  We have put into evidence the existence of an antiferromagnetic coupling
between iron epilayers separated by a ZnSe crystalline semiconductor. The
effect has been observed for ZnSe spacers thinner than 4 nm at
room-temperature. The coupling constant increases linearly with temperature
with a constant slope of ~5.5x 10-9 J/m2K. The mechanisms that may explain such
exchange interaction are discussed in the manuscript. It results that
thermally-induced effective exchange coupling mediated by spin-dependent on and
off resonant tunnelling of electrons via localized mid-gap defect states in the
ZnSe spacer layer appears to be the most plausible mechanism to induce the
antiferromagnetic coupling.
