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Table 1 Physical properties of important iron oxides [20,21,22]

From: Multifunctional magnetic iron oxide nanoparticles: diverse synthetic approaches, surface modifications, cytotoxicity towards biomedical and industrial applications

Molecular formulaFe3O4γ-Fe2O3α-Fe2O3
Density (g/cm3)5.184.875.26
Melting point (°C)1583-15971350
Type of magnetismFerrimagneticFerrimagneticWeakly ferromagnetic or antiferromagnetic
Curie temperature (K)850820–986956
The saturation magnetization (Ms) at 300 K (A-m2/kg)92–10060–800.3
Standard free energy of formation ΔGof (kJ/mol)− 1012.6− 711.1− 742.7
Crystallographic systemCubicCubic or tetragonalRhombohedral, hexagonal
Structure typeInverse spinelDefect spinelCorundum
Space groupFd3 mP4332 (Cubic),
P41212 (tetragonal)
R3c (hexagonal)
Lattice parameter (nm)a = 0.8396a = 0.83474 (cubic);
a = 0.8347, c = 2.501 (tetragonal)
a = 0.5034, c = 1.375 (hexagonal)
aRh = 0.5427, α = 55.3o (rhombohedral)