Percolation conductivity of single-crystal manganite Pr$_{1-x}$Sr$_x$MnO$_3$ ($x$ = 0.22; 0.24) in the phase-separation state

This paper presents an experimental study of the temperature dependences of the electrical resistivity, thermopower, and magnetoresistance of single-crystal manganite Pr$_{1-x}$Sr$_x$MnO$_3$ ($x$ = 0.22, 0.24). The results obtained have been analyzed in terms of the theory of hopping electrical conductivity of manganites in the phase-separation state and the main postulates of percolation theory. In the 2–400-K interval, hopping conductivity with temperature-dependent activation energy has been observed. Near the Curie temperature, the monotonic exponential growth of electrical resistivity with decreasing temperature becomes distorted by formation of finite metallic clusters. For $T\le$ 36 K, the conductivity of Pr$_{0.8}$Sr$_{0.22}$MnO$_3$ follows the Mott law.