• R M Tiwari

      Articles written in Journal of Chemical Sciences

    • Manganese-mediated ferromagnetism in La2Fe$_{1-x}$Mn$_{2x}$Cr$_{1-x}$O6 perovskite oxides

      R M Tiwari Mrudul Gadhvi Abanti Nag N Y Vasanthacharya J Gopalakrishnan

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      We have investigated the structure and magnetic properties of the perovskite oxides of the formula La2Fe$_{1-x}$Mn$_{2x}$Cr$_{1-x}$O6 ($0 < x < 1.0$). For $0 < x ≤ 0.5$, the members adopt the orthorhombic (Pbnm) structure, where the transition metal atoms are disordered at the 4b sites and the MO6 (M = Fe, Mn, Cr) octahedra become increasingly distorted with increasing 𝑥. For $0.65 ≤ x < 1.0$, the members adopt the rhombohedral (R-3c) structure that is similar to LaMnO$_{3+\delta}$ ($\delta ≥ 0.1$) where the MO6 octahedra are undistorted. While the magnetic properties of the latter series are largely similar to the parent LaMnO$_{3+\delta}$ arising from the double-exchange (DE) between mixed valent MnIII/MnIV, the magnetic properties of the orthorhombic members show a distinct (albeit weak) ferromagnetism ($T_C \sim 200$ K) that seems to arise from a MnIII-mediated superexchange (SE) between FeIII/CrIII in the disordered perovskite structure containing FeIII, MnIII and CrIII.

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