Magnetic and crystallographic characterization of Zn0.78Fe0.22Se and FeSe films on GaAs (001)

Abstract
We have grown single‐crystal (001) epilayers of the diluted magnetic semiconductor Zn1−xFexSe with 0≤x≤1 on GaAs(001) substrates by molecular‐beam epitaxy. The films retain the zinc‐blende structure for thicknesses up to at least 2 μm for x≤0.22, while epilayers with higher Fe concentrations can be stabilized up to some decreasing critical thickness. SQUID magnetometry data obtained for x=0.22 indicate Van Vleck paramagnetic behavior accompanied by a decrease in the fraction of magnetically free Fe2+ ions with increasing x. Conversion electron Mössbauer spectra of the FeSe epilayers show a dominant paramagnetic central peak at both 300 and 13.5 K, with small contributions from Zeeman‐split components at low temperature. The samples were further characterized with x‐ray rocking curve, θ‐2θ, and topography measurements.