OSCILLATORY MAGNETIC COUPLING IN FE AG/FE(100) SANDWICH STRUCTURES/

The magnetic coupling in Fe/Ag/Fe sandwich structures has been studied using scanning electron microscopy with polarization analysis (SEMPA) . when atomically well-ordered Ag spacer layers are grown epitaxially on an Fe whisker substrate, the coupling between the Fe substrate and the top Fe film is found to oscillate between ferromagnetic and antife rromagnetic as a periodic function of the Ag thickness. The magnetic c oupling is composed of two oscillatory components with periods of 2.37 +/- 0.07 and 5.73 +/- 0.05 Ag layers. The oscillations persist for Ag spacer films that are up to at least 50 layers thick. These periods a re consistent with theoretical models that predict that the oscillator y coupling length scale is determined by spanning vectors of the space r material's Fermi surface. Biquadratic coupling was also observed in these structures. The relative strength of biquadratic to bilinear cou pling was found to depend on the thickness of the top Fe film.