The Study of the Physical Properties of La0.67Sr0.33MnO3 / YBa2Cu3O7-δ Multi-layer Film Grown on SrTiO3 (001) using Pulsed Laser Deposition

• Main Authors: Marco Miguel Perez Parel, 貝馬可
• Other Authors: Hsiung Chou
• Format: Others
• Language: en_US
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/6g5vhp

碩士 === 國立中山大學 === 物理學系研究所 === 106 === Triplet superconductivity was proposed in 1958, two years after the discovery of BCS theory and became significant in the modern years for it is possible for new applications such as the nondissipational spintronic. However, triplet superconductivity was realized only for low-Tc-superconductor/ferromagnet heterojunction, and no further development since 2010, when the last experiment was conducted. To explore the possibility of triplet superconducting state in high-Tc-superconductor/ferromagnet system, this research aims to develop and study the physical properties of La0.67Sr0.33MnO3 / YBa2Cu3O7-δ multi-layer film grown on SrTiO3 (001) substrate. Pulsed laser deposition (PLD) was the deposition method used to grow YBCO single layer film, LSMO/YBCO double-layer, and LSMO/YBCO multi-layer film on STO (001). YBCO single layer film was grown for varying growing temperature, varying growing pressure, and varying number of laser pulses for a laser frequency of 5 Hz. LSMO/YBCO double-layer film was grown for varying growing pressure. LSMO/YBCO multi-layer film was grown for varying number of pulses used to grow the LSMO film for a laser frequency of 5 Hz. In order to study the physical properties of the film, Resistance-Temperature (R-T) and Current-Voltage (I-V) measurements, X-Ray Diffraction (XRD), Atomic Force Microscopy (AFM), Transmission Electron Microscopy (TEM) were carried out. For the growth of the YBCO single layer film, the optimum growing conditions were found to be 830°C, 200 mTorr, and 6000 pulses. For the growth of LSMO/YBCO double-layer film, the optimum growing pressure was 200 mTorr. For the growth of LSMO/YBCO multi-layer film, the film obtained a root mean square (RMS) as low as 0.80 ± 0.07 nm, a d005 spacing of 2.3388 Å with the lowest percent error of 0.0170%, a critical temperature (Tc) of the YBCO as high as 87 K with an onset at 90 K, and a transition temperature (TP) of the LSMO as high as 353 K. Moreover, our preliminary Ic-H measurements show that Ic decreases with stronger applied magnetic field. Whether or not these results indicate the existence of triplet superconducting state, no conclusion at the present state and further studies are needed. At least, these obtained data shows that the LSMO/YBCO multi-layer film was grown successfully on the STO (001) substrate. Our future plan is to conduct X-Ray Magnetic Circular Dichroism (XMCD) measurements to determine the magnetic properties between the interfaces of the heterostructure, and test the triplet superconducting properties of the material.