Ru Catalyst-Induced Perpendicular Magnetic Anisotropy in MgO/CoFeB/Ta/MgO Multilayered Films

Liu, Yiwei; Zhang, Jingyan; Wang, Shouguo; Jiang, Shaolong; Liu, Qianqian; Li, Xujing; Wu, Zhenglong; Yu, Guo

doi:10.1021/acsami.5b08385

Cited by 26 publications

(11 citation statements)

References 33 publications

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“…Specifically, for the regions in contact with Pt, μ 0 M eff false( Pt false) = 95.8 mT, and for the case of Ru, μ 0 M eff false( Ru false) = 75.8 mT, for an exchange constant A ex = 15.62 pJ/m and an i-DMI strength D = 1.1 mJ/m 2 in the Pt zones. In particular, the lower value of M eff in the region in contact with Ru can be ascribed not only to the perpendicular magnetic anisotropy but also to a reduction of the saturation magnetization due to the interdiffusion and dead layer formation at the Ru/CoFeB interface. − The positive value of M eff indicates a remanent state with in-plane magnetization, as found experimentally.…”

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confidence: 63%

Experimental Observation of Flat Bands in One-Dimensional Chiral Magnonic Crystals

et al. 2023

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Spin waves represent the collective excitations of the magnetization field within a magnetic material, providing dispersion curves that can be manipulated by material design and external stimuli. Bulk and surface spin waves can be excited in a thin film with positive or negative group velocities and, by incorporating a symmetry-breaking mechanism, magnetochiral features arise. Here we study the band diagram of a chiral magnonic crystal consisting of a ferromagnetic film incorporating a periodic Dzyaloshinskii–Moriya coupling via interfacial contact with an array of heavy-metal nanowires. We provide experimental evidence for a strong asymmetry of the spin wave amplitude induced by the modulated interfacial Dzyaloshinskii–Moriya interaction, which generates a nonreciprocal propagation. Moreover, we observe the formation of flat spin-wave bands at low frequencies in the band diagram. Calculations reveal that depending on the perpendicular anisotropy, the spin-wave localization associated with the flat modes occurs in the zones with or without Dzyaloshinskii–Moriya interaction.

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confidence: 63%

Experimental Observation of Flat Bands in One-Dimensional Chiral Magnonic Crystals

et al. 2023

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“…The efforts to engineer novel interface structures are often hindered by difficulties reconciling the properties of ultrathin films at macroscopic and microscopic scales. − The CoFeB/MgO interface forms the basis of magnetic tunnel junction (MTJ) technology due to its tunneling magnetoresistance (TMR) and perpendicular magnetic anisotropy (PMA). − Subjecting the thin MgO tunnel barrier in MTJs to repeated electrical stress induces breakdown, which limits the endurance of magnetoresistive random-access memory (MRAM) devices. This situation is similar to the time-dependent dielectric breakdown (TDDB) in complementary metal-oxide–semiconductor (CMOS) gate oxides. − Researchers have reported that the breakdown can be delayed by inserting an ultrathin film of metallic Mg into the CoFeB/MgO interface during MgO barrier formation to prevent CoFeB oxidization. − Mg termination has also been shown to suppress the magnetic dead layer in ferromagnetic electrodes. − …”

Section: Introductionmentioning

confidence: 99%

Insertion Trade-off Effects on the Spin-Transfer Torque Memory Explored by In Situ X-ray

Ramesh

Chen

Lin

et al. 2021

ACS Appl. Electron. Mater.

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Magnetoresistive random-access memory (MRAM) relies on magnetic tunnel junctions (MTJs) comprising heterostructures of CoFeB/MgO/CoFeB. Nonetheless, the dielectric breakdown of MgO limits the lifespan of MRAM devices. In the current study, we terminated MgO with a Mg surface facing the CoFeB free layer to reduce the mismatch in band alignment across the barrier. The Mg-modified interface was shown to enhance the breakdown voltage while reducing the switching current and asymmetric switching behavior, with a moderate sacrifice of perpendicular magnetic anisotropy, tunneling magnetoresistance, and resistance−area product. This performance trade-off was observed in all MTJs, regardless of cell size (180, 130, and 80 nm; each size has been tested with at least 20 cells). Visualization of the proposed junction via in situ X-ray absorption spectroscopy proved effective in elucidating the reconstruction of the interface within the context of energy barrier height, asymmetric switching behavior, and the voltage-driven movement of oxygen ions. A spindependent band diagram was constructed to correlate the tunneling/switching properties of the MTJ with such a trade-off scenario. The atomistic simulation of the magnetic properties revealed that Mg termination lowered the switching energy barrier with an effective domain wall motion within the CoFeB free layer.

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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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Ru Catalyst-Induced Perpendicular Magnetic Anisotropy in MgO/CoFeB/Ta/MgO Multilayered Films

Cited by 26 publications

References 33 publications

Experimental Observation of Flat Bands in One-Dimensional Chiral Magnonic Crystals

Experimental Observation of Flat Bands in One-Dimensional Chiral Magnonic Crystals

Insertion Trade-off Effects on the Spin-Transfer Torque Memory Explored by In Situ X-ray

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

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