薄膜Tb1-xDyxMnO3 的介電性質
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2013
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Abstract
在塊材Tb1-xEuxMnO3系統中，錳的磁性結構會隨著晶體的結構參數而改變，並且影響材料在低溫的介電特性。由粉末X-ray繞射得知ab平面Mn-O-Mn鍵角在隨著x的增加而變大，當x大於0.4~0.5，系統的低溫鐵電相變峰也隨之消失。
而塊材TbMnO3(TMO)的介電係數在28 K左右有相變峰，說明此溫度以下系統進入了鐵電相。但在薄膜TMO系統中，所有的研究都沒有找到在28 K左右的相變峰，也就是說在薄膜系統裡，鐵電相似乎是不存在的。原因可能是基板的應力造成晶格的扭曲，改變原本造成鐵電性出現的磁性結構。為了瞭解其應力的影響，將同樣在bulk也有鐵電的DyMnO3(DMO)摻雜到TbMnO3薄膜中，希望從RMnO3(R= Tb,Dy)晶格的改變能獲取更多的資訊。我們發現在厚度約300 nm 薄膜Tb1-xDyxMnO3中x = 0~0.2時，在30 K左右的介電係數有異常的行為變化，此溫度接近塊材TMO的鐵電相變溫度，而在x = 1時，19 K左右(DMO的鐵電溫度)卻沒有看到類似異常的行為; 然而隨著厚度增加，我們看到了T0.4D0.6MO以及DMO都有類似鐵電相變的介電係數異常行為出現。這可能是由於隨著厚度增加晶格扭曲減少，剛好有部份接近和薄膜TMO鐵電機制有關的結構，這裡還需要進一步的實驗才能確認其物理行為。
In the Tb1-xEuxMnO3 (0 ≤ x ≤ 1) (TDMO) system, magnetic structures of the Mn moment are correlated by the lattice structures, also connecting with dielectric property of materials in low temperature. By X-ray powder diffraction spectra of TDMO powder showed that, the angle of Mn-O-Mn of the ab-plane increases with increasing x doping, when x > 0.4~0.5, the FE-phase of system is vanished. In bulk TbMnO3 (TMO) film, the FE-phase is observed at 28 K. In contrast, previous studies showed that, the TMO film does not exhibit FE-phase at 28 K. This may be due to lattice stress of substrates and induce lattice distortions, in TMO and then modify magnetic structures of ferro-electricity. In order to understand the effect of stress, we used similar ferro-electricity property of DyMnO3 (DMO) to tune the lattice structures, and systematically doped Dy instead with Tb in TbMnO3 film. We find curve of dielectric constant of TMO changes around 30 K, the temperature close to Tlock of TMO, However, for anomalies behavior is not observed around 19 K (Tlock of bulk DMO). In the dielectric measurement, the behavior of thicker film of T0.4D0.6MO and DMO is similar to that of TMO 300 nm, this may be due to lattice distortion decreases with thickness increasing, and lattice relaxation cause behavior that is similar to TMO film.
In the Tb1-xEuxMnO3 (0 ≤ x ≤ 1) (TDMO) system, magnetic structures of the Mn moment are correlated by the lattice structures, also connecting with dielectric property of materials in low temperature. By X-ray powder diffraction spectra of TDMO powder showed that, the angle of Mn-O-Mn of the ab-plane increases with increasing x doping, when x > 0.4~0.5, the FE-phase of system is vanished. In bulk TbMnO3 (TMO) film, the FE-phase is observed at 28 K. In contrast, previous studies showed that, the TMO film does not exhibit FE-phase at 28 K. This may be due to lattice stress of substrates and induce lattice distortions, in TMO and then modify magnetic structures of ferro-electricity. In order to understand the effect of stress, we used similar ferro-electricity property of DyMnO3 (DMO) to tune the lattice structures, and systematically doped Dy instead with Tb in TbMnO3 film. We find curve of dielectric constant of TMO changes around 30 K, the temperature close to Tlock of TMO, However, for anomalies behavior is not observed around 19 K (Tlock of bulk DMO). In the dielectric measurement, the behavior of thicker film of T0.4D0.6MO and DMO is similar to that of TMO 300 nm, this may be due to lattice distortion decreases with thickness increasing, and lattice relaxation cause behavior that is similar to TMO film.
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Keywords
介電測量, TbMnO3, DyMnO3, YBCO, 薄膜, dielectric measurement, TbMnO3, DyMnO3, YBCO, films