Thermal robustness of magnetic tunnel junctions with perpendicular shape anisotropy

Lequeux, Steven; Perrissin, N.; Grégoire, Gabin; Tillie, Luc; Chavent, A.; Strelkov, N.; Vila, Laurent; Buda-Prejbeanu, L. D.; Auffret, S.; Sousa, R. C.; Prejbeanu, Ioan-Lucian; Russo, Enrico Di; Gautier, Éric; Conlan, Aidan P.; Cooper, David; Diény, B.

doi:10.1039/c9nr10366j

Cited by 21 publications

(25 citation statements)

References 30 publications

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“…Compared to previous reports of multi‐level switching with junction shape in nanowires, [ 18–20 ] the circular junctions used in our study are much preferred in p‐STT‐MRAMs. [ 2,21 ] Recent studies also showed the multi‐level states in 6 µm diameter in‐plane MTJs through the magnetic field sweeping. [ 22 ] However, the current‐induced switching is more advantageous in today's memories allowing a shared path for writing‐reading operation, but requiring the perpendicular anisotropy to reduce the writing current.…”

Section: Resultsmentioning

confidence: 99%

“…[ 16,18 ] In MTJs, the current driven DW motion was reported in the U shape [ 19 ] and T shape [ 20 ] nanowires with a very large aspect ratio, which cannot be directly implemented into memories since an aspect ratio close to 1 is expected. [ 21 ] The multi‐domain state was lately revealed in in‐plane MTJs through magnetic field sweeping, [ 22 ] but the demonstration of current‐driven multi‐state with perpendicular anisotropy is required for memory application. The magnetic domain properties of perpendicular CoFeB have been studied in unpatterned thin films.…”

Section: Introductionmentioning

confidence: 99%

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Multi‐Level Switching and Reversible Current Driven Domain‐Wall Motion in Single CoFeB/MgO/CoFeB‐Based Perpendicular Magnetic Tunnel Junctions

Fidalgo

Silva

et al. 2020

Adv Elect Materials

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One of the critical issues in spintronics‐based technologies is to increase the data storage density. Current strategy is based on shrinking the devices size down to tens of nanometers, or several nanometers, which is reaching its limit. A new proposal is to use multi‐level cells (MLCs) to store more than two bits in each cell. In this work, the multi‐level switching is realized in CoFeB/MgO/CoFeB based nano‐scale single perpendicular magnetic tunnel junctions (p‐MTJs) with three or four stable resistance states. A large range of writing currents for each state is obtained, accompanying with a good repeatability of set‐reset operations between different states. The developed multi‐domain model perfectly matches the experimental results, reflecting the magnetic behaviors during multi‐level switching. Furthermore, current‐driven domain wall (DW) motion is revealed in the circular p‐MTJs, where the DW position can be reversibly manipulated by applied current. To design high‐performance multi‐level p‐MTJs, the parameter diagrams are calculated, suggesting various feasible strategies to improve the multi‐level switching through materials optimization and devices geometry. In summary, the demonstration of multi‐level switching in single p‐MTJ shows the high potential of realizing the new generation of p‐MTJ‐based multi‐level spintronic devices, such as multi‐level memories and spin‐neuron devices.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Multi‐Level Switching and Reversible Current Driven Domain‐Wall Motion in Single CoFeB/MgO/CoFeB‐Based Perpendicular Magnetic Tunnel Junctions

Fidalgo

Silva

et al. 2020

Adv Elect Materials

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“…Perpendicular Shape Anisotropy (PSA) has been recently implemented in the storage layer of STT-MRAM to enhance its downsize scalabilty [49][50][51][52]. In these previous studies, the storage layer thickness was increased in order to enhance the thermal stability down to sub-10nm diameters where conventional STT-MRAM based on interfacial anisotropy is no longer stable.…”

Section: Substitution Of Co/pt By Using Psamentioning

confidence: 99%

Evaluating critical metals contained in spintronic memory with a particular focus on Pt substitution for improved sustainability

