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研究生:周祐仲
論文名稱:分子束磊晶Fe3O4/Mn3O4超晶格表面結構、磁異向性及溫度效應探討
指導教授:陳恭陳恭引用關係
學位類別:碩士
校院名稱:國立中正大學
系所名稱:物理系
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:2000
畢業學年度:88
語文別:中文
論文頁數:85
中文關鍵詞:磁異向性矯頑力場磁滯曲線交換耦合殘餘磁化量
外文關鍵詞:magnetic anisotropycoercive fieldhysteresis loopexchange couplingremanent magnetization
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摘 要
我們利用分子束磊晶(MBE)在MgO(001)單晶基板上製成兩組單晶Mn3O4/Fe3O4超晶格系統:
(1)﹝Mn3O4(50A)/Fe3O4(50A)﹞X12
(2)﹝Fe0.5Mn2.5O4(80A)/Fe3O4(20A)﹞X20
兩者具備類似的尖晶石結構,但Fe3O4為正方體,而Mn3O4是長方體,同時Mn3O4具有高磁異向性。在Mn3O4中添加少許的鐵會使得結構趨向正方體而磁異向性也大為減少,由於上述兩組的單層膜厚都小於100A,因此磁耦合(magnetic coupling)的效應十分明顯。而兩組超晶格中磁異向性的改變是為本論文探討重要的主題。在量測兩組超晶格的M-H圖和M-T圖,是用超導量子干涉儀(SQUID)量測的範圍包括外加磁場0-50kOe、溫度5-300K及膜面垂直和平行磁場兩種方式。從Mn3O4/Fe3O4(50A/50A)超晶格膜面平行磁場的M-H圖中,當溫度高於55K,磁滯曲線呈現和純粹Fe3O4薄膜的陶鐵性質相似的曲線,其Ms約為 210(emu/cm3);在溫度小於55K(約為Mn3O4的Tc)後,可以發現其磁滯曲線的面積和矯頑力(Hc)會隨溫度降低而明顯增加,當溫度從55K下降到5K時,矯頑力的增加量高達4.4倍,同時殘餘磁化量(Mr)卻隨溫度降低從131(emu/cm3)減少到117(emu/cm3),而這樣的現象在膜面平行磁場的M-T圖中也顯現在降低溫度時,在外加磁場小於10kOe時,M值會遞減,而在外加磁場大於10kOe時,M值才會遞增。這些結果不僅顯示出Fe3O4/Mn3O4超晶格界面上的磁矩交換耦合的直接證據,同時也顯示出Mn3O4的高磁異向性與Fe3O4的互相影響。
再以Fe0.5Mn2.5O4(80A)/Fe3O4(20A)超晶格的M-H圖和M-T圖作為對照,溫度高於55K,磁滯曲線大致和純粹Fe3O4薄膜的陶鐵性質一樣,其Ms約為 130(emu/cm3);從膜面平行的M-H圖中,當溫度從55K下降到5K,其矯頑力(Hc)會隨溫度降低而增加,高達3倍,但殘餘磁化量(Mr)卻隨溫度降低從48(emu/cm3)增加到56(emu/cm3)。而在膜面平行磁場M-T圖也明顯的看出在低磁場下,磁化強度隨溫度下降並沒有變小的趨勢。換言之,Mn3O4中加入微量的鐵,使得Fe0.5Mn2.5O4層的磁異向性變弱。進而在Fe0.5Mn2.5O4/Fe3O4的超晶格中顯示出外加磁場在垂直或平行膜面時類似的磁滯曲線。
此外,Fe3O4/Mn3O4超晶格與其他硬磁/軟磁的金屬多層膜比較,也有類似彈性效應(exchange spring)的現象。而Fe3O4和Mn3O4兩者的Tc分別為858K和43K,相差極大,因此在溫度55K以下,其彈性效應會隨溫度下降而快速變大。

