臺灣博碩士論文加值系統

在鉑/氧化鋁/鎳鐵三層結構中，可利用逆自旋霍爾產生之電壓來偵測來自鐵磁共振的純自旋流。本論文實驗中發現逆自旋霍爾電壓明顯隨著氧化鋁厚度增加而遞減。此外，當改變外加磁場與樣品垂直方向之夾角，鐵磁共振的吸收與逆自旋霍爾效應都會隨之改變。從鈷鐵/鎳鐵/氧化鋁/鎳鐵的磁性穿隧接面量測到非線性的電流-電壓關係以及其中有磁阻的表現，確定本實驗中鎳鐵磁性表現以及氧化鋁的完全氧化參數。結合以上的結果，可以確定純自旋流在鉑/氧化鋁/鎳鐵系統中傳輸機制：從鎳鐵穿隧經過氧化層，最後流至鉑並產生逆自旋霍爾電壓。其中，我們發現逆自旋霍爾電壓與氧化層厚度呈指數遞減關係。

The detection of spin current tunneling is being investigated by a technique of ferromagnetic resonance (FMR) with Inverse Spin Hall voltage (VISHE) measurement in Pt/AlOx/Py trilayer system. It is seen that the value of VISHE is apparently decreasing with the increasing thickness of oxide barrier. Furthermore,FMR and VISHE are also measured with the sample rotating out of plane with respect to the magnetic field direction. From the non-linear characteristic behaviour of I-V measurement in tunnelling magnetoresistance (MR) junction(CoFe/NiFe/AlOx/NiFe), it is confirmed that the quality of AlOx forms tunnelling junction. The combined results of FMR, VISHE and nonlinear I-V characteristic suggests that the spin transport mechanism from Py to Pt in Pt/AlOx/Py system is the tunnelling effect through the oxide barrier.

1 Introduction 1
2 Basic Concepts 3
2.1 Spin Pumping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1.1 Ferromagnetic Resonance (FMR) . . . . . . . . . . . . . . . . 4
2.1.2 Spectral Lineshape of Ferromagnetic Magnetic Resonance . . . 5
2.2 Spin Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.2.1 Origin of Spin Current [13] . . . . . . . . . . . . . . . . . . . . 6
2.2.2 Spin Mixing Conductance . . . . . . . . . . . . . . . . . . . . 7
2.3 Spin Hall Effect and Anomalous Hall Effect . . . . . . . . . . . . . . 8
2.3.1 Spin Hall Effect . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.3.2 Anomalous Hall Effect in Spin Pumping . . . . . . . . . . . . 12
2.3.3 Inverse Spin Hall Effect in Spin Pumping . . . . . . . . . . . . 14
3 Experimental Fabrication and Apparatus 16
3.1 UHV Sputtering System . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.2 Direct-Current Magnetron Sputtering . . . . . . . . . . . . . . . . . . 18
3.3 Radio Frequency Magnetron Sputtering . . . . . . . . . . . . . . . . . 19
3.4 Quartz Crystal Microbalance . . . . . . . . . . . . . . . . . . . . . . . 20
3.5 Contact Patterned Mask . . . . . . . . . . . . . . . . . . . . . . . . . 20
3.6 Electron Paramagnetic Resonance System . . . . . . . . . . . . . . . 21
3.7 Four-Probe Measurement . . . . . . . . . . . . . . . . . . . . . . . . . 22
3.8 Fitting Formula and Analysis . . . . . . . . . . . . . . . . . . . . . . 23
4 Experimental Results 24
4.1 Sample Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
4.2 I-V and Conductivity Measurement . . . . . . . . . . . . . . . . . . . 25
4.2.1 Tunneling Magnetoresistance Junction . . . . . . . . . . . . . 25
4.2.2 I-V measurement in Pt/ AlOx/ Py Tunneling Junction . . . . 27
4.2.3 Conductivities of Pt and Py . . . . . . . . . . . . . . . . . . . 27
4.3 Spin pumping in Pt/Py System . . . . . . . . . . . . . . . . . . . . . 28
4.3.1 Angle Dependence . . . . . . . . . . . . . . . . . . . . . . . . 29
4.3.2 Power Dependence . . . . . . . . . . . . . . . . . . . . . . . . 30
4.3.3 Absorption in FMR Spectrum . . . . . . . . . . . . . . . . . . 31
4.3.4 Estimation of Spin Current . . . . . . . . . . . . . . . . . . . 32
4.4 Spin Pumping in Pt/AlOx/Py System . . . . . . . . . . . . . . . . . 34
4.4.1 Angle Dependence . . . . . . . . . . . . . . . . . . . . . . . . 35
4.4.2 Power Dependence . . . . . . . . . . . . . . . . . . . . . . . . 35
4.4.3 Absorption and Resonance Field in FMR Spectrum . . . . . . 36
4.4.4 The Linewidth and Spin Mixing Conductance . . . . . . . . . 37
4.4.5 Thickness Dependence . . . . . . . . . . . . . . . . . . . . . . 38
5 Conclusion 40
6 Appedix 42
6.1 LabTalk script . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Bibliography 46

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