Effect of Dilute Rare-Earth Doping on Magnetodynamic Properties of Permalloy Films

Tunable magnetodynamic properties of magnetic materials will allow significant design freedom in spintronic devices. One of the most efficient methods to tailor magnetic properties is by element doping. Here, we study the effect of rare-earth (RE) doping on Permalloy (Py) films to modify the magnetic damping and exchange stiffness by both the ferromagnetic resonance uniform precession mode and the first perpendicular standing spin-wave mode. Results show that both static and dynamic magnetic properties of Py films are adjusted by doping with Gd, Tb, and Nd. The saturation magnetization is decreased by 59.4% with Tb, Gd, and Nd at concentrations of 10 at.%. The magnetic damping coefficient (α) is enhanced mostly by Tb dopant, followed by Nd and Gd, indicating that spin-orbit coupling may be one of the main mechanisms in determining α of RE-doped films. A 44.2% reduction of the exchange stiffness was achieved by doping with 3.3 at.% Nd. The results demonstrate that RE doping may be a viable technique for the control of magnetodynamic properties for spintronics applications.