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

Electrical and magnetic transitions in Pr1−x Srx MnO3 and Pr1−x Srx Mn0.95Fe0.05O3 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 TC is demonstrated in the Fe-doped x = 1/2 sample, which is caused by the Fe-doping-induced magnetic inhomogeneity. The transport behaviour above TC 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 TC by nearly 80 K; accordingly, two magnetoresistance peaks appear. One is around TC, and the other lies just at the I–M transition temperature. The possible underlying mechanism is discussed qualitatively. (Some figures in this article are in colour only in the electronic version)