本論文將討論磁性材料鑭銪錳氧化物(La1-xEuxMnO3) 系統及其他烯土族錳氧化物(RMO3)之結構、磁性及Mn離子的K吸收邊緣X光吸收光譜性質。
在單位化學式量體積,及A-type反鐵磁序尼爾轉變溫度(TN)範圍由鑭錳氧(LaMnO3)的139K到銪錳氧(EuMnO3)的42K,和小範圍的二維鐵磁擾動。構成軌道序的eg電子在反鐵磁序中形成一個很強的a-b平面鐵磁偶合,又t2g電子在c軸方向有一個很弱的反鐵磁性偶合,由這兩者的各向異性交互作用,使得鑭銪錳氧化物在低磁場中二維鐵磁轉變溫度高於尼爾轉變溫度。由於t2g電子會因為晶格場分裂和扭曲而變的更被局限的原因,所以隨著Eu的摻入係數x增加,二維鐵磁轉變溫度和尼爾轉變溫度會有不規則減少。另外,二維鐵磁轉變溫度和尼爾轉變溫度的值同時都隨著外加磁場的大小而變化,它們的轉變溫度在較高的外加磁場幾乎會合併。

Structural, magnetic and Mn K-edge X-ray absorption structure (XANES) spectrum studies for the La1-xEuxMnO3+d system and other rare earth manganite compounds are reported. The maximum formula unit volume Vf.u., appearance of A-type antiferromagnetic (AF) order with Néel temperature TN ranging from 139 K for LaMnO3 to 42 K for EuMnO3, and the two-dimensional (2D) ferromagnetic short-range fluctuation with T2D > TN in low field is the direct result of anisotropic superexchange interaction for the A-type AF order with strong basal plane ferromagnetic coupling of the orbital-ordered eg electrons (with orbital ordering temperature TOO > room temperature) and weak c-axis antiferromagnetic coupling of t2g electrons. The anomalous decreasing of T2D and TN with increasing Eu parameter x is due to more localized t2g electrons from stronger crystal field splitting and lattice distortion. Both T2D and TN are field dependent and nearly merges at higher applied field.

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