Investigation of Saturation Magnetization and Damping in Tb/Cr/Fe Trilayers

The Tb(4 nm)/Cr(t nm)/Fe(5 nm) trilayers with different thicknesses of Cr layer have been investigated by X-ray diffraction, vibrating sample magnetometer, and ferromagnetic resonance. When Cr is thinner than 1.8 nm, the ferromagnetic coupling of Tb and Fe leads to higher saturation magnetization (M_s) than that of Fe(5 nm) film. On the other hand, the Gilbert damping constant α in all the trilayers have been found to exceed the magnitude of the Fe. In particular, when Cr layer is 1 nm thick, α increases by 38% and M_s is increased by 6%; when Cr layer is 4 nm thick, α is increased by 46%, while Ms is only decreased by 5%. Accordingly, we have demonstrated a way for enhancing damping and magnetic moment simultaneously in the Tb(4 nm)/Cr(t nm)/Fe(5 nm) trilayers.