Mn-Rich BaMn_1−xFe_xO_3−δ Perovskites Revisited: Structural, Magnetic, and Electrical Properties of Two New 6H′ Polytypes

Abstract

The crystal and magnetic structures and electrical properties of two new Mn-rich 6H′-type hexagonal perovskites in the BaMn1−x Fe x O3−δ system have been investigated. Structural characterization performed by X-ray, electron, and neutron diffraction and high resolution electron microscopy indicates that both BaMn0.85Fe0.15O2.87 and BaMn0.6Fe0.4O2.72 crystallize in the 6H′ hexagonal polytype (P6̅m2 space group). The structure is formed by tetramers and dimers of face-sharing octahedra that are linked by corners. The anion deficiency is located at random through the hexagonal layers and increases with the Fe-content. In both phases, the central position of the tetramers is fully occupied by Mn, the remaining Mn and Fe cations being randomly distributed over different polyhedra. The Mössbauer spectroscopy data show Fe to be present only as FeIII in octahedral and tetrahedral coordination. The magnetic structure is formed by ferromagnetic sheets with the magnetic moments aligned along the x-axis and stacked antiferromagnetically perpendicular to the c-axis. The electrical properties have been characterized by impedance spectroscopy and reveal both compounds behave as leaky insulators at room temperature with bulk permittivity values <20.

Mixed Metallic Ba(Co,Fe)X0.2O3−δ (X = F, Cl) Hexagonal Perovskites: Drastic Effect of Fe-Incorporation on Structural and Electronic Features

“…A similar behavior for Fe was already observed in the mixed metallic oxide 6H′−BaMn 0.85 Fe 0.15 O 2.87 . 20 In the y = 0 Co compounds, a HS Co 3+ in tetrahedral coordination and LS Co 3+/4+ in octahedral coordination was proposed from DFT-band structure analysis. 21 In the Ba 5 Fe y Co 5−y X 1−x O 13−δ system, we still attribute the tetrahedral Co3 to HS-Co 3+ , but the valence state of the concomitant Fe3 is rather uncertain, taking into account the great stability of both Fe 3+ and Fe 4+ in various coordinations.…”

“…24(1) to +3.17(1)) compared to oxofluorides (from +3. 20(1) to +3.11(1)) taking into account the precision on the titration. For both series, even taking into account a possible halogen-site deficiency, it involves a significant concentration of oxygen vacancies.…”

Molecule-like cluster magnetism and cationic order in the new hexagonal perovskite Ba4Sn1.1Mn2.9O12

“…Many Mn-substituted BaM x Mn 1Àx O 3 systems have been investigated, for instance, with M ¼ Ca, 12,13 Ti, 14,15 In, 16,17 Sn, 18 Sb, 19 Fe, 20 Ru, 21,22 Ir, 23 and rare earth Ln. 24,25 This led to the uncovering of a range of M-cation (partially) ordered 12R perovskites Ba 4 Ti 2 Mn 2 O 12 , 14 Ba 4 InMn 3 O 11.5 , 16 Ba 4 REMn 3 O 12 (RE ¼ Ce and Pr), 24 Ba 4 YMn 3 O 11.5 , 26 and Ba 4 NbMn 3 O 12 .…”

New 10H perovskites Ba5Ln1−xMn4+yO15−δ with spin glass behaviour

“…Many doped BaM x Mn 1Àx O 3 systems have been explored, for example, with M ¼ Ca, 6,7 Ti, 8,9 Fe, 10,11 Co, 12,13 Ru, 14,15 Ir, 16 In, 17,18 and rare earths Ln. [19][20][21][22][23] This led to the discovery of a range of Mcation ordered 10H perovskites Ba 5 26 The Ba 5 MMn 4 O 15 10H perovskite structure consists of close packed BaO 3 layers in a (cchhh) 2 sequence.…”