Experimental verification of the van Vleck nature of long-range ferromagnetic order in the vanadium-doped three-dimensional topological insulator Sb(2)Te(3)

Mingda Li; Cui-Zu Chang; Lijun Wu; Jing Tao; Weiwei Zhao; Moses H W Chan; Jagadeesh S Moodera; Ju Li; Yimei Zhu

doi:10.1103/PhysRevLett.114.146802

Experimental verification of the van Vleck nature of long-range ferromagnetic order in the vanadium-doped three-dimensional topological insulator Sb(2)Te(3)

Phys Rev Lett. 2015 Apr 10;114(14):146802. doi: 10.1103/PhysRevLett.114.146802. Epub 2015 Apr 9.

Authors

Mingda Li^{1

2

3}, Cui-Zu Chang², Lijun Wu³, Jing Tao³, Weiwei Zhao⁴, Moses H W Chan⁴, Jagadeesh S Moodera^{2

5}, Ju Li^{1

6}, Yimei Zhu³

Affiliations

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

PMID: 25910148
DOI: 10.1103/PhysRevLett.114.146802

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.