Abstract
Two single crystalline Mn3O4/Fe3O4 superlattices were grown on MgO(001) substrate by molecular beam epitaxy technique:
(1)﹝Mn3O4(50A)/Fe3O4(50A)﹞X12
(2)﹝Fe0.5Mn2.5O4(80A)/Fe3O4(20A)﹞X20
Fe3O4 and Mn3O4 both have spinel structures, but Fe3O4 is cubic and Mn3O4 is tetragonal. Relatively, Mn3O4 has much higher magnetic anisotropy. The second sample, which contains small amount of Fe in Mn3O4, tends to become more cubic relative to parent Mn3O4 and its magnetic anisotropy depressed. Since the constituent layer thickness of both samples is<100A that the interface coupling is dominant (the magnetic response shows single loop hysteresis). The main purpose of this thesis is to explore the induced anisotropy of the superlattices and understand the detailed magnetic response of these materials. SQUID magnetometer is used to measure the magnetic properties including the magnetization vs. external field (from 0-50kOe) and the magnetization vs. temperature (5K-300K), and the directions of external field, either parallel or normal to the film surface. The results of the field parallel to surface in Mn3O4(50A)/Fe3O4(50A) superlattice show that when the temperature above 55K, the hysteresis loops are similar to the results of a pure Fe3O4 film, and Ms 210(emu/cm3). But at temperature below 55K, the hysteresis looses (the areas of hysteresis loop) shows strong temperature dependence. The coercive field increases substantially but the remanence only slightly drops with decreasing the temperature. The coercivity increases 4.4 times while the temperature decreases from 55K to 5K. However, the reduction of remanent magnetization only drops from 131(emu/cm3) to 117(emu/cm3). Moreover, the results of M-T measurements at relatively low external field (< 10kOe ) shows that the magnetization decreases with decreasing the temperature, which is consistent with the M-H hysteresis measurements. The present M-H and M-T results provide evidences showing that relative high magnetic anisotropy and high magnetization can be both achieved from these superlattice samples. On the other hand, M-T and M-H curves (external field parallel to the film surface) of Fe0.5Mn2.5O4/Fe3O4 superlattice, in comparison with Mn3O4/Fe3O4, shows different results of magnetic response. When temperature is above 55K, the hysteresis loop is similar to the result of a pure Fe3O4 film and Ms 130(emu/cm3). While the temperature decrease from 55K to 5K, the coercivity increases 3 times but the remanent magnetization increases from 48(emu/cm3) to 56(emu/cm3). The major different magnetic response of these two samples is shown on the hysteresis loop measured with external field perpendicular to the film surface. The results from Mn3O4/Fe3O4 superlattice (at T <55K) show that the magnetization saturates at much higher field indicating a characteristic of hard axis, which is originated with the anisotropy of Mn3O4. On the other hand, the result from Fe0.5Mn2.5O4/ Mn3O4 shows similar loops for both parallel and perpendicular direction.
Moreover, these superlattices represents exchange-spring phenomena, which has been observed originally from metallic hard/soft multilayered system. Since the Curie temperature of Fe3O4 and Mn3O4 is 858 and 43 K respectively. The exchange-spring effect only exists at T<55K and it quickly increases with decreasing temperature.

目錄
第一章 前言………………………………………….....1
1.1 簡介………………………………………………1
1.2 Fe3O4、Mn3O4、MgO物理性質簡介………… 7
1.3Mn3O4/Fe3O4超晶格(superlattice) ……………..12
1.4 磁異向能之簡介……………………………… 13
第二章 實驗儀器與步驟…………………… 16
2.1 實驗儀器系統簡介…………………………… 16
2.2 實驗步驟流程………………………………… 23
第三章 實驗結果與討論……………………… 25
3.1 SQUID 量測的結果與討論…………………… 31
3.2兩超晶格陶鐵磁層交換彈性(exchange spring)效應之
去磁曲線可逆對溫度的探討…….........................74
第四章 結論…………………………………… 82
Reference………………………………………… 84

Reference
【1】Baibich,M.N.,Broto.J.M.,Fert.A.,Petroff,F. Phys.Rev.Lett.61,21(1988)
【2】Dieny,B.,Speriosu,V.S.,Parkin, Phys.Rev.B 43,1
【3】K.B.Hathaway,Giant Theory of Exchange Coupling in Magnetic multilayers,in Ultrathin Magnetic Structures,edited by B.Heinrich and J.A.C.Bland,Vol.2,P45
【4】W.H.Meiklejohn and C.P.Bean.Phy.Rev.vol.102 P.1413(1956);Phy.Rev.vol.105 p904(1957)
【5】Y.Kamiguchi,Y.HayaKawa,and H.Fujimori.Appl.Phys.Lett 55 18,(1989)
【6】E.F.Kneller and R.Hawig,IEEE Trans.Magn.27 3588(1991)
【7】G.Chern.Lance Horng.T.Y. and M.Z.Lin.Appl.Phys.Lett.vol.76,5(2000)
【8】謝文國,碩士論文,中正大學
【9】G.Chern,S.D.Berry,D.M.Lind,H.Mathias,and L.R.Testardi,Phys.Rev.B 45,3644(1992).
【10】李淑媚, 碩士論文,中正大學P44
【11】Cullity:"introduction to magnetic materials".P184
【12】李淑媚,碩士論文,中正大學P31
【13】林銘哲,碩士論文,中正大學P44,P47,P50
【14】Mott"Metal-Insulator Transitions",P215
【15】曠文龍,碩士論文,輔仁大學
【16】Cullity:introduction to magnetic materials.P207
【17】Kirby Dwight and Norman menyuk ,Phys.Review.119,1470(1960)
【18】李學丹"真空沉積技術",浙江大學出版社P.58
【19】呂登復,"實用真空技術",P14,50,P116,P59
【20】Van Hove,M.A.(Michael A.)"surface crystallography by LEED,"P71
【21】賴耿陽, "薄膜製作工藝學",P59
【22】S.D.Berry,D.M.Lind,G.Chern and H.Mathias,J.magn.Mater.123,126(1993)
【23】林銘哲,碩士論文,中正大學,P59
【24】E.Goto,N.Hayashi,T.Miyashita,and K.Nakagawa,J.Appl.Phys.36,2951(1965)

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