Effects of pressure on the electrical resistivity of Pr 1Ba 2(Cu 1− xM x) 4O 8 with M=Zn, Ni and x=0, 0.01, 0.02

Abstract

We have measured the effect of pressure on the electrical resistivity of Pr 1Ba 2(Cu 1− x M x ) 4O 8 with M=Zn, Ni and x=0, 0.01, 0.02. At ambient the temperature coefficient of electrical resistivity was positive below 190 K and was negative above 190 K in non-doped Pr 1Ba 2Cu 4O 8; the resistivity attains a maximum at 190 K ( T m). The resistivity below T m was insensitive to pressure, whereas that above T m rapidly increased with pressure. The substitution of Zn for Cu increased the residual resistivity but did not seem to have a distinct effect on the behavior above T m. On the other hand, the substitution of Ni changed the metallic temperature dependence below T m to a semiconducting one. The pressure dependence in these doped compounds was basically the same as that of non-doped sample; the resistivity was still insensitive to pressure at low temperatures even after it changed the sign of temperature coefficient of resistivity with the substitution of Ni. We discuss the cause of the difference in pressure effects between below and above T m.