Isotropic non-local Gilbert damping driven by spin pumping in epitaxial Pd/Fe films on MgO(001) substrates

Abstract

Although both theoretical predictions and experimental observations have demonstrated that the Gilbert damping is anisotropic at ferromagnet/semiconductor interface possessing robust interfacial spin-orbit coupling, it is not well understood whether non-local Gilbert damping driven by spin pumping in heavy metal/ferromagnetic metallic bilayers is anisotropic or not. Here, we investigated the angular and frequency dependence of magnetic relaxation in epitaxial Pd/Fe films on MgO(001) substrates. After disentangling parasitic contributions, we unambiguously observe that the non-local Gilbert damping is isotropic in the Fe(001) plane, suggesting that the spin transport across the Pd/Fe interface is independent of the Fe magnetization orientation. First principles calculations reveal that the effective spin mixing conductance of the Pd/Fe interface is nearly invariant for different magnetization directions, in good agreement with the experimental observations. These results offer valuable insight into spin transport in metallic bilayers, and facilitate the development of nextgeneration spintronic devices.

Large spin to charge conversion in the topological superconductor β−PdBi2 at room temperature

“…However, for the Fe/β-PdBi2 structure, the superconductivity is not annihilated and just the critical temperature Tc decreases below 4 K. In addition, these films were also characterized by the MPMS magnetometer, which shows that the Fe layers have a saturation magnetization of 1.93 T at room temperature as shown inFig. 2(b), in good agreement with previously determined values for Fe films[27]. The saturation magnetization determined in this way, as well as the coercivity shown in the inset ofFig.…”

Characterizing the Magnetic Interfacial Coupling of the Fe/FeGe Heterostructure by Ferromagnetic Resonance

“…At 300 K, Δ H 0 and a are 44 Oe and 0.035, respectively. The latter is larger than the previously reported ∼0.006 in the Fe film . This can be attributed to the enhanced spin–phonon scattering, which is induced by the imperfect crystalline structure caused by the mismatch of Fe and FeGe lattices and the interdiffusion of Fe and Ge atoms .…”

“…The efficiency of the generated spin current, which is proportional to the enhancement of the Gilbert damping, has been estimated to replace the effective spin mixing conductance . The value is estimated as 154 nm –2 at 200 K. It is 1 order of magnitude larger than that of the conventional heavy metals like Pt and Pd . Once the magnetization of Fe is out of equilibrium (under FMR), the interfacial exchange coupling operates torques on both the magnets.…”

“…The latter is larger than the previously reported ∼0.006 in the Fe film. 23 This can be attributed to the enhanced spin−phonon scattering, which is induced by the imperfect crystalline structure caused by the mismatch of Fe and FeGe lattices and the interdiffusion of Fe and Ge atoms. 27 The interesting observation is the influence of interfacial exchange coupling on them.…”

“…26 The value is estimated as 154 nm −2 at 200 K. It is 1 order of magnitude larger than that of the conventional heavy metals like Pt and Pd. 23 Once the magnetization of Fe is out of equilibrium (under FMR), the interfacial exchange coupling operates torques on both the magnets. Then, the torque applied to the FeGe atoms causes their precession.…”