ELECTRON-PARAMAGNETIC-RESONANCE OF DOPED MAGNETIC FLUIDS - A NEW APPROACH TO PROBE THE PARTICLE-SIZE POLYDISPERSITY

Electron paramagnetic resonance is introduced as a characterization te chnique to obtain the particle size polydispersity of a Cu2+-doped CoF e2O4 water-based magnetic fluid. The polydispersity parameters based o n a log-normal distribution f(R,R(0),sigma) were obtained from the lin e-shape analysis of the Cu2+ resonance line. Excellent agreement betwe en the data obtained from the resonance measurements (R(0) = 7.8 nm an d sigma = 0.23) and from electron microscopy (R(0) = 7.8 nm and sigma = 0.25) was obtained for a large range of doping concentration.