title: Metal-Insulator Transition Induced by Spin Reorientation in Fe7Se8Grain Boundaries.
abstract: Fe7Se8exists as a hexagonal NiAs-like crystal structure with a large number of ordered intrinsic vacancies. It is an ideal candidate for studying the effect of defects on properties such as magnetism and electrical transport. In this work, highly crystalline Fe7Se8with the 3c crystal structure was synthesized by a solid-state reaction. Sharp changes in the magnetization at 100 K confirm a rotation of the spins from the ab plane to the c axis with decreasing temperature. We observe an interesting metal-insulator transition at the same temperature as the spin-direction changes. We propose that locked spins in the grain boundaries induce electron localization and result in the metal-insulator transition. Electron localization is confirmed by X-ray photoelectron spectroscopy of the Fe 2p peaks, which exhibit two characteristic satellite peaks. This mechanism is also verified by comparing it with the properties of the 4c-Fe7Se8crystal structure.
authors.affiliation: Zernike Institute for Advanced Materials, University of Groningen , Nijenborgh 4, 9747 AG Groningen, The Netherlands.
authors.forename: Guowei
authors.initials: G
authors.lastname: Li
authors.affiliation: School of Physics and Technology, University of Jinan , 336 West Road of Nan Xinzhuang, 250022 Jinan, P. R. China.
authors.forename: Baomin
authors.initials: B
authors.lastname: Zhang
authors.affiliation: Faculty of Physics, Moscow State University , Vorobyovy Gory, 119899 Moscow, Russia.
authors.forename: Tigran
authors.initials: T
authors.lastname: Baluyan
authors.affiliation: School of Materials Science and Engineering, Harbin Institute of Technology , 150001 Harbin, P. R. China.
authors.forename: Jiancun
authors.initials: J
authors.lastname: Rao
authors.affiliation: Zernike Institute for Advanced Materials, University of Groningen , Nijenborgh 4, 9747 AG Groningen, The Netherlands.
authors.forename: Jiquan
authors.initials: J
authors.lastname: Wu
authors.affiliation: Faculty of Physics, Moscow State University , Vorobyovy Gory, 119899 Moscow, Russia.
authors.forename: Alla A
authors.initials: AA
authors.lastname: Novakova
authors.affiliation: Zernike Institute for Advanced Materials, University of Groningen , Nijenborgh 4, 9747 AG Groningen, The Netherlands.
authors.forename: Petra
authors.identifier: http://orcid.org/0000-0002-4418-1769
authors.initials: P
authors.lastname: Rudolf
authors.affiliation: Zernike Institute for Advanced Materials, University of Groningen , Nijenborgh 4, 9747 AG Groningen, The Netherlands.
authors.forename: Graeme R
authors.initials: GR
authors.lastname: Blake
authors.affiliation: Zernike Institute for Advanced Materials, University of Groningen , Nijenborgh 4, 9747 AG Groningen, The Netherlands.|Institute for Molecules and Materials, Radboud University Nijmegen , Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands.
authors.forename: Robert A
authors.initials: RA
authors.lastname: de Groot
authors.affiliation: Zernike Institute for Advanced Materials, University of Groningen , Nijenborgh 4, 9747 AG Groningen, The Netherlands.
authors.forename: Thomas T M
authors.identifier: http://orcid.org/0000-0001-5239-3115
authors.initials: TT
authors.lastname: Palstra