Physical properties and x-ray absorption spectroscopy of La1-xMnO3 thin films
Chih Wen Chen
|關鍵字:||x光吸收光譜;鑭錳氧;x-ray absorption spectroscopy;La1-xMnO3 thin films|
We have studied La1-xMnO3 thin films, which show the metal-insulator transition similar to the divalent-doped system such as La1-xCaxMnO3. In order to compare, we also studied La0.67Ca0.33MnO3 and La0.67Sr0.33MnO3. The transport and magnetic properties were measured. In our experience, all the samples, except LaMnO3, show the coexistence of the metal-insulator transition and ferromagnetic transition. X-ray absorption spectroscopy was employed to investigate the electronic structure. Surprisingly, the electronic structure of La1-xMnO3, La0.67Ca0.33MnO3 and La0.67Sr0.33MnO3 shows large anisotropy in fluorescence yield mode although it is isotropy in total electron yield mode. This behavior tell us the thin films of La1-xMnO3 system, La0.67Ca0.33MnO3 and La0.67Sr0.33MnO3, are different between surface and bulk. From the change of O K edge XANES around Mn 3d associated peak, Mn 3d associated peak seem not to be responsible for the metal-insulator transition and the associated magnetic ordering. We also report the anisotropy of the O K edge spectra of La1-xMnO3 and the depression of the Mn 3d associated peak due to La deficiency. These results are explained in the context of a decrease in the Mn-O-Mn bond angle along the a, b axis.
|Appears in Collections:||Thesis|