论文标题
氧气缺陷型lamno $ _3 $由jahn-teller扭曲的结构引起的局部极化
Local polarization in oxygen-deficient LaMnO$_3$ induced by charge localization in the Jahn-Teller distorted structure
论文作者
论文摘要
已知过渡金属钙钛矿氧化物的功能特性是由磁性，极化，应变和化学计量学的复杂相互作用引起的。在这里，我们表明，对于具有合作式Jahn-Teller失真的材料，例如Lamno $ _3 $（LMO），轨道秩序还可以与缺陷化学融为一体并诱导新的材料特性。在低温下，LMO表现出强烈的Jahn-Teller失真，将高旋转Mn $^{3+} $ ions的$ e_g $轨道分开，并导致长，短和中间的Mn-o键交替。我们的DFT+$ u $计算表明，由于该轨道顺序，LMO中的电荷定位在氧气空位形成下与其他锰矿（如Srmno $ _3 $）不同，其中两个额外的电子降低了两个MN位点，降低了与空位相邻的两个MN站点。在LMO中，缺陷周围的松弛取决于哪种类型的Mn - O键被破坏，影响$ d $ - 轨道能量，并导致不对称，因此相对于空位而言，极性过多的电子定位。此外，我们表明MN-O键长，轨道顺序，因此电荷定位和极性可通过应变调谐。
The functional properties of transition metal perovskite oxides are known to result from a complex interplay of magnetism, polarization, strain, and stoichiometry. Here, we show that for materials with a cooperative Jahn-Teller distortion, such as LaMnO$_3$ (LMO), the orbital order can also couple to the defect chemistry and induce novel material properties. At low temperatures, LMO exhibits a strong Jahn-Teller distortion that splits the $e_g$ orbitals of the high-spin Mn$^{3+}$ ions and leads to alternating long, short, and intermediate Mn--O bonds. Our DFT+$U$ calculations show that, as a result of this orbital order, the charge localization in LMO upon oxygen vacancy formation differs from other manganites, like SrMnO$_3$, where the two extra electrons reduce the two Mn sites adjacent to the vacancy. In LMO, relaxations around the defect depend on which type of Mn--O bond is broken, affecting the $d$-orbital energies and leading to asymmetric and hence polar excess-electron localization with respect to the vacancy. Moreover, we show that the Mn--O bond lengths, orbital order and consequently the charge localization and polarity are tunable via strain.
