Although both theoretical predications and experimental observations demonstrated that the damping factor is anisotropic at ferromagnet/semiconductor interface with robust interfacial spin-orbit coupling, it is not well understood whether non-local Gilbert damping driven by spin currents in heavy metal/ferromagnetic metal (HM/FM) bilayers is anisotropic or not. Here, we investigated the in-plane angular- and frequency- dependence of magnetic relaxation of epitaxial Fe/MgO(001) films with different capping layers of Pd and Cu. After disentangling the parasitic contributions, such as two-magnon scattering (TMS), mosaicity, and field-dragging effect, we unambiguously observed that both local and non-local Gilbert damping are isotropic in Fe(001) plane, suggesting that the pure spin currents absorption is independent of Fe magnetization orientation in the epitaxial Pd/Fe heterostructure. First principles calculation reveals that the effective spin mixing conductance of Pd/Fe interface is nearly invariant for different magnetization directions in good agreement with the experimental observations. These results offer a valuable insight into the transmission and absorption of pure spin currents, and facilitate us to utilize next-generation spintronic devices.
@article{arxiv.1809.11020,
title = {Isotropic non-local Gilbert damping driven by spin currents in epitaxial Pd/Fe/MgO(001) films},
author = {Yan Li and Yang Li and Qian Liu and Zhe Yuan and Wei He and Hao-Liang Liu and Ke Xia and Wei Yu and Xiang-Qun Zhang and Zhao-Hua Cheng},
journal= {arXiv preprint arXiv:1809.11020},
year = {2018}
}