Conductivity-Like Gilbert Damping due to Intraband Scattering in Epitaxial Iron*

Confirming the origin of Gilbert damping by experiment has remained a challenge for many decades, even for some of the simplest ferromagnetic metals. Here, we experimentally identify Gilbert damping that increases with decreasing electronic scattering in thin films of BCC Fe. The observed conductivity-like damping, which cannot be accounted for by classical eddy current loss, is in excellent quantitative agreement with theoretical predictions of Gilbert damping due to intraband scattering. These results resolve the longstanding question since the 1970s about the role of intraband scattering in Gilbert damping. Our results also indicate that – somewhat counterintuitively – disorder can reduce intrinsic damping at low temperatures in ferromagnetic metals, such that optimally disordered films may be well suited for cryogenic spintronic and quantum applications.