伴隨著人工智慧、大數據的蓬勃發展，近年來對於資料儲存的需求日漸增加。在現存主流的記憶體中如DRAM，SRAM皆為揮發類性記憶體。這類記憶體如須保持資料儲存則須不間斷的供應電流，因此在能量損耗上相當可觀。而現存的非揮發性記憶體如Flash則有著讀寫速度上的劣勢。
磁性記憶體MRAM由於其非揮發的性質以及優異的讀寫速度，因此普遍被視為下個世代的記憶體。本篇論文主要在建立於第三世代的自旋軌道力矩磁性記憶體的基礎上，引入反鐵磁材料作為輔助用以達成零場翻轉。然而由於使用的反鐵磁材料有著特殊的結構，我們發現了其有著與玻璃相似的性質並可以透過自旋軌道力矩進行塑型，而用以固定零場翻轉的極性。
我們也在現有的反鐵磁理論上加入了嶄新的架構用以描述反鐵磁結構的性質，這篇論文不僅僅達成了第三世代磁性記憶體中的零場翻轉，更是給予了未來的反鐵磁相關研究點了一盞明燈。

Antiferromagnetic material (AFM) attracted fervent attention due to its multifunctional characteristic, making it become the most promising next generation memory devices. Although AFM is integrated into several application in contemporary memory devices, the realistic understanding of AFM is far below typically used Ferromagnetic material (FM) however. This thesis proposed an innovate idea to describe AFM and reveals the hidden properties beneath existing Néel order theory and we can further modify the spin configuration in AFM through spin orbit torque (SOT). Owing to the peculiar 3Q spin texture in polycrystalline IrMn, the shaped IrMn can assisted field free switching without apparent symmetry breaking term. Additionally, the field free switching polarity is fixed after training and cannot be rewrite afterwards. All the properties of AFM are carefully characterized by advance optical and electrical methods. This work proposed a new theory of AFM material, and the memorable characteristic of AFM definitely turns over a new leaf into AFM based spintronics device.

1 Hirsch, J. Spin hall effect. Physical review letters 83, 1834 (1999).
2 Slonczewski, J. C. Current-driven excitation of magnetic multilayers. Journal of Magnetism and Magnetic Materials 159, L1-L7 (1996).
3 Berger, L. Emission of spin waves by a magnetic multilayer traversed by a current. Physical Review B 54, 9353 (1996).
4 Apalkov, D. et al. Spin-transfer torque magnetic random access memory (STT-MRAM). ACM Journal on Emerging Technologies in Computing Systems (JETC) 9, 1-35 (2013).
5 Hall, E. H. On a new action of the magnet on electric currents. American Journal of Mathematics 2, 287-292 (1879).
6 Dyakonov, M. I. & Perel, V. Current-induced spin orientation of electrons in semiconductors. Physics Letters A 35, 459-460 (1971).
7 Kato, Y. K., Myers, R. C., Gossard, A. C. & Awschalom, D. D. Observation of the spin Hall effect in semiconductors. science 306, 1910-1913 (2004).
8 Miron, I. M. et al. Current-driven spin torque induced by the Rashba effect in a ferromagnetic metal layer. Nature materials 9, 230-234 (2010).
9 Prenat, G., Jabeur, K., Di Pendina, G., Boulle, O. & Gaudin, G. in Spintronics-based Computing 145-157 (Springer, 2015).
10 Shpiro, A., Levy, P. M. & Zhang, S. Self-consistent treatment of nonequilibrium spin torques in magnetic multilayers. Physical Review B 67, 104430 (2003).
11 Zhang, S., Levy, P. & Fert, A. Mechanisms of spin-polarized current-driven magnetization switching. Physical review letters 88, 236601 (2002).
12 Lee, K.-S., Lee, S.-W., Min, B.-C. & Lee, K.-J. Threshold current for switching of a perpendicular magnetic layer induced by spin Hall effect. Applied Physics Letters 102, 112410 (2013).
13 Gilbert, T. L. A phenomenological theory of damping in ferromagnetic materials. IEEE transactions on magnetics 40, 3443-3449 (2004).
14 Fukami, S., Anekawa, T., Zhang, C. & Ohno, H. A spin–orbit torque switching scheme with collinear magnetic easy axis and current configuration. nature nanotechnology 11, 621-625 (2016).
15 Yu, G. et al. Current-driven perpendicular magnetization switching in Ta/CoFeB/[TaOx or MgO/TaOx] films with lateral structural asymmetry. Applied Physics Letters 105, 102411 (2014).
