Review on Functional Mixed Anion Layered Compounds and Computational Chemical Analysis on a Representative MALC, Sr2VFeAsO3-δ

Y. Kamihara
Keio University,
Japan

Keywords: superconductivity, mixed anion layered compounds, MALC, superconducting wires, oxygen deficiency

Summary:

Mixed anion layered compounds (MALCs), which contain several different anions in crystallographic sites, are novel functional materials. Indeed, high-Tc superconductors [1], high-efficient thermoelectric conversion materials [2], transparent semiconductor [3], and electrical catalyst for oxygen evolution reaction [4] have been found in MALCs. In the conference, we demonstrate a review on the MALCs and magnetic properties of a representative MALC, Sr2VFeAsO3-δ. Sr2VFeAsO3-δ is a mixed anion layered compound with a thick-blocking layer composed by a perovskite-related vanadium oxide layer. In 2019, an electric and magnetic phase diagram as a function of oxygen deficiency (δ) on superconducting Sr2VFeAsO3-δ was experimentally demonstrated. In this study, the magnetic stability of V and Fe in Sr2VFeAsO3-δ (δ = 0, 0.25, 0.50) was theoretically verified based on the density functional theory. Stable magnetic phases of the V are antiferromagnetic ordered phase between two ferromagnetic V magnetic layers (so-called A-AFM) for δ = 0. And the stable magnetic phases of V are ferrimagnetic ordered phase (Ferri.) for δ = 0.25, 0.50. Magnetic phases of Fe are a stripe-type antiferromagnetic ordered phase (s-AFM) in δ = 0, 0.25, 0.50, although the magnetic phases of the Fe with δ = 0.25 shows almost the same formation energy between s-AFM and paramagnetic (PM) ordered phases. Theoretical magnetic ordered phases are qualitatively consistent with the experimental electronic and magnetic phase diagrams for Sr2VFeAsO3-δ, although quantitative differences appear between measured for amounts of element specific magnetic moments and theoretical ones. [1] Y. Kamihara, et al, J. Am. Chem. Soc. 130, 3296-3297 (2008). Iron-based layered superconductor La[O1-xFx]FeAs (x = 0.05-0.12) with Tc = 26 K [2] M. Ishizawa, et al, J. Appl. Phys. 123, 245104 (2018). [3] K. Ueda, et al, Phys. Rev. B 69, 155305_1-4 (2004). Single-atomic-layered quantum wells built in wide-gap semiconductors LnCuOCh (Ln=lanthanide, Ch=chalcogen). [4] S. Hirai, et al, J. Mater. Chem. A 6, 15102-15109 (2018). Oxygen vacancy-originated highly active electrocatalysts for the oxygen evolution reaction