Optical, magnetic and structural properties of one-step chemical decomposition approach Ag-Fe3O4 heterodimer structures are reported. We synthesized Ag-Fe3O4 nanoparticles where the Ag nanoparticles of less than 10 nm are physically attached to Fe 3O4 nanoparticles also less than 10 nm. The structural properties of the samples were characterized from X-ray diffraction (XRD) and transmission electron microscopy (TEM) data, which confirmed the existence of heterodimer structures in solution along with isolated magnetite nanoparticles. Optical properties of the obtained samples were studied using UV/vis spectra and compared with Fe3O4 reference nanoparticles in absence of metallic component. Magnetization hysteresis loops for the obtained samples along with Fe3O4 reference sample at 2 K (blocked regime), 50 K (intermediate regime) and 300 K (superparamagnetic regime) and with maximum applied field of ± 20 kOe were performed and correlated to the structural data. Also, magnetization versus temperature curves (Field Cooling-Zero Field Cooling) with static magnetic field of 50 Oe were measured, from which the blocking temperature of the heterodimer sample was about 77 K and for the reference less than 20 K. © 1965-2012 IEEE.