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采用自旋转移力矩效应增强或抑制微波磁损耗

Suppress or enhance microwave magnetic losses by spin transfer torque effect

摘要:基于微磁学模拟结果,发现由于单根纳米线两端处磁矩矢量方向与极化电流密度(J)方向的不一致,导致电子的自旋转移力矩(STT)只能作用于纳米线两端的磁矩。通过提高极化电流的自旋极化率(P),这个简化模型的微波磁谱中处在18 GHz的微波磁损耗可以得到明显的抑制,同时发现与微波损耗对应的自然共振频率大小却不受STT影响。在STT效应作用下,负的磁导率虚部也是可实现的。另外,模拟结果表明通过提高STT效应中非绝热效应项中的值,18GHz处的微波磁损耗可以得到显著的增强。基于STT效应中不同力矩的来源对磁化强度进动过程的有效阻尼常数(ɑe)的影响,上述的结果可以得到合理的解释:绝热力矩能降低ɑe数值,因而能抑制微波磁损耗的大小;非绝热力矩能提高ɑe数值,因而能增强微波磁损耗。我们的研究结果展示了一个创新性的、能主动地调控微波磁损耗的方法。

英文摘要:Using the micromagnetics simulations, it is shown that the spin transfer torques (STT) of electrons are only exerted on the magnetic moments at two ends of single nanowire where they are misaligned with the direction of polarized current density (J). By increasing the polarization rate (P) of current, microwave magnetic losses at 18 GHz can be obviously suppressed in this very simplified model. It is also found that the natural resonance frequency can no be changed by the STT effect. Negative imaginary parts of permeability are also shown feasible under the STT effect. On the other hand, the results also show that the microwave magnetic losses at 18 GHz can be enhanced by increasing the value in the non-adiabaticterm.Itcan be well understoodfrom the change of effective damping constant (ɑe)due to the different contributing torquesof STT effect. The adiabatic torque of STT will decrease ɑevalue and therefore suppress the microwave magnetic losses. The non-adiabatic torqueof STTwill increase ɑevalueand therefore enhance the microwave magnetic losses.These results show an active and innovative way to control the microwave magnetic losses.

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[V1] 2022-06-29 16:07:38 chinaXiv:202206.00194V1 下载全文
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