This work uses density-functional theory to model the magnetic properties of bismuth-based perovskite oxides under epitaxial strain. We augment the known transition in BiFeO${}_3$ between rhombohedral-like and tetragonal-like phases occurring at 4.2% compressive epitaxial strain with the variation in magnetic behavior near this boundary. This phase boundary coincides with a transition from G- to C-type magnetic order, as well as with a 90% decrease in the magnitude of the [001]-oriented coupling coefficients. The magnitude of iron magnetization is shown to vary by no more than 3% over the entire range of compressive strain considered. In the BiCrO${}_3$ system, we report a variation in chromium magnetization of over 20%, along with transitions from bulk G-type to regions of C-type order under tensile epitaxial strain and to F-type order under both tensile and compressive epitaxial strains. The region of F-type order stabilized under compression beyond 7.9% epitaxial strain corresponds to a “super-tetragonal” phase structurally similar to the well-known phase of BiFeO${}_3$ exhibiting spontaneous polarization on the order of 150 $\mu$C/cm${}^2$.

中文翻译：

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外延应变下BiFeO3和BiCrO3磁性能的密度泛函理论计算

这项工作使用密度泛函理论来模拟外延应变下铋基钙钛矿氧化物的磁性能。我们增加了 BiFeO 中的已知转变${}_3$在 4.2% 压缩外延应变下发生的类似菱形和类似四方的相之间，随着该边界附近磁行为的变化。该相界与从 G 型磁序到 C 型磁序的转变以及 [001] 取向耦合系数的幅度减小 90% 相吻合。在所考虑的整个压缩应变范围内，铁磁化强度的变化不超过 3%。在 BiCrO${}_3$在系统中，我们报告了超过 20% 的铬磁化变化，以及在拉伸外延应变下从体 G 型到 C 型有序区域以及在拉伸和压缩外延应变下从 F 型有序区域的转变。在超过 7.9% 外延应变的压缩下稳定的 F 型有序区域对应于结构类似于众所周知的 BiFeO 相的“超四方”相${}_3$ 表现出 150 量级的自发极化 $\mu$厘米/厘米${}^2$.