Search for Superconductivity in Cu-Chlorides and Ferromagnetism in Partially Oxidized CuCl*

The phase diagram of copper-halides shows a rich diversity not only in crystalline structure, but also in magnetic and electronic properties. In particular, the chemically unstable CuCl has been proposed several times as a candidate for high-temperature superconductivity. We present a search for superconductivity in systems of CuCl/Si and CuCl$_{2}$/Si, which leads to the observation of ferromagnetism with a Tc of 18 K in bulk CuCl samples [1]. The hitherto unreported magnetism is found to emerge in pure CuCl upon prolonged exposure to humid air. Magnetic field modulated microwave spectroscopy in addition to SQUID magnetometry and x-ray diffraction are used to identify phase transitions and compare them to the antiferromagnetic transitions in other Copper-chloride structures. \\[4pt] [1] T. Saerbeck, J. Pereiro, J. Wampler, J. Stanley, J. Wingert, O. G. Shpyrko, and Ivan K. Schuller, Journal of Magnetism and Magnetic Materials \textbf{346}, 161 (2013).