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This letter presents the first-principles study of a three-dimensional (3D) topological insulator (TI) Bi2Se3 doped with magnetic atoms of 3d-transition metal (TM), Cr or Fe. Calculations are performed within the density functional theory (DFT) and a modified potential of Becke and Johnson (MBJ). Using the MBJ scheme, we show that both systems are semiconductors with a direct gap of 0.21 eV (Bi2Se3:Cr) and 0.27 eV (Bi2Se3:Fe), respectively. The magnetic structures of studied materials are, however, different: Bi2Se3:Cr exhibits a clear ferromagnetic (FM) order, while Bi2Se3:Fe has an antiferromagnetic (AFM) order. In view of the great scientific and practical interest to the 3D FMTI systems, the optical and magneto-optical spectra of Bi2Se3:Cr are calculated. [ABSTRACT FROM AUTHOR]

Thin films of MnxSi1−x alloys with different Mn concentration grown by the pulsed-laser deposition (PLD) method onto the Al2O3 (0001) substrate were investigated in the temperature range 4–300 K using ferromagnetic resonance (FMR) measurements in the wide range of frequencies and magnetic fields . For samples with , FMR data show clear evidence of ferromagnetism (FM) with high Curie temperatures . These samples demonstrate the complex and unusual character of magnetic anisotropy described in the frame of phenomenological model as a combination of the essential second-order easy-plane anisotropy contribution and the additional fourth-order anisotropy contribution with the easy direction normal to the film plane. We explain the obtained results by a polycrystalline (mosaic) structure of the films caused by the film-substrate lattice mismatch. [ABSTRACT FROM AUTHOR]