Baibara O. Microstructure and properties of the ferromagnetic nanocomposites Co/Al2O3 and Co/SiO2

The effect of the technological magnetic field in the process of deposition on the microstructure of ferromagnetic Со/Al2O3 nanocomposites is revealed, which reduces the percolation threshold to 27 at.% Co. It was associated with a decrease in the tunneling barriers between Co nanoparticles. For the first time, a giant increase of the thermopower in a magnetic field for ferromagnetic nanocomposites Со/Al2O3 is shown and an explanation of this mechanism due to a decrease in the scattering of electrons by magnetic localization centers is presented. A decrease in the thermoelectric power in a magnetic field is revealed for Co/SiO2 ferromagnetic nanocomposites. This effect is explained by the chemical interaction of Co with Si and O2. For the first time for ferromagnetic nanocomposites Со/Al2O3 with a Co content in the range of 12–43 at.%, grown by the EB-PVD method, a small "magnetic exchange shift" (58 Е) was found. Anomalous low-temperature damping of superparamagnetic and ferromagnetic resonance in Со/Al2O3 ferromagnetic nanocomposites is revealed. The character of damping is analyzed taking into account the structure of the shells of nanoparticles.