Effective Tuning of Electromagnetic Properties in Sr0.9Y0.1FeO3-δ Ceramics via Higher Valence and Spin Mn Doping at the B-site

Abstract

The perovskite SrFeO3-δ system features a richly tunable structure, offering greater potential for performance regulation and application. Cubic perovskite Sr0.9Y0.1Fe1-xMnxO3-δ (x = 0-0.6) ceramics with A-site Y doping and B-site Mn3+/4+ doping were synthesized by the solid-state reaction method. While x = 0-0.4, the ceramics exhibit a single-phase structure with lattice contraction, due to the substitution of Fe3+/4+ by smaller Mn3+/4+ ions with a higher average valence, which also induces Jahn-Teller distortion along the c-axis of the MnO6 octahedra and reduces the crystal symmetry. When x = 0.6, a minor secondary phase of SrMnO3 appears. Donor doping of Mn leads to the reduction of Fe4+ to Fe3+ (Fe3+% = 50.86-61.98%) and a decrease in oxygen vacancies, reducing the intrinsic hole carrier concentration. The thermal activation energy Ea for small-polaron conduction increases (0.1135-0.1308 eV), resulting in a significant increase in resistivity. Meanwhile, it is discussed that the enhancement of Mn3+-O-Mn4+ double-exchange interactions and the weakening of Fe4+-O-Fe4+ super-exchange interactions lead to a decrease in Neel temperature TN (64-22 K) and a weakening of exchange bias. The introduction of HS-Mn3+/4+ (t2g3eg1/S=2, t2g3eg/S =3/2) promotes the partial transformation of HS-Fe4+ (t2g3eg1, S = 2) into LS-Fe3+(t2g5eg0, S = 1/2). The increase in the effective magnetic moment of B-site ions contributes to an enhancement in magnetization.