Bayerisches Geoinstitut, Universität Bayreuth, Universitätsstrasse 30, D-95447, Bayreuth, Germany.
The Institute for Solid State Chemistry, Russian Academy of Sciences, Urals Division, 91 Pervomayskaya Str., Yekaterinburg, 620990, Russia.
Nat Commun. 2018 Oct 8;9(1):4142. doi: 10.1038/s41467-018-06457-x.
A Verwey-type charge-ordering transition in magnetite at 120 K leads to the formation of linear units of three iron ions with one shared electron, called trimerons. The recently-discovered iron pentoxide (FeO) comprising mixed-valent iron cations at octahedral chains, demonstrates another unusual charge-ordering transition at 150 K involving competing formation of iron trimerons and dimerons. Here, we experimentally show that applied pressure can tune the charge-ordering pattern in FeO and strongly affect the ordering temperature. We report two charge-ordered phases, the first of which may comprise both dimeron and trimeron units, whereas, the second exhibits an overall dimerization involving both the octahedral and trigonal-prismatic chains of iron in the crystal structure. We link the dramatic change in the charge-ordering pattern in the second phase to redistribution of electrons between the octahedral and prismatic iron chains, and propose that the average oxidation state of the iron cations can pre-determine a charge-ordering pattern.
在 120K 时，磁铁矿中的 Verwey 型电荷有序转变导致了三个铁离子的线性单元的形成，这些单元共享一个电子，称为三聚体。最近发现的包含八面体链上混合价铁阳离子的五氧化二铁 (FeO) 在 150K 时表现出另一种不寻常的电荷有序转变，涉及铁三聚体和二聚体的竞争形成。在这里，我们通过实验表明，外加压力可以调节 FeO 中的电荷有序模式，并强烈影响有序温度。我们报告了两种电荷有序相，第一种可能包含二聚体和三聚体单元，而第二种则表现出涉及晶体结构中八面体和三角棱柱形铁链的整体二聚化。我们将第二相中电荷有序模式的剧烈变化与八面体和棱柱形铁链之间电子的重新分布联系起来，并提出铁阳离子的平均氧化态可以预先确定电荷有序模式。
