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 currentinduced 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. Spin transfer torque random access memory (STT-MRAM) is a next-generation non-volatile memory technology 1-4 that has the advantage of fast write times 5-7 , relatively low power consumption 8-11 , and shows promise of scalability down to at least 7 nm CMOS technology node 12,13. STT-MRAM has already found its applications in the form of stand-alone nonvolatile memory 14 , and efforts to realize embedded versions of STT-MRAM are under way 15,16. The core component of STT-MRAM is a nanoscale magnetic tunnel junction (MTJ) 17-19 that consists of ferromagnetic metallic layers separated by a non-magnetic insulating tunnel barrier as illustrated in Fig. 1(a). Since the MTJ does not contain semiconductor components, STT-MRAM can be radiation hard, i.e. robust to the effects of ionizing radiation. This makes STT-MRAM potentially attractive for applications in space and military technologies, particle accelerators, and nuclear reactors 20,21. In fact previous studies have shown the promise of the radiation hardness of MTJs 22-24 ; however, the effects of ionizing radiation on spin transfer torque switching in MTJs with properties required for scalable STT-MRAM technology have not been experimentally studied. An STT-MRAM bit is written by a current pulse that applies spin torque 25 to magnetization of the free layer ferromagnet and reverses its direction thereby changing the relative alignment of magnetic moments of the free and pinned layers of the MTJ between parallel and antiparallel 26-28. This free layer switching leads to a change of the MTJ resistance due to the tunneling magneto-resistance (TMR) effect 28 , which allows resi...
The reprocessing used nuclear fuel (UNF) releases volatile fission and activation products, including 129I, into the off-gas of a processing plant. Mitigation of the release of vapor phase radionuclides is necessary for meeting regulatory requirements in the United States and other countries. In an aqueous reprocessing plant, volatile radioiodine could be present in several forms, depending on the chemistry of the process used. Inorganic iodine will be the predominate species in any shearing or voloxidation pretreatment off-gas and dissolver off-gas (DOG). Organic iodides such as CH3I, C4H9I, and C12H25I have been proposed to be generated during solvent extraction; thus, these species must be captured from the vessel off-gas (VOG). The abatement of inorganic and organic iodide species to meet United States regulatory requirements has been demonstrated in laboratory experiments using Ag-based solid sorbents. The data presented in this paper includes the effect of gas composition (e.g., the presence of water vapor and NOx), iodine speciation (I2, CH3I, C4H9I, C12H25I), and sorbent bed parameters (e.g., temperature, sorbent age) on complete iodine capture on Ag-mordenite in an aqueous reprocessing plant.
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