Correlation between electrospinning parameters and magnetic properties of BiFeO3 nanofibers

Abstract BiFeO3 nanofibers of different morphologies and dimensions were produced by electrospinning varying the collector and thermal treatment. By thermogravimetric analyses (TGA) the thermal behavior of the as-spun nanofiberswas studied. The morphology of the nanofibers was examined by transmission and scanning electron microscopy (TEM and SEM, respectively) while the chemical composition and crystal structure were analyzed by energy dispersive x-ray spectrometry (EDS) and wide angle x-ray diffraction (WAXD). A vibrating sample magnetometer (VSM) was used to evaluate the magnetic properties. Different types of mats with different nanofibers´ dimensions were obtained; while some nanofibers were interconnected, otherswere completely separated and aligned. The thinnest nanofiberswere obtained using an aluminum substrate with folds and after annealing at 550∘C. All samples annealed at this temperature formed pure BiFeO3, while samples annealed at 550 and 750∘C formed an additional Bi2Fe4O9 phase. No iron impurities were detected; the crystallite size of all the nanofibers was between 30 and 36 nm. The saturation magnetization increased with the decrease of the nanofiber´s diameter and increase of nanofibers interconnectivity. Thus, this ferromagnetism behavior was attributed to the suppression of the spiral spin structure of BiFeO3 (which has a 62 nm period) and to the morphology of interconnected nanofibers.