Papers by Author: Ute Kaiser

Abstract: Copper matrix nanocomposites (materials for coatings) and reinforcements from nanodiamonds, nanosilica or diatomite were fabricated by mechanical alloying, and coatings were produced by the friction cladding method. Investigations included the study of material at all steps of the technological scheme: formation of granules during mechanical alloying; distribution of nanoparticles in the copper matrix after consolidation of granules; structure of coatings and distribution of reinforcements in the coatings. As the result of these investigations, optimal technological conditions of treatment were developed.

Abstract: Ferromagnetism persisting above 375 K and anisotropic ferromagnetic resonance (FMR) spectra have been detected for the first time in Si co-implanted with Mn and As and annealed under appropriate conditions. For comparison, semi-insulating GaAs samples have been implanted with the same ions and subsequently annealed. They also exhibit ferromagnetism with a Curie temperature well in excess of 375 K. High-resolution transmission electron microscopy (TEM) performed on the samples with the best magnetic characteristics has shown the presence of nanoclusters due to the segregation of the implanted species in both Si and GaAs. The angular dependence of the FMR spectra also reveals the existence of magnetic clusters with the hard magnetization axis aligned along the four equivalent <111> crystal axes. The spectra are very similar in Si and GaAs, indicating that the clusters in both materials probably consist of hexagonal MnAs.