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本論文研究 LiCu2-xZnxO2 單晶樣品與 HoxMn1-xS 多晶樣品的變 溫拉曼散射光譜分析。LiCu2-xZnxO2 單晶樣品的光譜分析有以下幾點 結論:

第一,室溫拉曼散射光譜展現 7 個 Ag 對稱性與 3 個 B1g 對稱 性拉曼活性振動模。隨 Zn 離子摻雜的濃度增加,LiCu2O2 內部沿 ab 平面振動的 O 原子拉曼峰展現紅移且半高寬變寬,這是因為 Zn 離 子取代位於 ab 平面的 Cu 二價離子時,會導致導致 ab 軸晶格常 數變大,與 H. C. Hsu 等人[23] 量測 x 光繞射能譜的結果一致。

第二,我們於室溫觀察到 106 cm-1 特徵峰,認為此屬於拉曼活 性振動模,且隨著無磁矩的 Zn 離子濃度增加,此 106 cm-1 的峰值 強度略為下降,且 Zn 離子濃度為 7 % 時,此峰值變為較寬廣,推 測為一般聲子行為,與 K. Y. Choi 等人[20]所推測之 two-magnon continuum 不符。

第三,LiCu2O2 隨著 Zn 離子摻雜濃度的增加,磁性相轉變溫度 從 24 K 下降至 14 K。當溫度下降,摻雜 7 % Zn 離子的 LiCu2O2 在 磁性相轉溫度 14 K 以下,492 cm-1 拉曼峰展現微小紅移,此振動模

用。

HoxMn1-xS 多晶樣品的光譜分析顯示以下三點結論:

第一,室溫 HoxMn1-xS 多晶樣品拉曼散射光譜展現 4 個拉曼活 性振動模,其頻率位置約為 135 cm-1、227 cm-1、333 cm-1 及 585 cm-1,隨著摻雜 Ho3+ 離子濃度的增加,333 cm-1 與 585 cm-1 拉曼峰 展現紅移,且從 x 光繞射能譜可以看到隨著摻雜 Ho3+ 離子濃度的 增加,(002) 峰值往低角度移動,這是由於 Ho3+ 離子半徑為 0.90 Å , 而 Mn2+ 離子的離子半徑為 0.83 Å ,當半徑較大的 Ho3+ 離子取代半 徑較小的 Mn2+ 離子所導致的現象。

第二,低溫下的 HoxMn1-xS 在摻雜濃度為 0.01 時,展現擴散式 電子響應的現象,當摻雜濃度為 0.1 時,擴散式電子響應消失,推 測強磁矩 Ho 離子摻雜的關係,電子較被侷限在晶格內,導致擴散 式電子響應不明顯,此與在低溫下摻雜濃度為 0.1 時電阻率高於摻 雜濃度為 0.01 的現象一致。

第三,HoxMn1-xS 在摻雜濃度為 x = 0.01 時,333 cm-1、585 cm-1 拉曼峰對應到其電阻率異常變化的溫度附近,其權重有明顯降低的現 象,且同溫度對應到晶格常數也有不連續的行為,推測此現象可能為 電子雲軌道有序性、或者電荷有序性有關。

拉曼散射光譜實驗,並進行第一原理的計算,以得知其內部原子振動 模式。另外,對於 HoxMn1-xS 多晶樣品,則希望進行高溫全頻反射 光譜實驗,探討高溫光學電導率,與高溫電阻率實驗結果進行比較,

並利用穿隧式電子顯微鏡進行電子繞射實驗、x 光散射實驗以及磁化 率隨溫度的變化,確認 HoxMn1-xS 多晶樣品於高溫時,電荷、軌道與 自旋有序性行為。

參考文獻

[1] M. Fiebig, T. Lottermoser, D. Frohlich, A. V. Goltsev, and R. V.

Pisarev, “Observation of coupled magnetic and electric domains”, Nature 419, 818 (2002).

[2] T. Kimura, T. Goto, H. Shintani, K. Ishizaka, T. Arima, and Y.

Tokura, ”Magnetic control of ferroelectric polarization”, Nature 426, 55 (2003).

[3] N. Hur, S. Park, P. A. Sharma, J. S. Ahn, S. Guha, and S. W. Cheong,

“Electric polarization reversal and memory in a multiferroic material induced by magnetic fields”, Nature 429, 392 (2004).

[4] S. S. Aplesnin, L. I. Ryabinkina, O. B. Romanova, O. N. Bandurina, M. V. Gorev, A. D. Balaev, and E. V. Ermin, “Spin glass effects in CoxMn1-xS solid solutions”, Bull. Russ. Acad. Sci. Phys. 73, 965 (2009).

[5] W. Eerenstein, N. D. Nathur, and J. F. Scott, “Multiferroic and magnetoelectric materials”, Nature 442, 759 (2006).

[6] 吳宗展,國立中山大學物理研究所碩士論文,91 年六月。

[7] 郭明憲,國立臺灣師範大學物理研究所碩士論文,92 年七月。

[8] C. Kittel, “Introductuion to Solid State Physics”, Wiley, New York, (1996).

