Presentations

鉄系高温超伝導体の内、最も高い超伝導転移温度を示すSmFeAsO1-xFxの低温合成温度の低減には、正方晶を示すSmFeAsOの結晶相出現条件のうち、最も低い温度を明らかにすることは有用である。過去に報告されたうち、最も低温でのSmFeAsO相出現を、電子顕微鏡とエネルギー分散型X線発光分析による解析を用いて明らかにする。

遷移金属ペロブスカイト酸化物層を単位格子中に含む、複合アニオン層状化合物Sr2TMFeAsO3-d (TM: V, Cr)の磁性と電気的性質に対する酸素欠損量の影響を概説し、あらたに発現した機能性を紹介する。

鉄系高温超伝導体の内, 最も高い超伝導転移温度を示すSmFeAsO1-xFxの母相であるSmFeAsOの合成温度の低温下への試みを報告する. SmFeAsOを常圧下で合成する場合、その最低温度は580C付近に存在することが明らかになった。

遷移金属ペロブスカイト酸化物層を単位格子中に含む、複合アニオン層状化合物Sr2VFeAsO3-deltaを使用した超伝導線作製とテープ状への加工による機能性向上を報告する。

Mixed anion layered compound (MALC) Sr2VFeAsO3-δ is one of the iron-based superconductors with an oxygen-deficient perovskite-related crystal structure of Sr2VO3-δ. The oxygen deficiency (δ) of Sr2VFeAsO3-δ affects to the superconductivity and magnetic ordering : bulk superconductivity with 0.031 =< δ =< 0.145 and V-3d ferrimagnetism with 0.124 =< δ =< 0.631. The ferrimagnetism can possibly enhance the thermoelectrical properties for Sr2VFeAsO3-δ. Sr2VFeAsO3-δ can be a promising thermoelectrical material due to the tenability of carrier by δ, the larger lattice volume and two-dimensional crystal structure. In this report, dimensionless figure of merit (ZT) = ~5×10-5 was demonstrated for Sr2VFeAsO3-δ with δ = 0.150(2), which does not show bulk superconductivity and show V-3d ferrimagnetism. The strategies to enhance ZT for Sr2VFeAsO3-δ will be discussed.

In this study, we demonstrate a Temperature (T)-Pressure (P) phase diagram for (Y,Gd)BCO thin film annealed at T = 573 K-673 K. The T-P phase diagram is an essential information to elucidate possible approach to demonstrate such an anion-doped (Y,Gd)BCO thin films. As-grown (Y,Gd)BCO thin films were made by metal organic depositions and processed on the best annealing condition for obtaining the highest transition temperature, 92.5 K. Crystallographic phase of annealed (Y,Gd)BCO thin films were checked by X-ray diffraction (XRD) (Rigaku, RINT2500Ultra18). XRD patterns of (Y,Gd)BCO are shown in the figure. The orthorhombic crystallographic phase of (Y,Gd)BCO thin films appears in a sample annealed at 673 K.

Sr2CrFeAsO3-δ consists of a carrier conducting FeAs layer and carrier blocking Sr2CrO3-δ layer. Polycrystalline Sr2CrFeAsO3-δ samples were prepared by a solid-state reaction. And hot-pressed (HP) Sr2CrFeAsO3-δ (δ=0.250) were prepared from polycrystalline Sr2CrFeAsO3-δ. The amounts of oxygen deficiency (δ) for the polycrystalline and HP samples were determined assuming a linear relation between δ and lattice volume (V). The c axis of HP Sr2CrFeAsO3-δ sample is slightly oriented along the pressure direction. Transport properties of HP Sr2CrFeAsO3-δ were measured at temperature (T) = 300?673 K. HP Sr2CrFeAsO3-δ exhibits a maximum electrical resistivity (ρ) 58 mΩ cm at 473 K. HP Sr2CrFeAsO3-δ also exhibits a minimum thermal conductivity (κ) 3.5 W m?1 K?1 at 300 K.

EuSn2As2 is magnetic material that was reported by Arguilla et al in 2017. The crystal structure of EuSn2As2 is classified in hexagonal lattice, and the space group is R3-m. In EuSn2As2, a layer of Eu2+ and two [Sn2As2]2- layers are alternately stacked by van der Waals attractoin force. In 2019, EuSn2P2 whose crystallographic structures are identical to EuSn2As2, was reported by Gui et al. Such kinds of crystallographic structures have been focused as candidates for thermoelectric materials from 1954. At present, these are studied again as a candidate substance for which topological transport phenomena may be observed. In this symposium, we demonstrate magnetization (M) as a function of magnetic field (H), Arrott plot, and temperature (T) dependence of spontaneous magnetic polarization (Ms) for polycrystalline EuSn2As2.

We demonstrate a possible electronic structures of the FeSe molecule layers whose properties are dominated by structures in the interface between FeSe and substrates based on density functional theory.

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. [1] 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. [2] And the stable magnetic phases of V are ferrimagnetic ordered phase (Ferri.) for δ = 0.25, 0.50. [3-5] 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.