NMR and Magnetic Studies of Mechanically Alloyed Co_<30>M_<70> (M=Cu, Ag, Au)(Condensed Matter : Electronic Structure, Electrical, Magnetic and Optical Properties)

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Zero-field ^<59>Co NMR, X-ray diffraction (XRD) and magnetization measurements have been made to investigate the mechanical alloying (MA) of ferromagnetic Co_<30>M_<70> (M=Cu, Ag and Au) powder as a function of milling time (MT). The MA in Co_<30>Cu_<70> proceeds rapidly with increasing MT by both the processes of dissolving Cu in the Co matrix and Co in the Cu matrix and is nearly completed for MT=100h. In Co_<30>Ag_<70> the MA hardly proceeds even for MT=300h or more. The MA in Co_<30>Au_<70> proceeds much more slowly than that in Co_<30>Cu_<70> with increasing MT up to 150h and takes place rapidly for MT≈200h. The magnetizations and NMR spectra of the Co_<30>Cu_<70> and Co_<30>Au_<70> samples for MT=200h are similar to each other, indicating that both the samples form similar supersaturated alloys. NMR results of the Co_<30>M_<70> samples milled for MT=200h show large spin fluctuations of Co atoms, which are due to fine sizes of clusters, suggesting that the samples milled for long times consist of nanometer-size clusters.
社団法人日本物理学会の論文
2005-09-15