CHARACTERIZATION OF NANOSIZED NICKEL PREPARED BY SURFACE-REACTIONS OFNI-SIGMA-ORGANYL COMPLEXES ON SILICA - AN ELECTRON-PARAMAGNETIC AND FERROMAGNETIC-RESONANCE STUDY

Dispersed atomic nickel(O) is formed during the reaction of the nickel -sigma-organyl complexes with silanol groups at temperatures below 373 K. That nickel is oxidized to Ni(I) by protons of the silanol groups in a consecutive step. The NL(I) portion amounts to about 70% w/w of t he Ni used. Six different Ni(I) species are detected by electron param agnetic resonance. They are stabilized by interaction with the silica surface and the organic moieties; they act as anchor ions for the Ni(O ) atoms. Ni(O) crystallites stabilized in this way are about 0.5 nm in diameter after a treatment at 373 K. The influence of the Ni(I) ions on the collective, magnetic properties of the clusters is revealed by calculation of ferromagnetic resonance (FMR) spectra using the indepen dent-grain approach according to Schlomann and Kotyukov. A strain of a bout 10 GPa is brought about in the nickel crystallites by the interac tion with NI(I) ions, (C) 1998 John Wiley & Sons, Ltd.