Synthesis of a α-Fe2O3 nanocrystal in its different morphological attributes:: growth mechanism, optical and magnetic properties

Nanospindle and nanorhombohedron and nanocube structured alpha-Fe2O3 was synthesized by the solvothermal method. An intermixing of ethylenediamine (EN) either with ethanol (EtOH) or water in different volume ratios (either 15:85, 50:50 or 85:15 in particular) was used to generate the structural forms of alpha-Fe2O3. The study showed that, during synthesis, EN functioned as a ligand and facilitated the growth of nanostructured samples. The probable growth mechanism is discussed in this paper. Field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM) investigations revealed that the nanostructures were formed through oriented attachment of primary nanocrystals. Fourier transform infrared spectroscopy (FTIR) results showed the presence of Fe-O or Fe-O-Fe vibrational bands whereas UV-vis-NIR optical absorbance spectra showed two prominent absorption bands around 540-560 and 670-680 nm. The room temperature magnetization measurement revealed that the remanence and coercivity depend on the morphological attributes of the nanocrystals. The magnetic hysteresis measurement also revealed that alpha-Fe2O3 nanostructures displayed weak ferromagnetic behaviour at room temperature.