The discovery of magnetization switching via spin transfer torque (STT) in PMA-based MTJs has led to the development of next-generation magnetic memory technology with high operating speed, low power consumption and high scalability. In this work, we theoretically investigate the influence of finite size and temperature on the mechanism of magnetization switching in CoFeB–MgO based MTJ to get better understanding of STT-MRAM fundamentals and design. An atomistic model coupled with simultaneous solution of the spin accumulation is employed. The results reveal that the incoherent switching process in MTJ strongly depends on the system size and temperature. At 0 K, the coherent switching mode can only be observed in MTJs with the diameter less than 20 nm. However, at any finite temperature, incoherent magnetization switching is thermally excited. Furthermore, increasing temperature results in decreasing switching time of the magnetization. We conclude that temperature dependent properties and thermally driven reversal are important considerations for the design and development of advanced MRAM systems.
The enhancement of domain wall resistance (DWR) in spintronic devices containing the domain wall is required for a full understanding since it represents the efficiency of spin transport and contributes to magnetoresistance phenomena. In this work, we theoretically investigate the effect of the domain wall width, injected current density, and temperature on DWR in magnetic nanowire by using the generalized spin accumulation model based on the Zhang, Levy, and Fert approach. The proposed model allows us to deal with a multilayer system with arbitrary orientation of magnetization. In addition, the temperature effect can be taken into account by considering the spin-dependent resistivity of the ferromagnet at any finite temperature. This leads to the calculation of temperature variation of spin transport parameters, and it eventually allows us to calculate the thermal effect on spin accumulation. The spin transport behavior and DWR can be calculated directly from the gradient of spin accumulation and spin current within the wall. The results show the increase in DWR with temperature as the thermal effect causes the reduction of transport parameters.
The study and understanding of spin-transport mechanisms including thermal fluctuation are required for the development and design of spintronic devices. In this paper, we present an approach to investigate the temperature dependence of spin-transport behavior within the magnetic structure by using the generalized spin accumulation model. The temperature affects not only the magnetization orientation, but also the spin-transport properties. Its effect on transport parameters can be taken into account by considering the spin-dependent resistivity at any finite temperature. This leads to the calculation of temperature-dependent spin-transport parameters and eventually allows the calculation of the thermal effects on spin accumulation, spin current, and spin torque. It is observed that increasing temperature is likely to decrease the value of key transport parameters relevant to the magnitude of spin torque. This study demonstrates the importance of thermal effects on spin-transport behavior which needs to be considered for spin-transfer torque based device design with high performance.
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