Abstract
Inspired by the recent demonstration that is a two-dimensional electride in which electrons near the Fermi level float between ionic layers, we have conducted a systematic search for 2D electrides by an approach combining crystal structure databases and ab initio electronic structure calculations. Starting from a set of working hypotheses, we have identified six 2D metallic electrides, of which one is nonmagnetic and five are nearly ferromagnetic ferrimagnets with a distinct spin texture. The latter five materials are the first magnetic electrides reported at ambient pressure.
- Received 9 November 2013
DOI:https://doi.org/10.1103/PhysRevX.4.031023
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Published by the American Physical Society
Popular Summary
Solids are typically classified into four categories: molecular, covalent, ionic, and metallic. In the first three types, the valence electrons are localized on individual atoms or a group of atoms. Metals, on the other hand, are characterized by “itinerant electrons” that migrate freely through the crystal without being bound to atoms. Electrides defy this traditional picture by having “floating” valence electrons that exist only in the voids between ions; these substances can accordingly be thought of as excess-electron materials. Known electrides have long been zero dimensional (electrons in cages) or one dimensional (electrons in tubular channels). However, the recent demonstration that dicalcium nitride () is a two-dimensional electride has sparked fresh interest in electrides because of the utility of two-dimensional materials in electronic devices and materials science. , in particular, is an effective electron emitter because of its low work function. We identify two-dimensional electrides other than (and its analogs and ) by combining material databases and ab initio electronic structure calculations.
We search two large-scale crystal structure databases for binary compounds satisfying a set of working hypotheses, and we carry out first-principles electronic structure calculations of the extracted materials. We identify six two-dimensional electrides, one nonmagnetic and five magnetic. The magnetic electrides are nearly ferromagnetic with a peculiar striped pattern of magnetization: Electrons of one spin orientation reside on the ionic layers, and the electrons of the opposite spin exist only in the gap between the ionic layers and are floating. Our discovery represents the first time that magnetic electrides have been found at ambient pressure.
Our work is a testimony to the power of data-driven research, and the magnetic electrides we found may catalyze a new avenue of condensed matter magnetism.
