Coexistence of superconductivity and magnetism in HTSC materials? μSR and magnetooptical studies

The evidences for coexistence of superconductivity and magnetic moments of Cu ions in HTSC materials are discussed in frames of different theoretical models. Main attention is paid to the evidences obtained by muon spin rotation (μSR) spectroscopy. The same models are used to analyze the negative result of series of magnetooptical studies of 123 and 214 films, which were directed to determine the magnitude of spin-carrier exchange interaction. The detection sensitivity of 10-5 was achieved in the measurements of magnetic circular dichroism, but in the films of good quality no measurable MCD signal was observed. (orig.)