Effects of field annealing on MnN/CoFeB exchange bias systems

Quarterman, Patrick; Hallsteinsen, Ingrid; Dunz, Mareike; Meinert, Markus; Arenholz, Elke; Borchers, J. A.; Grutter, Alexander J.

doi:10.1103/physrevmaterials.3.064413

Cited by 6 publications

(9 citation statements)

References 21 publications

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“…In this study, the median lateral grain size of the MnN was found to be 4.8 nm and the anisotropy constant at room temperature was estimated as K AF 6 × 10 5 J/m 3 . In polarized neutron reflectometry measurements, the films were found to be slightly rich in nitrogen and no magnetic scattering from the MnN films could be detected [27]. This excludes the possibility, that electrical switching of ferrimagnetic Mn 4 N precipitates contributes to the signals we investigate in the present study.…”

Section: Methodsmentioning

confidence: 62%

“…However, the spin orientation is controversial and might depend critically on the lattice constants. In previous studies, some of the authors of this article have shown its utility for exchange bias applications with large exchange bias fields at room temperature [22][23][24][25][26][27]. However, the critical thickness for the onset of exchange bias was observed to be around 10 nm at room temperature, leading to the conclusion that MnN has a small magnetocrystalline anisotropy energy density [22].…”

Section: Introductionmentioning

confidence: 91%

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Spin-orbit torque induced electrical switching of antiferromagnetic MnN

Dunz

Matalla-Wagner

Meinert

2020

Phys. Rev. Research

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Electrical switching and readout of antiferromagnets allows to exploit the unique properties of antiferromagnetic materials in nanoscopic electronic devices. Here we report experiments on the spin-orbit torque induced electrical switching of a polycrystalline, metallic antiferromagnet with low anisotropy and high Néel temperature. We demonstrate the switching in a Ta / MnN / Pt trilayer system, deposited by (reactive) magnetron sputtering. The dependence of switching amplitude, efficiency, and relaxation are studied with respect to the MnN film thickness, sample temperature, and current density. Our findings are consistent with a thermal activation model and resemble to a large extent previous measurements on CuMnAs and Mn2Au, which exhibit similar switching characteristics due to an intrinsic spin-orbit torque.

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Section: Methodsmentioning

confidence: 62%

Section: Introductionmentioning

confidence: 91%

Spin-orbit torque induced electrical switching of antiferromagnetic MnN

Dunz

Matalla-Wagner

Meinert

2020

Phys. Rev. Research

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“…The effects of field annealing were further investigated as a function of the thickness of the MnN layer and the field annealing temperature in Ta/MnN/CoFeB exchange-bias systems in a more recent paper [18]. It was found that for thick (48 nm) MnN films, the exchange bias increased due to an improvement in the crystallinity of the films.…”

Section: Exchange Bias: In-plane Studiesmentioning

confidence: 99%

Recent Developments on MnN for Spintronic Applications

Vallejo-Fernández

Meinert

2021

Magnetochemistry

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There is significant interest worldwide to identify new antiferromagnetic materials suitable for device applications. Key requirements for such materials are: relatively high magnetocrystalline anisotropy constant, low cost, high corrosion resistance and the ability to induce a large exchange bias, i.e., loop shift, when grown adjacent to a ferromagnetic layer. In this article, a review of recent developments on the novel antiferromagnetic material MnN is presented. This material shows potential as a replacement for the commonly used antiferromagnet of choice, i.e., IrMn. Although the results so far look promising, further work is required for the optimization of this material.

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“…Recent polarized neutron reflectometry [20] and Auger electron depth profile [12] studies of Ta 10 nm/ MnN 30 nm/ CoFeB 1.6 nm stacks revealed the crucial role of the Ta buffer layer on which MnN is grown for better crystallinity. By investigating the samples directly after preparation as well as after annealing, it was found that the nitrogen diffuses from MnN into the Ta buffer layer during the annealing process.…”

Section: Introductionmentioning

confidence: 99%

“…After annealing at high temperatures of T A > 500 • C, the Ta layer is fully saturated with nitrogen. It was proposed that, in terms of better thermal stability, using a thinner Ta buffer layer could be beneficial [20]. The thinner the Ta, the less nitrogen needs to diffuse from the MnN to the Ta layer for the latter to be saturated.…”

Section: Introductionmentioning

confidence: 99%

Improving thermal stability of MnN/CoFeB exchange bias systems by optimizing the Ta buffer layer

Dunz,

Meinert

2020

Preprint

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We investigated the influence of the Ta buffer layer on the thermal stability of polycrystalline Ta/ MnN/ CoFeB exchange bias systems, showing high exchange bias of about 1800 Oe at room temperature. The thermal stability of those trilayer systems is limited by nitrogen diffusion that occurs during annealing processes. Most of the nitrogen diffuses into the Ta buffer layer, which is necessary for good crystal growth of MnN and thus a crucial component of the exchange bias system. In order to improve the thermal stability, we prepared exchange bias stacks where we varied the Ta thickness to look for an optimum value that guarantees stable and high exchange over a broad temperature range. Our findings show that thin layers of 2 − 5 nm Ta indeed support stable exchange bias up to annealing temperatures of more than 550 • C. Furthermore, we found that the introduction of a TaNx layer between MnN and Ta, acting as a barrier, can prevent nitrogen diffusion. However, our results show that those measures, even though being beneficial in terms of thermal stability, often lead to decreased crystallinity and thus lower the exchange bias.

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Effects of field annealing on MnN/CoFeB exchange bias systems

Cited by 6 publications

References 21 publications

Spin-orbit torque induced electrical switching of antiferromagnetic MnN

Spin-orbit torque induced electrical switching of antiferromagnetic MnN

Recent Developments on MnN for Spintronic Applications

Improving thermal stability of MnN/CoFeB exchange bias systems by optimizing the Ta buffer layer

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