EFFECTS OF PRESSURE ON THE ELECTRICAL RESISTIVITIES OF PRBA2CU4O8 AND PR2BA4CU7O15-DELTA

We have investigated the effects of pressure on the electrical resistivities of PrBa2Cu4O8 (Pr124) and Pr2Ba4Cu7O15-delta (Pr247). The temperature coefficient of the resistivity is positive below 150-190 K (T-m) while that above T-m is negative for both systems. We found that the resistivity below T-m is insensitive to pressure in the pressure range 0-1 GPa and by contrast the resistivity above T-m remarkably increases with increasing pressure. At higher pressures the resistivity below T-m is also affected by pressure. We attribute the positive temperature coefficient of the resistivity below T-m to the metallic conduction along the double chains and the negative one above T-m to the semiconducting conduction through the CuO2 planes.