Structural transition and associated magnetic properties of heat treated electrospun one-dimensional CaFe2O4

An aqueous solution containing polyvinyl alcohol, calcium nitrate and ferric nitrate was electrospun to yield smooth nanocomposite fibers with diameter in the range of 160 nm. As-synthesized nanofibers were heat treated at different temperatures ranging from 400 to 1000 degrees C to remove the organic matter and induce crystallization of CaFe2O4. Room temperature X-ray diffraction studies showed that CaFe2O4 nanowires existed in single phase cubic structure in as-spun nanofibers heat treated up to 500 degrees C. However, a slow transformation of cubic spinel nanostructure to orthorhombic nanostructure was observed when heat treated above 500 degrees C. The sample heat treated at 1000 degrees C for 8 h yielded a single phase orthorhombic CaFe2O4 nanowires. Magnetization curves recorded at low temperatures indicated superparamagnetic behavior in cubic CaFe2O4 nanowires. Super paramagnetism persisted in cubic samples obtained by heat treated as-spun nanofibers up to 500 degrees C. As-spun nanofibers heat treated at 500 degrees C exhibited superparamagnetic characteristics with saturation magnetization of 18.45 emu/g whereas nanofibers heat treated at 1000 degrees C exhibited ferrimagnetic nature with saturation magnetization of 2.19 emu/g.

Automated summary

The aqueous solution containing polyvinyl alcohol, calcium nitrate, and ferric nitrate was electrospun to produce smooth nanocomposite fibers with a diameter of 160 nm. Heat treatment at different temperatures induced crystallization of CaFe2O4, with a transformation of the structure from cubic to orthorhombic observed above 500 degrees C. The nanofibers heat treated at 1000 degrees C exhibited a single phase orthorhombic CaFe2O4 structure with a ferrimagnetic nature.