Stochastic Nature of Voltage-Controlled Charge Dynamics in AlOx Magnetic Tunnel Junctions

Ch.Y. Chen, B.H. Huang, Y.H. Tang, C. González-Ruano, F. Aliev Kazanski, D.Ch. Ling, J.Y. Hong

Nano Letters Vol. 25, nº. 31, pp. 11776 - 11781

Summary:

Spintronic memristors based on ferromagnetic metal/oxide heterostructures have recently enabled reversible manipulation of both magnetic properties and resistive switching (RS), offering promising prospects for multibit memory and neuromorphic computing. In this study, we investigate the stochastic nature and relaxation processes of charge dynamics induced by localized oxygen vacancy (V_O) in AlO_x-based magnetic tunnel junctions (MTJs). We observe that random telegraph noise (RTN) exhibits charge stochasticity at specific bias voltages in the low resistance state (LRS), reflecting the competition and transition between charge capture and emission states against the thermal energy. This behavior reveals that the thermally unstable charge stochasticity originates from localized traps in the AlO_x barrier. In contrast, the high resistance state (HRS) favors the RTN emission states, indicating the dominance of direct tunneling effects. Through numerical calculations based on the tight-binding (TB) model and experimental results, we demonstrate that voltage-driven shifts in the V_O position within the AlO_x barrier, associated with RS, govern the charge dynamics of the MTJs investigated. These findings provide valuable insights and practical implications for the development of next-generation devices leveraging charge stochasticity in AlO_x-based MTJs.

Spanish layman's summary:

Las memorias magnéticas ofrecen un gran potencial para la computación. Aquí estudiamos el comportamiento de uniones túnel basadas en AlO_x. Presentan dos estados en función del voltaje y el campo magnético, que podrían ser útiles para los dispositivos informáticos de próxima generación.

English layman's summary:

Magnetic-based memories offer great prospects for computing. Here we study the charge dynamics in AlO_x-based magnetic tunnel junctions. They show two regimes depending on the voltage and magnetic field, with properties that could be valuable tools for next-generation computing devices.

Keywords: magnetic tunnel junction; memristor; resistive switching; random telegraph noise; oxygen vacancy

JCR-JIF Impact Factor and WoS quartile: 9,100 - Q1 (2025)

DOI reference: https://doi.org/10.1021/acs.nanolett.5c01332

Published on paper: August 2025.

Published on-line: July 2025.

Citation:
Ch.Y. Chen, B.H. Huang, Y.H. Tang, C. González-Ruano, F. Aliev Kazanski, D.Ch. Ling, J.Y. Hong, "Stochastic Nature of Voltage-Controlled Charge Dynamics in AlOx Magnetic Tunnel Junctions", Nano Letters, Vol. 25, nº. 31, pp. 11776 - 11781, August 2025. [Online: July 2025] doi: 10.1021/acs.nanolett.5c01332