PRESSURE EFFECT ON TC IN RBA2CU4O8 (R = SM, ER, DY) SUPERCONDUCTORS

The pressure dependence of Tc in RBa2Cu4O8 was investigated by the mea surements of electrical resistivity under high pressure up to 10 GPa. It was found that the pressure coefficient of Tc, dTc/dP, does not str ongly depend on the rare-earth element. Below 2 GPa, Tc increases almo st linearly with pressure at a rate of about 5K/GPa. At the higher pre ssure region, dTc/dP gradually decreases with increasing pressure. The origin for the change in Tc and the correlation between the R-depende nce and external pressures are also discussed. The results imply that the shortening of the in-plane Cu-O bond length contributes to the cha nge of Tc in the R124 compounds.