Study of structural, magnetic and electrical properties of the rare-earth manganite Nd0.67Sr0.16Ca0.17Mn0.75Fe0.25O3

We present a comprehensive investigation into the structural, magnetic, and electrical properties of polycrystalline Nd0.67Sr0.16Ca0.17Mn0.75Fe0.25O3 (NSCMFO). The NSCMFO perovskite manganite was synthesized using a conventional high-temperature solid-state reaction. X-ray diffraction (XRD) revealed an orthorhombic crystal structure with Pbnm symmetry, and Rietveld refinement was employed to determine precise structural parameters. Magnetic measurements, conducted between 0 and 300 K under a 0.05 T magnetic field, showed the simultaneous presence of antiferromagnetic (AFM) and ferromagnetic (FM) order at Néel temperature (TN) of 43 K, as evidenced by temperature-dependent magnetization curves in field-cooled (FC) and zero-field-cooled (ZFC) modes in addition to a charge ordering transition (TCO) observed at 397 K. Electrical resistivity measurements from 100 to 300 K demonstrated semiconducting behavior across the investigated temperature range. The persistent semiconductivity at the 25% Fe3+ doping level is attributed to a reduced number of available hopping sites for Mn eg(↑) electrons, a consequence of Mn3+ substitution by Fe3+ which weakens the double exchange (DE) interaction. Analysis of the resistivity data suggests that electrical transport is governed by a combination of adiabatic small polaron hopping (SPH) and variable range hopping (VRH) mechanisms, with the VRH model being the dominant conduction mechanism.