Colossal magnetoresistance of perovskite Nd_0.67Sr _0.33Mn_1-xFe_xO₃ single crystals

S0304-8853(00)00637-5 The effect of Fe doping on the Mn site in the ferromagnetic phases of the perovskite Nd_0.67Sr _0.33Mni_1-xFe_xO₃ single crystals grown by the floating zone method, has been studied. Conduction and ferromagnetism are suppressed by Fe doping. The material with x = 0.1 shows a cluster glass-like behavior with spin freezing temperature T_g = 70 K instead of a long-range ferromagnetic order for mother material (x = 0) with T_c = 240 K. The resistivity for x = 0.1 has a very large peak near T_g, where a metal-insulator transition takes place. Besides, the magnetic field causes the colossal magnetoresistance near T_g. The field of 7 T suppresses the resistivity by an order of magnitude 3 for x = 0.1 single crystal, which is to be compared with reduction of an order of magnitude 1,5 for the sister material, and much larger than the suppression of resistivity near T_c for x = 0 single crystal. Further doped material with x = 0.2 shows the spin-glass-like and insulating behaviors with rather small magnetoresistance. These results are ascribed to the frustration of random competing ferromagnetic and antiferromagnetic interactions with the introduction of Fe³⁺ ions, which do not participate in the double-exchange process.