Structure and magnetic properties of Ni-poly( p-xylylene) nanocomposites synthesized by vapor deposition polymerization

摘要

AbstractThe relationship between structure, electrical and magnetic properties of thin poly(p-xylylene) - nickel nanocomposite films with Ni concentrations from 5 to 30?vol% was studied. It was found that metal concentration strongly affects size and oxidation state of the nanoparticles and composites morphology. At nickel concentration below 5?vol% the nanoparticles are oxidized to NiO and homogeneously distributed within fine-grained polymer matrix. An increase of Ni concentration up to 10?vol% results in the development of coarse-grained morphology with preferable localization of the nanoparticles at the boundaries of polymeric grains. And finally, in the composite films with nickel concentration above 20?vol%, the fine-grained morphology is observed again, but the nanoparticles are mainly metallic. Effect of the filler content on electrical and magnetic properties of the nanocomposites was elucidated showing that they are determined by percolation phenomenon with the threshold value of about 10?vol%. The well-pronounced magnetic hysteresis as well as ferromagnetic ordering were observed at Ni content above the percolation threshold. The diagrams of magnetic properties of these composites as a function of composition and temperature were elaborated. It was demonstrated that film annealing can be used to control magnetic properties of the composites and strongly enhance magnetoresistance.Graphical abstractDisplay OmittedHighlights?Thin PPX-Ni nanocomposite films were synthesized by low-temperature VDP.?The relationship between structure, electrical and magnetic properties was studied.?Metal concentration strongly affects size and oxidation state of the nanoparticles.?The percolation threshold value is about 10?vol% of nickel.?Ferromagnetic ordering and magnetoresistance effect were observed at high Ni content.]]>