Effect of DC current injection on AC supercurrent carrying ability of ring shaped HTS thin films

The effect of DC current injection on the AC current carrying characteristics of superconducting thin film rings was analyzed because of the possibility for using similar ferromagnetic/high temperature superconducting (FM/HTS) structures for contactless investigation of the spin-injection process. It was shown, that the injection leads to decreasing of the critical current IC1, determined by using AC magnetic field. A superposition of AC and DC currents in the HTS ring and a breaking of Cooper pairs may cause this effect. The effect was investigated experimentally at 77 K in HTS Y1Ba2Cu3O7−x (YBCO) thin film samples with YBCO or La0.7Sr0.3MnO3 (LSMO) current injecting electrodes: IC1 of the last sample was found to be more sensitive to the injection process. The results allow concluding, that a change of the IC1 caused by both mechanisms can be evaluated separately and the contactless method can be successfully used for the investigation of the spin-injection effect.

► DC current based spin-injection can be contactless studied in FM/HTS samples using AC field.
► Contactless measured IC depends on currents superposition and pairs breaking effects.
► Contribution of both mechanisms to IC may be evaluated separately.
► Experiments in HTS YBCO films (77 K) with YBCO or LSMO current injecting electrodes confirm the results.