Palomino

Marty

Auffret

et al. 2021

Sustainable Materials and Technologies

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Thanks to their unique combination of properties: non-volatility, speed, density and write endurance, spintronic memory called spin transfer-torque Magnetic Random Access Memory (STT-MRAM) is expected to play a major role in the future development of the Internet of Things (IoT) and more generally in information and communication technologies. This type of spintronic device is usually made of materials, some of which can be classified as critical. Recent studies have evaluated critical materials contained in magnetic random access memory [1,2]. However, in those cases the type of memory analyzed belongs to the first generation of MRAMs developed in the early 2000s. Nowadays, the memory devices are magnetized perpendicularly to the plane of the layers and contain a synthetic antiferromagnet (SAF) that provides a high coercivity to the STT-MRAM reference layer with reduced stray field. This SAF is typically made of cobalt (Co) and platinum (Pt) multilayers antiferromagnetically coupled across a thin ruthenium (Ru) layer. Due to the high-embodied energy of platinum group metals (PGMs), a common concern when evaluating these materials is the environmental risk associated with their production. An evaluation of the environmental and economic risks of using such multilayers is first reported here, followed by a discussion of its supply risk. Substitution of Co/Pt multilayers by Co/Ni multilayers can lead to a reduction by 3-4 orders of magnitude in terms of energy requirements or global warming potential (GWP) associated with the use of these multilayers. An alternative concept based on perpendicular shape anisotropy (PSA) can also yield a reduction by 1-2 orders of magnitude in these quantities. However, for the case of STT-MRAM, tiny quantities of PGM layers are used in comparison with the mass of the silicon wafer on which these type of devices are grown. Therefore, the environmental and economic impact of the silicon wafer fabrication is found to be much higher than that of the PGM materials incorporated in the STT-MRAM stacks. Nonetheless, the high supply risk associated with PGMs remains a reason for awareness. One explored possibility is a SAF structure based on Co/Ni multilayers which can have similar performance. A second more challenging alternative is also proposed based on the aforementioned PSA concept. Finally, we address the case of several other metals identified by the European Commission as critical and used in MRAM such as W or Ta, both recently included in the EU's Conflict Minerals Regulation released in January 2021 [3].

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“…The energy barrier, ∆ E, which divides the two stable opposite states (AP, P), depends in a complex way on both M s and K u (and on the free layer volume) [19]. Nonetheless, in macrospin regime (r<30 nm) the barrier height, could be approximated, in a simplified way, as:…”

Section: B Thermal Stability and Retention Time Of The Stored Informationmentioning

confidence: 99%

SEU Mechanisms in Spintronic Devices: Critical Parameters and Basic Effects

Coi

Adrianjohany²,

Pendina

et al. 2021

IEEE Trans. Nucl. Sci.

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The paper investigates radiation-induced switching mechanisms, temperature effects, breakdown voltage, sensitive volume and critical charge definitions for Spin-Transfer Torque Magnetic Tunnel Junction. Thermal spike model is adopted to estimate the temperature reached during heavy ion irradiation and temperature effects are suggested to be responsible for the magnetic properties degradation and for upset processes.

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Thermal robustness of magnetic tunnel junctions with perpendicular shape anisotropy

Abstract: Perpendicular Shape Anisotropy based storage layer offers a bulk anisotropy much more robust against thermal fluctuations than the interfacial anisotropy, allowing to reduce the temperature dependence of the coercivity of sub-20 nm MTJ cells.

Cited by 21 publications

References 30 publications

Multi‐Level Switching and Reversible Current Driven Domain‐Wall Motion in Single CoFeB/MgO/CoFeB‐Based Perpendicular Magnetic Tunnel Junctions

Multi‐Level Switching and Reversible Current Driven Domain‐Wall Motion in Single CoFeB/MgO/CoFeB‐Based Perpendicular Magnetic Tunnel Junctions

Evaluating critical metals contained in spintronic memory with a particular focus on Pt substitution for improved sustainability

SEU Mechanisms in Spintronic Devices: Critical Parameters and Basic Effects

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