We have studied ferromagnetic resonance in amorphous trilayers of ${\mathrm{Co}}_x$(${\mathrm{Al}}_{0.70}{\mathrm{Zr}}_{0.30}{)}_{1-x}$. The trilayer composition is such that the outer layers are ferromagnetic, with distinct resonance frequencies, while the spacer layer composition is nominally paramagnetic. We observe two precessional modes, acoustic and optical, and follow these as the interlayer exchange coupling, mediated by a strong proximity-induced magnetization in the spacer, is varied by changing the spacer layer thickness. We find that both the interlayer exchange coupling and the induced magnetization have an exponential decay profile within the spacer, with contrasting decay lengths of ${\lambda }_{\mathrm{IEC}}$ = 0.44 nm and ${\lambda }_{\mathrm{PIM}}$ = 3.1 nm. This contrast exposes the difference in decay length of spin stiffness, reflected in resonance experiments, and proximity-induced magnetization or polarizability in these amorphous trilayers, from static magnetization measurements.

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• Magnetic coupling
• Magnetization dynamics
• Spin polarization
• Amorphous materials
• Magnetic multilayers
• Soft magnets
• Ferromagnetic resonance
• Physical vapor deposition