Colossal magnetoresistance of perovskite Nd 0.67Sr 0.33Mn 1− xFe xO 3 single crystals

Abstract

The effect of Fe doping on the Mn site in the ferromagnetic phases of the perovskite Nd 0.67Sr 0.33Mn 1− x Fe x O 3 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 Fe 3+ ions, which do not participate in the double-exchange process.