MAGNETIC COUPLING ACROSS A FERROMAGNETIC-METAL-ALKALI-METAL INTERFACE

We report on an experimental study of the interfacial magnetic couplin g in metallic bilayers consisting of an alkali metal and a thin ferrom agnetic film. The alkali metals used were either potassium or lithium, with the ferromagnetic metal consisting of either iron or Permalloy. This study began as part of a larger project consisting of a study of Larmor waves in potassium. Our observations will also be of interest t o those studying magnetic multilayers, in which the nature of the magn etic coupling between ferromagnetic and nonmagnetic metals plays an im portant role. In this paper, we show how the degree of magnetic coupli ng in these bilayer samples can be examined by studying the interactio n of the ferromagnetic resonance of the ferromagnetic film with the co nduction-electron spin resonance (CESR) of the alkali-metal layer. The se studies are carried out at cryogenic temperatures (down to 1.1 K) u sing microwave reflection spectroscopy at 12 GHz. We have also examine d the temperature dependence of the magnetic resonances. Between 1.1 a nd 25 K, for both lithium and potassium, an unexpected narrowing of th e CESR lines occurs with increasing temperature.