X-ray magnetic spectroscopy of MBE-grown Mn-doped Bi2Se3 thin films

We report the growth of Mn-doped Bi2Se3 thin films by molecular beam epitaxy (MBE), investigated by x-ray diffraction (XRD), atomic force microscopy (AFM), SQUID magnetometry and x-ray magnetic circular dichroism (XMCD). Epitaxial films were deposited on c-plane sapphire substrates by co-evaporation. The films exhibit a spiral growth mechanism typical of this material class, as revealed by AFM. The XRD measurements demonstrate a good crystalline structure which is retained upon doping up to similar to 7.5 atomic-% Mn, determined by Rutherford back-scattering spectrometry (RBS), and show no evidence of the formation of parasitic phases. However an increasing interstitial incorporation of Mn is observed with increasing doping concentration. A magnetic moment of 5.1 mu(B)/Mn is obtained from bulk-sensitive SQUID measurements, and a much lower moment of 1.6 mu(B)/Mn from surface-sensitive XMCD. At similar to 2.5 K, XMCD at the Mn L-2,L-3 edge, reveals short-range magnetic order in the films and indicates ferromagnetic order below 1.5 K. (C) 2014 Author(s).