Synthesis of α-Fe2O3 hexagons and their magnetic properties

alpha-Fe2O3 hexagons are synthesized by a composite-hydroxide-mediated (CHM) method at temperature of 200 degrees C for 24 h. The X-ray diffraction of the synthesized alpha-Fe2O3 sample demonstrates a hexagonal phase with space group of R3c(167) and lattice constants of a=500 angstrom and c=13.62 angstrom. Scanning electron microscopy shows well dispersed hexagons with an average diameter of 3 mu m and a thickness of 300-500 nm. The magnetic properties of the hexagons were also investigated. The plot of magnetization versus temperature (M-T) from 100 to 300 K under an applied field of 1000 Oe indicates that the Morin transition temperature is about 220 K, lower than the normal value (263 K) of bulk alpha-Fe2O3. The hysteresis loop exhibits weak ferromagnetic properties at temperature of 300K The curve of magnetization versus an applied magnetic field (M-H) at temperature of 10 K reveals the antiferromagnetic and hysteretic behaviors caused by surface spin disorder. (C) 2009 Elsevier B.V. All rights reserved.