Preparation Of LaCoO₃/YBa₂Cu₃O_7-x Embedded Heterojunction And Its Electromagnetic Properties

In ferromagnetlsuperconductor heterojunction,many novel physical phenomena are produced due to the competition between ferromagnetic and superconducting orders.These phenomena have great application potential in the fields of high temperature superconductivity and memory devices.The research in this field is currently mainly focused on the effect of ferromagnet/Yttrium Barium Copper Oxide(YBa2Cu3O7-x,YBCO)heterojunction on the superconductivity of Cu-O superconducting layer perpendicular to YBCO.However,it is difficult to prepare heterostructures that are affected by the Cu-O layer parallel to YBCO by traditional methods.Therefare,there are few reports on the effect of ferromagnet/YBCO heterojunction on the superconductivity parallel to the Cu-O layer.In this study,LaCoO3 dot matrix/YBCO thin film embedded heterojunction was fabricated by photosensitive sol-gel method and double-layer patterned process.The effects of the coupling characteristics of the boundary layer of the heterojunction structure on the superconducting properties were studied by characterization and analysis of the microstructure,fine pattern,electrical and magnetic properties of the films.The main research work of this paper are as follows:(1)The lanthalnum cobaltate(LCO)sol with photosensitive characteristics was prepared by the photosensitive sol-gel method,and the fine patterning process of the gel film was optimized(including pretreatment conditions,ultraviolet exposure time,elution process,etc.).Thus,the micron-level patterns of different shapes were obtained successfully.In addition,the performance of the LCO film were studied,such as phase and the micro-morphology,by modifying heat treatment temperature and single crystal substrate.A uniform and dense epitaxial LCO film was obtain ed on the(001)LaAlO3 su,bstrate with heat-treated temperature of 850?.(2)The fine pattern process of photosensitive YBCO sol was researched,an d the YBCO/LaAlO3 epitaxial film of fine pattern with c-axis orientation was obtained at a sintering temperature of 800?.We have designed a variety of microstructure double-layer engraving masks.And the 5?m,20 ?m,50 ?m and 100 ?m LCO lattice/YBCO composite thin films were fabricated by using UV mask method combined with the LCO and YBCO micro-pattern processing technology.By controlling the height of the LCO lattice to be slightly higher than the thickness of the YBCO layer(average between 98 nm and 109 nm),the lattice embedded heterojunction structure was successfully realized in LCO/YBCO composite thin film.(3)The result shown that there is no significant effect of LCO lattice embedded in the YBCO film on the critical temperature Tc.When without magnetic field,the small-size lattice embedded in the YBCO film will reduce the Jc and the critical current value I_c of YBCO.Under an external magnetic field(0 T-3 T),the LCO lattice/YBCO composite film delays the decay rate of Jc and I_c compared with YBCO film,which proves that the embedded heterojunction structure can effectively control the superconducting properties.In the 0 Oe magnetic field,the V-I curve of the 20 ?m LCO lattice/YBCO composite film is higher than that of other samples,and the critical current value I_c is increased.