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研究生:朱繼文
研究生(外文):Chu Chi-Wen
論文名稱:高溫低磁場磁阻鈣鈦礦結構氧化物材料研究
論文名稱(外文):Magnetoresistance in Perovskite Structure Oxides at High Temperature and Low Magnetic Fields
指導教授:陳立翰
指導教授(外文):L.H.Chen
學位類別:碩士
校院名稱:義守大學
系所名稱:材料科學與工程學系
學門:工程學門
學類:材料工程學類
論文種類:學術論文
論文出版年:2000
畢業學年度:88
語文別:中文
論文頁數:61
中文關鍵詞:巨磁阻金屬-半導體轉換溫度顯微組織磁阻。
外文關鍵詞:CMRT(M-I)microstructuremagnetoresistance
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本實驗經研磨、煆燒、壓胚、燒結等傳統粉末冶金程序,製作A位置離子短缺之La0.67CaXMnO3-Y(X=0.33、0.2、0.1、0) (LCMO) 及添加0-20﹪原子百分比Al2O3之La0.67AlZCaXMnO3-Y (LACMO)塊材,並利用直流磁控濺鍍法於(100)LaAlO3基板上濺鍍薄膜,探討Ca2+含量、Al2O3添加量與熱處理條件對塊材、薄膜磁阻比值、電阻及半導體-金屬轉換溫度等磁電行為之影響。由實驗結果得知,當Ca2+含量由0.33減少至0.2及0.1 時LCMO塊材之最大磁阻比值由27﹪分別變為20%及34%。且半導體-金屬轉換溫度由70K增為250K附近。LCMO薄膜經950℃持溫4小時熱處理後,隨Ca2+含量由0.33降至0.2及0.1時,La0.67CaXMnO3-Y薄膜電阻大幅下降,且最高磁阻比值由72﹪分別增至108﹪及134﹪。惟三組薄膜之半導體-金屬轉換溫度(TM-1)皆在240K-260 K間,並無明顯的差異。另Ca2+含量減至0時,薄膜及塊材之電阻係數大幅增加,且磁阻效應驟降,半導體-金屬轉換溫度及最大磁阻產升溫度也多下降。Ca2+含量改變對塊材及薄膜之磁阻及導電行為之影響,應與Mn4+/Mn3+比率及Mn-O-Mn鍵長度及角度改變有關。添加適量的Al2O3可提高LACMO塊材及薄膜之磁阻比值,但同時降低金屬-半導體轉換溫度。這可能與添加適量的Al2O3時,較小之Al3+溶入La0.67Ca0.1MnO3-Y晶格內部分取代La3+離子,晶格產生內壓應力有關。但添加過量之Al2O3時,Al2O3將以第二相析出於晶界上或晶粒內,提升材料之電阻。我們也發現薄膜之磁阻比值也遠比塊材者高出許多,此應與鍍於LaAlO3單晶基板上,薄膜晶格受到額外之侷限,導致晶格常數縮小,影響O-Mn-O鍵之長度及角度有關。另薄膜經熱處理後,減少組織中缺陷,也對磁阻比值提升有正面之作用。

In this research,the magnetoresistence behavior and microstructure have studied for the A-site ion (Ca2+)deficient La-Ca-Mn-O materials。The bulk prepared by conventional powder metaullurgy processes and films were deposition by DC sputtering。The Ca2+ deficient for La0.67CaXMnO3-X bulk material with x=0.2 and 0.1 decrease the resistivity and raise the semiconductor-material transition temperature near room temperature,the La0.67CaXMnO3-X thin films decreased The MR % increased from 72 ﹪、108 ﹪and 134 ﹪as the content of Ca2+ decreased from 0.33、0.2 and 0.1。 The La0.67Ca0.1MnO3 films doped with Al2O3 up to 20﹪at have been grown on the (100)LaAlO3 substrates at 400℃ by a d.c. magnetron sputtering process. The sputtered films have a polyerystalline structure, which shows a (100) preferential orientation. An Al2O3-rich second phase exists in the microstructure of films doping with Al2O3 more than 5%. It is found that the MR behavior of films is strongly influenced by the Al2O3 doping and annealing treatment. The film doping with 5% Al2O3, deposited at 400℃ and annealed at950℃for 4 hr, shows a MR ration as high as ~1200% at 120K and at 10kOe. Such a huge low-field MR behavior can be ascribed to the spin-polarized tunneling across grain boundaries whereas an Al2O3-rich second phase is believed to exist. such Ca2+deficient dependence of electron transport and magnetoresistence behavior is ascribed to the change of the angle and length of Mn-O-Mn bonding as a result of the change in the ratio of Mn3+/Mn4+。

............................................................................................................................頁次
中文摘要…………………………………............................I
英文摘要......................................................II
誌 謝.....................................................III
目 錄......................................................Ⅳ
