Enhancement of Magnetoresistance by Co Substitution in Pr0.6Sr0.4Mn1−<italic>x</italic>Co<italic>x</italic>O3

Abstract

We investigate the effect of Co substitution on magnetism, electrical resistivity, and magnetoresistance (MR) in Pr0.6Sr0.4Mn1− x Co x O3( $x=0-0.2$ ). The parent compound Pr0.6Sr0.4MnO3 is a double exchange (DE) ferromagnet with a ferromagnetic (FM) transition at $T_{C} = 305$ K. The long-range FM order persists for $x=0.05$ with a radical downshift in $T_{C}$ (260 K). A decrease in magnetization as well as a drastic increase in electrical resistivity ( $\rho \sim ~0.02~\Omega \cdot \text {cm}$ for $x=0$ to $\sim 10^{7}~\Omega \cdot \text {cm}$ for $x=0.2$ at 10 K) with Co doping indicates the weakening of DE interaction and the evolution of glassy magnetic ground state. For both $x=0$ and 0.05, $\rho $ shows a prominent peak at their respective $T_{C}$ , whereas such a feature is absent for $x\ge 0.1$ . A large enhancement in MR at low temperatures occurs with increasing Co doping (from −45% for $x=0$ to −85% for $x=0.2$ at 10 K at 7 T magnetic field). The occurrence of such a huge MR at low temperatures for Co-doped compounds could be either due to spin-dependent tunneling between FM clusters with the spin-glass-like interface within grains or suppression of spin fluctuations.