Measurement of spin mixing conductance in Ni_(81)Fe_(19)/α-Wand Ni_(81)Fe_(19)/β-W heterostructures via ferromagnetic resonance

摘要

We present measurements of interfacial Gilbert damping due to the spin pumping effect in Ni81Fe19/W heterostructures. Measurements were compared for heterostructures in which the crystallographic phase of W, either alpha(bcc)-W or beta(A15)-W, was enriched through deposition conditions and characterized using X-ray diffraction and high-resolution cross-sectional transmission electron microscopy. Single-phase Ni81Fe19/alpha-W heterostructures could be realized, but heterostructures with beta-W were realized as a mixed alpha-beta phase. The spin mixing conductances for W at interfaces with Ni81Fe19 were found to be significantly lower than those for similar heavy metals such as Pd and Pt, but comparable to those for Ta, and independent of enrichment in the beta phase.