  We have developed a simple precipitation route to synthesize magnetite
(Fe3O4) nano-particles with controlled size without any requirement of
calcination step at high temperatures. The study of these nano-particles
indicates an enhancement in saturation magnetization with reduction in size
down to ~10 nm beyond which the magnetization reduces. The latter is attributed
to surface effects becoming predominant as surface to core volume ratio
increases. From the view -point of applications, 10 nm size of magnetite
particles seems to be the optimum.
