A different degree of internal structural disorder is observed in almost id
entical and uniform gamma -Fe2O3 nanoparticles of about 3.5 +/- 0.6 nm, pre
pared by laser pyrolysis, by high-resolution transmission electron microsco
py (HRTEM) and Mossbauer spectroscopy. This structural disorder is responsi
ble for a different degree of spin frustration that takes place not only at
the surface but also inside the particles depending on the preparation met
hod and it has a great influence on the magnetic properties of the material
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