Co-doped Y2O3 optical functional nanoparticles and novel self-assembly squama-like aggregates
Co-doped Y2O3 optical functional nanoparticles with size of 4-10 nm have been synthesized by the plasma arc-discharge method. Meanwhile, novel three-dimensional squama-like macro-aggregates were self-assembled by disordered nanoparticles synthesized simultaneously in the arc-discharge process. The formation mechanism of the aggregates is ascribed to the periodic coagulation of Y nanoparticles. The valence states of Co in Y2O3 lattice can be determined as +2 from XPS spectrum with an etching depth of 6 nm. For Co-doped Y2O3 nanoparticles, upon excitation with 426 nm, a red emission (620 nm) has been observed which originates from 4A2(4F) → 4T1(4P) d-d transitions of Co2+ ions in tetrahedral co-ordination.
Liu,Du,Geng,Ma,Liang,Tong,Zhang
p. 517 - 521
(2009/02/03)
Muon diffusion and relaxation in YCo2
Muons were expected to gain additional information about the spin fluctuations proposed for this enhanced paramagnetic system. At the lowest temperatures the μ+SR signal can be explained by a static Kubo-Toyabe relaxation function. On raising the temperature an interplay is suggested to occur between muon diffusion and electronic relaxation of `Co-clusters' surrounding a Co vacancy yielding a maximum in the fluctuation rate versus temperature curve. This behaviour is similar to that found in the case of paramagnetic impurities in nonmagnetic metals, the `Co-cluster' moment being the analogue to the impurity spin.
Wiesinger,Reichl,Gratz,Mietniowski,Figiel
p. 307 - 310
(2008/10/08)
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