Temperature dependence of the spin relaxation time of Fe3O4 and hemozoin superparamagnetic nanocrystals

We report experimental temperature and concentration dependences of the natural spin relaxation time of superparamagnetic Fe3O4 and hemozoin nanocrystals. We recorded the H-1 NMR spectrum of 0.5% benzene dissolved in CS2 in function of superparamagnetic particle concentration and temperature, interpreting the 7.261 +/- 0.002 ppm beniene line broadening. Our model for the line broadening includes natural, hyperfine magnetic dipole-dipole, and contact hyperfine contributions. The latter arises due to excharige interaction between benzene molecules and suspended nanoparticles. Estimated frequency of fluctuation in the 1 cm(3) sample volume is in the 10(7) Hz scale. Estimated natural electron spin-lattice relaxation frequencies of the superparamagnetic nanocrystals using frequency of fluctuations, and developed theoretical model applied to analysis of experimental data are in good agreement between each other. Thus the presently developed approach may be used to study fluctuations and natural spin-lattice relaxation frequencies in different media. Published by Elsevier B.V.