Growth, structure, electronic, and magnetic properties of MgO/Fe(001) bilayers and Fe/MgO/Fe(001) trilayers - art. no. 134411

Single-crystal epitaxial MgO thin films were grown directly onto high-quali ty Fe single crystal and Fe whisker substrates and covered with Fe/Au layer s. Reflection high-energy electron diffraction and low-energy electron diff raction patterns and scanning tunneling microscopy images showed that the g rowth of MgO proceeded pseudomorphically in a nearly layer-by-layer mode up to six monolayers. A misfit dislocation network is formed for MgO layers t hicker than six monolayers. The thin MgO films were characterized electrica lly by scanning tunneling spectroscopy. The tunneling barrier in MgO was fo und to depend on the MgO layer thickness, starting from 2.5 eV at two monol ayer thickness to the expected full barrier of MgO of 3.6 eV at six monolay ers. A small fraction of the scanned area showed randomly placed spikes in the tunneling conductance. Tunneling I-V curves at the defects showed a low er tunneling barrier than that in the majority of the MgO film. The total t unneling current integrated over areas of 100x 100 nm(2), however, was not dominated by spikes of higher conductance. These local defects in the MgO b arrier were neither related to atomic steps on the Fe substrates nor to ind ividual misfit dislocations. Magnetic anisotropies and exchange coupling in Fe/MgO(001) and Fe/MgO/Fe(001) structures were studied using ferromagnetic resonance and Brillouin light scattering.