  We report on the enhancement of antiferromagnetic coupling in epitaxial
Fe/Si/Fe structures by voltage-driven spin-polarized tunneling currents. Using
the ballistic electron magnetic microscopy we established that the hot-electron
collector current reflects magnetization alignment and the magnetocurrent
exceeds 200% at room temperature. The saturation magnetic field for collector
current corresponding to parallel alignment of magnetizations rises up with the
tunneling current, thus demonstrating stabilization of the antiparallel
alignment and increasing antiferromagnetic coupling. We connect the enhancement
of antiferromagnetic coupling with local dynamic spin torques mediated by
tunneling electrons
