Stabilization and Reversal of Skyrmion Lattice in Ta/CoFeB/MgO Multilayers

Qin, Zhaogang; Wang, Ying; Zhu, Shimeng; Jin, Chendong; Fu, Jiecai; Liu, Qingfang; Cao, Jian

doi:10.1021/acsami.8b12694

Cited by 29 publications

(20 citation statements)

References 46 publications

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“…In this first series of images, the number of magnetic skyrmions is low. To obtain more magnetic skyrmions, the sample was saturated in an in-plane direction, as reported in previous studies (Qin et al, 2018;Li et al, 2020). The in-plane magnetic field was applied in situ in the TEM by tilting the sample to 80°and exciting the conventional microscope objective lens fully (corresponding to an applied magnetic field of approximately 1.4 T) for a few seconds.…”

Section: Magnetic and Crystalline Structure Of The Samplementioning

confidence: 99%

Visibility and Apparent Size of Néel-Type Magnetic Skyrmions in Fresnel Defocus Images of Multilayer Films

et al. 2021

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Multilayers that comprise thin films of heavy metals and ferromagnets have been shown to host Néel-type magnetic skyrmions at room temperature. Fresnel defocus imaging in Lorentz transmission electron microscopy is a widely used technique for recording magnetic information about skyrmions. However, the visibility of Néel-type skyrmions in Fresnel defocus images is typically low, both because only a small component of their magnetic field contributes to the signal and because of the presence of diffraction contrast from the polycrystalline multilayer structure. Here, we take advantage of the out-of-plane hysteresis in such samples to record background-subtracted Fresnel defocus images. We demonstrate an improvement in magnetic signal-to-noise ratio and spatial resolution by a factor of 3 for a (Pt/Co/NiFe)×5 multilayer. We also use simulated Fresnel defocus images of Néel-type magnetic skyrmions to understand the influence of defocus on apparent skyrmion size.

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Section: Magnetic and Crystalline Structure Of The Samplementioning

confidence: 99%

Visibility and Apparent Size of Néel-Type Magnetic Skyrmions in Fresnel Defocus Images of Multilayer Films

et al. 2021

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“…In particular, a high-density skyrmion phase is instrumental for the realization and optimization of theoretically proposed unconventional skyrmion-based computing models (e.g., probabilistic computing, reservoir computing) [25][26][27] . Note that although there is a report on skyrmion lattices observed in magnetic multilayers 28 , isolated skyrmions have been the norm in most magnetic multilayer systems, raising questions about the widespread application of multilayer-based ultrahigh-density skyrmion memory and computing devices.…”

Section: Introductionmentioning

confidence: 99%

High-density Néel-type magnetic skyrmion phase stabilized at high temperature

et al. 2020

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The discovery of a thermally stable, high-density magnetic skyrmion phase is a key prerequisite for realizing practical skyrmionic memory devices. In contrast to the typical low-density Néel-type skyrmions observed in technologically viable multilayer systems, with Lorentz transmission electron microscopy, we report the discovery of a high-density homochiral Néel-type skyrmion phase in magnetic multilayer structures that is stable at high temperatures up to 733 K (≈460 °C). Micromagnetic simulations reveal that a high-density skyrmion phase can be stabilized at high temperature by deliberately tuning the magnetic anisotropy, magnetic field, and temperature. The existence of the high-density skyrmion phase in a magnetic multilayer system raises the possibility of incorporating chiral Néel-type skyrmions in ultrahigh-density spin memory devices. Moreover, the existence of this phase at high temperature shows its thermal stability, demonstrating the potential for skyrmion devices operating in thermally challenging modern electronic chips.

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“…The key to achieve a perpendicular-anisotropy CoFeB/MgO MTJ is the very thin thickness of CoFeB layer. 23,24 The PMA was attributed entirely to the CoFeB-MgO interfacial anisotropy by Ikeda et al, 8 while the Ta seed layer, not just the MgO at the top interface, was demonstrated to be critical to achieving perpendicular magnetic anisotropy. 25 The microscopic origin of the PMA in the CoFeB/MgO structure is still far from clear.…”

Section: Introductionmentioning

confidence: 99%

Element-specific spin and orbital moments and perpendicular magnetic anisotropy in Ta/CoFeB/MgO structures

Yan

Liu

et al. 2020

Journal of Applied Physics

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Ultrathin CoFeB-based magnetic tunnel junction (MTJ) is the key for the next generation magnetic random-access memory (MRAM). However, the underlying mechanism of the perpendicular magnetic anisotropy (PMA) in Ta/CoFeB/MgO structure is still unclear. Herein, the PMA in the Ta/CoFeB/MgO system has been studied using X-ray magnetic circular dichroism and vibrating sample magnetometry. The ratios of the orbital to spin magnetic moments of Co atoms in the Ta/CoFeB/MgO structures with PMA have been found to be enhanced by 100%, compared with the Ta/CoFeB/Ta structure without PMA. The orbital moments of Co are as large as 0.30 µ B , more than half of their spin moments in the perpendicularly magnetised Ta/CoFeB/MgO structures. The results indicate that the PMA observed in the Ta/CoFeB/MgO structures is related to the increased spin-orbital coupling of the Co atoms. This work offers experimental evidence of the correlation between PMA and the element specific spin and orbital moments in the Ta/CoFeB/MgO systems.

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Stabilization and Reversal of Skyrmion Lattice in Ta/CoFeB/MgO Multilayers

Cited by 29 publications

References 46 publications

Visibility and Apparent Size of Néel-Type Magnetic Skyrmions in Fresnel Defocus Images of Multilayer Films

Visibility and Apparent Size of Néel-Type Magnetic Skyrmions in Fresnel Defocus Images of Multilayer Films

High-density Néel-type magnetic skyrmion phase stabilized at high temperature

Element-specific spin and orbital moments and perpendicular magnetic anisotropy in Ta/CoFeB/MgO structures

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