Giant damping enhancement induced by exchange coupling in Y3Fe5O12/Co2FeAl0.5Si0.5 bilayers

Gilbert damping enhancement induced by the spin pumping effect is investigated in Y3Fe5O12(YIG)/heavy metal bilayers. Because its spin polarization is high and Gilbert damping is low, Co2FeAl0.5Si0.5 (CFAS) is deemed a promising ferromagnetic material in spintronics devices. We studied microwave dynamic magnetizations in YIG/CFAS bilayers combined with ferromagnetic resonance measurement using a vector network analyzer to reveal a 5-fold giant damping enhancement compared with that for the YIG/Pt bilayers. This phenomenon was attributed to both the exchange coupling effect and spin pumping effect. By inserting a 10-nm Cu spacer, direct exchange coupling can be suppressed. A spin mixing conductance g(eff)(up arrow down arrow) of 7.75 x 10(18) m(-2) generated by spin pumping was obtained. The study provides an effective approach to tailor the damping in magnetic thin films. (C) 2018 Elsevier B.V. All rights reserved.