Department of Physics , Virginia Polytechnic Institute and State University , Blacksburg , Virginia 24060 , United States.
Advanced Light Source, Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States.
Nano Lett. 2018 Jul 11;18(7):4273-4278. doi: 10.1021/acs.nanolett.8b01261. Epub 2018 Jun 8.
Pure spin currents, unaccompanied by dissipative charge flow, are essential for realizing energy-efficient nanomagnetic information and communications devices. Thin-film magnetic insulators have been identified as promising materials for spin-current technology because they are thought to exhibit lower damping compared with their metallic counterparts. However, insulating behavior is not a sufficient requirement for low damping, as evidenced by the very limited options for low-damping insulators. Here, we demonstrate a new class of nanometer-thick ultralow-damping insulating thin films based on design criteria that minimize orbital angular momentum and structural disorder. Specifically, we show ultralow damping in <20 nm thick spinel-structure magnesium aluminum ferrite (MAFO), in which magnetization arises from Fe ions with zero orbital angular momentum. These epitaxial MAFO thin films exhibit a Gilbert damping parameter of ∼0.0015 and negligible inhomogeneous linewidth broadening, resulting in narrow half width at half-maximum linewidths of ∼0.6 mT around 10 GHz. Our findings offer an attractive thin-film platform for enabling integrated insulating spintronics.
纯自旋电流，不伴随耗散电荷流，对于实现节能的纳米磁性信息和通信设备至关重要。薄膜磁性绝缘体被认为是自旋电流技术的有前途的材料，因为它们的阻尼比其金属对应物低。然而，绝缘行为并不是低阻尼的充分要求，因为具有低阻尼的绝缘体选择非常有限。在这里，我们展示了一类基于最小化轨道角动量和结构无序的设计准则的新型纳米级超低阻尼绝缘薄膜。具体来说，我们在具有零轨道角动量的 Fe 离子产生的磁化的 20nm 厚尖晶石结构镁铝铁氧体（MAFO）中展示了超低阻尼。这些外延 MAFO 薄膜表现出约为 0.0015 的 Gilbert 阻尼参数和可忽略的非均匀线宽展宽，导致在约 10GHz 时半最大值线宽的窄半宽度为约 0.6mT。我们的发现为实现集成绝缘自旋电子学提供了一个有吸引力的薄膜平台。
