La_(1-x)Ca_xMnO_3薄膜的Raman光谱

测量了１３Ｋ到室温下外延生长的Ｌａ１－ｘＣａｘＭｎＯ３薄膜的Ｒａｍａｎ光谱，发现当冷却样品穿过磁有序温度时，纯的和掺Ｃａ２＋的样品的一些Ｒａｍａｎ模式发生红移，而散射强度在转变点附近形成极大值。为了检查散射张量的对称性，进行了左旋和右旋入射光偏振实验，发现当温度降低时，两种入射偏振下散射强度差明显增大，这表明散射过程中有磁激发涉入。这些事实提出了这类材料中单声子－单磁振子散射机制的可能

Raman Scattering in La 1-x Ca xMnO 3 Thin Films

Abstract Raman spectra of epitaxially grown La 1-x Ca xMnO 3 (x=0,0.1,0.33) thin films have been measured from 13 K to room temperature. Red shifts of some Raman Modes in both doped and undoped samples were observed upon cooling the films across the magnetic ordering temperature. The scattering intensities of the corresponding Raman modes exhibit maximum near the magnetic transition temperature. In order to check the symmetry of the Raman tensor involved, right and left circular polarized (RCP and LCP) incident light were used. It was found that with decreasing temperature, intensity differences of some modes were observed for the two scattering geometries, which indicated a strong involvement of magnetic excitations. These facts strongly suggest that the one phonon one magnon scattering mechanism may play an important role in the scattering process in these materials.