Inter-particle interactions and magnetism in manganese-zinc ferrite nanoparticles

Manganese-zinc ferrite (MnxZn1-xFe2O4) nanoparticles were synthesized by reverse micelle technique using two different surfactant media-(1) bis-(2-ethylhex1) sodium sulfosuccinate (AOT) and (2) mix of nonylphenol poly(oxyethylene)(5) and nonylphenol poly(oxyethylene)(9) (NP) followed by annealing of precursors to remove the surfactant coating and to obtain better crystalline phase. A comparison of the magnetic properties showed distinct differences in blocking temperature, coercivity and saturation magnetization. Radio-frequency (RF) transverse susceptibility (TS) measurements were in agreement with the static magnetization data. Our precise TS measurements further revealed features associated with anisotropy fields that were dependent on the grain size, crystallinity and interparticle interactions. Overall, we have demonstrated that RF TS is an excellent probe of the dynamic magnetization and influence of effects such as crystallinity and inter-particle interactions in soft ferrite nanoparticles. (C) 2004 Elsevier B.V. All rights reserved.