Resonant amplification of intrinsic magnon modes and generation of new extrinsic modes in a two-dimensional array of interacting multiferroic nanomagnets by surface acoustic waves
Resonant amplification of intrinsic magnon modes and generation of new extrinsic modes in a two-dimensional array of interacting multiferroic nanomagnets by surface acoustic waves
复制标题
DOI：
10.1039/d1nr01177d
复制
发表时间：
2021-05-14
期刊：
影响因子：
6.7
通讯作者：
Barman, Anjan
中科院分区：
文献类型：
--
作者：
De, Anulekha;Drobitch, Justine Lynn;Barman, Anjan
使用时间分辨磁光克尔效应（TR-MOKE）显微镜，我们在压电LiNbO3基板上制造的椭圆Co纳米磁体的密集二维阵列中展示了表面声波（SAW）引起的本征自旋波（SW）模式的共振放大，以及在SAW频率下产生新的外在或驱动模式。该系统可以有效地充当磁振晶体（MC），其中固有的形状各向异性和强烈的元素间静磁相互作用在没有任何偏置磁场的情况下触发纳米磁体磁化的非相干进动，从而产生“固有”SW模式。当沿着纳米磁体的主轴发射SAW时，磁弹性耦合会导致丰富多样的SW现象，例如当应用的SAW频率与这些频率谐振时，本征模式（3、4、7和10 GHz）放大4-7倍，以及在非谐振SAW频率下产生新的外在模式。然而，当沿着短轴发射 SAW 时，在所应用的 SAW 频率处会出现主导驱动模式。这表明 SW 和 SAW 之间的磁弹性耦合本质上是各向异性的。微磁模拟结果与实验观察结果定性一致，并阐明了潜在的动力学。我们的研究结果为无偏置场磁振子学奠定了基础，其中声表面波可以有效地调整SW行为。它在节能片上微波器件、SW 逻辑和嵌入式应用的极端亚波长超小型微波天线的设计中具有重要的应用。
Using time-resolved magneto-optical Kerr effect (TR-MOKE) microscopy, we demonstrate surface-acoustic-wave (SAW) induced resonant amplification of intrinsic spin-wave (SW) modes, as well as generation of new extrinsic or driven modes at the SAW frequency, in a densely packed two-dimensional array of elliptical Co nanomagnets fabricated on a piezoelectric LiNbO3 substrate. This system can efficiently serve as a magnonic crystal (MC), where the intrinsic shape anisotropy and the strong inter-element magnetostatic interaction trigger the incoherent precession of the nanomagnets' magnetization in the absence of any bias magnetic field, giving rise to the 'intrinsic' SW modes. The magnetoelastic coupling leads to a rich variety of SW phenomena when the SAW is launched along the major axis of the nanomagnets, such as 4-7 times amplification of intrinsic modes (at 3, 4, 7 and 10 GHz) when the applied SAW frequencies are resonant with these frequencies, and the generation of new extrinsic modes at non-resonant SAW frequencies. However, when the SAW is launched along the minor axis, a dominant driven mode appears at the applied SAW frequency. This reveals that the magnetoelastic coupling between SW and SAW is anisotropic in nature. Micromagnetic simulation results are in qualitative agreement with the experimental observations and elucidate the underlying dynamics. Our findings lay the groundwork for bias-field free magnonics, where the SW behavior is efficiently tuned by SAWs. It has important applications in the design of energy efficient on-chip microwave devices, SW logic, and extreme sub-wavelength ultra-miniaturized microwave antennas for embedded applications.