Understanding stability diagram of perpendicular magnetic tunnel junctions

Skowroński, Witold; Czapkiewicz, M.; Ziętek, Sławomir; Chęciński, Jakub; Frankowski, Marek; Rzeszut, Piotr; Wrona, Jerzy

doi:10.1038/s41598-017-10706-2

Cited by 19 publications

(8 citation statements)

References 31 publications

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“…thin W capping layer is inserted to absorb the B away from the MgO interfaces upon annealing [6,12,23]. The magnetization of the bottom reference layer is pinned by a synthetic antiferromagnet (SAF).…”

Section: Methodsmentioning

confidence: 99%

“…The main properties of the memory MTJ cell can be extracted from their writing voltage-field (V-H) diagram [9]. Experimental observations and theoretical modelling of such diagrams in collinear [6,[10][11][12] and non-collinear geometries [13] give an almost complete description of STT-induced switching processes in MTJ. However, at high voltages (typically above 0.4 V-0.8 V depending on the junction resistance), most experimental diagrams show deviation from the theoretically predicted behavior.…”

Section: Introductionmentioning

confidence: 99%

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Impact of Joule heating on the stability phase diagrams of perpendicular magnetic tunnel junctions

et al. 2018

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Measured switching voltage-field (V-H) diagrams of perpendicular magnetic tunnel junctions (pMTJ) exhibit unexpected behavior at high voltages associated with significant heating of the storage layer. The boundaries deviate from the critical lines corresponding to the coercive field, which contrasts with the theoretically predicted behavior of a standard macrospin-based model. Combining recent experimental studies of the temperature dependence of spin polarization and perpendicular magnetic anisotropy (PMA) we are proposing a modified model. Our approach takes into account the Joule heating during the writing pulse, which reduces the spin polarization and the anisotropy, thereby reducing the spin torque efficiency and the coercive field during the switching. The numerical macrospin simulations based on this model are in agreement with our experimental measurements and consistent with the results derived from the linearization of Landau-Lifshitz-Gilbert equation.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Impact of Joule heating on the stability phase diagrams of perpendicular magnetic tunnel junctions

et al. 2018

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“…This assumption can be justified for low values of the TMR, when the resistance difference between P and AP configurations is small. However, modern perpendicularly magnetized MTJs (p-MTJs) possess a large TMR of typically around 200% [11]. In this case the simplified description offered by (2b) is not accurate.…”

Section: Modelmentioning

confidence: 99%

“…Moreover, as the magnetization of the free layer is not uniform at switching, but depends on the position, so does the local tunneling conductance. The assumption of a constant current density adopted in the description of STT-MRAM switching is violated, especially in advanced MTJs with a tunneling magnetoresistance ratio (TMR) of about 200% and higher [11].…”

Section: Introductionmentioning

confidence: 99%

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Analysis of Switching Under Fixed Voltage and Fixed Current in Perpendicular STT-MRAM

Fiorentini

Orio

Selberherr

et al. 2020

IEEE J. Electron Devices Soc.

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In spin-transfer torque magnetoresistive random access memory, the magnetization dynamics of a free layer is usually assumed to be determined by the torque created via a position-independent current density. In circuits, however, it is the voltage, not the current density, which stays fixed during switching. Therefore, the approximate evaluation of the torque based on a fixed current density becomes questionable in modern magnetic tunnel junctions with a tunneling magnetoresistance ratio of about 200%, where the current density across the structure can vary by a factor of three. In this work, we compare the switching times obtained within a fixed voltage assumption with those from the approximate fixed current density assumption. We demonstrate that the assumption of a fixed current can reproduce the correct switching if the current is appropriately adjusted. It is shown that the correction to the current is not universal and depends on various factors such as TMR, temperature, the size of the structure and resistance area.

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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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Understanding stability diagram of perpendicular magnetic tunnel junctions

Cited by 19 publications

References 31 publications

Impact of Joule heating on the stability phase diagrams of perpendicular magnetic tunnel junctions

Impact of Joule heating on the stability phase diagrams of perpendicular magnetic tunnel junctions

Analysis of Switching Under Fixed Voltage and Fixed Current in Perpendicular STT-MRAM

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

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