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研究生:蘇柏龍
研究生(外文):Po-Lung Su
論文名稱:異常能斯特效應在磁性材料中厚度的相依性
論文名稱(外文):Thickness dependence of anomalous Nernst effect in ferromagnetic metals
指導教授:黃斯衍
口試委員:林文欽郭光宇
口試日期:2016-07-19
學位類別:碩士
校院名稱:國立臺灣大學
系所名稱:應用物理研究所
學門:自然科學學門
學類:物理學類
論文種類:學術論文
論文出版年:2016
畢業學年度:104
語文別:英文
論文頁數:94
中文關鍵詞:自旋電子異常能斯特效應磁性金屬自旋極化電流自旋相依熱電壓
外文關鍵詞:spintronicsanomalous Nernst effectferromagnetic metalsspin-polarized currentspin-dependent thermal voltage
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近年來,由於在效率、應用及能源上具有極大的潛力,熱激發自旋電子越來越被重視,其中一個重要的效應: 異常能斯特效應是在磁性材料中將熱能轉換為具有自旋相依性的電能訊號,在此效應中電子、熱能以及自旋,皆參與其中。雖然利用此效應的元件、多層膜結構、熱電偶近幾年來皆被大家關注且廣泛的研究,但是異常能斯特效應在磁性材料中對厚度的相關性如此重要議題卻從來沒有被人重視並研究過。在這篇論文中,我們使用垂直方向的熱傳輸研究異常能斯特效在鐵磁性材料中如: 鎳鐵合金、鈷以及鐵的厚度相依性,在研究中我們發現鐵的訊號和鈷還有鎳鐵合金是相反的,並且無論是哪種鐵磁性材料,在厚度大於十奈米時皆是常數,在小於十奈米的薄膜時,鈷以及鎳鐵的異常能斯特訊號隨著厚度減少而減少直至兩奈米時訊號測量不到,即使在此厚度下仍存在著磁性,另外我們發現了鐵的特殊現象,在小於六奈米時,異常能斯特效應的訊號和塊材的鐵訊號相反,更重要的是訊號隨著厚度減少而增加,我們推測這種現象是與厚度強烈相關的鐵的自身特性,在我們的研究中,我們深入探討這些厚度相依性的現象並且展示異常能斯特的厚度相依性在現今多層膜的研究中扮演的重要角色。

The connection between thermoelectricity and spintronics has recently attracted much attention because of its potential application for the high-efficiency electric devices and the iste heat recycling. In particular, anomalous Nernst effect (ANE), the conversion of thermal energy into the spin-dependent electric signal in ferromagnetic metals(FMs), is one of the most important mechanism to study the coupling between charge, spin, and heat. Although, the spintronic devices based on the ANE, including the multilayer structure and ferromagnetic thermal thermopile, have been extensively investigate, the issue for the thickness dependence of ANE has never been addressed.
In this work, by using a vertical temperature gradient, we systematically study the thickness dependence of the ANE in several ferromagnetic metals (FMs), including permalloy (Py), iron (Fe), and cobalt (Co) at room temperature. The sign of the ANE can immediately tell that the sign of the Nernst angle in Fe is opposite to that of Py and Co. In the thickness-dependent measurement, we report that the ANE signal in all FMs samples are constant in thick films region while the signal decreases with decreasing thicknesses (less than 10 nm, except for ultra-thin Fe). Importantly, there is no measurable ANE signal when thickness is less than 2 nm, even the ferromagnetic ordering with Curie temperatures still above room temperature. After taking the thickness dependence of the resistivity and magnetization into account, we are able to determine the intrinsic ANE coefficient in ferromagnetic metals for the first time.
More surprisingly, we observed the sign change of ANE signal between thick and thin Fe samples. In addition, unlike other FMs, the ANE voltage showed increased instead of decreased signal, when the thickness of Fe sample is less than 6 nm. We suggest this enhancement signal is origin from the intrinsic property of ultra-thin Fe film. Our results provide an important insight on how the role of thickness effect has a strong influence on the development of multilayer structure or ferromagnetic thermal thermopile devices.


