title: Experimental verification of the van Vleck nature of long-range ferromagnetic order in the vanadium-doped three-dimensional topological insulator Sb(2)Te(3).
abstract: We demonstrate by high resolution low temperature electron energy loss spectroscopy (EELS) measurements that the long range ferromagnetic (FM) order in the vanadium- (V-)doped topological insulator Sb_{2}Te_{3} has the nature of van Vleck-type ferromagnetism. The positions and the relative amplitudes of two core-level peaks (L_{3} and L_{2}) of the V EELS spectrum show unambiguous change when the sample is cooled from room temperature to T=10  K. Magnetotransport and comparison of the measured and simulated EELS spectra confirm that these changes originate from the onset of FM order. Crystal field analysis indicates that in V-doped Sb_{2}Te_{3}, partially filled core states contribute to the FM order. Since van Vleck magnetism is a result of summing over all states, this magnetization of core level verifies the van Vleck-type ferromagnetism in a direct manner.
authors.affiliation: Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.|Francis Bitter Magnet Lab, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.|Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors.forename: Mingda
authors.initials: M
authors.lastname: Li
authors.affiliation: Francis Bitter Magnet Lab, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Cui-Zu
authors.initials: CZ
authors.lastname: Chang
authors.affiliation: Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors.forename: Lijun
authors.initials: L
authors.lastname: Wu
authors.affiliation: Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors.forename: Jing
authors.initials: J
authors.lastname: Tao
authors.affiliation: The Center for Nanoscale Science and Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802-6300, USA.
authors.forename: Weiwei
authors.initials: W
authors.lastname: Zhao
authors.affiliation: The Center for Nanoscale Science and Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802-6300, USA.
authors.forename: Moses H W
authors.initials: MH
authors.lastname: Chan
authors.affiliation: Francis Bitter Magnet Lab, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.|Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Jagadeesh S
authors.initials: JS
authors.lastname: Moodera
authors.affiliation: Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.|Department of Material Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Ju
authors.initials: J
authors.lastname: Li
authors.affiliation: Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors.forename: Yimei
authors.initials: Y
authors.lastname: Zhu