Heavy-Ion-Induced Displacement Damage Effects in Magnetic Tunnel Junctions With Perpendicular Anisotropy

We evaluate the resilience of CoFeB/MgO/CoFeB magnetic tunnel junctions (MTJs) with perpendicular magnetic anisotropy (PMA) to displacement damage induced by heavy-ion irradiation. MTJs were exposed to 3-MeV Ta 2+ ions at different levels of ion beam fluence spanning five orders of magnitude. The de...

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Bibliographic Details
Published in:IEEE transactions on nuclear science 2021-05, Vol.68 (5), p.581-587
Main Authors: Xiao, T. Patrick, Bennett, Christopher H., Mancoff, Frederick B., Manuel, Jack E., Hughart, David R., Jacobs-Gedrim, Robin B., Bielejec, Edward S., Vizkelethy, Gyorgy, Sun, Jijun, Aggarwal, Sanjeev, Arghavani, Reza, Marinella, Matthew J.
Format: Article
Language:English
Subjects:
Anisotropy
Displacement
Displacement damage
heavy ion irradiation
Heavy ions
Interfaces
Ions
Junctions
magnetic random access memory
magnetic random access memory (MRAM)
magnetic tunnel junction
magnetic tunnel junction (MTJ)
Magnetic tunneling
Magnetoresistance
Magnetoresistivity
MRAM
non-volatile memory
nonvolatile memory
NUCLEAR PHYSICS AND RADIATION PHYSICS
Perpendicular magnetic anisotropy
perpendicular magnetic anisotropy (PMA)
Polarization (spin alignment)
Propagation modes
Radiation effects
Random access memory
Resistance
Scatter propagation
spin-transfer-torque MRAM (STT-MRAM)
Structural damage
STT-MRAM
Switches
Tunnel junctions
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Summary:We evaluate the resilience of CoFeB/MgO/CoFeB magnetic tunnel junctions (MTJs) with perpendicular magnetic anisotropy (PMA) to displacement damage induced by heavy-ion irradiation. MTJs were exposed to 3-MeV Ta 2+ ions at different levels of ion beam fluence spanning five orders of magnitude. The devices remained insensitive to beam fluences up to 10^{11} ions/cm 2 , beyond which a gradual degradation in the device magnetoresistance, coercive magnetic field, and spin-transfer-torque (STT) switching voltage were observed, ending with a complete loss of magnetoresistance at very high levels of displacement damage (>0.035 displacements per atom). The loss of magnetoresistance is attributed to structural damage at the MgO interfaces, which allows electrons to scatter among the propagating modes within the tunnel barrier and reduces the net spin polarization. Ion-induced damage to the interface also reduces the PMA. This study clarifies the displacement damage thresholds that lead to significant irreversible changes in the characteristics of STT magnetic random access memory (STT-MRAM) and elucidates the physical mechanisms underlying the deterioration in device properties.
ISSN:0018-9499
1558-1578
DOI:10.1109/TNS.2021.3057348