Spin pumping into a partially compensated antiferromagnetic/paramagnetic insulator

Spin pumping from a metallic ferromagnet (FM) into an insulating antiferromagnet has been studied across the magnetic phase transition by means of temperature-dependent, broad-band ferromagnetic resonance (FMR) experiments. A set of spin pumping heterostructures consisting of Permalloy (Ni80Fe20) as FM and Zn1−xCoxO with x = 0.3, 0.5 and 0.6 (Co:ZnO) as antiferromagnetic insulator has been used where previous experiments have already pointed out the possibility of the existence of spin-pumping. The present experiment allow to reliably separate the various contributions of the temperature-dependent Gilbert damping parameter to the FMR line-width. A careful analysis of the obtained data demonstrates a significant increase of the temperature-dependence of the Gilbert damping parameter alpha(T ) around the magnetic phase transition of Co:ZnO which extends up to room temperature, confirming spin pumping into the fluctuating spin sink of an antiferromagnetic/paramagnetic insulator.