Dynamic exchange via spin currents in acoustic and optical modes of ferromagnetic resonance in spin-valve structures
Dynamic exchange via spin currents in acoustic and optical modes of ferromagnetic resonance in spin-valve structures
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DOI：
10.1103/physrevb.89.144410
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发表时间：
2014-01
影响因子：
3.7
通讯作者：
A. Timopheev;Y. Pogorelov;S. Cardoso;P. Freitas;G. Kakazei;N. Sobolev
中科院分区：
文献类型：
--
作者：
A. Timopheev;Y. Pogorelov;S. Cardoso;P. Freitas;G. Kakazei;N. Sobolev
然而，通过厚的正常金属间隔层磁性解耦的两个铁磁层可以经由自旋泵发射的自旋电流动态耦合，并且通过相邻界面处的自旋扭矩效应吸收。由于在每一层中的角动量泄漏的部分补偿的阻尼在这两个层中的减少先前观察到的两个铁磁共振的重合。在非零磁耦合的情况下，这种动态交换将取决于层中磁矩的相互旋进。的共振峰的线宽的差异是预期的声学和光学制度的岁差。然而，层间耦合使层的谐振响应杂交，因此也可以改变它们的线宽。这两种机制之间的相互作用以前从未被考虑过。本文研究了弱耦合NiFe/CoFe/Cu/CoFe/MnIr自旋阀多层膜中杂化和非局域阻尼对线宽的联合影响。结果表明，自旋流的动态交换在光学模式和声学模式下是不同的，这种差异取决于层间耦合强度。与声学进动模式相反，光学模式中的动态交换作为附加阻尼源工作。在Landau-Lifshitz-吉尔伯特方法的框架下，对两个磁耦合和自旋耦合的铁磁层进行了数值模拟，将非局域阻尼的影响与共振模的杂化分离开来.在我们的样品中，这两种机制带来了相同数量级的线宽变化，但导致明显不同的角度行为。所得到的结果是相关的一个广泛的类的耦合磁性多层膜的自旋输运弹道制度。
Two ferromagnetic layers magnetically decoupled by a thick normal metal spacer layer can be, nevertheless, dynamically coupled via spin currents emitted by the spin-pump and absorbed through the spin-torque effects at the neighboring interfaces. A decrease of damping in both layers due to a partial compensation of the angular momentum leakage in each layer was previously observed at the coincidence of the two ferromagnetic resonances. In case of non-zero magnetic coupling, such a dynamic exchange will depend on the mutual precession of the magnetic moments in the layers. A difference in the linewidth of the resonance peaks is expected for the acoustic and optical regimes of precession. However, the interlayer coupling hybridizes the resonance responses of the layers and therefore can also change their linewidths. The interplay between the two mechanisms has never been considered before. In the present work, the joint influence of the hybridization and non-local damping on the linewidth has been studied in weakly coupled NiFe/CoFe/Cu/CoFe/MnIr spin-valve multilayers. It has been found that the dynamic exchange by spin currents is different in the optical and acoustic modes, and this difference is dependent on the interlayer coupling strength. In contrast to the acoustic precession mode, the dynamic exchange in the optical mode works as an additional damping source. A simulation in the framework of the Landau-Lifshitz-Gilbert formalism for two ferromagnetic layers coupled magnetically and by spin currents has been done to separate the effects of the non-local damping from the resonance modes hybridization. In our samples both mechanisms bring about linewidth changes of the same order of magnitude, but lead to a distinctly different angular behavior. The obtained results are relevant for a broad class of coupled magnetic multilayers with ballistic regime of the spin transport.