ИСТИНА

Magnetic nanoparticles are supposed to find applications in a huge variety of fields, including data record and storage, medical diagnosis and treatment, catalysis of chemical reactions and even magnetic greases. In each field the samples should meet special requirements. For example, the nanoparticles designed for medical purposes have to be biocompatible and their magnetic properties should be tuneable in specific ranges. No wonder the most popular base for design of such samples is biocompatible magnetite Fe3O4. The spinel structure of magnetite itself is very flexible and can absorb a huge variety of ions on two crystal sites octahedral [B] and tetrahedral (A). This makes the search among the magnetite-based spinels very prospective. In our study we focused on a series of the Fe1+xGa2-xO4 nanoparticles synthesized by the combustion method. We investigated the structure, magnetic and electronic properties in a wide temperature range of 5 – 300 K From the comparative analysis by XRD, EDS, Raman and Mössbauer spectroscopy it was established the creation of a new spinel phase γ-FeGaO3 mainly located on the particle surface. As a result, we ascertained that the composition consists of the FeGa2O4 core covered by the FeGaO3 shell. Different properties of the samples such as particle size, blocking temperature, anisotropy energy, magnetic and electronic state were observed and discussed as dependent of temperatures of annealing. The evolution of Mossbauer spectra in the series of nanocomposites with different particle size helped us to define the composition of the samples and deduce the correlation between annealing temperature and amount of different ions in different sites of the spinel structure [1]. In addition, we synthesized the bulk FeGaO3 samples and investigated its structure and properties to confirm our statement that the obtained nano-samples consist of the combination of the FeGa2O4 and FeGaO3 phases. Magnetic measurements in combination with Mossbauer data revealed the spin-glass behaviour in nanoparticles, previously observed in bulk samples [2,3].