Experimental Verification of Van Vleck Nature of Long-Range Ferromagnetic Order in Vanadium-Doped Three-Dimensional Topological Insulator Sb2Te3

1 Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA 2 Francis Bitter Magnet Lab, Massachusetts Institute of Technology, Cambridge, MA 02139, USA 3 Condensed Matter Physics & Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973, USA 4 Department of Material Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA 5 Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA 6 The Center for Nanoscale Science and Department of Physics, The Pennsylvania State University, University Park, PA 16802-6300, USA