Fabrication, structure, and magnetic properties of electrospun Ce0.96Fe0.04O2 nanofibers

We report room temperature ferromagnetism in ∼30-60 nm nanofibers of Ce0.96Fe0.04O2 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 Ce0.96Fe0.04O2 nanofibers have a cubic perovskite structure without any secondary phase. The as-spun samples exhibit a diamagnetic behavior, whereas the calcined Ce0.96Fe0.04O2 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 Ce0.96Fe0.04O2 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 Ce0.96Fe0.04O2 nanofibers. Our results indicate that the ferromagnetic properties of Ce0.96Fe0.04O2 system are intrinsic and are not a result of any secondary magnetic phase or cluster formation. It is suggested that the electrospun Ce0.96Fe0.04O2 nanofibers can be further developed for many applications including ferrofluids, magnetic recording, biomedicine, and spintronics.