CONTENTS

口試委員會審定書 i
中文摘要 ii
ABSTRACT iii
ACKNOWLEDGEMENT v
LIST OF FIGURES xi
CONTENTS vii
Chapter 1 Introduction and motivation 1
Chapter 2 Background knowledge 8
2.1 Thermoelectric effect 8
2.1.1 Seebeck effect 8
2.1.2 Peltier effect 9
2.2.3 Hall effect and Nernst effect 9
2.2 Magnetism 12
2.2.1 Magnetism of material 12
2.2.2 Hysteresis loop 16
2.2.3 Surface and Finite-size effect 18
2.2.4 Magnetoresistance(MR) 19
2.3 Spintronic and thermoelectric 22
2.3.1 Spin current 22
2.3.2 Spin Hall effect and inverse spin Hall effect 22
2.3.3 Longitudinal spin Seebeck effect 24
2.3.4 Anomalous Nernst effect and anomalous Hall effect 25
Chapter 3 Experiment method 27
3.1 Sample preparation 27
3.1.1 Photolithography 27
3.1.2Magnetron Sputtering System 28
3.2 Structural and morphological analysis 30
3.2.1 Atomic-force microscopy 30
3.2.2 Vibrating sample magnetometer measurement 32
3.2.3 Four-point measurement and setup 34
3.2.4 Thermal transport measurement and setup 35
Chapter 4 Experimental results and discussion 37
4.1 Permalloy result 37
4.1.1 Thickness dependence of resistivity 39
4.1.2 Thickness dependence of magnetization 40
4.1.3 ANE signal of Py in thickness dependence 42
4.2 Cobalt result 44
4.2.1 Thickness dependence of resistivity 45
4.2.2 Thickness dependence of magnetization 46
4.2.3 ANE signal of Co in thickness dependence 47
4.3 Iron result 49
4.3.1 Thickness dependence of resistivity 52
4.3.2 Thickness dependence of magnetization 54
4.3.3 ANE signal of Fe in thickness dependence 56
4.4 Discussion of Anomalous Nernst coefficient 58
4.4.1 Thickness dependence of CANE in Py, Co and Fe 58
4.4.2 Thickness dependence of Sxy in Py, Co and Fe 60
4.4.3 Discussion for CANE and θANE 62
4.5 Behavior of ultra-thin film for Fe 63
4.5.1 Sign change at small thickness 64
4.5.2 Enhancement at small thickness 69
4.6 ANE Signal of Multilayer [MgO/Fe]n 73
4.7 GMR and ANE measurement in exchange bias spin valve 83
Chapter 5 Conclusion 87
REFERENCE 89



1.K. Uchida, S. Takahashi, K. Harii, J. Ieda, W. Koshibae, K. Ando, S. Maekawa, and E. Saitoh "Observation of the spin Seebeck effect." Nature 455, 778-781 (2008)
2.M. Weiler, M. Althammer, F. D. Czeschka, H. Huebl, M. S. Wagner, M. Opel, I.-M. Imort, G. Reiss, A. Thomas, R. Gross, et al. “Local charge and spin currents in magnetothermal landscapes.” Phys. Rev. Lett. 108.10, 106602 (2012)
3.R. Ramos, M. H. Aguirre, A. Anadon, J. Blasco, I. Lucas, K. ´ Uchida, P. A. Algarabel, L. Morellon, E. Saitoh, and M. R. ´ Ibarra. “Anomalous Nernst effect of Fe3O4 single crystal.” Phys. Rev. B 90, 054422 (2014)
4.A. Slachter, F. L. Bakker, and B. J. van Wees. “Anomalous Nernst and anisotropic magnetoresistive heating in a lateral spin valve.” Phys. Rev. B 84, 020412(R) (2011)
5.C. Fang, C.H. Wan, Z.H. Yuan, L. Huang, X. Zhang, H. Wu, Q.T. Zhang, X.F. Han. “Scaling relation between anomalous Nernst and Hall effect in [Pt/Co] n multilayers.” Phys. Rev. B 93, 054420 (2016)
6.S. Sangiao, L. Morellon, G. Simon, J. M. De Teresa, J. A. Pardo, J. Arbiol, and M. R. Ibarra. “Anomalous Hall effect in Fe (001) epitaxial thin films over a wide range in conductivity.” Phys. Rev. B 79.1, 014431 (2009).
