Spin Dynamic Damping of Py Induced by Gd Capping

Magnetic dynamic damping is significantly important in determining the relaxation time of magnetic moments and the speed of magnetic memory devices. Here, magnetic dynamic behaviors of permalloy (Py) films capped with gadolinium (Gd) are studied, and the effects of the interface are investigated by the Cu insert layer. For Py/Gd bilayer films, both the saturation magnetization ( {M}_{s} ) and the surface anisotropy constant ( {K}_{{\bot }} ) are decreased with increasing Gd thickness, while the Gilbert damping ( \alpha ) is enhanced. With the insert of Cu at Py/Gd interface, the above tendencies of {M}_{s} , {K}_{\bot } , and \alpha are suppressed. We attribute these phenomena to the antiferromagnetic coupling between Gd and Py near the interface, which are caused by the magnetic proximity effect (MPE) instead of the spin relaxation in the rare earth Gd themselves.