Magnetic and magnetotransport properties of Bi2Se3 thin films doped by Eu

Structural, magnetic and magnetotransport properties of (Bi1-xEux)2Se3 thin films have been studied experimentally as a function of Eu content. The films were synthesized by MBE. It is demonstrated that Eu distribution is not uniform, it enter quint-layers forming inside them plain (pancake-like) areas containing Eu atoms, which sizes and concentration increase with the growth of Eu content. Positive magnetoresistance related to the weak antilocalization was observed up to 15 K. The antilocalization was not followed by weak localization as theory predicts for nontrivial topological states. Surprisingly, the features of antilocalization were seen even at Eu content x=0.21. With the increase of Eu content the transition to ferromagnetic state occurs at x about 0.1 and with the Curie temperature ≈8 K, that rises up to 64 K for x=0.21. At temperatures above 1-2 K, the dephasing length is proportional to T-1/2 indicating the dominant contribution of inelastic e-e scattering into electron phase breaking. However, at low temperatures the dephasing length saturates, that could be due to the scattering on magnetic ions.