7.K.-D. Lee, D.-J. Kim, H. Yeon Lee, S.-H. Kim, J.-H. Lee, K.-M. Lee, J.-R. Jeong, K.-S. Lee, H.-S. Song, J.-W. Sohn et al. “Thermoelectric signal enhancement by reconciling the spin seebeck and anomalous Nernst effects in ferromagnet/non-magnet multilayers.” Scientific reports 5 (2015).
8.R. Ramos, T. Kikkawa, M. H. Aguirre, I. Lucas, A. Anadon, ´ T. Oyake, K. Uchida, H. Adachi, J. Shiomi, P. A. Algarabel, L. Morellon, S. Maekawa, E. Saitoh, and M. R. Ibarra. “Unconventional scaling and significant enhancement of the spin Seebeck effect in multilayers.” Phys. Rev. B 92, 220407(R) (2015)
9.R. Gupta, M. Gupta, T. Gutberlet, Pramana. “Magnetization in permalloy thin films.” Pramana 71.5, 1123-1127 (2008).
10.J.-G. Zhu, Y. Zheng, and G. Prinz. “Ultrahigh density vertical magnetoresistive random access memory.” J. Appl. Phys. 87. 9, 6668-6673 (2000).
11.S. Geprags, A. Kehlberger, F. D. Coletta, Z. Qiu, E.-J. Guo, T. Schulz, C. Mix, S. Meyer, A. Kamra, M. Althammer, H. Huebl, G. Jakob, Y. Ohnuma, H. Adachi, J. Barker, S. Maekawa, G. E. W. Bauer, E. Saitoh, R. Gross, S. T. B. Goennenwein, and M. Klaui. "Origin of the spin Seebeck effect in compensated ferrimagnets." Nature communications 7 (2016).
12.Shafi, Md Nahid Akter, et al. “Comparative Study of Magnetization of Co Thin Films Deposited on Glass, GaAs (001) and Si (001) Substrates.” International Journal of Thin Films Science and Technology 4.3, 193 (2015).
13.G. A. Prinz. “Stabilization of bcc Co via epitaxial growth on GaAs”. Phys. Rev. Lett. 54.10 1051 (1985).
14.H. Danan, A. Herr, and A.J. P. Meyer. “New determinations of the saturation magnetization of nickel and iron.” Journal of Applied Physics 39, 669 (1968).
15.F. K. Dejene, J. Flipse, and B. J. van Wees. "Spin-dependent Seebeck coefficients of Ni 80 Fe 20 and Co in nanopillar spin valves." Phys. Rev. B 86.2, 024436 (2012).
16CRC Handbook of chemistry and Physics, 95th edition
17S. Sangiao, L. Morellon, G. Simon, J. M. De Teresa, J. A. Pardo, J. Arbiol, and M. R. Ibarra. “Anomalous Hall effect in Fe (001) epitaxial thin films over a wide range in conductivity.” Phys. Rev. B 79, 014431 (2009).
18Parkin, S. S. P. “Origin of enhanced magnetoresistance of magnetic multilayers: Spin-dependent scattering from magnetic interface states.” Phys. Rev. Lett. 71.10, 1641 (1993).
19M. Weiler, M. Althammer, F. D. Czeschka, H. Huebl, M. S. Wagner, M. Opel, I.-M. Imort, G. Reiss, A. Thomas, R. Gross, and S. T. B. Goennenwein. “Local charge and spin currents in magnetothermal landscapes.” Phys. Rev. Lett. 108, 106602 (2012)
20K. I. Uchida, T. Kikkawa, T. Seki, T. Oyake, J. Shiomi, Z. Qiu, K. Takanashi, and E. Saitoh. "Enhancement of anomalous Nernst effects in metallic multilayers free from proximity-induced magnetism." Phys. Rev. B 92, 094414 (2015)
21L. Zhou, V. L. Grigoryan, S. Maekawa, X. Wang, and J. Xiao. “Spin Hall effect by surface roughness.” Phys. Rev. B 91, 045407 (2015)
22V. Korenman and H. D. Drew. “Size and temperature effects on the Seebeck coefficient of thin bismuth films.” Phys. Rev. B 35.12, 5990 (1987).