圖 索 引......................................................V
第一章:緒論..................................................1
1-1 前言......................................................1
1-2 研究動機與目的............................................2
第二章:理論基礎與文獻回顧....................................3
2-1 磁阻特性..................................................3
2-1-1磁阻現象.............................................3
2-1-2磁阻類別.............................................3
2-1-3磁阻材料的種類.......................................4
2-2 超巨磁阻理論.............................................10
2-2-1鈣鈦礦結構..........................................11
2-2-2雙交換理論..........................................12
2-3 濺鍍原理.................................................15
2-3-1直流濺鍍理論........................................17
2-3-2直流濺鍍............................................17
2-3-3磁控濺鍍............................................17
第三章:實驗方法與內容.......................................18
3-1實驗流程.........................................18
3-2塊材及靶材製備...................................18
3-3基板前處理….....................................18
3-4真空系統與濺鍍製程...............................21
3-4-1真空系統.......................................21
3-4-2基板加熱系統...................................21
3-5熱處理...........................................21
3-6塊材與薄膜特性量測與分析.........................23
3-6-1膜厚量測.......................................23
3-6-2顯微結構及成分分析.............................23
3-6-3磁阻量測.......................................23
第四章:結果與討論...........................................28
4-1試片成分與參數制定...............................28
4-2 Ca+2含量對La0.67CaXMnO3-Y電傳輸特性之影響.......29
4-2-1 La0.67CaXMnO3-Y(X=0、0.1、0.2、0.3)塊材.....29
4-2-1-1結晶構造與顯微組織.........................29
4-2-1-2 Ca+2含量對La0.67CaXMnO3-Y塊材電阻係數之影
響........................................32
4-2-1-3 Ca+2含量對La0.67CaXMnO3-Y塊材磁阻特性之影
響........................................33
4-2-2薄膜...........................................34
4-2-2-1結晶構造之分析.............................35
4-2-2-2 Ca2+含量對La0.67CaXMnO3-Y薄膜電阻之影響...37
4-2-2-3 Ca2+含量對La0.67CaXMnO3-Y薄膜磁阻之影響...38
4-3添加Al2O3對LACMO塊材與薄膜電傳輸特性之影響.......39
4-3-1塊材...........................................39
4-3-1-1結晶構造與顯微組織.........................39
4-3-1-2 Al2O3含量與La0.67AlZCa0.1MnO3-Y塊材電阻
係數之關係................................43
4-3-1-3 Al2O3含量與La0.67Ca0.1AlZMnO3-Y塊材磁阻比值之
關係......................................44
4-3-2薄膜...........................................45
4-3-2-1 Al2O3添加對La0.67AlZCa0.1MnO3-Y薄膜結晶結構
之影響....................................45
4-3-2-2 Al2O3 添加對La0.67AlZCa0.1MnO3-Y薄膜電阻係數
之影響....................................46
4-3-2-3 Al2O3添加對La0.67AlZCa0.1MnO3-y薄膜磁阻比值
之影響....................................47
4-3-2-4 La0.67AlZCa0.1MnO3-Y薄膜室溫及低磁場的磁阻行
為........................................50
4-4熱處理對含5﹪Al2O3之La0.67AlZCa0.1MnO3-y薄膜電傳輸特
性之影響.........................................53
4-4-1熱處理對結晶結構之影響.......................53
4-4-2熱處理對LACMO薄膜溫度係數之影響..............54
4-4-3熱處理對La0.67AlZCa0.1MnO3-y薄膜磁阻行為之影
響...........................................56
第五章 結論.................................................58
