We report the dielectric properties of improper ferroelectric hexagonal (h-)ErMnO₃. From the bulk characterization, we observe a temperature and frequency range with two distinct relaxation-like features, leading to high and even “colossal” values for the dielectric permittivity. One feature trivially originates from the formation of a Schottky barrier at the electrode–sample interface, whereas the second one relates to an internal barrier layer capacitance (BLC). The calculated volume fraction of the internal BLC (of 8%) is in good agreement with the observed volume fraction of insulating domain walls (DWs). While it is established that insulating DWs can give rise to high dielectric constants, studies typically focused on proper ferroelectrics where electric fields can remove the DWs. In ${\mathrm{h}\text{-}\mathrm{ErMnO}}_3$, by contrast, the insulating DWs are topologically protected, facilitating operation under substantially higher electric fields. Our findings provide the basis for a conceptually new approach to engineer materials exhibiting colossal dielectric permittivities using domain walls in improper ferroelectrics.

中文翻译：

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将不正确的铁电畴壁绝缘，作为坚固的势垒层电容器

我们报告了不合适的铁电六角形（h-）ErMnO ₃的介电性能。从整体特征来看，我们观察到温度和频率范围具有两个明显的类似松弛的特征，从而导致介电常数高甚至“巨大”的值。一个特征很简单地源于在电极-样品界面处形成的肖特基势垒，而第二个特征与内部势垒层电容（BLC）有关。内部BLC的计算体积分数（为8％）与观察到的绝缘畴壁（DWs）的体积分数非常吻合。虽然已经确定绝缘DW可以产生高介电常数，但研究通常集中在适当的铁电体上，其中电场可以去除DW。在${\mathrm{H}\text{--}\mathrm{二氧化锰}}_3$相比之下，绝缘DW在拓扑上得到了保护，从而有助于在更高的电场下工作。我们的发现为在不正确的铁电材料中使用畴壁来展示具有巨大介电常数的工程材料提供了一种概念上新方法的基础。