23R. Cheng, S. D. Bader, and F. Y. Fradin. “Strong magnetic surface anisotropy of ultrathin Fe on curved Pt (111).” Phys. Rev. B 77, 024404 (2008)
24S. Ingvarsson, G. Xiao, S. S. P. Parkin, and W. J. Gallagher. “Thickness-dependent magnetic properties of Ni81Fe19; Co90Fe10 and Ni65Fe15Co20 thin films” Journal of Magnetism and Magnetic Materials 251, 202–206 (2002).
25G. Y. Guo, S. Murakami, T.-W. Chen, and N. Nagaosa. “Intrinsic spin Hall effect in platinum: first-principles calculations.” Phys. Rev. Lett. 100, 096401 (2008)
26S. A. Crooker, M. Furis, X. Lou, C. Adelmann, D. L. Smith, C. J. Palmstrom, and P. A. Crowell. "Imaging spin transport in lateral ferromagnet/semiconductor structures." Science 309.5744, 2191-2195 (2005).
27B. F. Miao, S. Y. Huang, D. Qu, and C. L. Chie. “Inverse Spin Hall Effect in a Ferromagnetic Metal” Phys. Rev. Lett. 111, 066602 (2013)
28S. Hu, H. Itoh, and T. Kimura. “Efficient thermal spin injection using CoFeAl nanowire” NPG Asia Materials 6, e127 (2014)
29Patent US4724318 - Atomic-force microscope and method for imaging surfaces
with atomic resolution.
30Smith, D. O. “Development of a Vibrating‐Coil Magnetometer.” Review of
Scientific Instruments 27.5, 261-268 (1956).
31 Foner, Simon., et al. “Versatile and sensitive vibrating‐sample magnetometer.” Review of Scientific Instruments 30.7, 548-557 (1959).
32K. Uchida, H. Adachi, T. Ota, H. Nakayama, S. Maekawa, and E. Saitoh. “Observation of longitudinal spin-Seebeck effect in magnetic insulators” Appl. Phys. Lett. 97, 172505 (2010).
33PRESENT, I. "Cramming more components onto integrated circuits." Readings in computer architecture 56 (2000).
34Y. Sakuraba, K., Sakuraba, Y., Hasegawa, K., Mizuguchi, M., Kubota, T., Mizukami, S., Miyazaki, T., & Takanashi, K. “Anomalous Nernst Effect in L1 0-FePt/MnGa Thermopiles for New Thermoelectric Applications” Appl. Phys. Express 6, 033003 (2013).
35Nagaosa, N., Sinova, J., Onoda, S., MacDonald, A. H., & Ong, N. P. “Anomalous Hall effect.” Rev. Mod. Phys. 82, 1539 (2010).
36Uchida, K. I., Nonaka, T., Yoshino, T., Kikkawa, T., Kikuchi, D., & Saitoh, E. “Enhancement of Spin-Seebeck Voltage by Spin-Hall Thermopile.” Appl. Phys. Express 5, 093001 (2012).
37Nave, Carl L. "Magnetic Properties of Solids".
38B. D. Cullity and C. D. Graham, Introduction to Magnetic Materials
39Halliday & Resnick Fundamentals of Physics.
40K. Uchida, H. Adachi, T. Kikkawa, A. Kirihara, M. Ishida, S. Yorozu, S. Maekawa, and E. Saitoh. “Thermoelectric generation based on spin Seebeck effects.” (2016).
41H. B. Nie, S. Y. Xu1, C. K. Ong1, Q. Zhan, D. X. Li and J. P. Wang. “In-plane magnetic anisotropy in RF sputtered Fe thin films.” Thin Solid Films 440.1, 35-40 (2003).


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