參考文獻.....................................................61
圖索引
圖2-1 磁阻之類別............................................5
圖2-2 鐵磁性金屬及其合金之磁阻行為(a)低溫下(b)高溫(近居里
溫度)................................................7
圖2-3 超晶格【鐵/鉻】覆膜之巨磁阻行為.......................8
圖2-4 巨磁複膜結構圖........................................10
圖2-5 LaCaMnO3之磁矩排列構造................................11
圖2-6 五個電子軌域..........................................14
圖2-7 dε與dγ能階圖........................................15
圖2-8 雙交換機構示意圖......................................15
圖2-9 輝光放電在陰極附近的氣體分子狀態......................16
圖3-1 實驗流程圖............................................19
圖3-2 塊材,靶材製作流程圖...................................20
圖3-3 塊材,靶材製作流程圖...................................22
圖3-4 α-STEP示意圖.........................................24
圖3-5 Van der Pauw method任意四邊行測量法...................25
圖3-6 低溫系統示意圖........................................27
圖4-2-1 Ca2+含量分別為(a)0.33(b)0.2(c)0.1(d)0之
La0.67CaXMnO3-Y塊材之X光繞射圖......................29
圖4-2-2 Ca2+含量分別為(a)0.33、(b)0.2、(c)0.1及(d)0之
La0.67CaXMnO3-Y塊材SEM顯微織........................31
圖4-2-3 不同Ca2+含量(a)0.33、(b)0.2、(c)0.1及(d)0
La0.67CaXMnO3-Y塊材之電阻係數--溫度曲線.............32
圖4-2-3 不同Ca2+含量(a)0.33、(b)0.2、(c)0.1及(d)0
La0.67CaXMnO3-Y塊材之磁阻溫度曲線圖.................33
圖4-2-5(a)添加不同Ca2+含量分別為(a)0.33 (b)0.2(C)0.1(d)0
La0.67CaXMnO3-x初鍍膜之X光繞射圖....................35
圖4-2-5(b)Ca2+含量分別為(a)0.33(b)0.2(c)0.1(d)0之
La0.67CaXMnO3-Y薄膜經950℃持溫4小時之X光繞射圖......36
圖4-2-6 Ca2+含量分別為(a)0.33,(b)0.2,(c)0.1及(d)0之
La0.67CaXMnO3-Y薄膜電阻係數--溫度曲線圖.............37
圖4-2-7 Ca2+含量分別為(a) 0.33、(b)0.2、(c)0.1及(d)0之
La0.67CaXMnO3-Y 薄膜磁阻比值--溫度曲線圖............38
圖4-3-1 Al2O3含量為(a)0﹪、(b)2﹪、(c)5﹪、(d)10﹪及(e)
20﹪La0.67AlZCa0.1MnO3-Y塊材之XRD繞射圖.............39
圖4-3-2 Al2O3含量為(a)0﹪,(b)5﹪,(c)10﹪,(d)15﹪及
(e)20﹪La0.67AlZCa0.1MnO3-y塊材之SEM顯微組織......42
圖4-3-3 Al2O3﹪含量為(a)0﹪,(b)2﹪,(c)5﹪,(d)10﹪
,(e)20﹪La0.67AlZCa0.1MnO3-y塊材之電阻係數與溫度的關
係曲線圖...........................................43
圖4-3-4 Al2O3﹪含量為(a)0﹪,(b)2﹪,(c)5﹪,(d)10﹪
,(e)20﹪La0.67AlZCa0.1MnO3-y塊材之電阻係數與溫度的關
係曲線圖...........................................44
圖4-3-5 Al2O3含量分別為(0﹪、2﹪、5﹪、10﹪、20﹪)時
La0.67AlZCa0.1MnO3-Y薄膜之X-RAY繞射圖。試片皆由經950℃
持溫4小時熱處理.....................................45
圖4-3-6 Al2O3﹪含量為(a)0﹪、(b)2﹪、(b)5﹪(d)10﹪及(e)
20﹪之La0.67AlzCa0.1MnO3-y薄膜添加之電阻係數與溫度的關
係曲線圖............................................47
圖4-3-7 Al2O3﹪含量分別為 (a)0﹪、(b)2﹪、(c)5﹪、(d)
10﹪及(e)20﹪La0.67AlZCa0.1MnO3-y.薄膜之磁阻比值與溫
度的關係曲線圖......................................48
圖4-3-8 La0.67AlZCa0.1MnO3-Y塊材(曲線a)與薄膜(曲線b)之室溫磁
阻比值與Al2O3含量之關係曲線圖.......................50
圖4-3-9 La0.67AlZCa0.1MnO3-Y+5%Al2O3薄膜於不同溫度下(300K、
120K、110K、70K)之電阻係數隨外加磁場變化之曲線(a)
10000Oe磁場內(b)1000Oe............................52
圖4-4-1 含5﹪Al2O3 La0.67AlzCa0.1MnO3-Y(a)初鍍膜、(b)
1000℃、(c)950℃、(d)900℃持溫4小時退火熱處理的XRD
圖..................................................53
圖4-4-2 添加5﹪Al2O3 La0.67AlZCa0.1MnO3-y(a)初鍍膜及(b)
1000℃、(c)950℃、(d)900℃持溫4小時 熱處理後的電阻
係數與溫度的關係圖..................................54
圖4-4-3 添加5﹪Al2O3之 La0.67AlZCa0.1MnO3-y薄膜於(a) 初鍍態及
(b)1000℃、(c)950℃、(d)900℃持溫4小時熱處理後之
磁阻比值與溫度關係圖...............................56

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