鐵銠薄膜之結構與磁相變性質之研究｜國立清華大學博碩士論文庫

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研究生：	張庭瑋 Chang, Ting-Wei.
論文名稱：	鐵銠薄膜之結構與磁相變性質之研究 Study the phase transition of structures and magnetic properties of FeRh thin films
指導教授：	李志浩 Lee, Chih-Hao
口試委員:	曾院介 Tseng, Yuan-Chieh 洪雪行 Hung, Hsueh-Hsing
學位類別：	碩士 Master
系所名稱：	原子科學院 - 工程與系統科學系 Department of Engineering and System Science
論文出版年：	2017
畢業學年度：	105
語文別：	中文
論文頁數：	80
中文關鍵詞：	鐵銠、磁相變、X光繞射、濺鍍、薄膜
外文關鍵詞：	FeRh, phase transition, X-ray diffraction, Sputtering, thin film
相關次數：	點閱：2 下載：0
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反鐵磁與鐵磁介面的交換耦合偏移效應是發展自旋電子科技的關鍵之一。化學有序結構的FeRh在室溫附近，可藉由加熱至370 K具有反鐵磁相轉變成鐵磁相之第一磁相變的性質，此磁相變往往伴隨著體積的膨脹、電阻的改變、巨大磁熵的改變。本論文利用磁控濺鍍方式製備FeRh薄膜，選用兩種不同基板，一是MgO基板，另一為SrTiO3基板鍍上BaTiO3當作緩衝層，並經過不同溫度的熱退火處理，以及厚度的改變，比較兩者的不同。並且展示反鐵磁相與鐵磁相之間的磁特性及結構等變化，透過X光繞射、 X光反射率量測、掃描式電子顯微鏡、物理性質量測系統量測FeRh薄膜，分析其晶體結構、序化程度、厚度、磁性、電性等性質。特別的是在磁性分析上觀察到交換耦合偏移現象。這是第一次在同質材料中觀察到異質介面的交換耦合偏移現象。推測其一可能的原因為應力造成FeRh薄膜有不同層，另一原因為高溫退火下，造成基板與材料之間原子的擴散，最後可能造成FeRh本身具有不同相變溫度。

The exchange bias effect at ferromagnetism (FM)/antiferromagnetism(AFM) interface is a key on developing spintronic technologies with new functionality. It is well known that chemically ordered FeRh alloys with the CsCl structure show the fascinating first order magnetic phase transition from the antiferromagnetic to ferromagnetic states at around 370 K upon heating from room temperature, accompanied by an isotropic volume expansion of about 1%, a large reduction in the resistivity and a large change in entropy. FeRh thin films were prepared by magnetron sputtering on MgO(001) substrates and annealed in the temperature range of 700-900 ℃. The structure was characterized by X-ray diffraction and it showed an epitaxial FeRh thin film on MgO(001) substrates and on BaTiO3 buffered SrTiO3(001) substrates. In this paper, the structures and magnetic properties of phase transition are analyzed by using X-ray diffraction, X-ray reflectivity, scanning electron microscope and physical property measurement system. In particular, here we probe the AFM/FM of FeRh interface magnetization, and identify a new exchange bias phenomena. This is the first homogenous system with exchange bias without having a hetergenous interface of FM/AFM layer. One of the possible reason is due to the strain at interface which induced an AFM FeRh layer under the FM FeRh layer. The other possibility could be due to the interdiffusion of atoms from neighboring layer into FeRh at higher temperature resulting in change of FM/AFM phase transition temperature, so that AFM is formed in the heavy doped FeRh layer under the FM FeRh layer.

摘要    i
Abstract    ii
致謝    iii
目錄    iv
表目錄    vii
圖目錄    ix
第一章    緒論    1
1前言    1
2 磁性基本理論    2
2.1 物質磁性的分類    2
2.2 交換磁異相性    4
3 FeRh的特性    5
4 FeRh的應用    8
4.1 熱輔助磁紀錄    8
4.2 磁致冷卻    9
5文獻回顧    10
5.1 磁場對相轉變的影響    10
5.2 摻雜微量元素對相轉變的影響    11
5.3 結構對相轉變的影響    12
5.4 應力對相轉變的影響    14
6動機    16
第二章    實驗方法    17
1實驗儀器與原理    17
1.1濺鍍系統(Sputtering System)    17
1.1.1直流濺鍍(DC Sputtering)    17
1.1.2交流濺鍍(RF Sputtering)    18
1.1.3磁控濺鍍(Magnetron Sputtering)    19
1.4掃描式電子顯微鏡 (Scanning Electron Microscope)    20
1.5同步輻射(Synchrotron Radiation)    22
1.6 X光繞射(X-ray Diffraction)    23
1.7 X光反射率(X-ray Reflectivity)    25
1.8 物理性質量測系統(Physical Properties Measurement)    27
2薄膜之製備    28
2.1 FeRh單層不同退火溫度之製成參數    28
2.2 FeRh單層不同退火厚度之製成參數    29
2.3 FeRh與BTO雙層不同退火溫度之製成參數    30
2.4 FeRh與BTO雙層FeRh不同厚度之製成參數    31
第三章    結果與討論    32
1 FeRh單層不同退火溫度之分析    32
1.1 XRD分析    32
1.2 XRR與SEM分析    42
1.3電性分析    46
1.4磁性分析    48
2 FeRh單層不同退火厚度之分析    50
2.1 XRD分析    50
2.2 磁性分析    54
3 FeRh與BTO雙層不同退火溫度之分析    55
3.1 XRD分析    55
4 FeRh與BTO雙層不同FeRh厚度之分析    61
4.1 XRD分析    61
4.2 SEM cross section & XRR    66
4.3電性分析    68
4.4磁性分析    70
第四章    結論    74
未來展望    75
文獻參考    76
附錄    79


                                

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