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Interplay between ferromagnetism, surface states, and quantum corrections in a magnetically doped topological insulator

Author(s): Zhang, Duming; Richardella, Anthony; Rench, David W; Xu, Su-Yang; Kandala, Abhinav; et al

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Abstract: The breaking of time-reversal symmetry by ferromagnetism is predicted to yield profound changes to the electronic surface states of a topological insulator. Here, we report on a concerted set of structural, magnetic, electrical, and spectroscopic measurements of Mn-Bi2Se3 thin films wherein photoemission and x-ray magnetic circular dichroism studies have recently shown surface ferromagnetism in the temperature range 15 K <= T <= 100 K, accompanied by a suppressed density of surface states at the Dirac point. Secondary-ion mass spectroscopy and scanning tunneling microscopy reveal an inhomogeneous distribution of Mn atoms, with a tendency to segregate towards the sample surface. Magnetometry and anisotropic magnetoresistance measurements are insensitive to the high-temperature ferromagnetism seen in surface studies, revealing instead a low-temperature ferromagnetic phase at T less than or similar to 5 K. The absence of both a magneto-optical Kerr effect and an anomalous Hall effect suggests that this low-temperature ferromagnetism is unlikely to be a homogeneous bulk phase but likely originates in nanoscale near-surface regions of the bulk where magnetic atoms segregate during sample growth. Although the samples are not ideal, with both bulk and surface contributions to electron transport, we measure a magnetoconductance whose behavior is qualitatively consistent with predictions that the opening of a gap in the Dirac spectrum drives quantum corrections to the conductance in topological insulators from the symplectic to the orthogonal class.
Publication Date: 15-Nov-2012
Electronic Publication Date: 26-Nov-2012
Citation: Zhang, Duming, Richardella, Anthony, Rench, David W, Xu, Su-Yang, Kandala, Abhinav, Flanagan, Thomas C, Beidenkopf, Haim, Yeats, Andrew L, Buckley, Bob B, Klimov, Paul V, Awschalom, David D, Yazdani, Ali, Schiffer, Peter, Hasan, M Zahid, Samarth, Nitin. (2012). Interplay between ferromagnetism, surface states, and quantum corrections in a magnetically doped topological insulator. PHYSICAL REVIEW B, 86 (10.1103/PhysRevB.86.205127
DOI: doi:10.1103/PhysRevB.86.205127
ISSN: 1098-0121
Type of Material: Journal Article
Journal/Proceeding Title: PHYSICAL REVIEW B
Version: Author's manuscript

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