Paramagnetism in copper monoxide systems

Abstract

This paper describes the problem of high-temperature superconductivity related to investigations of the magnetic susceptibility, electron paramagnetic resonance, and O Kα x-ray emission spectra of samples from the following systems based on copper monoxide: CuO-Cu, CuO-Cu₂O and CuO-MgO. In all these systems, thermal processing results in a paramagnetism which is not observed in the individual components of these systems before they are processed. O Kα spectra of the interface of a Cu-single-crystal CuO film structure indicate the presence of not only Cu²⁺ but also Cu¹⁺ ions in the layer of CuO in close contact with Cu. Possible reasons for the appearance of paramagnetism in these systems are discussed. It is proposed that a paramagnetic layer at the contact between the antiferromagnetic copper monoxide and the other copper-oxide phases or with copper could be the cause of the impurity metastability observed previously in the high-T _c superconducting phase.