Experimental study on transverse relaxation rate of protons in water suspensions of magnetite nanoclusters: Dependence of cluster sizes, volume fraction, inter-echo time, and waiting time

► T2 of protons in water suspensions of relatively large magnetite clusters is studied systematically. ► Four experimental dependences of T2 are carefully compared with theoretical predictions. ► The results may be used for the design of contrast agents of magnetic resonance imaging.