Preparation of all-oxide ferromagnetic/ferroelectric/ superconducting heterostructures for advanced microwave applications

As candidates for functional layers, 3d transition metal oxides with perovs kite structures show some interesting properties, such as ferromagnetism, f erroelectricity and superconductivity. Accordingly, combinations of these p roperties can be used to create new tunable microwave devices. Ferromagneti c/ferroelectric/superconduct multistructures, such as La0.70Sr0.30MnO3 (LSM O)/Pb(Zr0.52Ti0.48)O-3 (PZT)/YBa2Cu3O7-y (YBCO) and YBCO/PZT/LSMO, have bee n fabricated by ArF excimer laser deposition on LaSrGaO4 (LSGO) [001] and ( La0.30Sr0.70)(Al0.65Ta0.35)O-3 (LSAT) [001] substrates. The resulting trila yer films have a highly c-axis oriented structure. Epitaxial YBCO films for med on PZT/LSMO/LSAT have a zero-resistance temperature of 87 K. Moreover, D-E and M-H hysteresis loop are observed for the LSMO/PZT/YBCO//LSGO struct ure using a conventional Sawyer-Tower circuit and a superconducting quantum interference device (SQUID). The remanent polarization and coercive field of the PZT layer are found to be 19 mu C cm(-2) and 275 kV cm(-1) at 70 K, respectively. The remanent magnetic moment and coercive magnetic field are about 2.6 mu(B)/site and 50 Oe respectively at 78 K. Furthermore. the micro wave surface resistance (R-S) (22 GHz) of the YBCO him in the YBCO/PZT/LSMO structure was 1.32 m Omega at 77 K. These results suggest that LSMO/PZT/YB CO structures are favourable for use in superconducting microwave applicati ons such as tunable phaseshifters and filters.