Influence of solvothermal growth condition on morphological formation of hematite spheroid and pseudocubic micro structures and its magnetic coercivity

Influence of solvothermal growth condition on morphological formation and population of defects of hematite spheroid and pseudocubic micro structures and its magnetic properties were studied. Spheroid shaped crystals with different size were obtained from growth solution made of methanol, methanol water, propanol and pseudocubic crystallites with dimension of 1.281 pm size were obtained with propanol-water solution combination at a growth temperature of 200 degrees C. UV absorption and magnetic properties of spheroid and pseudocubic micro structures were size and shape dependant. Spheroid shaped sample grown from precursor solution made of methanol gives intense UV absorption peaks at 360 nm and high coercivity (5.23 KOe) at room temperature. Reduction in magnetic coercivity and remanence of all samples at 5 K with respect to 300 K is attributed to antiferromagnetic nature of hematite with spheroid and pseudocubic morphology. High coercivity (6.2 KOe) at room temperature was observed from micro pseudocubic sample grown with propanol-water combination which is contributed to high aspect ratio, inter particle interaction and crystalline defects. (C) 2016 Elsevier Ltd. All rights reserved

Improved Coercivity of Solvothermally Grown Hematite (alpha-Fe2O3) and Hematite/Graphene Oxide Nanocomposites (alpha-Fe2O3/GO) at Low Temperature

alpha-Fe2O3 and alpha-Fe2O3/graphene oxide (GO) nanocomposites are synthesized by solvothermal method in acetonitrile medium at 200 degrees C. XRD studies reveals the formation of alpha-Fe2O3 and alpha-Fe2O3/GO nanocomposites. Raman studies indicate that GO in alpha-Fe2O3/GO system was more disordered than GO. The enhanced low temperature magnetic saturation and coercivity in alpha-Fe2O3 and alpha-Fe2O3/GO are related to frozen canted spins. Blocking temperature of alpha-Fe2O3/GO is 348 K, which also shows higher coercivity of the order of about 3064 Oe at 5 K. The alpha-Fe2O3/GO composite exhibits thermal hysteresis at Morin transition (Delta T-M = 11K)