论文标题
应变引起的静态jahn-teller失真在o $^*$ - la $ _ $ _ {7/8} $ sr $ _ {1/8} $ mno
Strain induced stabilization of a static Jahn-Teller distortion in the O$^*$-phase of La$_{7/8}$Sr$_{1/8}$MnO$_3$
论文作者
论文摘要
在室温下，散装la $ _ {7/8} $ sr $ _ {1/8} $ mno $ _3 $处于动态的jahn-teller o $^*$ eptair中，但在较低温度下过渡到静态的，磁性有序的Jahn-Teller阶段。在这里，我们研究了在Srtio $ _3 $上生长的该化合物的$ 6 $单元细胞薄膜，由于晶格不匹配的$ \ lyssim 0.2 \％$，导致小压缩应变。我们将X射线吸收光谱与多重配体场理论相结合，以研究膜中MN的局部电子和磁性。我们确定Mn $ d_ {3z^2-r^2} $轨道的$ 0.13 \; \ text {ev} $比$ d_ {x^2-y^2} $要低，这是一个不成比例的较大的散布，鉴于较小的压缩应变。我们将其解释为由于应变而产生的，从而提供了MNO $ _6 $ octahedra的优先方向，后者在相变附近非常容易受到这种变形的影响。因此，他们沿着$ c $ axis的静态jahn-teller安排集体拉长。此外，我们演示了La $ _ {7/8} $ sr $ _ {1/8} $ MNO $ _3 $的强烈共价特征，并贡献了近50 $ 50 \％的单位式配置$ D^{5} {5} \ underline {l}^1 $ to the Enternate the Egner the Internate the Internement the Indore Waveuttion。最后，我们发现该系统处于高速构型配置，量化轴上本地磁矩的投影约为$ 3.7 \;μ_ {\ text {b}}/\ text {mn} $。但是，我们表明该系统接近高旋转 - 高旋转过渡，这可能是由晶体场效应触发的。
At room temperature, bulk La$_{7/8}$Sr$_{1/8}$MnO$_3$ is in the dynamic Jahn--Teller O$^*$ phase, but undergoes a transition to a static, magnetically ordered Jahn--Teller phase at lower temperatures. Here we study a $6$ unit cells thin film of this compound grown on SrTiO$_3$, resulting in small compressive strain due to a lattice mismatch of $\lesssim 0.2\%$. We combine X-ray absorption spectroscopy with multiplet ligand field theory to study the local electronic and magnetic properties of Mn in the film. We determine the Mn $d_{3z^2-r^2}$ orbital to be $0.13\;\text{eV}$ lower in energy than the $d_{x^2-y^2}$, which is a disproportionately large splitting given the small degree of compressive strain. We interpret this as resulting from the strain providing a preferential orientation for the MnO$_6$ octahedra, which are strongly susceptible to such a deformation in the vicinity of the phase transition. Hence, they collectively elongate along the $c$ axis into a static Jahn--Teller arrangement. Furthermore, we demonstrate the strongly covalent character of La$_{7/8}$Sr$_{1/8}$MnO$_3$, with a contribution of nearly $50\%$ of the one-ligand-hole configuration $d^{5} \underline{L}^1$ to the ground state wavefunction. Finally, we find the system to be in a high-spin configuration, with the projection of the local magnetic moment on the quantization axis being about $3.7\;μ_{\text{B}}/\text{Mn}$. We show, however, that the system is close to a high-spin--low-spin transition, which might be triggered by crystal field effects.
