Fe-doping effects on the electrical and magnetic transitions in polycrystalline Pr 1-xSr xMnO 3 (x = 1/4, 3/8, and 1/2)

Abstract

Electrical and magnetic transitions in Pr 1-xSr xMnO 3 and Pr 1-xSr xMn 0.95Fe 0.05O 3 ceramic samples with x = 1/4, 3/8, and 1/2 have been investigated. It is proved that 5% Fe doping in the system suppresses electrical conduction and ferromagnetism severely, but favours antiferromagnetism. The existence of spin clusters at temperatures above the ferromagnetic transition T C is demonstrated in the Fe-doped x = 1/2 sample, which is caused by the Fe-doping-induced magnetic inhomogeneity. The transport behaviour above T C in this sample is governed by variable-range hopping of the magnetic polarons. For the Fe-doped x = 1/4 sample, the insulator-to-metal (I-M) transition drops behind T C by nearly 80 K; accordingly, two magnetoresistance peaks appear. One is around T C, and the other lies just at the I-M transition temperature. The possible underlying mechanism is discussed qualitatively.