Magnetic field and pressure effects on the electrical resistivity of single crystal Pr_2/3(Ca,Pb)_1/3MnO₃

The effects of magnetic field (H) and pressure (P) on the temperature (T) dependence of electrical resistivity (ρ) are reported for a new manganese-containing compound, Pr_2/3 (Ca,Pb)_1/3MnO₃, which was grown in single-crystal form by a flux method. The material was found to order magnetically with applied-field strength below 175 K, but have zero remanence (M_R) as H→O, i.e., there was no spontaneous magnetization (M_S), only field-induced magnetization (M_i). A zero-field `insulator' to metal transition occurred at 146 K and this transition temperature (T_IM) was found to increase with increasing field strength. The change in resistivity with field, ρ₀-ρ_H, normalized with respect to ρ_H, was 900% at 146 K and H = 5 T. On application of hydrostatic pressure the zero-field resistivity decreased by 200%/GPa above room temperature. The electrical transport observed was consistent with a thermally-activated process, and this process was found to be relatively independent of pressure (0-4 GPa) in the temperature region (300 K-400 K) studied.