Ferromagnetism in thin-film Cr-doped topological insulator Bi2Se3

We report on the observation of ferromagnetism in epitaxial thin films of the topological insulator compound Bi2Se3 with chromium doping. The structural, magnetic, and magnetoelectrical properties of Bi2Se3 were investigated for Cr concentrations up to 10%. For a Cr content up to similar to 5% the films are of good crystalline quality, with the lattice parameter a decreasing and the lattice parameter c increasing with increasing Cr concentration. The Curie temperature reached a maximum T-C=20K for 5.2% Cr. Well-defined ferromagnetic hysteresis in the magnetization and in the magnetoresistance was also observed in these films. (C) 2012 American Institute of Physics. [doi:10.1063/1.3688043

Initial/final state selection of the spin polarization in electron tunneling across an epitaxial Fe/GaAs(001) interface

Spin dependent electron transport across epitaxial FeGaAs (001) interfaces has been investigated using photoexcitation techniques. Spin filtering is observed in the forward bias regime and its sign is switched by using different photon energies. First principles calculations suggest that the spin polarization of the Fe layer is positive within the energy region into which spin polarized electrons tunnel. The authors attribute this sign switching to the initial and final states of the electrons tunneling across the interface, whose spin polarizations are determined by the selection rules in GaAs during photoexcitation and spin polarization of the Fe(001) layer, respectively. © 2007 American Institute of Physics