Magnetic and transport properties of the perovskite Nd0.67Sr0.33M1-xFexO3 (M = Mn, Co)

The effect of Fe doping on the M site in the perovskite Nd0.67Sr0.33M1-xFex O3 (x less than or equal to 0.3) has been studied. Both mother materials ar e ferromagnetic metals with T-c = 260 K for M = Mn and 170 K for M = Co. Nd 0.67Sr0.33Mn0.9Fe0.1O3 shows a spin-glass-like behavior with T-g = 80 K and also a very large resistivity peak near T-g with colossal magnetoresistanc e, which is much larger than that of mother material, Nd0.67Sr0.33Co0.9Fe0. 1O3 keeps a long-range ferromagnetic order with T-c = 140 K. Further doped materials with x = 0.3 for both systems show the typical spin glass and ins ulating behaviors. These results are ascribed to the frustration of random competing ferromagnetic and antiferromagnetic interactions with the introdu ction of Fe3+ ions, which do not participate in the double-exchange process . (C) 2000 Elsevier Science B.V. All rights reserved.