Interlayer magnetic coupling in single-crystalline Fe/Cr/Fe and Fe/MgO/Fe structures grown on GaAs(0 0 1)

Single-crystalline Fe/MgO/Fe magneto-tunnel junctions were grown epitaxially on GaAs(0 0 1). Independent magnetization switching was achieved by pinning the magnetization of one of the Fe electrodes by antiferromagnetic coupling via Cr to another Fe layer (GaAs/Fe/Cr/Fe/MgO/Fe). For the antiparallel magnetization orientation in the Fe/Cr/Fe trilayer, “reversed” minor hysteresis loops are measured with longitudinal MOKE. The shape of the loop corresponding to the top “free-Fe” electrode is determined by four-fold magnetic anisotropy with the easy-axis along [1 0 0], superimposed by a weak uniaxial anisotropy with [0 1 0] easy-axis. The loops are asymmetric due to a delicate balance between the uniaxial anisotropy and magnetic interlayer coupling between the Fe electrodes separated with a thin MgO spacer.