples are 0.08–0.38 eV smaller than that of bulk CeO2. X-ray photoelectron spectroscopy shows that the concentration of Ce3+ is higher than 20% for CeO2 samples. All the as-synthesized CeO2 samples exhibit the room temperature ferromagnetism (RTFM), and the saturation magnetization (Ms) gradually increases with the increase of Eg up to 2.92 eV and then decreases with Eg increasing more. The highest Ms of 0.167 emu/g is obtained from the CeO2 nanopoles synthesized within 100 h. The RTFM mechanism of CeO2 nanopoles has been proposed which can be mainly attributed to the influence of oxygen vacancies and Ce3+ ions.