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鎳鈀,鎳銅多層膜界面異向性磁阻 / Interfacial anisotropic magnetoresistance of Ni/Pd and Ni/Cu multilayers李信甫, Lee, Hsin Fu Unknown Date (has links)
在磁性材料中的電阻率會隨著磁場與電流的夾角不同而改變且磁場平行於電流時會大於磁場垂直於電流時的值(ρH‖I > ρH⊥I),此現象稱作異向性磁阻(Anisotropic Magnetoresistance, AMR)效應。而在薄膜材料中,因為和塊材的形狀差異,磁場垂直於電流的電阻率又可以分為磁場方向平行於膜面(ρ⊥HIP)和磁場方向垂直於膜面 (ρ⊥HPP)。而依這兩者在單層膜與多層膜中不一樣的行為又可以分作兩種效應。在Co、Ni的單層膜中ρ⊥HIP > ρ⊥HPP,此現象稱為幾何尺寸效應(Geometric Size Effect, GSE),而在Co/Pt的多層膜中ρ⊥HPP > ρ⊥HIP,與幾何尺寸效應果相反,此現象稱為異向性界面磁阻(Anisotropic Interface Magnetoresistance, AIMR)。而我們在Pd/Ni、Cu/Ni多層膜中更是看到磁場方向垂直於膜面 (ρ⊥HPP)大於磁場平行於電流(ρH‖I),這是和異向性磁阻(Anisotropic Magnetoresistance, AMR)效應完全相反的現象,我們稱作反常異向性磁阻(Inverse AMR)效應
本實驗製作的樣品皆為磁性層與非磁性層交錯的多層膜,磁性層材料為鎳(Ni),非磁性層的材料則選用接近滿足Stoner 準則(Stoner criterion)之一的鈀(Pd),以及遠離此準則且自旋軌道交互作用很弱的銅(Cu)當對照組。而為了釐清其發生機制,所以分別做了兩種類型的樣品,第一類是固定單層膜厚改變層數,第二類是固定層數及磁性層(非磁性層)改變非磁性層(磁性層)。完成後的樣品首先以XRD確認樣品的膜厚與品質,接著在10 K和300 K的溫度量測電阻與角度的關係及磁場平行(LMR)、垂直(PMR)於電流時的磁阻,在10K時,以Pd/Ni為材料的多層膜中有看到反常異向性磁阻(Inverse AMR)效應,在300K時,以Cu/Ni為材料的第一類樣品有看到此效應,之後我們還有在不同溫度下量測電阻與角度的關係並找到其效應轉變的溫度。
由實驗結果推論,不同材料中觀察到的結果,物理機制並不相同;應該與介面性質有關。但是物理理論上的解釋還需要更進一步地探討。
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鈷/鉑垂直磁化多層膜中結構對磁耦合及電性的影響 / Influence of structure on magnetic coupling and electric properties in cobalt/platinum multilayer with spontaneously perpendicular-magnetization曾嘉裕, Tseng, Chia Yu Unknown Date (has links)
本論文主要在研究多層膜之垂直異向性結構組成及其介面特質,本實驗多層膜選取的材料為鐵磁性的鈷(Co)以及貴重金屬的鉑(Pt),並利用濺鍍(Sputtering)系統來製作(鈷/鉑)多層膜樣品,最初的實驗為尋找(鈷/鉑)多層膜結構組成最佳垂直易性發生之條件,所以分別變化鐵磁層鈷之厚度、一般金屬層鉑之厚度、(鈷/鉑)雙層層數及緩衝buffer layer層鉑之厚度,並利用震動樣品磁度儀(VSM)及超導量子干涉儀(SQUIDE)分別量測垂直及平行磁場方向之磁化強度M對磁場field H的關係,再由M-H圖進行判別其垂直異向性的程度。
在最初的實驗部分可了解如何得到最佳(鈷/鉑)垂直異向性多層膜之結構,並從中可得不同緩衝層鉑之厚度、(鈷/鉑)雙層層數及雙層內鉑之厚度的矯頑場有一趨勢存在,於第二部分的實驗即利用這些矯頑場之趨勢來製作一系列產生巨磁效應之三層膜結構,其中的鐵磁層由(鈷/鉑)垂直異向性多層膜取代,並對此結構做一系列量測,利用震動樣品磁度儀(VSM)量測其磁化強度對磁場的關係、利用LR700系統及物理低溫量測系統(PPMS)量測其異常Hall effect霍爾效應(EHE)現象和電阻對磁場的關係,再將這一系列的量測結果分析其中被一般金屬層鉑所隔開的上下(鈷/鉑)垂直異向性多層膜之間耦合程度。 / The topic of this thesis is about the property of the interface and structure in the multilayers with perpendicular anisotropy. The materials of this multilayers are ferromagnetic cobalt and platinum. We use sputtering system to fabricate cobalt/platinum multilayer with various thicknesses. The initial experiment is to search for the optimum condition that develop cobalt/platinum multilayer with perpendicular anisotropy. Then, the influenceof the buffer layer of platinum is studied. We use Vibrating sample magnetometer (VSM) and superconducting quantum interference device (SQUID) magnetometer to measure the magnetization vs. magnetic field relation by applied magnetic fields in both out of plane and in plane directions to distinguishe the degree of perpendicular anisotropy from the M-H figures.
