Preparation of perovskite type manganite on Al2O3 substrate as an excellent buffer layer for YBa2Cu3O7-δ growth

The perovskite type ferromagnetic manganite Pr_0.8Ca_0.2MnO₃ (PCMO) buffer layers for superconducting microwave devices were examined in order to allow Al₂O₃ single crystal to be used as a substrate for YBa₂Cu₃O_7-δ (YBCO) growth and to provide functionality for microwave devices. The use of magnetic buffer layers with YBCO is effective to magnetically controllable superconducting microwave devices. The (0001) surface of the Al₂O₃ and [113]-oriented YBCO are used in this study due to the similarity of ion configurations at the interface. YBCO grown on the PCMO buffer shows a critical temperature of 87.5 K. The straight line of YBCO grown on the Al₂O₃ (0001) buffered by the PCMO shows relatively good transmission property with the insertion loss of less than 0.7 dB below 70 K measured at 2 GHz. These results indicate that PCMO is a suitable magnetic buffer layer for YBCO growth on Al₂O₃ (0001).