论文标题
三重Perovskite irate Ba $ _ {3} $ coir $ _ {2} $ o $ $ $ _ {9} $
Phase coexistence and negative thermal expansion in the triple perovskite iridate Ba$_{3}$CoIr$_{2}$O$_{9}$
论文作者
论文摘要
分层3 $ d $ -5 $ d $ d $的异常热扩展基于三重perovskite irate ba $ _ {3} $ coir $ _ {2} $ o $ $ $ _ {9} $，使用高分辨率synchrotron衍射进行研究。在107 \ k处的磁结构过渡下方，抗铁磁序的发作与六边形结构的单斜畸变有关。在磁有序状态更深，单斜相变的一部分进一步扭曲，这两个结构相共存至最低的测量温度。我们观察到该阶段共存状态下的负热膨胀，似乎与这些单斜相阶段的温度驱动相对部分密切相关。在该系统中观察到的显着NTE可以由磁交换效果驱动，并且与许多具有明显旋转轨道相互作用的系统相关。
The anomalous thermal expansion in a layered 3$d$-5$d$ based triple perovskite iridate Ba$_{3}$CoIr$_{2}$O$_{9}$ is investigated using high resolution synchrotron diffraction. Below the magneto-structural transition at 107\,K, the onset of antiferromagnetic order is associated with a monoclinic distortion of the hexagonal structure. Deeper within the magnetically ordered state, a part of the monoclinic phase distorts even further, and both these structural phases co-exist down to the lowest measured temperatures. We observe negative thermal expansion in this phase co-existence regime, which appears to be intimately connected to the temperature driven relative fractions of these monoclinic phases. The significant NTE observed in this system could be driven by magnetic exchange striction, and is of relevance to a number of systems with pronounced spin orbit interactions.
