Impact of operating temperature on the electrical and magnetic properties of the bottom-pinned perpendicular magnetic tunnel junctions

• Published in: Applied physics letters 2018-10, Vol.113 (14)
• Main Authors: Wu, Y. C., Kim, W., Rao, S., Garello, K., Van Beek, S., Couet, S., Liu, E., Swerts, J., Kundu, S., Souriau, L., Yasin, F., Crotti, D., Jochum, J. K., Van Bael, M. J., Van Houdt, J., Groeseneken, G., Kar, G. S.
• Format: Article
• Language: English
• Subjects: Applied physics; Cobalt; Computer memory; Electrical junctions; Ferromagnetism; High temperature effects; Magnetic properties; Magnetic saturation; Magnetoresistance; Magnetoresistivity; Multilayers; Ohmic dissipation; Operating temperature; Performance evaluation; Performance measurement; Resistance heating; Switching; Temperature; Temperature dependence; Thermal stability; Tunnel junctions
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.5042028

Analogous device parameters in both the parallel (P) and anti-parallel (AP) states ensure a symmetric spin-transfer-torque magnetic random-access memory operation scheme. In this study, however, we observe an increasing asymmetry in the performance metrics with operating temperature of the bottom-pinned perpendicular magnetic tunnel junction (p-MTJ) devices. A temperature-dependent increase in the contribution of the stray field is observed in the tunneling magnetoresistance loop analysis. The switching current for P-to-AP decreases by 30% in the thermally activated switching regime by increasing the temperature from 300 K to 400 K, while it remains similar for AP-to-P. In addition, with the same temperature range, the thermal stability factor for the P state decreases 20% more than that for the AP state. We attribute those observations to the increase in the overcompensation of the stray field from the synthetic anti-ferromagnet structure. Saturation magnetization (MS) of the [Co/Pt]x-based multilayers is much less affected by temperature [MS(400 K)/MS(300 K) = 97%] compared to that of the CoFeB-based multilayers (88%). Such an impact can be more severe during the electrical switching process due to the Joule heating effect. These results suggest that, to understand and to evaluate the performance in a wide range of temperatures, it is crucial to consider the contribution of the entire magnetic components in the p-MTJ stack.