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The role of iron doping on magnetic properties of hydrothermal anatase TiO2:57Fe (0–1 at. %) nanoparticles is investigated by combining superconducting quantum interference device magnetometry with Mössbauer and electron paramagnetic resonance techniques. The results on both as-prepared and thermally treated samples in reduced air atmosphere reveal complexity of magnetic interactions, in connection to certain iron ion electron configurations and defects (oxygen vacancies, F-center, and Ti3+ ions). The distribution of iron ions is predominantly at nanoparticle surface layers. Formation of weak ferromagnetic domains up to 380 K is mainly related to defects, supporting the bound magnetic polaron model.

X- and Q-band electron paramagnetic resonance (EPR) investigation of different crystalline Alq3 (tris(8-hydroxyquinoline)aluminium (III)) fractions formed by a train sublimation method are reported. Several paramagnetic defect centres corresponding to 1/2, 1, and 3/2 spin are observed at room temperature. Their intensity is dependent on the temperature, nature of the crystalline phase, and preparation conditions. Spectra simulation and analysis based on the spin Hamiltonian appropriate to a high spin system (S≥1) suggest the existence of randomly oriented triplets and quartets in annealed Alq3 fractions. The crystalline Alq3 phases responsible for the EPR powder spectra have been identified by transmission electron microscopy measurements performed on these sample fractions.

-Fe2O3 nanoparticles dispersed in a polymer matrix have been characterized by x-ray diffraction (XRD) and transmission electron microscopy (TEM). The electron paramagnetic resonance (EPR) in 64 Å particles of -Fe2O3 dispersed in a polymer matrix has been investigated in the range 136 - 286 K.