Magneto-resistance, thermal conductivity, thermo-electric power and specific heat of superconductor Gd0.95Pr0.05Ba2Cu2.94M0.06O7−δ (M=Fe, Ni, Zn and Mn)

In the present paper, we present thermal and electrical transport properties of pristine and co-doped samples of high temperature superconductors Gd0.95Pr0.05Ba2Cu2.94M0.06O7−δ. It is found that all the samples, except the Mn co-doped sample, show metallic behavior in the normal state. It is observed that the upper critical field has a correlation with the substituent site of the co-dopant. Thermal conductivity κ ( T ) of all the samples, except the one with Zn co-doping, exhibits a hump like structure around their respective transition temperatures. A negative sign of the measured thermo-power ( S ) in Gd-123 indicates that electron-like carriers dominate the heat transport in the pristine sample; whereas a sign reversal in S , as a consequence of the change of dominant carrier upon doping, is observed. Specific heat ( C P ) measurements show a jump around the transition temperature ( T C ) for the pristine sample, however, such a jump in C P is strongly suppressed for the doped samples.