利用X光吸收光譜和磁圓偏振二向性研究多鐵異質結構CoFe2O4-PbTiO3的原子與電子結構及磁特性

The Atomic, Electronic Structures and Magnetic Properties of Multiferroic Hetero-structures CoFe2O4-PbTiO3 Studied by X-ray Absorption Spectroscopy and Magnetic Circular Dichroism

王孝祖(Hsiao-Tsu Wang)

指導教授 ： 彭維鋒

淡江大學/理學院/物理學系碩士班/碩士(2012年)

https://doi.org/10.6846/TKU.2012.00448

摘要

本論文利用Co、Fe與Ti K-edge延伸Ｘ光吸收精細結構(Extended X-ray Absorption Fine Structure, EXAFS)及磁圓二向性(X-ray Magnetic Circular Dichrism, XMCD)研究一系列的不同幾何形狀如:0維CoFe2O4嵌入三維PbTiO3以及二維CoFe2O4與PbTiO3交互推疊而成的多鐵異質結構CoFe2O4-PbTiO3的原子與電子及磁性特質。從Fe與Co的 EXAFS分析結論，CoFe2O4並非是完美的反尖晶石結構，Co與Fe皆能共存於四面體與八面體之間。根據X光繞射圖(X-Ray Diffraction, XRD)的實驗數據，推測PbTiO3因不同的幾何形狀造成CoFe2O4受到不同的應力，進而導致CoFe2O4離子重新組合的可能。根據Ti XMCD並未觀察Ti因介面效應而產生磁性。說明樣品之磁性皆源自CoFe2O4之幾何形狀差異。利用 XMCD發現到樣品隨著幾何結構改變時，對於磁性造成的改變與CoFe2O4的離子交換及反相磁域有關。

關鍵字

X光吸收光譜 ； X光磁圓二向性譜 ； 元素解析之磁滯曲線 ； 多鐵材料

並列摘要

Investigation has been made on electronic, atomic structures and magnetic properties of multiferroics composite [CoFe2O4 (CFO) particles embedded in PbTiO3 (PTO) matrix (0-3 type)] and multilayer [CFO-PTO multilayered (2-2 type)] samples by using Extended X-ray Absorption Fine Structure (EXAFS) and X-ray Magnetic Circular Dichroism (XMCD). Co and Fe K-edge indicates the cation distribution of CFO in these (0-3 and 2-2 type) samples were deviated from the perfect inverse spinel structure, suggesting the changes of local atomic structure from inverse spinel to normal spinel due to induced strain effect of adjacent PTO. The Ti reveal no any magnetic moment due to interface effect, measurement by XMCD, which attributes the observed change in magnetic properties are basically coming from the CoFe2O4. The decrease in magnetic moment were also observed in multiferroics composite (0-3 type) and multilayer (2-2 type) samples, in comparison to CFO particles. The significant changes in magnetic moments suggest the antiferromagnetic (AF) alignment of cations due to the cation distribution and Anti-phase domin.

並列關鍵字

EXAFS ； XMCD ； ESMH ； Multiferroic ； CoFe2O4 ； PbTiO4

參考文獻

38. G. van der Laan, E. Arenholz, R. V. Chopdekar, Y. Suzuki, Phys.

1. J. G. Wan, X. W. Wang, Y. J. Wu, M. Zeng, Y. Wang, H. Jiang, W. Q.

35. Cínthia Piamonteze, Hélio C. N. Tolentino, Aline Y. Ramos, Nestor E. Massa, Jose A. Alonso, Maria J. Martínez-Lope, Maria T. Casais, Phys. Rev. B.71, 012104 (2005)

Chang, K. C. Kuo, P. K. Tseng, J. F. Lee, S. C. Chung, C. I. Chen, K. L. Tsang, C. T. Chen, Phys. Rev. B 54, 16641 (1996).

C. L. Yeh, K. C. Huang, H. C. Hsueh, W. F. Pong, M.-H. Tsai, H. H.