[9] M. P. Marder, “Condensed Matter Physics”, Wiley Interscience, New York, (2000).

[10] W. Eerenstein, N. D. Mathur, and J. F. Scott, “Multiferroic and magnetoelectric materials”, Nature 442, 17 (2006).

[11] J. Okamoto, D. J. Huang, C. Y. Mou, K. S. Chao, H. J. Lin, S. Park, S. W. Cheong, and C. T. Chen, “Symmetry of multiferroicity in a frustrated magnet TbMn2O5”, Phys. Rev. Lett. 98, 157202 (2007).

[12] M. Mostovoy, “Ferroelectricity in spiral magnets”, Phys. Rev. Lett.

96, 067601 (2006).

[13] 黃詩雯、黃迪靖,以軟 x 光探索『多鐵相變』,物理雙月刊,

[14] L. C. Chapon, G. R. Blake, M. J. Gutmann, S. Park, N. Hur, P. G.

Radaelli, and S. W. Cheong, “Structural anomalies and multiferroic behavior in magnetically frustrated TbMn2O5”, Phys. Rev. Lett. 93, 177402 (2004).

[15] I. E. Sergienko, C. Sen, and E. Dagotto, “Ferroelectricity in the magnetic E-phase of orthorhombic perovskites”, Phys. Rev. Lett. 97, 227204 (2006).

[16] I. A. Sergienko and E. Dagotto, “Role of the Dzyaloshinskii-Moriya interaction in multiferroic perovskites”, Phys. Rev. B 73, 094434 (2006).

[17] H. Katsura, N. Nagaosa, and A. V. Balatsky, “Spin current and magnetoelectric effect in noncollinear magnets”, Phys. Rev. Lett. 95, 057205 (2005).

[18] S. Park, Y. J. Choi, C. L. Zhang, and S. W. Cheong, “Ferroelectricity in an S = 1/2 chain cuprate”, Phys. Rev. Lett. 98, 057601 (2007).

[19] S. Seki, Y. Yamasaki, M. Soda, M. Matsuura, K. Hirota, and Y.

Tokura, “Correlation between spin helicity and electric polarization vector in quantum-spin chain magnet LiCu2O2”, Phys. Rev. Lett. 100, 127201 (2008).

[20] K. Y. Choi, S. A. Zvyagin, G. Cao, and P. Lemmens, “Coexistence of dimerization and long-range magnetic order in the frustrated spin- chain system LiCu2O2 : Inelastic light scattering study”, Phys. Rev.

B 69, 104421 (2004).

[21] S. W. Huang, D. J. Huang, J. Okamoto, C. Y. Mou, W. B. Wu, K. W.

Yeh, C. L. Chen, M. K. Wu, H. C. Hsu, F. C. Chou, and C. T. Chen,

“Magnetic ground state and transition of a quantum multiferroic LiCu2O2”, Phys. Rev. Lett. 101, 077205 (2008).

[22] S. Zvyagin, G. Cao, Y. Xin, S. McCall, T. Caldwell, W. Moulton, L.

C. Brunel, A. Angerhofer, and J. E. Crow, “Dimer liquid state in the quantum antiferromagnet compound LiCu2O2”, Phys. Rev. B 66, 064424 (2002).

[23] H. C. Hsu, J. Y. Lin, W. L. Lee, M. W. Chu, T. Imai, Y. J. Kao, C. D.

Hu, H. L. Liu, and F. C. Chou, “Nonmagnetic impurity perturbation to the quasi-two-dimensional quantum helimagnet LiCu2O2”, Phys.

Rev. B 82, 094450 (2010).

[24] S. S Aplesnin, А. M. Kharkov, A. I. Galyas, and V. V.

[25] Y. Yasui, K. Sato, Y. Kobayashi, and M. Sato, “Studies of multiferroic system LiCu2O2 I. sample characterization and relationship between magnetic properties and multiferroic nature”, J.

Phys. Soc. Jpn. 78 8084720 (2009).

[26] 鄧勃、寧永成、劉密新著,儀器分析,清華大學出版社出版,

中華民國八十年五月第一版。

[27] T. Masuda, A. Zheludev, A. Bush, M. Markina, and A. Vasiliev,

“Competition between helimagnetism and commensurate quantum spin correlation in LiCu2O2”, Phys. Rev. Lett. 92, 177201 (2004).

[28] Y. Kobayashi, K. Sato, Y. Yasui, T. Moyoshi, M. Sato, and K. Kakura,

“Studies of multiferroic system of LiCu2O2 : II. magnetic structures of two ordered phases with incommensurate modulations”, J. Phys.

Soc. Japan 78, 084721 (2009).

[29] B. Roessli, U. Staub, A. Amato, D. Herlach, P. Pattison, K. Sablina, and G. A. Petrakovskii, “Magnetic phase transition in the double spin-chains compound LiCu2O2”, Physica B 296, 306 (2001).

[30] A. Rusydi, I. Mahns, S. Müller, M. Rübhausen, S. Park, Y. J. Choi, C.

