Regensburg 2007 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 8: Superconductivity - Poster Session

TT 8.17: Poster

Monday, March 26, 2007, 14:00–17:45, Poster A

Novel superconducting graphite compound: CaC₆ - synthesis and conduction electron spin resonance study — •Ferenc Murányi, Grzegorz Urbanik, Vladislav Kataev, and Bernd Büchner — Leibniz Institute for Solid State and Materials Research Dresden, 01171 Dresden, PO BOX 270116, Germany

The superconductivity in calcium intercalated graphite (CaC₆) with transition temperature (T_c) of 11.5 K was discovered in 2005. The new material attracts great attention because of its high T_c among intercalated graphite compounds, highly anisotropic critical field (H_c2) and layered structure like MgB₂ or high temperature superconductors. Bulk intercalated samples were prepared during 10 days’ heat treatment of graphite pieces at 350 ^∘C in Li rich Ca/Li alloy. Conduction Electron Spin Resonance (CESR) lines were observed in the temperature range from 4 K to 300 K at 9.5 GHz, in two magnetic field orientations, H∥ c and H∥ ab. The lineshape can be described as a Dysonian line which is characteristic of thick slabs of metals. The g factor (g_c = g_ab = 1.9984 +/- 0.0005), the linewidth (w_c = w_ab = 4 +/- 0.5 G) and the intensity are typical for the metallic state, in both magnetic field orientations.