Intercalation effect on hyperfine parameters of Fe in FeSe superconductor with T_c = 42 K

¹ Institute of Inorganic and Analytical Chemistry, Johannes Gutenberg-University Mainz - Staudingerweg 9, D-55099 Mainz, Germany
² Department of Chemistry, Taras Shevchenko National University of Kyiv - Volodymyrska 64/13, 01601 Kyiv, Ukraine
³ Department of Chemistry, University of Oxford - Oxford OX1 3QR, UK
⁴ Department of Physics, University of Paderborn - D-33095 Paderborn, Germany
⁵ Max Planck Institute for Chemical Physics of Solids - D-01187 Dresden, Germany

^(a) ksenofon@uni-mainz.de

Received: 30 January 2015
Accepted: 12 March 2015

Abstract

⁵⁷Fe-Mössbauer spectra of superconducting β-FeSe, the Li/NH₃ intercalate product and a subsequent sample of this intercalate treated with moist He gas have been measured in the temperature range 4.7–290 K. A correlation is established between hyperfine parameters and critical temperature in these phases. A strong increase of the isomer shift upon intercalation is explained by a charge transfer from the Li/NH₃ intercalate to the FeSe layers resulting in an increase of up to 42 K. A significant decrease of the quadrupole splitting above 240 K has been attributed to diffusive motion of Li⁺ ions within the interlamellar space.