Origin of the collapse of tunnel magnetoresistance at high annealing temperature in CoFeB/MgO perpendicular magnetic tunnel junctions

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

doi:10.1063/1.3671669

Cited by 56 publications

(27 citation statements)

References 21 publications

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“…Moreover, the TMR curve lost its sharp transition between the AP and P states, suggesting that the PMA is entirely vanished and the CoFeB layer now behaves superparamagnetically. This is in good agreement with previous studies on Ta/CoFeB/MgO MTJs, 21,22 in which annealing at temperatures higher than 350 C rapidly destroys the PMA and TMR of the structure. In contrast, the MTJ with Mo as the buffer layer showed a more than 20% increase in its TMR values (black line).…”

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confidence: 92%

Enhanced tunneling magnetoresistance and perpendicular magnetic anisotropy in Mo/CoFeB/MgO magnetic tunnel junctions

Almasi

Hickey

Newhouse-Illige

et al. 2015

Applied Physics Letters

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Structural, magnetic, and transport studies have been performed on perpendicular magnetic tunnel junctions (pMTJ) with Mo as the buffer and capping layers. After annealing samples at 300 °C and higher, consistently better performance was obtained compared to that of conventional pMTJs with Ta layers. Large tunneling magnetoresistance (TMR) and perpendicular magnetic anisotropy (PMA) values were retained in a wide range of samples with Mo layers after annealing for 2 h at 400 °C, in sharp contrast to the junctions with Ta layers, in which superparamagnetic behavior with nearly vanishing magnetoresistance was observed. As a result of the greatly improved thermal stability, TMR as high as 162% was obtained in junctions containing Mo layers. These results highlight the importance of the heavy-metal layers adjacent to CoFeB electrodes for achieving larger TMR, stronger PMA, and higher thermal stability in pMTJs.

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supporting

confidence: 92%

Enhanced tunneling magnetoresistance and perpendicular magnetic anisotropy in Mo/CoFeB/MgO magnetic tunnel junctions

Almasi

Hickey

Newhouse-Illige

et al. 2015

Applied Physics Letters

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“…The reason for such a small TMR for Ta samples is due to the lack of well-defined antiparallel state at this annealing condition (420 C for 10 min). 22,43 In contrast to Ta behavior, samples containing any amount of Mo showed reasonably high TMR and sharp magnetization switching for the entire range of MgO thicknesses studied here. As we started to introduce 0.45 nm Mo as a dusting layer to the pure Ta buffer and capping layers, we see immediate increase of TMR to values larger than pure Mo sample.…”

mentioning

confidence: 95%

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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“…Mn is present in both the 4d and 2b positions, and, for x > 1, the anisotropy constant changes sign, going from easy-axis to easy-plane. We have previously found [29] that for Mn 3 Ga the 4d site has perpendicular anisotropy, while the 2b site possesses in-plane anisotropy. Therefore, when the Mn 2b occupation is sufficiently high, the net magnetocrystalline anisotropy of Mn changes from easy-axis (due to 4d) to easyplane (due to 2b) in MFG.…”

Section: X-ray Absorption and Magnetic Circular Dichroismmentioning

confidence: 99%

“…A thermally stable storage element with lateral dimensions below 10 nm and a thickness of less than 3 nm therefore requires a material or structure with K eff ∼ 1 MJ m −3 . Currently, the most studied storage system is Ta/ultrathin CoFeB/MgO-based heterostructures where the perpendicular magnetic anisotropy (PMA) is obtained via the surface/interface anisotropy of CoFeB/MgO [1][2][3]. The structure exhibits a moderate K eff ∼ 0.2 MJ m −3 , due to the competition between interface and shape anisotropy associated with the sizable magnetization.…”

Section: Introductionmentioning

confidence: 99%

Structure, site-specific magnetism, and magnetotransport properties of epitaxial D022 -structure Mn2FexGa thin

et al. 2017

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Ferrimagnetic Mn 2 Fe x Ga (0.26 x 1.12) thin films have been characterized by x-ray diffraction, magnetometry, x-ray absorption spectroscopy, x-ray magnetic circular dichroism, and Mössbauer spectroscopy with the aim of determining the structure and site-specific magnetism of this tetragonal, D0 22 -structure Heusler compound. High-quality epitaxial films with low root-mean-square surface roughness (∼0.6 nm) are grown by magnetron cosputtering. The tetragonal distortion induces strong perpendicular magnetic anisotropy along the c axis with a typical coercive field μ 0 H ∼ 0.8 T and an anisotropy field ranging from 6 to 8 T. On increasing the Fe content x, substantial uniaxial anisotropy, K u 1.0 MJ m −3 , can be maintained over the full x range, while the magnetization of the compound is reduced from 400 to 280 kA m −1 . The total magnetization is almost entirelygiven by the sum of the spin moments originating from the ferrimagnetic Mn and Fe sublattices, with the latter being coupled ferromagnetically to one of the former. The orbital magnetic moments are practically quenched and have negligible contributions to the magnetization. The films with x = 0.73 exhibit an anomalous Hall angle of 2.5% and a Fermi-level spin polarization above 51%, as measured by point contact Andreev reflection. The Fe-substituted Mn 2 Ga films are tunable with a unique combination of high anisotropy, low magnetization, appreciable spin polarization, and low surface roughness, making them strong candidates for thermally stable spin-transfer-torque switching nanomagnets with lateral dimensions down to 10 nm.

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Origin of the collapse of tunnel magnetoresistance at high annealing temperature in CoFeB/MgO perpendicular magnetic tunnel junctions

Cited by 56 publications

References 21 publications

Enhanced tunneling magnetoresistance and perpendicular magnetic anisotropy in Mo/CoFeB/MgO magnetic tunnel junctions

Enhanced tunneling magnetoresistance and perpendicular magnetic anisotropy in Mo/CoFeB/MgO magnetic tunnel junctions

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

Structure, site-specific magnetism, and magnetotransport properties of epitaxial D022 -structure Mn2FexGa thin

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