Review Version 1 Preserved in Portico This version is not peer-reviewed
Peculiar Magnetic Features and Superconductivity in Sulfur Doped Amorphous Carbon
Version 1 : Received: 3 August 2016 / Approved: 5 August 2016 / Online: 5 August 2016 (07:16:18 CEST)
A peer-reviewed article of this Preprint also exists.
Felner, I. Peculiar Magnetic Features and Superconductivity in Sulfur Doped Amorphous Carbon. Magnetochemistry 2016, 2, 34. Felner, I. Peculiar Magnetic Features and Superconductivity in Sulfur Doped Amorphous Carbon. Magnetochemistry 2016, 2, 34.
We report on magnetic studies of inhomogeneous commercial and synthesized amorphous carbon (a-C) and a-C doped with sulfur (a-CS) powders which exhibit (i) peculiar magnetic behavior and (ii) traces of two superconducting (SC) phase ~ Tc=33 and at 65 K. (i) The temperature dependence of zero-field-cooled (ZFC) curves measured up to room temperature show a well distinguish elusive peaks around 50-80 K, their origin is not yet known. These peaks are totally washed-out in the second ZFC sweeps and in the FC branches as well. As a result, in the vicinity of the peaks, the FC curves lie below the ZFC peaks (FC<ZFC), a phenomenon which is rarely observed. These magnetic anomalies are intrinsic properties of a-C and a-CS materials (ii) SC was observed in three different a-C sources: (a) The commercial a-C powder contains 0.21% of sulfur and it is suggested that two different a-CS phases (at 33 and 65 K) are the origin of the two SC states observed. The compositions of these two phases are not yet unknown. The small SC volume fractions of the 33 K phase can be enhanced by a solid reaction with additional sulfur at 250 ºC. (b) The synthesized a-C powder (obtained from decomposition of sucrose) is not SC. However, when mixed with sulfur and heated at 400 ºC under a protective atmosphere, the a-CS powder obtained also show traces of a SC phase at TC= 42 K. (c)The same occurs in a-C thin films. The as-grown films are not SC but a SC phase at Tc = 34 K emerges after the films were reacted with sulfur at elevated temperatures. It is concluded therefore, that all SC phases observed are due to different unknown a-CS phases. Since the a-C and a-CS powders possess SC and magnetic states, we believe that these powders resemble the high TC curates and Fe-As based systems in which the SC and the magnetic states are closed related to each other.
amorphous carbon; sulfur; superconductivity; peculiar magnetic behavior
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