Spinel
ferrite MFe2O4 (M = Mn, Fe, Co, Ni,
and Zn) nanoparticles, coordinated with oleylamine, oleic acid, and
trioctylphosphine oxide, were effectively synthesized by the microwave-assisted
rapid synthesis in 1-dodecanol. Spinel ferrite nanoparticles were
structurally analyzed using HRTEM, SAED, HAADF-STEM, XRD, XRF, XPS,
and EXAFS measurements, which suggested that MFe2O4 nanoparticles have 3.2–4.3 nm in diameter and a spinel
cubic structure with space group Fd3̅m. The metal composition retains an initially charged molar
ratio (Fe: M = 2: 1), and both corresponding elements exist within
a particle. EXAFS analysis performed quantitative determination of
cation distribution in the tetrahedral and octahedral sites of the
spinel structure to gain a deep insight into the influence of the
cation distribution (i.e., the degree of inversion) to their magnetic
properties. Compared with the magnetic properties of the bulk spinel
structure, small spinel ferrite particles at nanoscale showed some
promising applications for the magnetic data storage, catalysts, sensors,
and ferrofluids, due to the significant effect of their particle sizes,
surface coordinating environments, and the cation distributions.