In this work, nanocrystalline powders of iron-doped zinc oxide ZnO (iron content 3, 5, and 10 at.%) were prepared utilizing co-precipitation method. X-ray diffraction, scanning electron microscopy, and the Mössbauer spectroscopy were used as complementary methods to investigate the structure and hyperfine interactions of the material. It was found that Fe dopant is incorporated into the ZnO würtzite structure. As confirmed by energydispersive X-ray spectroscopy the distribution of Fe dopant in the obtained samples is homogeneous up to 5 at.%. For 10 at.% of iron, spinel ZnFe2O4 phase was registered both by X-ray diffraction and the Mössbauer techniques. Paramagnetic behavior in Fe-doped ZnO was observed in the Mössbauer spectra at room temperature. Hyperfine interactions parameters indicate the presence of Fe 3+ ions substituting Zn 2+ ions at tetrahedral sites both in the crystallite interior and near the surface of grains.

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Magnetoelectric multiferroics are solid-state materials which exhibit a coupling between ferroelectric and magnetic orders. This phenomenon is known as the magnetoelectric (ME) effect. Multiferroic materials possess a wide range of potential applications in such fields as metrology, electronics, energy harvesting & conversion, and medicine. Multiferroic research is facing two main challenges. Firstly, scientists are continuously trying to obtain a material with sufficiently strong, room-temperature ME coupling that would enable its commercial application. Secondly, the measurement techniques used in multiferroic research are often problematic to implement in a laboratory setting and fail to yield reproducible results. The aim of the present work is to discuss three most commonly used methods in multiferroic studies; the lock-in technique, the Sawyer-Tower (S-T) circuit and dielectric constant measurements. The paper opens with a general description of multiferroics which is followed by mathematical representation of the ME effect. The main body deals with the description of the aforementioned measurement techniques. The article closes with a conclusion and outlook for future research.