Preparation of perovskite type manganite on Al/sub 2/O/sub 3/ substrate as an excellent buffer layer for YBa/sub 2/Cu/sub 3/O/sub 7-(delta)/ growth

The perovskite type ferromagnetic manganite Pr/sub 0.8/Ca/sub 0.2/MnO/sub 3/ (PCMO) buffer layers for superconducting microwave devices were examined in order to allow Al/sub 2/O/sub 3/ single crystal to be used as a substrate for YBa/sub 2/Cu/sub 3/O/sub 7-(delta)/ (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 Al/sub 2/O/sub 3/ 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 Al/sub 2/O/sub 3/ (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 Al/sub 2/O/sub 3/ (0001).