| Abstract
| - To understand the influence of surface interactions upon the magnetic properties of magneticnanoparticles, the surface of manganese ferrite, MnFe2O4, nanoparticles have been systematically modifiedwith a series of para-substituted benzoic acid ligands (HOOC−C6H4-R; R = H, CH3, Cl, NO2, OH) andsubstituted benzene ligands (Y-C6H5, Y = COOH, SH, NH2, OH, SO3H). The coercivity of magneticnanoparticles decreases up to almost 50% upon the coordination of the ligands on the nanoparticle surface,whereas the saturation magnetization has increased. The percentage coercivity decrease of the modifiednanoparticles with respect to the native nanoparticles strongly correlates with the crystal field splitting energy(CFSE) Δ evoked by the coordination ligands. The ligand inducing largest CFSE results in the strongesteffect on the coercivity of magnetic nanoparticles. The change in magnetic properties of nanoparticlesalso correlates with the specific coordinating functional group bound onto the nanoparticle surface. Thecorrelations suggest the decrease in spin−orbital couplings and surface anisotropy of magnetic nanoparticlesdue to the surface coordination. Such surface effects clearly show the dependence on the size ofnanoparticles.
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