Baker A A, Figueroa A I, Pingstone D, Lazarov V K, van der Laan G, Hesjedal T
Department of Physics, Clarendon Laboratory, University of Oxford, Oxford, OX1 3PU, United Kingdom.
Magnetic Spectroscopy Group, Diamond Light Source, Didcot, OX11 0DE, United Kingdom.
Sci Rep. 2016 Oct 18;6:35582. doi: 10.1038/srep35582.
We present a study of the interaction mechanisms in magnetic trilayer structures with an MgO barrier grown by molecular beam epitaxy. The interlayer exchange coupling, A, is determined using SQUID magnetometry and ferromagnetic resonance (FMR), displaying an unexpected oscillatory behaviour as the thickness, t, is increased from 1 to 4 nm. Transmission electron microscopy confirms the continuity and quality of the tunnelling barrier, eliminating the prospect of exchange arising from direct contact between the two ferromagnetic layers. The Gilbert damping is found to be almost independent of the MgO thickness, suggesting the suppression of spin pumping. The element-specific technique of x-ray detected FMR reveals a small dynamic exchange interaction, acting in concert with the static interaction to induce coupled precession across the multilayer stack. These results highlight the potential of spin pumping and spin transfer torque for device applications in magnetic tunnel junctions relying on commonly used MgO barriers.
我们展示了一项关于通过分子束外延生长的具有MgO势垒的磁性三层结构中相互作用机制的研究。使用超导量子干涉仪磁力测量法和铁磁共振（FMR）来确定层间交换耦合A，当厚度t从1纳米增加到4纳米时，其呈现出意想不到的振荡行为。透射电子显微镜证实了隧道势垒的连续性和质量，排除了两层铁磁层直接接触产生交换作用的可能性。发现吉尔伯特阻尼几乎与MgO厚度无关，这表明自旋泵浦受到抑制。X射线检测的FMR这种元素特异性技术揭示了一种小的动态交换相互作用，它与静态相互作用协同作用，在整个多层堆叠中诱导耦合进动。这些结果突出了自旋泵浦和自旋转移矩在依赖常用MgO势垒的磁性隧道结器件应用中的潜力。
