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Abstract: The discovery of spin torque transfer STT has lead to a significant advancein the development of spintronic devices. Novel structures and materials havebeen studied in order to improve the performance of the magnetic tunneljunctions MTJs performances and understand the fundamental physics in spintorque transfer. The adiabatic spin torque effect, which is due to the spatialnon-uniformity of magnetic properties, has been predicted in theory anddemonstrated experimentally in magnetic nanowires. However, this important spintorque has been rarely concerned in the magnetic tunnel junctions MTJ becauseof its extremely weak effect in conventional MTJs. This paper reports for thefirst time a giant adiabatic spin torque in MTJ devices with a hybrid freelayer structure. The generation of the giant adiabatic spin torque was realizedthrough the introduction of a spatial magnetic non-uniformity in a hybrid freelayer along the current direction. It is observed that the giant adiabatic spintorque can substantially promote the current-induced switching process in theMTJ devices: the adiabatic spin torque can be larger than the in-plane spintorque, which allows for the switching with a single-polar current underdifferent bias fields. Moreover, the adiabatic spin torque, which isproportional to the level of spatial non-uniformity, increases during theswitching process. The observed effects are confirmed by numerical simulations.These results have far-reaching implications for the future of high-densitySTT-MRAM devices.



Author: Xiaofeng Yao 1, Yisong Zhang 1, Andrew Lyle 1, Roger Malmhall 2, Rajiv Ranjan 2, Lei Lu 3, Mingzhong Wu 3, Hao Wang 1, Ying Jing

Source: https://arxiv.org/







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