The present article reports an energy efficient method for the synthesis of superparamagnetic ferrite (Fe3O4) nanoparticles (10-40 nm) and their annealing effect on the morphology, size, curie temperature and magnetic behavior at 50, 300, 400 and 500 degrees C. The synthesized nanoparticles were characterized by various spectroscopic techniques like FT-IR and UV-visible. The crystalline structure and particle size were estimated through solid phase as well as the liquid phase using XRD, TEM and DLS techniques. Superparamagnetic behavior of nanoparticles was confirmed by VSM. The EPR study reveals that the main feature of X-Band solid state EPR spectrum has strong transition at g(eff) similar to 3.23 (2100G) and a relatively weak transition at g(eff) similar to 2.05 (3300G). The later transition further confirms the super paramagnetic nature of these nano ferrites. The activation energy and order of weight losses of nano ferrites were found to be: 39.6 KJ mol(-1) and 0.21 orders (600-800 degrees C), respectively, analyze with the help of TGA while the specific surface area (23.1 m(2) g(-1)) and pore size (9 angstrom) were determined by Quanta chrome BET instrument. (C) 2011 Elsevier B.V. All rights reserved.