Giant nonlinear damping in nanoscale ferromagnets
Giant nonlinear damping in nanoscale ferromagnets
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DOI：
10.1126/sciadv.aav6943
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发表时间：
2019-10-01
期刊：
影响因子：
13.6
通讯作者：
Krivorotov, I. N.
中科院分区：
文献类型：
--
作者：
Barsukov, I.;Lee, H. K.;Krivorotov, I. N.
磁阻尼是基于磁性纳米颗粒的新兴技术的关键指标，例如自旋扭矩存储器和高分辨率生物磁成像。尽管它的重要性，在纳米级铁磁体的磁耗散的理解仍然难以捉摸，阻尼往往被视为一个现象学常数。在这里，我们报告了一个巨大的频率依赖性的非线性阻尼，强烈地改变了纳米铁磁体的自旋扭矩和微波磁场的响应的发现。这种阻尼机制起源于三磁振子散射，该散射通过磁振子在纳米磁体中的几何限制而强烈增强。我们表明，巨大的非线性阻尼可以逆转纳米磁体上的自旋扭矩的影响，从而导致反阻尼扭矩导致意想不到的电流诱导阻尼增强。我们的工作推进了对纳米铁磁体和自旋扭矩器件中磁动力学的理解。
Magnetic damping is a key metric for emerging technologies based on magnetic nanoparticles, such as spin torque memory and high-resolution biomagnetic imaging. Despite its importance, understanding of magnetic dissipation in nanoscale ferromagnets remains elusive, and the damping is often treated as a phenomenological constant. Here, we report the discovery of a giant frequency-dependent nonlinear damping that strongly alters the response of a nanoscale ferromagnet to spin torque and microwave magnetic field. This damping mechanism originates from three-magnon scattering that is strongly enhanced by geometric confinement of magnons in the nanomagnet. We show that the giant nonlinear damping can invert the effect of spin torque on a nanomagnet, leading to an unexpected current-induced enhancement of damping by an antidamping torque. Our work advances the understanding of magnetic dynamics in nanoscale ferromagnets and spin torque devices.