Shape Evolution of “Multibranched” Mn–Zn Ferrite Nanostructures with High Performance: A Transformation of Nanocrystals into Nanoclusters

Abstract

Monodisperse magnetic Mn–Zn ferrite nanostructures with various morphologies have been successfully synthesized via high-temperature decomposition of metal acetylacetonate (acac) in the presence of oleic acid (OA) and oleyamine (OAm). In a classical crystal nucleation/growth process, differential stabilization of OA on specific crystal facets may alter relative crystal growth rates, resulting in the formation of zero-dimensional (0-D) spherical, cubical, and starlike nanocrystals (ca. 9, 11, 16 nm), respectively. Furthermore, shortening nucleation duration might bring a deficient nucleation and a rapid increase in monomer concentration, which accelerates the subsequent growth process of nanocrystals, leading to the formation of the starlike nanocrystals with larger size (ca. 19–23 nm). They are further oriented to assemble reciprocally, gradually forming initial three-dimensional (3-D) “branched” nanoclusters (ca. 30–40 nm) to minimize the magnetostatic energy, owing to their size-dependent magnetic dipol...