title: First-principles calculations of the electronic structure of tetragonal alpha-FeTe and alpha-FeSe crystals: evidence for a bicollinear antiferromagnetic order.
abstract: By the first-principles electronic structure calculations, we find that the ground state of PbO-type tetragonal alpha-FeTe is in a bicollinear antiferromagnetic order, in which the Fe local moments (approximately 2.5 microB) align ferromagnetically along a diagonal direction and antiferromagnetically along the other diagonal direction on the Fe square lattice. This novel bicollinear order results from the interplay among the nearest, the next-nearest, and the next-next-nearest neighbor superexchange interactions, mediated by Te 5p band. In contrast, the ground state of alpha-FeSe is in a collinear antiferromagnetic order, similar to those in LaFeAsO and BaFe2As2. This finding sheds new light on the origin of magnetic ordering in Fe-based superconductors.
authors.affiliation: Department of Physics, Renmin University of China, Beijing 100872, China.
authors.forename: Fengjie
authors.initials: F
authors.lastname: Ma
authors.forename: Wei
authors.initials: W
authors.lastname: Ji
authors.forename: Jiangping
authors.initials: J
authors.lastname: Hu
authors.forename: Zhong-Yi
authors.initials: ZY
authors.lastname: Lu
authors.forename: Tao
authors.initials: T
authors.lastname: Xiang