MRAM (Magnetic Random Access Memory)
Among the emerging technologies that have been developed to overcome the scaling problem of current Si-based electronics, MRAM, made of magnetic thin films, seems particularly promising as it allows the development of non-volatile memory device with high operation speed and high density. For that reason, MRAM is widely investigated by major Semiconductor companies for next generation memory device.
MRAM is not only suitable as conventional memory device, but it can also be used in alternative computing system such as 'Neuromorphic computing', 'Probabilistic computing' and 'Processing in memory'. These new technologies are at the center of interest in current Semiconductor industry and research.
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SOT (spin-orbit torque) MRAM
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SOT allows the switching of magnetization using in-plane current flowing through the heavy metal (HM) layer in HM/FM(ferromagnet)/oxide structure. There are many challenges in SOT-MRAM such as:
- Field free switching
- Energy efficient SOT channel materials
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By controlling the optimum composition of Pt/X (=Ta, W) energy efficiency of SOT-MRAM could be improved by both reduction of the resistivity and increase of spin hall angle
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The figure of merit (FOM) we suggest is:
[1] Ji-won Yoon, et al., Energy efficiency analysis of spin–orbit torque MRAM using composition dependent resistivity and spin Hall angle in Pt/W multilayer structure, APL Mater. 13, 021101 (2025)
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VCMA (Voltage controlled magnetic anisotropy) MRAM
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Voltage-controlled magnetic anisotropy (VCMA) is a technology that manipulates the magnetic anisotropy of the magnetic layer via electric field.
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In MRAM, switching the magnetization direction requires overcoming an energy barrier between the two magnetization states. When an electric field is applied to the system, the energy barrier can be manipulated through mechanisms such as voltage-induced redox reactions, charge accumulation and depletion, and Rashba effect [1].
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By reducing the energy barrier, the switching energy can be lowered to the fJ/bit and fast switching can be achieved for sub-ns level [2]. In addition, if the device operates based on a voltage-induced redox reaction mechanism, it can exhibit non-volatile properties and help overcome the limitations of leakage currents and power wall issues in CMOS technology [3].
[1] Wen, Z. et al., ”Voltage control of magnetic anisotropy in epitaxial Ru/Co2FeAl/MgO heterostructures”, Scientific Reports 7, 45026 (2017).
[2] Kang, W. et al., "Voltage-controlled MRAM for working memory: Perspectives and challenges“, Design, Automation & Test in Europe Conference & Exhibition (DATE), 542-547 (2017).
[3] Baek, S.-C. et al., ”Complementary logic operation based on electric-field controlled spin–orbit torques”, Nature Electronics 1, 398–403 (2018).