Symmetry influence on interlayer coupling in epitaxial Co/Cr trilayers grown on MgO (1 0 0) and (1 1 0) substrates

Abstract

Trilayers of Co(15 Å)/Cr(x)/Co(17 Å) have been epitaxially sputtered onto MgO (1 0 0) and (1 1 0) substrates coated with Cr(1 0 0) and (2 1 1) buffer layers, respectively. The Cr thickness x is varied from 6 to 50 Å. Both sample sets have the Co c-axis lying in the plane of the film, however, due to the four-fold symmetry of MgO (1 0 0), the Co layers form bicrystals with perpendicularly oriented c-axis. Ferromagnetic resonance measurements clearly show large two-fold and four-fold magnetic in-plane anisotropy for MgO (1 1 0) and MgO (1 0 0) samples, respectively. Magnetization measurements reveal interlayer coupling strengths peaked at a Cr thickness of approximately 10 Å for both symmetries, but the strength decreases more slowly with increasing t Cr in the MgO(1 0 0) system.