Ferromagnetism in (Zn,Cr)Se layers grown by molecular beam epitaxy

Magnetization measurements of MBE grown epilayers of (Zn, Cr) Se with relatively large Cr content of 0.014 and 0.021 are presented. We evidence the presence of a strong ferromagnetic coupling between Cr ions, but also suggest a significant clustering due to a pronounced superparamagnetic behavior found in the layers. We estimate the intraparticle Curie temperature to be about 100 K, which combined with other arguments appears to indicate that some magnetic properties of Cr-rich layers might be dominated by the presence of small grains of A(II)-Cr-2-B-4(VI) spinels.