Pressure Studies for 1111 and 11 Type Iron-based Superconductors
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1254-L02-02
Pressure studies for 1111 and 11 type iron-based superconductors
Hiroki Takahashi1,2 , Hironari Okada1,2, Hiroyuki Takahashi3, Yoichi Kamihara2,4, Satoru Matsuishi5, Masahiro Hirano5,6, Hideo Hosono4,5,6, Yoshikazu Mizuguch2,7,8 and Yosihiko Takano2,7,8 1
College of Humanities and Sciences, Nihon University, Sakurajosui, Setagaya-ku, Tokyo 156-8550,
Japan 2
Transformative Research-Project on Iron Pnictides (TRIP), Japan Science and Technology
Agency (JST), Sanbancho, Chiyoda-ku, Tokyo 102-0075, Japan 3
Graduate School of Integrated Basic Sciences, Nihon University, Sakurajosui, Setagaya-ku,
Tokyo 156-8550, Japan 4
Materials and Structures Laboratory, Tokyo Institute of Technology, Nagatsuta, Midori-ku,
Yokohama 226-8503 , Japan 5
Frontier Research Center, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama
226-8503, Japan 6
JST, ERATO-SORST, Frontier Research Center, Tokyo Institute of Technology, Nagatsuta,
Midori-ku, Yokohama 226-8503, Japan 7
National Institute for Materials Science, Sengen, Tsukuba, 305-0047, Japan
8
University of Tsukuba, Tennodai, Tsukuba, 305-8577, Japan
ABSTRACT In the recent development of the studies in iron-based superconductors, high-pressure experiments have been played an important role. Large enhancement of Tc with applying pressure and pressure-induced superconductivity were reported in LaFeAsO1-xFx. In this work, electrical, magnetic and structural measurements on 1111 type Ca(Fe1-xCox)AsF and 11 type Fe(Se1-xTex)0.92 under high pressure have been performed. For Ca(Fe1-xCox)AsF, the substitution of Co suppressed the magnetic and structural transitions and raised superconductivity. Pressureinduced superconductivity was observed for x = 0.0 and 0.05. The highest Tc was obtained in parent compound under high pressure, in contrast to LaFeAsO1-xFx. These results suggest that the substitution of Co increases carrier concentration and induces disorder in the FeAs superconducting layer. For FeTe0.92, pressure-induced superconductivity was not detected under high pressure up to 19 GPa, although the resistive anomaly due to the structural and magnetic phase transition was suppressed by applying pressure.
INTRODUCTION The discovery of an iron-based superconductor LaFeAsO1-xFx [1] with Tc of 26 K had a significant impact in the field of condensed matter physics and had triggered the rapid development of extensive investigation of superconductivity. Right after the discovery of LaFeAsO1-xFx, applying pressure on optimally doped one increased Tc to 43 K [2], which is the significantly large enhancement of Tc, compared with the cuprate superconductors. In this way, these results indicate that the compression is one of the important means to investigate the ironbased superconductors. The crystal structure of LaFeAsO1-xFx is tetragonal (space group P4/nmm) and comprises a stack of alternation LaO and FeAs layers. Undoped LaFeAsO does not show superconductivity but exhibits an orthorhombic to tetragonal transition at 165 K [3] and a paramagnetic to antiferrom
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