Ferromagnetic behaviour of Fe-doped ZnO nanograined films

Abstract

SummaryThe influence of the grain boundary (GB) specific area s GB on the appearance of ferromagnetism in Fe-doped ZnO has been analysed. A review of numerous research contributions from the literature on the origin of the ferromagnetic behaviour of Fe-doped ZnO is given. An empirical correlation has been found that the value of the specific grain boundary area s GB is the main factor controlling such behaviour. The Fe-doped ZnO becomes ferromagnetic only if it contains enough GBs, i.e., if s GB is higher than a certain threshold value s th = 5 × 104 m2/m3. It corresponds to the effective grain size of about 40 μm assuming a full, dense material and equiaxial grains. Magnetic properties of ZnO dense nanograined thin films doped with iron (0 to 40 atom %) have been investigated. The films were deposited by using the wet chemistry “liquid ceramics” method. The samples demonstrate ferromagnetic behaviour with J s up to 0.10 emu/g (0.025 μB/f.u.ZnO) and coercivity H c ≈ 0.03 T. Saturation magnetisation depends nonmonotonically on the Fe concentration. The dependence on Fe content can be explained by the changes in the structure and contiguity of a ferromagnetic “grain boundary foam” responsible for the magnetic properties of pure and doped ZnO.

Doping Induced Tailoring in the Morphology, Band-Gap and Ferromagnetic Properties of Biocompatible ZnO Nanowires, Nanorods and Nanoparticles

“…As it is clear from the above morphology and PL results that sp-d exchange interactions and presence of defects are increased with increasing Fe concentration, which may be responsible for the origin of observed FM in Fe doped ZnO nanostructures. Moreover, it has been reported that grain boundaries and grain sizes also play a significant role in the ferromagnetic properties of TM doped ZnO [35]. The ferromagnetic behavior of Fe doped ZnO is believed to be more prominent, if it is comprised of nano-grains [36].…”

Magnetic and superconductivity studies on (In1−Fe )2O3 thin films

“…Hence the magnetic order in our samples could be ferromagnetic regions due to Fe 3+ -F-center-Fe 3+ pairs and paramagnetic sites due to isolated F-centers. Further amorphous grain boundaries may also contribute to the observed ferromagnetism as seen in TM-doped ZnO [40,41] and In 2 O 3 [42] thin films, as our grains are around 100 nm. It was found that polycrystalline samples with high specific area of grain boundaries, i.e.…”

Synthesis of ZnO nanoparticles by hydrothermal method in aqueous rinds extracts of Sapindus rarak DC

“…This is due to the influence of the addition of the surfactant S. rarak on the growth of ZnO nanoparticles. Although the exact non-trivial behavior of ZnO nanocrystals could not be described, the properties may be driven by the grain boundaries in studied samples [12]. On the other hand, the SEM analysis also confirms that ZnO nanoparticles have different morphologies by varying the concentration of the medium.…”