Abstract Neutron diffraction and magnetization measurements of the Bi0.85Ca0.15Fe1-xMnxO3+δ (x = 0.4, 0.5) compounds have been performed at room and low temperatures to disclose the effect of the mixed-valence Mn substitution on the magnetic structure and properties of the Ca-doped bismuth ferrites near the polar/nonpolar phase boundary. It has been confirmed that the Mn substitution results in the filling of anion vacancies produced by the aliovalent replacement of Bi3+ by Ca2+. The Bi0.85Ca0.15Fe0.6Mn0.4O3+δ compound has the acentric structure specific to the pure BiFeO3 (space group R3c) and displays a G-type antiferromagnetic order at room temperature (m300K = 1.35(2) μB). The magnetic moments localized on the Fe/Mn ions are directed along the polar axis. The spin-reorientation transition from the c to a axis takes place with decreasing temperature. An increase in the Mn concentration gives rise to the polar → nonpolar (R3c → Pnma) structural phase transformation. The nonpolar (x = 0.5) compound has a G-type antiferromagnet structure (TN = 210 K) with spins aligned along the orthorhombic b axis. The low-temperature magnetic moments (m5K = 2.67(2) μB and m5K = 1.80(3) μB for the samples with x = 0.4 and x = 0.5, respectively) are considerably smaller than those predicted for complete spin ordering of the interacting ions of Fe3+, Mn3+ and Mn4+ (>4 μB). While the neutron diffraction measurements reveal no contribution associated with a long-range ferromagnetic order at T = 5 K, a significant increase in the magnetization of the samples, suggesting the formation of a glassy phase, is observed with decreasing temperature.

中文翻译：

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极性/非极性相界附近Ca、Mn掺杂的铋铁氧体的磁性结构和性能

摘要 在室温和低温下对 Bi0.85Ca0.15Fe1-xMnxO3+δ (x = 0.4, 0.5) 化合物进行了中子衍射和磁化测量，以揭示混合价锰取代对磁结构和性能的影响Ca掺杂的铋铁氧体在极性/非极性相界附近。已经证实，Mn 取代导致填充由 Ca2+ 异价置换 Bi3+ 产生的阴离子空位。Bi0.85Ca0.15Fe0.6Mn0.4O3+δ 化合物具有纯 BiFeO3（空间群 R3c）特有的无心结构，并在室温下显示 G 型反铁磁有序（m300K = 1.35(2) μB）。定位在 Fe/Mn 离子上的磁矩沿极轴定向。从 c 轴到 a 轴的自旋重定向转变随着温度的降低而发生。Mn 浓度的增加引起极性→非极性（R3c→Pnma）结构相变。非极性 (x = 0.5) 化合物具有 G 型反铁磁结构 (TN = 210 K)，自旋沿正交 b 轴排列。低温磁矩（对于 x = 0.4 和 x = 0.5 的样品，分别为 m5K = 2.67(2) μB 和 m5K = 1.80(3) μB）远小于相互作用离子完全自旋排序的预测值Fe3+、Mn3+ 和 Mn4+ (>4 μB)。虽然中子衍射测量显示在 T = 5 K 时与长程铁磁有序无关，但样品的磁化强度显着增加，表明形成了玻璃相，