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Is it possible to stabilize the 1144-phase pnictides with tri-valence cations?

TitleIs it possible to stabilize the 1144-phase pnictides with tri-valence cations?
Publication TypeJournal Article
Year of Publication2018
AuthorsSong, BQ, Nguyen, MC, Wang, CZ, Canfield, PC, Ho, KM
JournalPhysical Review Materials
Date Published10
Type of ArticleArticle
ISBN Number2475-9953
Accession NumberWOS:000446564500002
Keywordsfamily, Materials Science, rb, rbfe2as2, superconductivity, t-c

A lately discovered 1144 phase has generated significant interest for its high superconducting temperatures, disorder-free doping, and various chemical substitutions. However, it has only been found in iron arsenides (ABFe(4)As(4)), and cations are limited to +1 or +2 valence states (e.g., alkali metals, alkaline earth elements, and Eu). Whether more 1144 phases could be stabilized and whether intriguing properties exist are questions of general interest. In this work, we investigate 1144 iron and cobalt arsenides with tri-valence cations (La, Y, In, Tl, Sm, Gd). We study phase stability among other competing phases: 122 solution phase and phase decomposition. With La as the cation, we predict room-temperature stable 1144 structures: LaAFe(4)As(4) (A = K, Rb, and Cs). Other La-contained 1144 structures tend to form solution phase. The solubility of La is estimated and compared with the experiment. By contrast, we do not find stable 1144 structures with Y as the cation. For In and Tl as cations, two 122-phase compounds are remarkably stable: InCo2As2 and TICo2As2 , which adds to our knowledge about the In(TO-Co-As phase diagram. Stable 1144 phases are found in InKCo4As4 and InRbCo4As4. With Sm and Gd as cations, 1144- or 122-phase iron arsenides are generally unstable. Among structures investigated, we recognize two critical factors for 1144-phase stability: size effect and charge balance, which yields a merging picture with the rule found in previous 1144 systems. Moreover, LaAFe(4)As(4) (A = K, Rb, and Cs), InCo2As2, and TICo2As2 are exhibiting semimetal features and a two-dimensional Fermi surface, similar to iron superconductors.

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Exploratory Theory

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Complex States

Alternate JournalPhys. Rev. Mater.