L. Zhang, S. W. Cheong, S. Smadici, P. Abbamonte, M. V.

Zimmermann, and G. A. Sawatzky, “Multiferroicity in the spin-1/2 quantum matter of LiCu2O2”, Appl. Phys. Lett. 92, 262506 (2008).

[31] L. I. Ryabinkina, O. B. Romanova, and S. S. Aplesnin, “Sulfide compounds MexMn1-xS (Me = Cr, Fe, V, Co) : technology, transport properties, and magnetic ordering”, Bull. Russ. Acad. Sci. Phys. 72, 1050 (2008).

[32] R. Berger, A. Meetsma, S. V. Smaalen, and M. Sundberg, “The structure of LiCu2O2 with mixed-valence copper from twin-crystal data”, J. Less-Common Met. 175, 119 (1991).

[33] A. A. Gippius, E. N. Morozova, A. S. Moskvin, A. V. Zalessky, A. A.

Bush, M. Baenitz, H. Rosner, and S. L. Drechsler, “NMR and local-density-approximation evidence for spiral magnetic order in the chain cuprate LiCu2O2”, Phys. Rev. B 70, R020406 (2004).

[34] H. G. V. Schnering, R. F. D. Stansfield, and G. J. McIntyre, “X-ray and neutron diffraction study of the crystal structure of MnS2”, Z.

Kristallogr. 199, 13 (1992).

[35] Y. Yao, X. Zhu, H. C. Hsu, F. C. Chou, and M. El-Batanouny,

surface of LiCu2O2”, Surface science 604, 692 (2010).

[36] K. Y. Choi, V. P. Gnezdilov, P. Lemmens, L. Capogna, M. R. Johnson, M. Sofin, A. Maljuk, M. Jansen, and B. Keimer, “Magnetic excitations and phonons in the spin-chain compound NaCu2O2”, Phys. Rev. B 73, 094409 (2006).

[37] P. G. Klemens, “Anharmonic decay of optical phonons”, Phys. Rev.

148, 845 (1966).

[38] M. K. Singh and R. S. Katiyar, “Phonon anomalies near the magnetic phase transitions in BiFeO3 thin films with rhombohedral R3c symmetry”, J. Appl. Phys. 109, 07D916 (2011).

[39] H. C. Hsu, W. L. Lee, J. Y. Lin, H. L. Liu, and F. C. Chou,

“Disrupted long-range spin-spiral ordering and electric polarization in the Zn-substituted quantum helimagnet LiCu2−xZnxO2”, Phys. Rev.

81, 212407 (2010).

[40] A. Milutinović, Z. V. Popović, N. Tomić, and S. Dević, “Raman spectroscopy of polycrystalline α-MnSe”, Mater. Sci. Forum 453, 299 (2004).

[41] S. S. Aplesnin, G. A. Petrakovskii, L. I. Ryabinkina, G. M. Abramova, N. I. Kiselev, and O. B. Romanova, “Influence of magnetic ordering on resistity anisotropy of α-MnS single crystal”, Solid State Comm.

129, 195 (2004).

[42] S. Yoon, H. L. Liu, G. Schollerer, and S. L. Cooper, “Raman and optical spectroscopic studies of small-to-large polaron crossover in the perovskite manganese oxides”, Phys. Rev. B 58, 2795 (1998).

[43] H. Kuroe, J. Sasaki, T. Sekine, N. Koide, Y. Sasago, K. Uchinokura, and M. Hase, “Spin fluctuations in CuGeO3 probed by light scattering”, Phys. Rev. B 55, 409 (1997).

[44] S. Aplesnin, O. Romanova, A. Harkov, D. Balaev, M. Gorev, A.

Vorotinov, V. Sokolov, and A. Pichugin, ”Metal-semiconductor transition in SmxMn1-xS solid solutions”, Phys. Status Solidi B 249, 812 (2011).

[45] S. Miyasaka, J. Fujioka, and M. Iwama, “Raman study of spin and orbital order and excitations in perovskite-type RVO3 (R = La, Nd, and Y)”, Phys. Rev. B 73, 224436 (2006).

[46] H. Kuwahara, Y. Tomioka, A. Asamitsu, Y. Moritomo, and Y. Tokura,

“A first-order phase transition induced by a magnetic field”, Science

“Phonon thermal conductivity and stripe correlations in La2-xSrxNiO4 and Sr1.5La0.5MnO4”, Phys. Rev. B 59, R10397 (1999).

[48] K. Yamamoto, T. Kimura, T. Ishikawa, T. Katsufuji, and Y. Tokura,

“Raman spectroscopy of the charge-orbital ordering in layered manganites”, Phys. Rev. B 61, 14706 (2000).

[49] J. Herrero-Martin, J. Blasco, J. Garcia, G. Subias, and C. Mazzoli,

“Structural changes at the semiconductor-insulator phase transition in the single-layered perovskite La0.5Sr1.5MnO4”, Phys. Rev. B 83, 184101 (2011).

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