From the initial experiments we can understand how to get the optimum structure of cobalt/platinum perpendicular anisotrpy multilayer. There is a tendency exists in the coercivity depending on different thicknesses of the ferromagnetic layer cobalt, the normal noble platinum, the number of bilayers of cobalt/platinum, and the buffer layer of platinum. In the second part of this experiment we used the difference of coercivities to fabricate a series of trilayers structures that produce giant magnetoresistance effect. The individual ferromagnetic layer was cobalt/platinum perpendicular anisotropy multilayer. The structures was measured by VSM to study magnetization vs. field relation. A LR700 resistance bridge and a physical properties measurement system (PPMS) were used to measure the Anomalous Hall Effect (AHE) and resistant vs. field relation.
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自旋波在磁性奈米線中的微磁模擬 與 鈷/鉑,鈷/鈀,鉑/鈀多層膜的電、磁特性 / Micromagnetic simulations of spin waves in magnetic nanowires and electrical, magnetic properties of Co/Pt, Co/Pd, and Pt/Pd multilayers謝智勛, Hsieh, Chih Hsun Unknown Date (has links)
本論文分為兩部分,第一部分探討使用OOMMF磁性材料模擬軟體來模擬奈米線波導中的自旋波特性,除了以往文獻所熱門的水平異向性薄膜合金中的自旋波,還模擬了垂直異向性的材料,我們模擬了在奈米線一端施加0 ~ 100 GHz外加磁場的自旋波響應。在模擬的結果中,我們發現了水平異向性與垂直異向性的重要差別,垂直異向性比水平異向性波導在頻率小於10 GHz時,少了複雜的自旋波傳遞。而在改變線寬的條件中,我們發現了垂直異向性波導在線寬夠大時,會因退磁場的效應,使得磁矩翻轉,形成許多磁壁,而水平異向性材料則不會,從水平異向性波導大於120 nm線寬的波型中,則會發現自旋波在波導中產生破碎的相位改變。而模擬具有水平寬度變化與垂直厚度變化的週期性邊界,則發現兩者所具有的濾波效果非常相似,而濾波的三個頻段,則是水平寬度變化所截止的頻段,寬於垂直厚度變化的頻段。
第二部分為 ,使用離子濺鍍製成總厚度200 nm,改變交錯層數的(Co/Pt)×N、(Co/Pd) ×N與(Pt/Pd) ×N,三種多層膜的磁性電性分析。Co/Pt與Co/Pd多層膜在Co厚度小於1 nm時為熱門垂直異向性材料,而本實驗專注於Co厚度大於1 nm時介面的特性以及兩種材料的差別。在磁阻的量測上面,得到不同於一般異向性磁阻的規律,一般的異向性磁阻的現象為,平行於電流施加磁場比垂直電流施加磁場所量測的電阻,前者電阻較大(ρ_(H∥I)>ρ_(H⊥I)),但是同為垂直於電流的平行於膜面磁場的電阻(ρ_(H⊥I,in-plane H))與垂直膜面磁場(ρ_(H⊥I,H perpendicular to plane))則呈現了不一樣的行為,尤其為垂直加場的部分,在某些條件的多層膜,會有明顯的垂直方向的異向性磁阻,是為介面所造成額外的垂直方向異向性磁阻,稱作”異向性介面磁阻”(Anisotropic Interface Magnetoresistance)。異向性磁阻與異性向介面磁阻都具有高電阻軸與垂直此軸的低電阻平面,而兩者差別在於異向性磁阻為電流方向軸,而異向性介面磁阻為膜面法向量軸,對於本實驗的量測方法來說,兩軸相差90度角,也因此可辨析兩者不同現象間的差異,並且在我們的分析之中發現,異向性介面磁阻在Co厚度為7 nm以下,才會明顯的顯現。 / The thesis is divided into two main parts. The first part discusses the properties of spin waves propagation in magnetic nanowire waveguide by micromagnetic simulation software OOMMF. In addition to in-plane magnetic anisotropy (IMA) in the thin film alloys, we simulate the perpendicular magnetic anisotropy (PMA) of the material. A transverse magnetic field is applied at one end of the waveguide wire and the frequency range is from 0 to 100 GHz. When frequency is less than 10 GHz, we observed that complex modes were generated in the IMA waveguide but there is no spin wave propagates in the PMA waveguide. We also studied the spin wave propagations in wires with different width. Irregular domain wall was generated by demagnetizing field in wider PMA waveguide but IMA waveguide does not have this behavior. In width-modulated and thickness-modulated waveguide spin wave simulations, these two filters have similar results with three band gaps from 0 to 100 GHz and the band gaps in width-modulated wire is wider than in thickness-modulated one.
The second part is experimental measurements of the electrical and magnetic properties of (Co/Pt)×N, (Co/Pd) ×N, and (Pt/Pd) ×N multilayers, which are deposited by sputtering and the total thickness is 200nm. Co/Pt and Co/Pd were popular PMA materials when Co thickness is less than 1 nm. We focused on the multilayers with Co thicker than 1nm and the difference between these multilayers. In magnetoresistance measurement, the R-H curve is different from normal anisotropic magnetoresistance (AMR). AMR effect has different resistivity when H∥I or H⊥I, but the measurement results show that ρ_(H⊥I,in-plane H) and ρ_(H⊥I,H perpendicular to plane) also have different MR ratio in specific multilayer configuration. The effect is caused by the interface so it is anisotropic interface magnetoresistance (AIMR) as discussed in the literature. AMR and AIMR have both high resistivity axis and low resistivity plane which is perpendicular to the axis. The difference of two MRs is that the high resistivity axis is parallel to current in AMR and perpendicular to plane in AIMR. In the analysis, the AIMR effect is observed in multilayer with Co thickness less than 7 nm.
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