Fabrication, structure, and magnetic properties of electrospun Ce_0.96Fe_0.04O₂ nanofibers

Highlights: • Intrinsic ferromagnetism in electrospun nanofibers of Ce_0.96Fe_0.04O₂ is reported. • The prepared samples were well characterized by XRD, TEM, XANES, XPS, and VSM. • Ce_0.96Fe_0.04O₂ samples are ferromagnetic having Ms of 0.002–0.923 emu/g at 10 kOe. • Oxygen vacancies play an important role to induce room temperature ferromagnetism. • Ferromagnetism observed in Ce_0.96Fe_0.04O₂ is intrinsic. - Abstract: We report room temperature ferromagnetism in ∼30–60 nm nanofibers of Ce_0.96Fe_0.04O₂ calcined at 500, 600, 700, and 800 °C. The as-spun nanofibers were fabricated by electrospinning technique. Nanofibers of the as-spun and calcined samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), and vibrating sample magnetometer (VSM). The XRD and TEM with selected electron diffraction (SEAD) analysis results indicate that the Ce_0.96Fe_0.04O₂ nanofibers have a cubic perovskite structure without any secondary phase. The as-spun samples exhibit a diamagnetic behavior, whereas the calcined Ce_0.96Fe_0.04O₂ samples are ferromagnetic having the specific magnetizations of 0.002–0.923 emu/g at 10 kOe. The results from XAS spectra show the valence state of Fe³⁺ and Fe²⁺ mixed in the Ce_0.96Fe_0.04O₂ samples indicating oxygen vacancies in the nanofibers. Similarly, the results XPS spectra show that there are oxygen vacancies in the nanofibers as a result of Ce³⁺ on the surface. These oxygen vacancies play an important role to induce room temperature ferromagnetism (RT-FM) in the calcined Ce_0.96Fe_0.04O₂ nanofibers. Our results indicate that the ferromagnetic properties of Ce_0.96Fe_0.04O₂ system are intrinsic and are not a result of any secondary magnetic phase or cluster formation. It is suggested that the electrospun Ce_0.96Fe_0.04O₂ nanofibers can be further developed for many applications including ferrofluids, magnetic recording, biomedicine, and spintronics.