Title Page
Abstract
국문 요약
Contents
1. Introduction 17
1.1. Present and Future Memory 17
1.2. New memory concept 21
1.3. MRAM application 24
1.4. Processing In-memory 25
1.5. Summary 27
2. Background based on spintronics 31
2.1. LLG Equations 31
2.2. Magnetic Tunnel Junctions (MTJ) 33
2.3. Spin-Orbit Torque 36
3. Enhanced Spin-Orbit Torque Efficiency with NdNiO₃ Contact 38
3.1. Introduction 38
3.2. Experimental Methods 40
3.3. Magnetic Characterization and Device Fabrication 42
3.4. Quantification of DL and FL torques using 2nd Harmonic Measurements[이미지참조] 44
3.5. Study of Ferromagnetic Resonance (FMR) 49
3.6. Conclusion 52
3.7. Reference 55
4. Quantification of Spin-Orbit Torque Efficiency in Synthetically Coupled Magnets 59
4.1. Preface 59
4.2. Introduction 59
4.3. Experimental Methods 62
4.3.1. Stack Design and Sample Fabrication 62
4.3.2. Thin Film Characterization and Results 64
4.3.3. Device Quality Investigation with VSM Results 67
4.4. AHE-Based Loop Shift Measurements 69
4.5. Results and Discussion 70
4.6. Conclusion 74
4.7. Reference 77
Scientific Contributions 82
Table 1. Benchmark table of the performance of emerging memories and their comparison with typical memories 28
Table 1. Summary of the harmonic measurement and resistivity results (J = 1.75 × 10⁷ A/cm² and the Oersted field ≈ 0.44 mT at 300 K). 54
TABLE I. Summary of the results obtained loop shift and VSM measurement 76
Figure 1. Classification of Semiconductor memories and computer memories 17
Figure 2. Schematics of (a) DRAM with one transistor and one capacitor (b) SRAM with six transistors (c) Flash memory with floating gate 20
Figure 3. Next generation non-volatile memory concept 23
Figure 4. Magnetic tunnel junction (left) Data storage mechanism, showing two magnetically stable states separated by an energy barrier (right) 24
Figure 5. A simple schematic of proposed solutions with PIM 26
Figure 6. Memory hierarchy present (left) and in the future (right). 29
Figure 7. Different MRAM technologies. In field-switching MRAM, an Oersted field is generated by a current in the bit-line to switch the free layer (left) In STT-MRAM, a current-driven spin-torque... 30
Figure 8. Illustration of the LLG equation by adding a damping term 32
Figure 9. Schematics of in-plane MTJ (i-MTJ) and perpendicular MTJ (p-MTJ). 35
Figure 10. Schematic of the anti-damping torque and field-like torque in NM/FM bilayer structures 37
FIG. 1. (a) HR-TEM and elemental mapping images of NNO/Py/Pt. (b) AFM images of the bare NNO surface (left) and the film surface after Py deposition... 43
FIG. 2. (a) Schematic image of a Hall bar device with measurement coordinates θ and φ, which represent the polar and azimuthal angles, respectively. (b) Rω xy vs. φ...·[이미지참조] 47
FIG. 3. (a) The inverse effective field dependence of R²ωAD+ R²ωVT. Inset: AC cur- rent-induced magnetization oscillations due to AD-SOT. (b) R²ωFL+Oe as a func-...[이미지참조] 48
FIG. 4. (a) Schematic image of the FMR apparatus. The derivative FMR spectra of (b) NNO/Py/Pt and (c) Py/Pt between 4 and 11 GHz at room tem-... 51
FIG. 1. (a) Schematic drawing of the three different FL stacks. (b) Schematic illustrations of a Hall bar device 63
FIG. 2. Normalized out-of-plane (OOP) and in-plane (IP) magnetization curve of SAF-based FL in (a) SFM-based FL in (b) and a single FL stack in... 66
FIG. 3. R AH curves of SAF-Based FL in (a) SFM-based FL in (b) and a single FL stack in (c) measured when sweeping an external field along z-direction. (d)...[이미지참조] 68
FIG. 4. (a) R AH loops for a SAF-based FL with I DC = 15mA and in-plane bias field H x = 800 Oe. H z eff represents the shift of the AH loops. (b) R AH loops for...[이미지참조] 73
FIG. 5. Experimental parameter for maximum efficiency in (a) and the effective field in (b). (c) The summary of calculated resistivity for three different FL Hall-... 75