Magnetic properties, Fe-57 Mossbauer spectroscopy and H-1 NMR relaxometry of epsilon-Fe2-xGaxO3 nanoparticles: The effect of gallium doping on magnetic and MRI performance
Abstrakt
Magnetic nanoparticles of epsilon-Fe1.76Ga0.24O3 were prepared by thermal treatment of a mesoporous silica matrix impregnated with nitrates. The chosen Ga-doping enhanced magnetization and suppressed the low-temperature spin-reorientation transition typical for epsilon-Fe2O3.
Despite the small mean size of 11 nm, the nanoparticles were in the blocked state over the whole temperature range under study, unlike standard superparamagnetic contrast agents based on other iron oxides or ferrites. The role of Ga-doping in local magnetic properties of the epsilon polymorph of ferric oxide was probed by Fe-57 Mossbauer spectroscopy.
The particles were further coated with silica and their performance in MRI was tested both in relaxometry and ultra-high-field imaging. The obtained dependences of relaxivity on temperature and thickness of the coating were placed in the context of relevant theoretical models of particle-induced relaxation - motional averaging and static dephasing regimes. (C) 2020 Elsevier B.V.
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