Investigation of perpendicular magnetic anisotropy of CoFeB by x-ray magnetic circular dichroism

Tsai, Wen‐Hui; Liao, Shu-Hsien; Hou, Hao-Cheng; Yen, Cheng-Tyng; Wang, Y. H.; Tsai, Hsiu-Min; Chang, Fan; Lin, Hong‐Ji; Lai, Chih‐Huang

doi:10.1063/1.4707380

Cited by 28 publications

(10 citation statements)

References 20 publications

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“…The normalized XAS peak of both Fe and Co in Ta/CoFeB/MgO exhibits a shoulder at the high energy side (~710 eV for Fe and ~780 eV for Co) particularly for the thin CoFeB films. This indicates that Fe and Co atoms are partially oxidized 27 28 29 . In contrast, the spectra for Co in Pt/Co/Pt show little dependence on the Co thickness with almost no sign of oxidation.…”

Section: Resultsmentioning

confidence: 99%

Enhanced orbital magnetic moments in magnetic heterostructures with interface perpendicular magnetic anisotropy

Ueno

Sinha

Inami

et al. 2015

Sci Rep

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We have studied the magnetic layer thickness dependence of the orbital magnetic moment in magnetic heterostructures to identify contributions from interfaces. Three different heterostructures, Ta/CoFeB/MgO, Pt/Co/AlOx and Pt/Co/Pt, which possess significant interface contribution to the perpendicular magnetic anisotropy, are studied as model systems. X-ray magnetic circular dichroism spectroscopy is used to evaluate the relative orbital moment, i.e. the ratio of the orbital to spin moments, of the magnetic elements constituting the heterostructures. We find that the relative orbital moment of Co in Pt/Co/Pt remains constant against its thickness whereas the moment increases with decreasing Co layer thickness for Pt/Co/AlOx, suggesting that a non-zero interface orbital moment exists for the latter system. For Ta/CoFeB/MgO, a non-zero interface orbital moment is found only for Fe. X-ray absorption spectra shows that a particular oxidized Co state in Pt/Co/AlOx, absent in other heterosturctures, may give rise to the interface orbital moment in this system. These results show element specific contributions to the interface orbital magnetic moments in ultrathin magnetic heterostructures.

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Section: Resultsmentioning

confidence: 99%

Enhanced orbital magnetic moments in magnetic heterostructures with interface perpendicular magnetic anisotropy

Ueno

Sinha

Inami

et al. 2015

Sci Rep

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“…11,45 Other experimental work also shows similar results. [46][47][48] Generally, the PMA decreases for Mg insertion layer thicknesses other than Region III. However, the PMA of the CoFeB shows a small increase when a very thin Mg insertion layer is inserted (Region I).…”

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confidence: 95%

Enhancement of voltage-controlled magnetic anisotropy through precise control of Mg insertion thickness at CoFeB|MgO interface

Fitzell

et al. 2017

Applied Physics Letters

103

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We studied the impact of different insertion layers (Ta, Pt, and Mg) at the CoFeBjMgO interface on voltage-controlled magnetic anisotropy (VCMA) effect and other magnetic properties. Inserting a very thin Mg layer of 0.1-0.3 nm yielded a VCMA coefficient of 100 fJ/V-m, more than 3 times higher than the average values of around 30 fJ/V-m reported in TajCoFeBjMgO-based structures. Ta and Pt insertion layers also showed a small improvement, yielding VCMA coefficients around 40 fJ/V-m. Electrical, magnetic, and X-ray diffraction results reveal that a Mg insertion layer of around 1.2 nm gives rise to the highest perpendicular magnetic anisotropy, saturation magnetization, as well as the best CoFe and MgO crystallinity. Other Mg insertion thicknesses give rise to either under-or over-oxidation of the CoFejMgO interface; a strong over-oxidation of the CoFe layer leads to the maximum VCMA effect. These results show that precise control over the Mg insertion thickness and CoFe oxidation level at the CoFeBjMgO interface is crucial for the development of electric-field-controlled perpendicular magnetic tunnel junctions with low write voltage.

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“…22, possibly as a result of an antiferromagnetic phase formation 39 at the CoFeB/MgO interface. 33,40,41 Based on Refs. 39, 42, and 43, the estimated effect of magnetostriction on magnetic anisotropy is much smaller than the effects of field dependent magnetic anisotropy observed in this study.…”

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Field-dependent perpendicular magnetic anisotropy in CoFeB thin films

Barsukov¹,

Fu²,

Gonçalves³

et al. 2014

Applied Physics Letters

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We report ferromagnetic resonance measurements of perpendicular magnetic anisotropy in thin films of Ta/Co20Fe60B20/MgO as a function of the Co20Fe60B20 layer thickness. The first and second order anisotropy terms show unexpectedly strong dependence on the external magnetic field applied to the system during the measurements. We propose strong interfacial spin pinning as a possible origin of the field-dependent anisotropy. Our results imply that high-field anisotropy measurements cannot be directly used for quantitative evaluation of zero-field performance parameters of CoFeB-based devices such as spin torque memory.

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Investigation of perpendicular magnetic anisotropy of CoFeB by x-ray magnetic circular dichroism

Cited by 28 publications

References 20 publications

Enhanced orbital magnetic moments in magnetic heterostructures with interface perpendicular magnetic anisotropy

Enhanced orbital magnetic moments in magnetic heterostructures with interface perpendicular magnetic anisotropy

Enhancement of voltage-controlled magnetic anisotropy through precise control of Mg insertion thickness at CoFeB|MgO interface

Field-dependent perpendicular magnetic anisotropy in CoFeB thin films

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