Phase transition behavior in Fe2O3 nanofibers

Abstract Hematite (α-Fe2O3) nanofibers were fabricated using the electro-spinning technique and followed by an annealing process in air. The crystalline structure and morphology of the nano-fibers were studied using XRD, SEM, Raman spectra and high-resolution TEM. Zero-field-cooled (ZFC), field-cooling (FC) and field heated (FH) type temperature dependence of magnetization curves of α-Fe2O3 nanofibers are measured in the temperature range 15–390 K. Two kinds of magnetization steps were observed in the temperature dependence of magnetization curves, one is at 300 k which is very weak and the other is in the temperature range of 245–257 K with large thermal hysteresis (12 K). The tiny step at 300 K can be attributed to normal Morin transition in α-Fe2O3 and this was suppressed by the consequent α- to β- phase transition, which caused the pronounced step in the temperature dependence of magnetization curves. This α- to β- phase transition in Fe2O3 nanofibers was further confirmed by in situ TEM observations. This is the first study to describe novel α- to β-phase transition upon cooling.