We present measurements of the exchange stiffness $D$ and the exchange constant $A$ of a sputtered 80 nm ${\mathrm{Tb}}_{0.3}{\mathrm{Dy}}_{0.7}{\mathrm{Fe}}_2$ film. Using a broadband ferromagnetic resonance setup in a wide frequency range from 10 to 50 GHz, multiple perpendicular standing spin-wave resonances were observed with the external static magnetic field applied in-plane. The field corresponding to the strongest resonance peak at each frequency is used to determine the effective magnetization, the $g$ factor, and the Gilbert damping. Furthermore, the dependence of spin-wave mode on field position is observed for several frequencies. The analysis of spin-wave resonance spectra at multiple frequencies allows precise determination of the exchange stiffness $D=\left(2.79\pm 0.02\right)\times {10}^{-17}\mathrm{T}{\mathrm{m}}^2$ for an 80 nm thick film. From this value, we calculated the exchange constant $A=(9.1\pm 0.1)\mathrm{pJ}{\mathrm{m}}^{-1}$.

• Received 18 December 2015
• Revised 2 February 2016

DOI:https://doi.org/10.1103/PhysRevB.93.064425