我們對磁性錳氧化物、鋰鈦氧化物，及具有巨磁熱效應的材料，進行晶格結構及光譜學的研究。首先在對單晶La1-xSrxMnO3樣品的系列研究中，我們的光譜顯示，隨著Sr含量增加，晶格的楊-泰勒扭曲效應變小。此外，我們在拉曼散射譜發現，當Sr含量高於0.15時，材料的結構會從正交變成菱形晶格。藉由分析聲子頻率隨溫度的變化，我們也第一次發現，當Sr含量很小的時候，樣品在低溫的時候，自旋跟晶格間的耦合常數會很大。我們經過模型的計算，得到這些晶格跟自旋間的耦合常數的大小，比其他的磁性錳氧化物大一個數量級。另外，我們也研究了層狀的錳氧化物系統La1.2(Sr1.8−xCax)Mn2O7。在Ca含量低的時候，我們觀察到內部伸張振動的拉曼聲子頻率會在居里溫度以下產生藍位移現象。結合我所作的變溫晶格研究，我們發現這個頻率的變化，與晶格無關。我們反而可以用偏極子的傳輸模型來解釋。而這個拉曼聲子頻率的異常變化會隨著Ca含量的增加而消失，代表摻Ca會改變晶格環境，從而影響偏極子的傳輸性質。 接著，我在超導性Li1+xTi2O4的研究裡發現，Li1+xTi2O4在中紅外區2000個波數附近，有一個吸收峰，這在高溫超導體銅氧化物是常見的特徵。最後，我們對巨磁熱效應材料，Gd5(Ge2-xFex)Si2，進行了變溫及加磁場的X光繞射實驗，分析其晶格的變化。我們發現對x = 0.05的樣品而言，它的晶格結構在低溫是正交晶格，當溫度升到居里溫度以上，結構會變成單斜晶格。而對x = 0.20的樣品而言，溫度高於居里溫度時，兩種晶格結構的成份會同時存在。而當我們對這兩種樣品使處於比居里溫度略高的溫度並且施加外場時，材料中具有正交晶格與鐵磁性質的成份會增加，單斜部份會減少。我們的結果顯示，材料中兩種結構的比例隨溫度與外加磁場的增減，與樣品表現出的磁性質有緊密的關連性。

We present the optical and structural studies of manganites, lithium-based oxides, and magnetocaloric compounds. The optical reflectance spectra of single crystalline La1-xSrxMnO3 show that the Sr doping reduces the Jahn-Teller distortions. In addition, Raman-scattering measurements show that the crystal structure changes when Sr doping range is up to x = 0.15 at room temperature. Interestingly, we observe giant hardening of some of the infrared- and Raman-active phonon modes in La0.95Sr0.05MnO3 below TCA, which could be caused by spin-phonon coupling; we obtained extremely large spin-phonon coupling constants (6000 ~ 15000 cm-2).. In the case of double layered perovskite, La1.2(Sr1.8−xCax)Mn2O7, we observed that the internal stretching Raman phonon shows a hardening below TC. This hardening phenomenon is not associated with lattice anomalies, and can be well described by a polaron transport model. In addition, the phonon frequency hardening gradually vanishes with increasing the Ca doping level, showing the Ca doping changes the environment of MnO6 octahedral and reduces the double-exchange transport. For the superconducting Li1+xTi2O4 samples, the Raman-scattering spectra show no structure anomaly with decreasing temperature. The optical conductivity exhibits the mid-infrared absorption band around 2000 cm-1, which can be related to electron-electron correlation. Finally, the X-ray powder diffraction patterns of Gd5(Ge2-xFex)Si2 show clearly the structural transition from the orthorhombic to the monoclinic structure for the x = 0.05 sample and structural phases co-existence for the x = 0.20 sample above TC. By applying magnetic field, the monoclinic structure is suppressed but the orthorhombic structure is enhanced for both samples just above TC, which closely relates to the magnetization process. These results suggest that only a small amount of sample participates in phase transformation.

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