16 Aharoni, A. Introduction to the Theory of Ferromagnetism. Vol. 109 (Clarendon Press, 2000).
17 Hu, A.-Y. & Wang, H.-Y. The exchange interaction values of perovskite-type materials EuTiO3 and EuZrO3. Journal of Applied Physics 116, 193903 (2014).
18 Feng, W. et al. Topological magneto-optical effects and their quantization in noncoplanar antiferromagnets. Nature communications 11, 1-9 (2020).
19 Jenkins, S. et al. Atomistic origin of exchange anisotropy in noncollinear γ− IrMn 3–CoFe bilayers. Physical Review B 102, 140404 (2020).
20 Nakatsuji, S., Kiyohara, N. & Higo, T. Large anomalous Hall effect in a non-collinear antiferromagnet at room temperature. Nature 527, 212-215 (2015).
21 Meiklejohn, W. H. & Bean, C. P. New magnetic anisotropy. Physical review 102, 1413 (1956).
22 Tsang, C. Magnetics of small magnetoresistive sensors. Journal of Applied Physics 55, 2226-2231 (1984).
23 Tehrani, S. et al. Recent developments in magnetic tunnel junction MRAM. IEEE Transactions on magnetics 36, 2752-2757 (2000).
24 Fukami, S., Zhang, C., DuttaGupta, S., Kurenkov, A. & Ohno, H. Magnetization switching by spin–orbit torque in an antiferromagnet–ferromagnet bilayer system. Nature materials 15, 535-541 (2016).
25 Lin, P.-H. et al. Manipulating exchange bias by spin–orbit torque. Nature materials 18, 335-341 (2019).
26 Peng, S. et al. Exchange bias switching in an antiferromagnet/ferromagnet bilayer driven by spin–orbit torque. Nature Electronics, 1-8 (2020).
27 Fina, I. et al. Anisotropic magnetoresistance in an antiferromagnetic semiconductor. Nature communications 5, 1-7 (2014).
28 Wang, Y. et al. Room-temperature perpendicular exchange coupling and tunneling anisotropic magnetoresistance in an antiferromagnet-based tunnel junction. Physical review letters 109, 137201 (2012).
29 Wang, Y. et al. Anti‐Ferromagnet Controlled Tunneling Magnetoresistance. Advanced Functional Materials 24, 6806-6810 (2014).
30 Olejník, K. et al. Antiferromagnetic CuMnAs multi-level memory cell with microelectronic compatibility. Nature communications 8, 1-7 (2017).
31 Saidl, V. et al. Optical determination of the Néel vector in a CuMnAs thin-film antiferromagnet. Nature Photonics 11, 91-96 (2017).
32 Wadley, P. et al. Electrical switching of an antiferromagnet. Science 351, 587-590 (2016).
33 Wadley, P. et al. Current polarity-dependent manipulation of antiferromagnetic domains. Nature nanotechnology 13, 362-365 (2018).
34 Meinert, M., Graulich, D. & Matalla-Wagner, T. Electrical switching of antiferromagnetic Mn 2 Au and the role of thermal activation. Physical Review Applied 9, 064040 (2018).
35 Hu, J.-M., Li, Z., Chen, L.-Q. & Nan, C.-W. High-density magnetoresistive random access memory operating at ultralow voltage at room temperature. Nature communications 2, 1-8 (2011).
36 Yan, H. et al. Electric‐Field‐Controlled Antiferromagnetic Spintronic Devices. Advanced Materials 32, 1905603 (2020).
37 Schryer, N. L. & Walker, L. R. The motion of 180 domain walls in uniform dc magnetic fields. Journal of Applied Physics 45, 5406-5421 (1974).
38 Beach, G. S., Nistor, C., Knutson, C., Tsoi, M. & Erskine, J. L. Dynamics of field-driven domain-wall propagation in ferromagnetic nanowires. Nature materials 4, 741-744 (2005).
39 Tatara, G. & Kohno, H. Theory of current-driven domain wall motion: Spin transfer versus momentum transfer. Physical review letters 92, 086601 (2004).
40 Berger, L. Exchange interaction between ferromagnetic domain wall and electric current in very thin metallic films. Journal of Applied Physics 55, 1954-1956 (1984).
41 Berger, L. Motion of a magnetic domain wall traversed by fast‐rising current pulses. Journal of applied physics 71, 2721-2726 (1992).
42 Khvalkovskiy, A. et al. Matching domain-wall configuration and spin-orbit torques for efficient domain-wall motion. Physical Review B 87, 020402 (2013).