Revealing the Effects of Trace Oxygen Vacancies on Improper Ferroelectric Manganite with In Situ Biasing

Abstract

Multiferroic materials, which exhibit multiple orderings, are promising for next generation data‐storage device applications. YMnO3, in particular, because of the coexistence of the ferroelectricity and (anti)ferromagnetism within one single material, has drawn special attentions to application‐based research. However, the role of defect chemistry related to the behaviors of the ferroelectric polarization has been seldomly studied due to its complexity. In this work, a novel switching behavior of multiferroic YMnO3 single crystal is reported using in situ biasing and Landau based numerical calculation. It is revealed that the domain switching only happens at the topmost surface, which can be well explained by the electric field redistribution due to the trace amount of oxygen vacancies. These in situ observations demonstrate that defect chemistry plays an important role in domain switching and can be utilized as an additional parameter for controlling the distribution of electric field within the multiferroic materials.

Intrinsic and extrinsic conduction contributions at nominally neutral domain walls in hexagonal manganites

“…In general, whenever the local strain field around a specific point defect is similar to that at domain walls, local minimization of the total energy will promote segregation of this type of defect, leading to an accumulation at the domain walls. 24,29,42,43 In contrast, different local strain fields are expected to promote a depletion of point defects at domain walls. Taking such strain effects into account, Figure 3 summarizes previously reported oxygen point defect segregation enthalpies.…”

“…On the one hand, the results reveal that VO segregate away from the neutral walls, with a positive segregation enthalpy of +0.12 eV relative to the bulk. 29 Note that the oxygen vacancy defect chemistry of YMnO3 is dominated by VO4, 29,42,43 which has a 10-20% lower formation energy compared to the other oxygen vacancies. 29 On the other hand, oxygen interstitials tend to segregate towards neutral walls with a negative segregation enthalpy of -0.03 eV relative to the bulk.…”

Unusual electrical conductivity driven by localized stoichiometry modification at vertical epitaxial interfaces

“…Alternatively, a highly 3 attractive device architecture is generated in epitaxial vertically aligned nanocomposite ( VAN) thin films formed by self-assembled phase segregation where the interfaces are flipped perpendicular to the film surface. [21][22][23] The vertical epitaxial interfaces in such VAN structures enables more effective strain coupling and demonstrates profound impact on magnetic coupling, 24,25 magnetoresistance 26 and electrical and ionic transport. 27 Specifically, we previously reported on establishment of a well-ordered VAN architecture using NiO and ferromagnetic LSMO (x = 0.3), and realized perpendicular exchange bias for tailoring magnetotransport.…”

In-situ electron microscopy study of non-volatile resistive switching in Mott insulator VO2

“…In-situ transmission electron microscopy (TEM) has been widely used for resolving the nanoscale changes (both structurally and electronically) on the functional devices. [1][2][3] VO2, a typical Mott insulator, has near room temperature metal-insulator-transition (MIT), which has great potential in the applications for electronic devices. [4,5] The MIT is the result of the rutile-monoclinic structure transition and features volatile resistive switching.…”