Two-Monolayer Oscillations in the Antiferromagnetic Exchange Coupling Through Manganese in Fe/Mn/Fe Sandwich Structures

Oscillations with a period corresponding to two Mn monolayers (MLs) were measured in the antiferromagnetic exchange coupling between ultrathin Fe layers and bulk Fe single-crystal whiskers separated by epitaxial Mn layers. The films were deposited by molecular-beam epitaxy. Electron diffraction showed that the Mn grew monolayer by monolayer in a body-centered-tetragonal structure (a = 2.87 A, c = 3.27 A) up to 15-25 MLs. The coupling was determined using the magneto-optic Kerr effect. It was antiferromagnetic for all thicknesses > 4-7 MLs Mn, with five strong peaks in the 0-0.2 mJ/m exp 2 range.