Iron oxide nanoparticles have attracted much interest because of their wide application abilities in biological separation, drug delivery, magnetic liquids, diagnostic imaging, solar energy transformation, magnetic devices, microelectronics industry, and as catalysts of different organic reactions. [1,2,3] One of the methods to obtain heteroatomic iron-oxide nanoparticles with transitional metals is using as precursors heteronuclear carboxy clusters. This method is developed during many years in the Laboratory of Bioinorganic Chemistry and Nanocomposites of the Institute of Chemistry of Academy of Sciences of Moldova. In the present work we present the mixed iron-chromium oxides from the trinuclear complex compound with the composition [Fe2CrO(C4H3OCOO)6(CH3OH)3]·NO3·H2O, used as precursor for nanoparticles synthesis. The product obtained under thermal decomposition, and further separation was studied with thermal and elemental analysis, which confirm the formation of mixed oxides with the Fe:Cr ratio of 2:1. The TEM analysis confirm that the obtained oxides are nanoparticles of about 6-20 nm (Figure 1a).figureFig.1a. TEM image. Fig.1b. Mossbauer spectrum. Iron based nanoparticles were also studied by FTIR and Mossbauer Spectroscopy. The obtained Mossbauer spectrum, at room temperature represents a doublet and a sextet (Figure 1b). The obtained data are characteristic to trivalent iron with the spin equal to 5/2.