Carrier induced ferromagnetism in epitaxial Sn1−xMnxTe layers

Thin layers of semimagnetic (diluted magnetic) Sn1−xMnxTe semiconductor with Mn content x⩽0.04 and layer thickness 0.2–2μm were grown by molecular beam epitaxy (MBE) on BaF2 (111) substrates with SnTe buffer layer. Apart from SnTe and Mn fluxes, we employed an additional Te flux to provide the efficient way of controlling the deviation from stoichiometry in the layers. By manipulating the MBE growth conditions we obtained SnMnTe crystalline layers with the conducting hole concentration in the range from p=5×1019cm−3 (no extra Te flux) to p=2×1021cm−3 (additional Te flux present). In the layers grown under extra Te flux conditions we observe ferromagnetic transition with the Curie temperature TC⩽6K (depending on both x and p). Layers with the same Mn content but grown with no extra Te flux are paramagnetic. This dramatic change of magnetic properties, referred to as a carrier concentration-induced ferromagnetic transition, can be understood in the framework of a model attributing the ferromagnetic interactions in SnMnTe to the mechanism of indirect exchange via conducting holes (Ruderman–Kittel–Kasuya–Yosida interaction).