Low Magnetic Damping of Ferrimagnetic GdFeCo Alloys

We investigate the Gilbert damping parameter for rare earth (RE)-transition metal (TM) ferrimagnets over a wide temperature range. Extracted from the field-driven magnetic domain-wall mobility, the Gilbert damping parameter was as low as 0.0072 and was almost constant across the angular momentum compensation temperature, starkly contrasting previous predictions that the Gilbert damping parameter should diverge at the angular momentum compensation temperature due to vanishing total angular momentum. Thus, magnetic damping of RE-TM ferrimagnets is not related to the total angular momentum but is dominated by electron scattering at the Fermi level where the TM has a dominant damping role.