Insulator-metal transition induced by Cr and Co doping in Pr0.5Ca0.5MnO3

The study of the perovskite manganites Pr0.5Ca0.5Mn1-xMxO3 with M = Cr and Co has been carried out. It shows that the doping of the insulating antiferromagnetic phase Pr0.5Ca0.5MnO3 with chromium or cobalt induces an insulator to metal transition. This behavior is exceptional since such a transition has never been observed to date in charge ordered manganites Ln(0.5)Ca(0.5)MnO(3) with an A-site cation of such a small size (Ln = Pr). The transition temperature to the ferromagnetic metallic state ranges from 110 to 150 K and from 60 to 80 K for chromium and cobalt, respectively. These Cr- and Co-doped manganites exhibit colossal magnetoresistance properties with resistance ratios (R-0/R-7T) ranging from 3x10(4) at 60 K to 30 at 150 K for chromium and from 3x10(6) at 60 K to 2x10(4) at 75 K for cobalt. (C) 1997 Academic Press.