- 學位論文
基板應力對La0.85Zr0.15MnO3薄膜其電子結構及磁性影響之研究
Strain Effect on Electronic and Magnetic Properties of Epitaxial La0.85Zr0.15MnO3 Thin Films
摘要
本論文主要以X光吸收光譜實驗研究成長於SrTiO3 (STO) (對LZMO薄膜僅具些微的壓縮應力) 以及MgO (對LZMO薄膜具拉撐應力) 基板的鑭鋯錳氧 (LZMO) 薄膜其電荷、軌道、自旋、傳輸和磁性特質的相關性。實驗包含在不同溫度下Mn K、L3,2-edge X光吸收近邊緣結構 (XANES)、線二向性 (XLD)、磁圓二向性 (XMCD) 以及 Mn K-edge延伸X光吸收精細結構 (EXAFS)。X光線二向性實驗發現在室溫時，LZMO/STO Mn 3d eg電子，傾向較多之佔據在 x2-y2 軌域；LZMO/MgO傾向較多之佔據在 3z2-r2 軌域。在80K時則呈現相反的趨勢，LZMO/STO Mn 3d eg電子，傾向較多之佔據在 3z2-r2 軌域； LZMO/MgO傾向較多之佔據在 x2-y2 軌域。由Mn K、L3,2-edge XANES得知在LZMO薄膜其多重價數由 Mn2+、 Mn3+、 Mn+4所貢獻。對LZMO/STO而言，傾向較多佔據在 3z2-r2 軌域、多重價數的雙交換機制與Mn-Mn鍵結變短，導致電荷傳輸與磁性變強。
並列摘要
The correlation among the charge, orbital, spin, transport and magnetic properties of strained tetravalent ion-doped La0.85Zr0.15MnO3 (LZMO) thin films epitaxially grown on two substrates, SrTiO3 (STO) and MgO, were extensively studied using the x-ray absorption near-edge structure (XANES), x-ray linear dichroism (XLD), x-ray magnetic circular dichroism (XMCD) and the extended x-ray absorption fine structure (EXAFS) at the Mn L3,2- and K-edge at various temperatures. The Mn 3d eg preferential orbital occupation of LZMO/STO changed from in-plane x2-y2 to out-of-plane 3z2-r2 as the temperature was reduced from room temperature to below the transition temperatures of 80 K, while LZMO/MgO, the eg orbital occupation changed oppositely from 3z2-r2 to x2-y2. Mn3+/Mn4+ and Mn+2 multiple valence states were involved in the double-exchange mechanism, the stabilization of a preferential orbital occupation of the out-of-plane 3z2-r2 orbital of Mn ions and the shortening of the Mn-Mn bond distance, all of which may play an important role in improving the transport and magnetic properties, owing to the distortion of the MnO6 octahedron by the strain in the LZMO/STO.