Controlled growth of single-crystalline, nanostructured dendrites and snowflakes of α-Fe₂O₃: influence of the surfactant on the morphology and investigation of morphology dependent magnetic properties

Abstract

Single-crystalline, nanostructured dendrites, single and double-layered snowflakes of hematite (α-Fe2O3) were synthesized by a well controlled, surfactant-assisted hydrothermal reaction of K3[Fe(CN)6]. By varying the preparatory conditions such as precursor concentration and type of surfactant, we could establish precise control on the morphology of the sample. X-Ray diffraction, Raman analysis and X-ray photoelectron spectroscopic studies have confirmed that the as grown morphologies were hematite. Dendrites were obtained due to weak dissociation of the precursor and controlled diffusion of α-Fe2O3 nanoparticles under non-equilibrium conditions which attach and grow along certain preferred crystal facets. In the presence of a surfactant, single and double-layered snowflakes were formed. The type of surfactant and the nature of micelle formation were proposed to be the key factor for the observed snowflakes and the single or double-layered growth. Magnetic studies have shown morphology dependent magnetic properties with variation in the coercivity values for dendrites, single and double-layered snowflakes.