Highly localized surface modes in epitaxial W/Ni/W films

Non-propagating surface resonance modes have been observed on epitaxial W/Ni/W and W/Ni films. These modes are excited when the surface of the W buffer layer exhibits some roughness. The resonance fields of the modes are independent of the thickness of the Ni, the modes exhibit exceptionally small linewidths and very weak intensities. The results are interpreted using the model of surface spin waves, related to the variations of the exchange constant near the interfaces.