Preparation of directly stacked YBa₂Cu₃O7−δ/oxide magnetic material thin films on Al₂O₃(0001) substrate

The incorporation of magnetic material buffer layers for superconducting microwave devices is examined in order to allow Al 2 O 3 single crystal to be used as a substrate for YBa 2 Cu 3 O 7−δ (YBCO) growth and to provide functionality for microwave devices. Two magnetic materials are examined; Ni 0.35 Zn 0.65 Fe 2 O 4 (NZFO), which is a spinel-type ferrite, and Pr 0.8 Ca 0.2 MnO 3 (PCMO), a perovskite-type ferromagnetic material. The use of magnetic buffer layers with YBCO is applicable to magnetically controllable superconducting microwave devices. The (0001) surface of the Al 2 O 3 and [113]-oriented YBCO are used in this study due to the similarity of ion configuration at the interface. YBCO grown on Al 2 O 3 (0001) buffered with NZFO does not exhibit superconducting behaviour, whereas that grown on the PCMO buffer superconducts at a critical temperature of 87.5 K. This result indicates that PCMO is a suitable magnetic buffer layer for YBCO growth on Al 2 O 3 (0001). This paper was presented at the 8th International Superconductive Electronics Conference, Osaka, Japan, 19–22 June 2001.