MAGNETIC COUPLING IN CO FACE-CENTERED-CUBIC FE/CO SANDWICHES/

Ferromagnetic (FC) and antiferromagnetic coupling (AFC) of Co layers a cross a metastable fee Fe spacer layer has been observed. Room-tempera ture-grown Fe on Co/Cu(100) was chosen as a spacer layer because it ex hibits three distinct structural and magnetic phases depending on the thickness range: fct and ferromagnetic (region I), fee and nonferromag netic (region II), bcc and ferromagnetic (region III) (listed in order of increasing thickness). Co/Fe/Co sandwiches were grown on Cu(100) b y molecular beam epitaxy with a base pressure of similar to 2x10(-10) Ton, and characterized by low-energy electron diffraction and reflecti on high-energy electron diffraction. The magnetic properties were stud ied in situ using surface magneto;optic Ken effect. Using a wedged Fe spacer layer, we investigated the magnetic coupling between Co films a cross many thicknesses of Fe. We found FC in region I, strong AFC at t he boundary between regions I and II, and weak AFC in region II. We al so studied the effect of just the Co overlayer on the metastable fee F e. We find that Co/Fe/Cu(100) differs qualitatively from Fe/Co/Cu(100) . Finally, we find an oscillation in the AFC with a periodicity of sim ilar to 12 Angstrom by artificially increasing the thickness range of region II. (C) 1996 American Institute of Physics.