Reduction Effects in the Electron-Doped High-Tc Cuprates Pr2CuO4 Single Crystal Studied by X-ray Absorption Fine Structure and Transport Property

Dec. 1 12:35-12:50

*Riku Okada1, Yusuke Nagakubo1, Takashi Udagawa1, Eri Takagaki1, Koki Kawabata1, Hideki Kuwahara1, Motofumi Takahama2, Takanori Taniguchi2, Shun Asano2, Kenji Ishii3, Daiju Matsumura4, Takuya Tsuji4, Masaki Fujita2, Tadashi Adachi1
Department of Engineering and Applied Sciences, Sophia University, Kioi-cho, Tokyo 102-8554, Japan1
Institute for Materials Research, Tohoku University, Katahira, Sendai 980-8577, Japan2
Synchrotron Radiation Research Center, National Institutes for Quantum Science and Technology, Sayo, Hyogo 679-5148, Japan3
Materials Sciences Research Center, Japan Atomic Energy Agency, Sayo, Hyogo 679-5148, Japan4

In high temperature cuprate superconductors, doping carriers into parent antiferromagnetic (AF) Mott insulators destroys the AF order and brings about the superconductivity. In 2009, it has been reported that the superconductivity appears in a parent compound and in a wide range of electron concentration through the appropriate reduction of excess oxygen in the so-called T’-type thin films [1] and polycrystals [2], resulting in a phase diagram different from the well-known one. To investigate the superconductivity in the parent T’-cuprates, we performed measurements of the ab-plane electrical resistivity ρab, Hall resistivity and Cu K-edge X-ray absorption fine structure (XAFS) using parent T’-Pr2CuO4 single crystals. Pr2CuO4 single crystals were reduced by the protect annealing [3], followed by the low-temperature [4] and dynamic annealing [5]. XAFS measurements were conducted at BL14B1 in SPring-8, Japan.

Figure shows the difference XAFS spectra of Pr2CuO4 reduced in vacuum at 10-5 Pa. For the protect annealed sample, the absorption intensity around 8981 eV, corresponding to the formation of Cu+ [6], is large, and the additional low-temperature and dynamic annealing brings about further increase of the absorption intensity. These suggest that electrons are doped by the reduction annealing due to the removal of excess oxygen. Comparing the protect annealing at 10-5 Pa and 10-4 Pa, the amount of oxygen deficiency and electron doping were larger at 10-4 Pa. ρab and Hall resistivity revealed that the sample annealed at 10-4 Pa is more conductive than 10-5 Pa. These suggest that Pr2CuO4 becomes conductive by the oxygen deficiency and electron doping.

[1] O. Matsumoto et al., Physica C 469, 924 (2009).
[2] T. Takamatsu et al., Appl. Phys. Express 5, 073101 (2012).
[3] T. Adachi et al., J. Phys. Soc. Jpn. 82, 063713 (2013).
[4] Y. Krockenberger et al., Sci. Rep. 3, 2235 (2013).
[5] Y. L. Wang et al., Phys. Rev. B 80, 094513 (2009).
[6] S. Asano et al., J. Phys. Soc. Jpn. 87, 094710 (2018).

Keywords: T’-type Cuprate Superconductor, X-ray absorption fine structure, Electrical Resistivity, Hall Resistivity