Dynamic magnetic properties of ZnO nanocrystals incorporating Fe

Research highlights: → We have studied the magnetic properties of ZnO(Fe) nanocrystalline samples. → The aim of this paper was to compare the dynamic magnetic properties of ZnO(Fe) nanocrystals for two methods of synthesis. → We observed different type of dynamic magnetic behavior for two types of magnetic nanocrystals synthesized by hydrothermal and coprecipitation-calcination methods. → For nanocrystals synthesized by hydrothermal process the results of low-field AC susceptibility are satisfactorily explained by superparamagnetic model including inter-particle interactions. → For samples synthesized by calcinations process we observed the spin-glasslike behavior. - Abstract: The aim of the present work is to study the magnetic properties of ZnO(Fe) nanocrystalline samples prepared by two methods of synthesis. We have used the microwave assisted hydrothermal synthesis and traditional wet chemistry method followed by calcination. The detailed structural characterization was performed by means of X-ray diffraction and micro-Raman spectroscopy measurements. The dynamic magnetic properties were studied by means of AC susceptibility χ. The measurements were performed at small AC magnetic field with amplitude not exceeding 5 Oe and different frequency values (from 7 Hz to 9970 Hz). The AC susceptibility maxima have been found for in-phase susceptibility Re(χ) and for out of phase susceptibility Im(χ). We analyzed the observed frequency dependence of the peak temperature in the AC susceptibility curve using the empirical parameter Φ that is a quantitative measure of the frequency shift and is given by the relative shift of the peak temperature per decade shift in frequency, as well as Vogel-Fulcher law.