日本金属学会誌

J. Japan Inst. Metals, Vol. 63, No. 9 (1999),
pp. 1117-1120

Electrical and Magnetic Percolations in a Two-Dimensional AssemblingProcess of Cobalt Clusters

Saeki Yamamuro, Takehiko Hihara,Kenji Sumiyama and Kenji Suzuki

Institute for Materials Research, Tohoku University, Sendai 980-8577

Abstract:

We have deposited monodispersed Co clusters on substrates using a plasma-gas-condensation-type cluster deposition system. We have studied their two-dimensional assembling process by transmission electron microscopy, in situ electrical conductivity and magnetization measurements in terms of the percolation theory. The electrical conductivity measurement indicates that the critical thickness and conductivity critical exponent depend strongly on the cluster size. The soft-percolation model, which takes into account the wide distribution of connectivity between clusters, is a candidate model to explain this nonuniversality. The critical coverage of clusters (0.63) is much higher than the predicted one (0.45) irrespective of d, due mainly to the partial overlapping of deposited clusters, and partly to an attractive interaction between clusters. The magnetic properties evolve at around and/or below geometrical and electrical percolation thresholds for all the samples.


(Received April 28, 1999)

Keywords:

plasma-gas-condensation, cobalt cluster, cluster deposition, cluster-assembling process, percolation, transmission electron microscopy, electrical conductivity, magnetization


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