We report on the effect of agglomeration forced by strong electric field in fine particles of nearly ferroelectric YBa2Cu3O7-d superconductor. It turns out that the particles from agglomerates exhibit different morphology than the rest of powder that
attaches to high-voltage electrodes. Study by means of electron paramagnetic resonance revealed in the powder attached to electrodes a narrow spectrum superimposed on Cu2+ anisotropic spectrum common for YBa2Cu3O7-d superconductors. We assume that this narrow spectrum originates from nanopolar regions generated by strong electric discharges taking place during the experiment. Consequently, the effect of agglomeration can be explained in terms of electrostatic interactions between the particles containing nanopolar regions with strong electric dipolar moments.
We report on the effect of organic acid capping on the behavior of magnetite nanoparticles. The nanoparticles of magnetite were obtained using microwave activated process, and the magnetic properties as well as the electron magnetic resonance behavio
r were studied for the Fe3O4 nanoparticles capped with alginic acid. The capped nanoparticles exhibit improved crystalline structure of the surface which leads to an enhanced magnetization. The saturation magnetization Ms increases to ~75% of the bulk magnetization. The improved structure also facilitates quantization of spin-wave spectrum in the finite size nanoparticles and this in turn is responsible for unconventional behavior at low temperatures. In magnetic resonance these anomalies are manifested as an unusual increase in the resonant field Hr(T) and also as a maximum of the spectroscopic splitting geff parameter at low temperatures. The unconventional behavior of the nanoparticles also leads to pronounced upturn of magnetization at low temperatures and a deviation from the Bloch law M(T) T^3/2.
