Unconventional spin pumping and magnetic damping in an insulating compensated ferrimagnet

Recently, the interest in spin pumping has escalated from ferromagnets into antiferromagnetic systems, potentially enabling fundamental physics and magnonic applications. Compensated ferrimagnets are considered alternative platforms for bridging ferro- and antiferromagnets, but their spin pumping and the associated magnetic damping have been largely overlooked so far despite their seminal importance for magnonics. Herein, we report an unconventional spin pumping together with magnetic damping in an insulating compensated ferrimagnet Gd3Fe5O12. Remarkably, we unambiguously identified the divergence of the nonlocal effective magnetic damping induced by spin pumping close to the compensation temperature in Gd3Fe5O12/Cu/Pt heterostructures. Furthermore, the coherent and incoherent spin currents, generated by spin pumping and spin Seebeck effect respectively, undergo a distinct direction change with the variation of temperature. The physical mechanisms underlying these observations are self-consistently clarified by the ferrimagnetic counterpart of spin pumping and the handedness-related spin-wave spectra. Our findings broaden the conventional paradigm of the ferromagnetic spin pumping model and open new opportunities for exploring the ferrimagnetic magnonic devices.