Experimental study on T2 relaxation time of protons in water suspensions of iron-oxide nanoparticles: Waiting time dependence

The T2 relaxation time of protons in water suspensions of iron-oxide particle clusters is found to increase with the waiting time tw after the sample is inserted in the gap of the magnet with 1.41 T field, owing to field induced cluster aggregation. In order to compare the experimental results with existing theories, the measured T2 has to be extrapolated to tw=0, for which a power-law T2 increment versus tw relation is proposed. The extrapolated T2(0) is found to be inversely proportional to the volume fraction v of iron oxide.