異質結構鐵磁材料/高溫超導材料：La2/3Ca1/3MnO3/YBa2Cu3O7-x薄膜之不同接面研究

Abstract

本論文藉由脈衝雷射鍍膜(Pulse Laser Deposition，PLD)的技術探討 鐵磁材料與高溫超導材料(Ferromagnetic/Superconducting)的雙層薄膜(bilayers)在不同接面(La,Ca-O/Cu-O & Mn-O/Ba-O)產生的效應。我們選用的是龐磁阻材料La2/3Ca1/3MnO3與高溫超導材料YBa2Cu3O7-x 。利用同步輻射中心X光源進行X近緣吸收結構(XANES)實驗，探討Mn L-edge在不同接面上所發生的電子結構改變，以及LD(Linear Dichroism)效應。實驗發現不同接面的吸收光譜有明顯的能量偏移，原因是因為Mn和Cu在接面上週遭環境與單一塊材的不同，使得電子軌域重新排列，造成Mn 3d與O p軌域交互作用有所不同。而我們用LD(Linear Dichroism)驗證了Mn的3d軌域確實在不同接面的情況下軌域組成有所變化，使得LD(Linear Dichroism)效應顯著。

In this study, epitaxial bilayers of ferromagnetic of La2/3Ca1/3MnO3 (LCMO) and superconducting YBa2Cu3O7-x (YBCO) were grown on SrTiO3 (001) substrates by pulsed laser deposition assisted with high pressure reflection high energy electron diffraction. Two different interfaces (La,Ca-O/Cu-O & Mn-O/Ba-O) have been designed and created to be a model template to understand the coupling behaviors at the interfaces. X-ray absorption near edge spectroscopy (XANES) have been applied to study the electronic structures of LCMO/YBCO with different interfaces. We demonstrate that extensive charge transfer occurs between LCMO and YBCO. In addition, our experiments show there is obvious energy shift in the absorption spectrum Mn L edge of different interfaces. Different interfaces lead to the difference of orbital reconstructions, which confirmed by linear dichroism (LD) effect. This study opens new venue to design the functional interfaces.