Back-Hopping in Spin-Transfer-Torque Devices: Possible Origin and Countermeasures
Back-Hopping in Spin-Transfer-Torque Devices: Possible Origin and Countermeasures
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DOI：
10.1103/physrevapplied.9.054010
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发表时间：
2017-02
影响因子：
4.6
通讯作者：
C. Abert;H. Sepehri-Amin;F. Bruckner;C. Vogler;M. Hayashi;D. Suess
中科院分区：
文献类型：
--
作者：
C. Abert;H. Sepehri-Amin;F. Bruckner;C. Vogler;M. Hayashi;D. Suess
通过自旋扩散模型研究了磁性多层系统中不良高频自由层切换（称为反向跳频）的影响。发现反向跳频效应的可能根源是固定层的不稳定，这导致两层的永久切换。通过微磁模拟获得了不同材料参数对自由层和固定层临界开关电流的影响。研究发现，选择具有低极化 $\beta$ 和饱和磁化强度 $M_s$ 的自由层材料以及具有高 $\beta$ 和 $M_s$ 的固定层材料会导致较低的自由层临界电流和较高的固定层临界电流，从而降低反向跳变的可能性。虽然在各种类型的设备中都观察到了反向跳跃，但只有少数实验在垂直磁化系统中表现出这种效应。然而，我们的模拟表明，由于减小器件尺寸时固定层各向异性的损失，这种情况可能会发生变化。
The effect of undesirable high-frequency free-layer switching in magnetic multilayer systems, referred to as back hopping, is investigated by means of the spin-diffusion model. A possible origin of the back-hopping effect is found to be the destabilization of the pinned layer which leads to perpetual switching of both layers. The influence of different material parameters on the critical switching currents for the free and pinned layer is obtained by micromagnetic simulations. It is found that the choice of a free-layer material with low polarization $\beta$ and saturation magnetization $M_s$, and a pinned-layer material with high $\beta$ and $M_s$ leads to a low free-layer critical current and a high pinned-layer critical current and hence reduces the likelihood of back hopping. While back hopping was observed in various types of devices, there are only few experiments that exhibit this effect in perpendicularly magnetized systems. However, our simulations suggest, that this is likely to change due to loss of pinned-layer anisotropy when decreasing device sizes.