Detailed magnetic structure of Zn_(1-x)Ni_xFe_2O_4 nanoparticles

摘要

The structural and the magnetic properties of Zn_(1-x)Ni_xFe_2O_4 (x=0, 0.20, 0.40, 0.60, 0.80, and 1.00) nanoparticles were investigated. The structure and the particle size were measured by x-ray diffraction and scanning electron microscopy. For ZnFe_2O_4 nanoparticle, particle-size reduction induces the ionic exchange between Zn and Fe ions and promotes the formation of ferrimagnetic (FI) clusters. For NiFe_2O_4, particle-size reduction causes surface spin disorder in nanoparticles, suppressing the ferrimagnetism. For the Zn-rich Zn_(1-x)Ni_xFe_2O_4 (x=0.20 and 0.40) nanoparticles, the Ni doping in ZnFe_2O_4 promotes the ionic redistribution, resulting in the enhancement of FI clusters and a strong ferrimagnetism. For the Ni-rich Zn_(1-x)Ni_xFe_2O_4 (x=0.60 and 0.80), the Zn doping in NiFe_2O_4 also induces strong ferrimagnetism since it decreases the magnetic moment of A sublattices and weakens the surface spin disorder in nanoparticles. Spin-glasslike behavior in the series of samples is reported. Especially for NiFe_2O_4, through measuring the ac susceptibility and employing the critical power and the Vogel-Fulcher models, the dynamics of spin-glasslike state is discussed.