Immunity of nanoscale magnetic tunnel junctions with perpendicular magnetic anisotropy to ionizing radiation

Eric Arturo Montoya,Jen-Ru Chen,Randy Ngelale,Ozdal Boyraz,Lei Wan,Ilya N Krivorotov,Han Kyu Lee,Nader Bagherzadeh,En Yang,Hsin-Wei Tseng,Patrick Braganca,Mikael Nilsson

doi:10.1038/s41598-020-67257-2

Abstract

Spin transfer torque magnetic random access memory (STT-MRAM) is a promising candidate for next generation memory as it is non-volatile, fast, and has unlimited endurance. Another important aspect of STT-MRAM is that its core component, the nanoscale magnetic tunneling junction (MTJ), is thought to be radiation hard, making it attractive for space and nuclear technology applications. However, studies on the effects of ionizing radiation on the STT-MRAM writing process are lacking for MTJs with perpendicular magnetic anisotropy (pMTJs) required for scalable applications. Particularly, the question of the impact of extreme total ionizing dose on perpendicular magnetic anisotropy, which plays a crucial role on thermal stability and critical writing current, remains open. Here we report measurements of the impact of high doses of gamma and neutron radiation on nanoscale pMTJs used in STT-MRAM. We characterize the tunneling magnetoresistance, the magnetic field switching, and the current-induced switching before and after irradiation. Our results demonstrate that all these key properties of nanoscale MTJs relevant to STT-MRAM applications are robust against ionizing radiation. Additionally, we perform experiments on thermally driven stochastic switching in the gamma ray environment. These results indicate that nanoscale MTJs are promising building blocks for radiation-hard non-von Neumann computing.

Highlights

Spin transfer torque magnetic random access memory (STT-MRAM) is a promising candidate for generation memory as it is non-volatile, fast, and has unlimited endurance
Modern STT-MRAM is based upon nanoscale magnetic tunneling junction (MTJ) with strong perpendicular magnetic anisotropy (PMA) that forces the easy magnetization axis to be perpendicular to the plane of the sample, or so called perpendicular MTJs; this is due to the fact that unlike in-plane MTJs, pMTJs provide a route towards scalable STT-MRAM technology[12]
Quantitative analysis given in Supplementary Material note S1 shows that ensemble averages of irradiation-induced changes in these parameters do not exceed one standard deviation of these changes over the ensemble, with the exception of Hw for the elliptical pMTJs whose observed change is slightly larger than one standard deviation; we find that apparent irradiation-induced changes in Hw and Iw in all cases do not exceed the thermal spread of these parameters, ie. we do not observe any changes in parameter greater than our measurement error

Summary

Introduction

Spin transfer torque magnetic random access memory (STT-MRAM) is a promising candidate for generation memory as it is non-volatile, fast, and has unlimited endurance Another important aspect of STT-MRAM is that its core component, the nanoscale magnetic tunneling junction (MTJ), is thought to be radiation hard, making it attractive for space and nuclear technology applications. To determine the viability of practical STT-MRAM technology for radiation hard applications, studies of the effect of ionizing radiation an spin transfer torque switching in pMTJs are required In this Article, we report experimental studies of the effect of extreme doses of ionizing gamma and neutron radiation on nanoscale pMTJs, whose dimensions and magnetic anisotropy are very similar to those currently employed in STT-MRAM technology. Both the gamma and neutron TIDs in this study are 1–2 orders of magnitude greater than previous studies on MTJs22–24

Methods

Results

Conclusion