Thickness-dependent magnetoelasticity and its effects on perpendicular magnetic anisotropy in Ta/CoFeB/MgO thin films

Gowtham, Praveen; Stiehl, Gregory M.; Ralph, Daniel; Buhrman, R. A.

doi:10.1103/physrevb.93.024404

Cited by 57 publications

(53 citation statements)

References 37 publications

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“…The fit to the Hf dusting series (A) gives a saturation magnetization of M s ¼ 1260 emu=cm 3 and a very small apparent "dead layer" thickness t d % 0:1 nm; both are consistent with previous results from as-deposited Ta/FeCoB/MgO structures. 1,11,14 In contrast, the series B samples indicate t d % 0:8nm and a much larger M s ¼ 1800 emu=cm 3 ; the results are comparable to some previous studies of annealed ($300 C) Ta/FeCoB/MgO samples where the dead layer 15 has been attributed to the undesirable diffusion of Ta into FeCoB, perhaps to the ferromagnet/oxide interface. 16 Thus, we tentatively attribute the thick dead layer in series B samples to the intermixing of Ta and FeCoB during the deposition of the Ta dusting layer.…”

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confidence: 75%

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Strong perpendicular magnetic anisotropy energy density at Fe alloy/HfO2 interfaces

Ralph

Buhrman

2017

Applied Physics Letters

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We report on the perpendicular magnetic anisotropy (PMA) behavior of heavy metal (HM)/ Fe alloy/MgO thin film heterostructures after an ultrathin HfO 2 passivation layer is inserted between the Fe alloy and the MgO. This is accomplished by depositing one to two atomic layers of Hf onto the Fe alloy before the subsequent rf sputter deposition of the MgO layer. This Hf layer is fully oxidized during the subsequent deposition of the MgO layer, as confirmed by X-ray photoelectron spectroscopy measurements. As the result a strong interfacial perpendicular anisotropy energy density can be achieved without any post-fabrication annealing treatment, for example 1.7 erg/cm 2 for the Ta/Fe 60 Co 20 B 20 /HfO 2 /MgO heterostructure. Depending on the HM, further enhancements of the PMA can be realized by thermal annealing to at least o 400 C . We show that ultra-thin HfO 2 layers offer a range of options for enhancing the magnetic properties of magnetic heterostructures for spintronics applications.

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confidence: 75%

“…While Ta/FeCoB/MgO structures with a thin FM layer typically only exhibit, at most, a weak perpendicular magnetic anisotropy (PMA) in the as-deposited state, 3,14,15 we obtained robust PMA behavior in as-deposited structures with the HfO 2 dusting layer. For example, in Figure 2( …”

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confidence: 78%

Strong perpendicular magnetic anisotropy energy density at Fe alloy/HfO2 interfaces

Ralph

Buhrman

2017

Applied Physics Letters

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“…3 (a), the thickness of MgO spacer within a range of 0.9 -1.25 nm had almost no influence on the fitting parameters, therefore, the values of fitting parameters 4πM ef f , g, α, and ∆H 0 are typical for all samples with various MgO thickness. Parameters determined from VNA-FMR spectra for the as-deposited in films with PMA is often strongly nonlinear due to either intermixing at interfaces [22] or magnetoelastic effects [15], with K ef f × t ef f exhibiting a maximum as a function of decreasing t ef f and with the PMA eventually being lost for small t ef f of, for example, 0.7 nm.…”

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confidence: 99%

CoFeB/MgO/CoFeB structures with orthogonal easy axes: perpendicular anisotropy and damping

Głowiński

Żywczak²,

Wrona³

et al. 2017

J. Phys.: Condens. Matter

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We report on the Gilbert damping parameter α, the effective magnetization [Formula: see text], and the asymmetry of the g-factor in bottom-CoFeB(0.93 nm)/MgO(0.90-1.25 nm)/CoFeB(1.31 nm)-top as-deposited systems. Magnetization of CoFeB layers exhibits a specific noncollinear configuration with orthogonal easy axes and with [Formula: see text] values of [Formula: see text] kG and [Formula: see text] kG for the bottom and top layers, respectively. We show that [Formula: see text] depends on the asymmetry [Formula: see text] of the g-factor measured in the perpendicular and the in-plane directions revealing a highly nonlinear relationship. In contrast, the Gilbert damping is practically the same for both layers. Annealing of the films results in collinear easy axes perpendicular to the plane for both layers. However, the linewidth is strongly increased due to enhanced inhomogeneous broadening.

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“…37 K S contains contributions from both with and without strain and ideally, we would like to separate the electric-field effects on each of the terms. Assuming that electric-field modulates only the interfacial terms, eqn.…”

Section: -4 Lourembam Et Al Aip Advances 8 055915 (2018)mentioning

confidence: 99%

Role of CoFeB thickness in electric field controlled sub-100 nm sized magnetic tunnel junctions

2017

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We report a comprehensive study on the role of the free layer thickness (tF) in electric-field controlled nanoscale perpendicular magnetic tunnel junctions (MTJs), comprising of free layer structure Ta/Co40Fe40B20/MgO, by using dc magnetoresistance and ultra-short magnetization switching measurements. Focusing on MTJs that exhibits positive effective device anisotropy (Keff), we observe that both the voltage-controlled magnetic anisotropy (ξ) and voltage modulation of coercivity show strong dependence on tF. We found that ξ varies dramatically and unexpectedly from ∼−3 fJ/V-m to ∼−41 fJ/V-m with increasing tF. We discuss the possibilities of electric-field tuning of the effective surface anisotropy term, KS as well as an additional interfacial magnetoelastic anisotropy term, K3 that scales with 1/tF2. Voltage pulse induced 180° magnetization reversal is also demonstrated in our MTJs. Unipolar switching and oscillatory function of switching probability vs. pulse duration can be observed at higher tF, and agrees well with the two key device parameters — Keff and ξ.

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Thickness-dependent magnetoelasticity and its effects on perpendicular magnetic anisotropy in Ta/CoFeB/MgO thin films

Cited by 57 publications

References 37 publications

Strong perpendicular magnetic anisotropy energy density at Fe alloy/HfO2 interfaces

Strong perpendicular magnetic anisotropy energy density at Fe alloy/HfO2 interfaces

CoFeB/MgO/CoFeB structures with orthogonal easy axes: perpendicular anisotropy and damping

Role of CoFeB thickness in electric field controlled sub-100 nm sized magnetic tunnel junctions

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