The iron oxide nanoparticles hematite (alpha-Fe2O3), maghemite (gamma-Fe2O3), magnetite (Fe3O4) and wustite (FeO) were synthesized via solid-state thermolysis of a chiral, 3D anhydrous potassium tris(oxalato) ferrate( III) (K-3[Fe(C2O4)(3)]) precursor. A controlled heat treatment for the precursor material in air forms these four iron oxide polymorphs. Powder X-ray diffraction (XRD) and Raman spectroscopy were used to identify the different iron oxide nanoparticle polymorphs. The morphology of the obtained iron oxide nanoparticles was determined using a field emission scanning electron microscope (FE-SEM). The magnetic properties of the as-synthesized iron oxide nanoparticles was studied using a superconducting quantum interference device (SQUID), and the results indicated that they are weakly ferromagnetic, ferrimagnetic and paramagnetic in nature. (C) 2014 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.