Magnetothermopower of nanocomposites in the vicinity of the percolation threshold

Abstract

The field dependences of the thermopower of composites with Co and Co{sub 45}Fe{sub 45}Zr{sub 10} nanoparticles in the Al{sub 2}O{sub n} insulator matrix are studied in magnetic fields up to 10 kOe at room temperature with compositions up to the percolation threshold (i.e., in the region where tunnel conductivity takes place). In composites obtained in argon, negative magnetothermopower (i.e., a decrease in the thermopower in strong magnetic fields) is observed, while positive magnetothermopower is observed in composites obtained in the atmosphere of argon and oxygen. It is shown that the theory developed for tunnel magnetothermopower in nanocomposites makes it possible to explain the results on a qualitative level in the case when the local density of electron states at the surface of nanoparticles depends on the sputtering conditions. Nanocomposites CoFeZr{sub x}(Al{sub 2}O{sub n}){sub 100-x}) obtained in argon and nitrogen display a strong asymmetry of magnetothermopower relative to the magnetic field direction; this anisotropy is associated with anisotropy of these nanostructures.