AC-Susceptibility Measurements of the Superparamagnetic Relaxation in Systems of Ni_1−xZn_xFe₂O₄ Nanoparticles

Abstract

We present preliminary results from AC-susceptibility experiments aimed at investigating the superparamagnetic relaxation in systems of Ni 1-x Zn x Fe 2 O 4 nanoparticles (average size <D>=7±3 nm) as a function of the Zn content x (0≤ x ≤0.75). We obtained the average blocking temperature <T B > from the characteristic temperature dependence of the imaginary susceptibility χ imag and we found that the relationship between the observation time τ obs and the blocking temperature is excellently described by an Arhenius-type law. The effective energy barrier to magnetization reversal U eff exhibits a strong dependence on the Zn content x, with a pronounced maximum for x=0.5. The average blocking temperature (measured in an 100 Hz oscillating field) exhibits a similar behavior. Our results illustrate the ability to control the superparamagnetic relaxation of ferromagnetic spinel nanoparticles through chemical manipulation.

Structural and magnetic properties of zinc ferrite thin films irradiated by 90 keV neon ions

“…Similarly than for the magnetization, no quantitative dependency on the fluence can be extracted from our data. present study was achieved from the ZFC curve maxima [46][47]. From Figure 7 curves, the ZFC and FC are almost overlapped above , indicating the presence of the small sized particles [48].…”