Abstract
Monovalent-doped Pr
0.75
Na
0.05
K
0.20
Mn
1–
x
Fe
x
O
3
(
x
= 0–0.04) manganites were prepared using conventional solid-state reaction method to study the effect of Fe
3+
substitution on magnetic and electrical properties and magnetoresistance (MR) effect. An X-ray diffraction measurement analysed using the Rietveld refinement method revealed that all the samples crystallised in orthorhombic structure with
Pnma
space group with a slight increase in unit cell volume from 230.44 (
x
= 0) to 231.27 Å (
x
= 0.04). Fe substitution at
x
= 0.02 reduced metal–insulator transition temperature from 122 (
x
= 0) to 80 K. At
x
= 0.04, the sample exhibited insulating properties in the whole measured temperature region, indicating a weakened double exchange mechanism. The decrease of Curie temperature,
T
C
for all samples from 140.73 (
x
= 0) to 131.59 K (
x
= 0.02) and 126.87 K (
x
= 0.04) indicates weakened ferromagnetic interaction between Mn ions, which may be due to competition between antiferromagnetic and ferromagnetic interaction in the Fe-substituted samples. The increase in hopping energy is attributed to the reduction of available hopping sites because of the reduction of Mn
3+
concentration due to Fe substitution. Fe substitution improved intrinsic MR as evidenced by the increase of MR peak value from 22 to 40% for
x
= 0 and
x
= 0.02, respectively, while high concentration of Fe at
x
= 0.04 increased the extrinsic MR effect. The findings indicate that the MR behaviour can be tuned from intrinsic to extrinsic MR because of Fe substitution at the Mn site.
Graphical abstract