Dependence of magnetic anisotropy on MgO thickness and buffer layer in Co20Fe60B20-MgO structure

Yamanouchi, Michihiko; Koizumi, Ryo; Ikeda, Shoji; Sato, Hideyuki; Mizunuma, K.; Miura, Katsuya; Gan, Huadong; Matsukura, F.; Ohno, Hideo

doi:10.1063/1.3554204

Cited by 118 publications

(75 citation statements)

References 15 publications

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“…• C exhibited an out-of-plane direction as the easy axis, which is consistent with the results reported by other groups, 18 and at 300…”

Section: Resultssupporting

confidence: 82%

Influence of inserted Mo layer on the thermal stability of perpendicularly magnetized Ta/Mo/Co20Fe60B20/MgO/Ta films

Lü

et al. 2016

AIP Advances

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We studied the thermal stability of perpendicular magnetic anisotropy (PMA) in Ta/Mo/CoFeB/MgO/Ta films with and without inserted Mo layers. In the absence of a Mo layer, the films show PMA at annealing temperatures below 300 °C. On the other hand, the insertion of a Mo layer preserves PMA at annealing temperatures of up to 500 °C; however, a higher annealing temperature leads to the collapse of PMA. X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM) were used to study the microstructure of the films to understand the deterioration of PMA. The XPS results show that the segregation of Ta is partly suppressed by inserting a Mo layer. Once inserted, Mo does not remain at the interface of Ta and CoFeB but migrates to the surface of the films. The HRTEM results show that the crystallization of the MgO (001) texture is improved owing to the higher annealing temperature of the Mo inserted sample. A smooth and clear CoFeB/MgO interface is evident. The inserted Mo layer not only helps to obtain sharper and smoother interfaces but also contributes to the crystallization after the higher annealing temperature of films.

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“…• C exhibited an out-of-plane direction as the easy axis, which is consistent with the results reported by other groups, 18 and at 300…”

Section: Resultssupporting

confidence: 82%

Influence of inserted Mo layer on the thermal stability of perpendicularly magnetized Ta/Mo/Co20Fe60B20/MgO/Ta films

Lü

et al. 2016

AIP Advances

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“…On the other hand, amorphous Ta is more easily interdiffused with CoFeB during the annealing process and, consequently, degrade the magneto-transport properties. 23 In addition, diffusion toward CoFeB/MgO interface and forming different oxides is more likely to happen for Ta samples owing to their more negative energy of formation compared to those of Mo and Mg. 45 Finally, since the average enthalpy of formation of borides for Mo, À47.5 kJ/mol, is higher than that of Ta, À66 kJ/mol, one expects that Ta is better B absorbent leading to better crystallization of adjacent CoFeB layers. Therefore, by using ultrathin Mo layer between Ta and CoFeB layers, Mo can prevent the interdiffusion of Ta and CoFeB and at the same time can allow small boron atoms to be absorbed more efficiently by Ta layers.…”

mentioning

confidence: 99%

“…However, both TMR and PMA were reported to be deteriorated upon annealing at temperatures above 400 C for Ta/CoFeB/MgO junctions. 22,23 Several other underlayers such as Pt (Pd), 24 Hf, [25][26][27] Mo, [28][29][30][31][32] and W 33,34 have been studied to improve thermal stability, TMR, PMA, electric field, and spin orbit torque effects in pMTJs. Furthermore, doping of Ta buffer with nitrogen 35 or using a thin sacrificial Mg layer 36 was also reported to improve PMA and TMR in pMTJs.…”

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confidence: 99%

Effect of Mo insertion layers on the magnetoresistance and perpendicular magnetic anisotropy in Ta/CoFeB/MgO junctions

Almasi

et al. 2016

Applied Physics Letters

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The effect of a thin Mo dusting layer inserted at the interface of Ta/CoFeB of perpendicular magnetic tunneling junction with MgO barriers was investigated. Unlike thick Mo layers that exhibited a strong (110) crystalline texture, the inserted Mo layer between Ta/CoFeB had little negative influence on the crystallization of CoFe (001), therefore combining the advantages of Mo as a good thermal barrier and Ta as a good boron sink. For optimized Mo dusting thickness, a large tunneling magnetoresistance of 208% was achieved in perpendicular magnetic tunneling junctions with superior thermal stability at 500 °C.

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“…This diffusion mechanism limits the thermal budget that a pMTJ stack can tolerate. 10,11 Using the Ta cap layer, it is difficult to obtain pMTJs with a high PMA storage layer (SL) and back-end-of-line (BEOL) annealing tolerance which is 400 C for 30 min. Hence, a detailed investigation of magnetic properties of the top storage layer as a function of annealing temperature was carried out using the W material in the cap layer.…”

mentioning

confidence: 99%

Enhanced annealing stability and perpendicular magnetic anisotropy in perpendicular magnetic tunnel junctions using W layer

Chatterjee

Sousa

Perrissin

et al. 2017

Applied Physics Letters

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The magnetic properties of the perpendicular storage electrode (buffer/MgO/FeCoB/Cap) were studied as a function of annealing temperature by replacing Ta with W and W/Ta cap layers with variable thicknesses. W in the cap boosts up the annealing stability and increases the effective perpendicular anisotropy by 30% compared to the Ta cap. Correspondingly, an increase in the FeCoB critical thickness characterizing the transition from perpendicular to in-plane anisotropy was observed. Thicker W layer in the W(t)/Ta 1 nm cap layer makes the storage electrode highly robust against annealing up to 570 °C. The stiffening of the overall stack resulting from the W insertion due to its very high melting temperature seems to be the key mechanism behind the extremely high thermal robustness. The Gilbert damping constant of FeCoB with the W/Ta cap was found to be lower when compared with the Ta cap and stable with annealing. The evolution of the magnetic properties of bottom pinned perpendicular magnetic tunnel junctions (p-MTJ) stack with the W2/Ta1 nm cap layer shows back-end-of-line compatibility with increasing tunnel magnetoresistance up to the annealing temperature of 425 °C. The pMTJ thermal budget is limited by the synthetic antiferromagnetic hard layer which is stable up to 425 °C annealing temperature while the storage layer is stable up to 455 °C.

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Dependence of magnetic anisotropy on MgO thickness and buffer layer in Co20Fe60B20-MgO structure

Cited by 118 publications

References 15 publications

Influence of inserted Mo layer on the thermal stability of perpendicularly magnetized Ta/Mo/Co20Fe60B20/MgO/Ta films

Influence of inserted Mo layer on the thermal stability of perpendicularly magnetized Ta/Mo/Co20Fe60B20/MgO/Ta films

Effect of Mo insertion layers on the magnetoresistance and perpendicular magnetic anisotropy in Ta/CoFeB/MgO junctions

Enhanced annealing stability and perpendicular magnetic anisotropy in perpendicular magnetic tunnel junctions using W layer

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