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High Speed MRAM with Voltage Control of Magnetic Anisotropy (VCMA) Effect KU Leuven

Yueh Chang Wu
Magnetic random access memory (MRAM) is gaining intensive interest for embedded and stand-alone memory applications. Its inherent non-volatility is believed to address the large stand-by energy consumption issues in the present memory hierarchy. In recent years, the spin-transfer torque (STT)-MRAM has gradually matured and started to appear in the market. Typically, STT writing of perpendicular magnetic tunnel junction (pMTJ) is limited to a few ...

Synthetic-Ferromagnet Pinning Layers Enabling Top-Pinned Magnetic Tunnel Junctions for High-Density Embedded Magnetic Random-Access Memory KU Leuven

Enlong Liu, Yueh Chang Wu, S Couet, S Mertens, S Rao, W Kim, K Garello, D Crotti, S Van Elshocht, Johan De Boeck, et al.
© 2018 American Physical Society. Magnetic tunnel junctions (MTJs) with perpendicular magnetic anisotropy (PMA) have been developed for decades for spin-transfer-torque magnetic random-access memory. Common stack designs use a hard layer (HL) with strong PMA to pin the reference layer (RL) by forming a synthetic antiferromagnet through a thin nonmagnetic coupling layer. Compared to bottom-pinned MTJs, very limited progress has been made to ...

Top-Pinned STT-MRAM Devices With High Thermal Stability Hybrid Free Layers for High-Density Memory Applications KU Leuven

Enlong Liu, Johan Swerts, Yueh Chang Wu, Adrien Vaysset, Sebastien Couet, Sofie Mertens, Siddharth Rao, Woojin Kim, Sven Van Elshocht, Johan De Boeck, et al.
© 1965-2012 IEEE. The hybrid free layer (HFL) design consisting of a single layer of CoFeB coupled via a spacer to [Co/Ni] multilayers was proposed previously to increase perpendicular magnetic anisotropy in the free layer of top-pinned magnetic tunnel junction stacks. It is thus expected that a high thermal stability factor (Δ) can be achieved in devices with small dimensions, which is required for data retention in high-density memory ...

Impact of operating temperature on the electrical and magnetic properties of the bottom-pinned perpendicular magnetic tunnel junctions KU Leuven

Yueh Chang Wu, W Kim, S Rao, K Garello, Simon Van Beek, S Couet, E Liu, J Swerts, S Kundu, L Souriau, et al.
© 2018 Author(s). Analogous device parameters in both the parallel (P) and anti-parallel (AP) states ensure a symmetric spin-transfer-torque magnetic random-access memory operation scheme. In this study, however, we observe an increasing asymmetry in the performance metrics with operating temperature of the bottom-pinned perpendicular magnetic tunnel junction (p-MTJ) devices. A temperature-dependent increase in the contribution of the stray ...

Thermal stability analysis and modelling of advanced perpendicular magnetic tunnel junctions KU Leuven

Simon Van Beek, Koen Martens, Philippe Roussel, Yueh Chang Wu, Woojin Kim, Siddharth Rao, Johan Swerts, Davide Crotti, Dimitri Linten, Gouri Sankar Kar, et al.
© 2017 Author(s). STT-MRAM is a promising non-volatile memory for high speed applications. The thermal stability factor (Δ = Eb/kT) is a measure for the information retention time, and an accurate determination of the thermal stability is crucial. Recent studies show that a significant error is made using the conventional methods for Δ extraction. We investigate the origin of the low accuracy. To reduce the error down to 5%, 1000 cycles or ...