Characterization and flux flow experiments in CeRu2

We have carried out the flux dow experiments for two single crystal samples with the residual resistivity ratio RRR = 240 and 12 which differ highly i n quality. The peak structure, which is observed in the vicinity of H-c2, i s dominant for the RRR = 12 sample, while it is slightly observed for the R RR = 240 sample. The flux flow, however, starts at a low field for the RRR = 12 sample, compared to that for the RRR = 240 sample. It means that a pin ning force for the RRR = 12 sample is smaller than that for the RRR = 240 s ample. These characteristic features might be closely related to layered de fects and Ru-vacancies which exist heavily in the RRR = 12 sample. (C) 1999 Elsevier Science B.V. All rights reserved.