Folded sheet mesoporous (FSM-16) materials with different Si/Fe ratios (Si/Fe = 90 60 10) have been synthesized by microwave-hydrothermal (M-H) process and characterized by several spectroscopic techniques Electrons spin resonance and Mossbauer spectroscopies along with electron microscopy and X-ray diffraction allowed differentiation of several iron species These species correspond to hematite particles very small "isolated or oligomeric Fe-III species possibly incorporated in the mesoporous silica wall and Fe-III xide clusters either isolated or agglomerated forming rafts at the surface of the silica and exhibiting ferromagnetic ordering Because of their agglomeration these clusters appear with a two-peak size distribution with one peak corresponding to the Isolated clusters formed in the mesopores and still embedded in them (ca 2 nm diameter) and the other corresponding to the agglomerates spread on the surface of the mesoporous silica particles (ca 9 nm) (c) 2010 Elsevier B V All rights reserved