Colossal magnetoresistance and spin-glass behavior of the perovskite Nd0.67Sr0.33Mn1-xFexO3

The effect of Fe doping on the Mn site in the ferromagnetic phases of the p erovskite Nd0.67Sr0.33Mn1-xFexO3 (x less than or equal to 0.3) has been stu died. Conduction and ferromagnetism are suppressed by Fe doping. The materi al with x = 0.1 shows a spin-glass-like behavior with spin freezing tempera ture T-g = 80 K instead of a long-range ferromagnetic order for mother mate rial (x = 0) with T-c = 260 K, which has been well confirmed by the DC magn etization and nonlinear AC susceptibility measurements. The resistivity for x = 0.1 has a very large peak near T-g, where a metal-insulator transition seems to take place. Besides, the magnetic field of 7 T causes the colossa l magnetoresistance of 97%, which is much larger than 57% for x = O observe d near T-c. Further doped materials with x = 0.2 and 0.3 show the typical s pin glass and insulating behaviors with very small magnetoresistance. These results are ascribed to the frustration of random competing ferromagnetic and antiferromagnetic interactions with the introduction of Fe3+ ions, whic h do not participate in the double-exchange process. (C) 2000 Elsevier Scie nce B.V. All rights reserved.