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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

Properties

Magnetite

Maghemite

Hematite

Molecular formula

Fe3O4

γ-Fe2O3

α-Fe2O3

Density (g/cm3)

5.18

4.87

5.26

Melting point (°C)

1583-1597

–

1350

Hardness

5.5

5

6.5

Type of magnetism

Ferrimagnetic

Ferrimagnetic

Weakly ferromagnetic or antiferromagnetic

Curie temperature (K)

850

820–986

956

The saturation magnetization (Ms) at 300 K (A-m2/kg)

92–100

60–80

0.3

Standard free energy of formation ΔGof (kJ/mol)

− 1012.6

− 711.1

− 742.7

Crystallographic system

Cubic

Cubic or tetragonal

Rhombohedral, hexagonal

Structure type

Inverse spinel

Defect spinel

Corundum

Space group

Fd3 m

P4332 (Cubic),

P41212 (tetragonal)

R3c (hexagonal)

Lattice parameter (nm)

a = 0.8396

a = 0.83474 (cubic);

a = 0.8347, c = 2.501 (tetragonal)

a = 0.5034, c = 1.375 (hexagonal)

aRh = 0.5427, α = 55.3o (rhombohedral)